Ecological sensitive area urban open cut tunnel group construction method

Abstract

The invention discloses a method for constructing an urban open-cut tunnel group in an ecological sensitive area. The method comprises the following steps: step 1, confirming construction; step 2, enclosure construction; thirdly, a foundation pit is excavated; 4, supporting construction is conducted; 5, main body construction; sixthly, auxiliary engineering construction is conducted; according to design requirements, each tunnel is divided into a plurality of foundation pits, each foundation pit is provided with two working faces, line production takt is formed between procedures, competition between the working faces is formed, a reward and penalty incentive mechanism is formulated, a typical mechanism is established, and on the premise that engineering safety is guaranteed, construction of the multiple tunnels is conducted at the same time. The implementation of a standardized construction site and the on-time and on-time implementation of a construction progress target are ensured, and the construction efficiency is improved; the construction quality of a tunnel main body structure is effectively guaranteed through dewatering and drainage of the foundation pit and waterproof construction of the tunnel; the advanced foundation pit safety management method is summarized according to foundation pit deformation monitoring data under the urban multi-bin excavation condition.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel group construction, and in particular to a method for constructing an open-cut tunnel group in an ecologically sensitive urban area. Background Art

[0002] With the progress of urban construction and the development of urbanization, in order to adapt to the requirements of economic globalization and the information age, it is necessary to adjust the urban layout, strengthen urban infrastructure construction, improve the quality of urban construction, and vigorously develop the tertiary industry to meet the increasing living needs;

[0003] The growing urban population and the pursuit of quality of life have brought increasing urban traffic pressure year by year. The existing transportation system can no longer meet the requirements of urban travel. The construction of urban underground tunnels will greatly ease urban traffic pressure, facilitate travel, and accelerate personnel mobility and urban development.

[0004] However, the existing urban tunnel construction still has some shortcomings. First, the existing urban tunnel construction mainly consists of the gradual construction of a single tunnel, and the construction efficiency is low. Second, the existing urban tunnel construction has high requirements on the construction quality of the main structure of the tunnel. Third, most of the existing urban tunnel construction does not use foundation pit deformation monitoring data and lacks a set of advanced foundation pit safety management methods. Therefore, it is necessary to design a method for the construction of urban open-cut tunnel groups in ecologically sensitive areas. Summary of the invention

[0005] The purpose of the present invention is to provide a method for constructing an open-cut tunnel group in an ecologically sensitive area in an urban area to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a method for constructing an open-cut tunnel group in an ecologically sensitive area, comprising the following steps: step 1: construction confirmation; step 2: enclosure construction; step 3: foundation pit excavation; step 4: support construction; step 5: main body construction; step 6: ancillary project construction;

[0007] In the above step 1, the order of tunnel segment construction is confirmed and corresponding traffic diversion is carried out;

[0008] In the above step 2, constructing the tunnel enclosure structure;

[0009] In the above step 3, excavation of the tunnel foundation pit is carried out;

[0010] In the above step 4, the support structure engineering is constructed;

[0011] In the above step 5, the main structure of the tunnel is constructed;

[0012] In the above step six, the earthwork is backfilled and the remaining structural works are constructed.

[0013] As a further technical solution of the present invention, in the step one, firstly, an in-depth investigation is conducted on the urban planning and traffic demand of the ecologically sensitive area to understand the geographical location, surrounding environment, traffic flow and other factors of the tunnel group, and at the same time, the length, width, burial depth and other technical parameters of each tunnel are analyzed to provide a basis for determining the construction sequence. Based on the investigation and analysis results, each tunnel is divided into several construction sections. When dividing, it is necessary to consider factors such as the feasibility of the construction technology, the balance of construction difficulty, and the convenience of traffic diversion. Combined with urban planning and traffic needs, the principle of starting with the easy and then the difficult, and starting with the outside and then the inside is followed to determine the construction sequence of each open-cut tunnel and construction section to reduce interference and impact on traffic. During the construction period, temporary roads are set up to meet traffic needs. The setting of temporary roads should consider parameters such as the width, length, and traffic capacity of the road to ensure smooth traffic. At the same time, obvious traffic signs should also be set up. Signs and markings are used to guide vehicles and pedestrians to pass in an orderly manner. According to the traffic flow and road conditions during the construction period, the timing and phase of traffic lights are adjusted to improve the road's traffic capacity. In addition, traffic warning signs and warning lights are set up during the construction period to remind vehicles and pedestrians to pay attention to safety. Detailed traffic diversion measures are formulated, including traffic control during the construction period, the deployment of traffic diversion personnel, emergency traffic plans, etc., to ensure that during the construction period, the traffic order is in order and the occurrence of traffic congestion and traffic accidents is reduced; an open-cut tunnel is determined as the first construction section of the tunnel group, and the construction of other open-cut tunnels will start in sequence according to the progress of pipeline relocation. The tunnels are constructed in parallel. Each tunnel is divided into several foundation pits according to the design requirements. Two working faces are opened in each foundation pit. A flow operation rhythm is formed between each process, forming a competition between working faces, and a reward and punishment incentive mechanism is formulated and a typical mechanism is established.

[0014] As a further technical solution of the present invention, in the step 2, bored piles and bored interlocking piles are first constructed. The bored piles are all made of full casing plus rotary drilling rigs. The bored piles are combined with high-pressure rotary jet piles to form a water-stop curtain. The adjacent single piles of the bored interlocking piles are interlocked with each other to form a pile wall. Among them, the bored piles first need to construct a reinforced concrete guide wall on the top of the pile. The guide wall is 3.5m wide and 35cm thick, and the material is C25 concrete. Then the center position of the pile is accurately determined as the control point for positioning the drilling rig. After the pile foundation is in place, 2.5 to 3m of soil is first taken to remove obstacles, and then a steel casing is sunk into the fully weathered rock layer using a puller to detect the verticality. If it is unqualified, it is corrected. If it is qualified, soil is taken downward until the designed bottom elevation of the hole is reached. Then a steel cage is made and hoisted by a crane. The designed elevation can be calculated from the casing top elevation. The elevation must be guaranteed during installation. The calculation is correct, and the allowable error is ±10mm. When the steel cage is lowered, it is manually assisted to align the hole position, keep it vertical, put it gently and slowly, and generally use positive and reverse rotation to slowly sink it step by step to prevent collision. It should be fixed immediately after it reaches the designed elevation; if it is difficult to lower it, it should be stopped immediately, and the cause should be dealt with after it is found out, and then concrete is poured. The reinforced piles use underwater C35 concrete, and the plain piles use super slow-setting C35 concrete. The concrete pouring conduit is connected by a screw buckle sleeve rubber sealing ring with an inner diameter of 25cm. After the connection is completed, it is checked in detail to ensure that the conduit is sealed and pressure-resistant. The conduit is slowly lowered into the hole by a crane. The bottom of the conduit should be 30 to 50cm higher than the bottom of the hole to ensure the discharge space at the lower outlet. The upper end of the conduit is connected to a concrete funnel, and the upper end of the conduit is sealed with a water stopper. Concrete flows into the funnel through the chute. When conditions are difficult, a crane can be used to lift it into the funnel through the hopper, and 2m 3After the above concrete is poured, pull out the bottom cover of the funnel, pour concrete into the conduit, and maintain continuous pouring of concrete. After the pouring starts, the construction should be compact and continuous, and it is strictly forbidden to stop work halfway. During the pouring process, pay attention to the rise and fall of the water level in the hole, measure the actual height of the concrete surface at any time and calculate the buried depth of the conduit to ensure that the bottom end of the conduit is buried 2 to 6 meters below the concrete surface. The conduit should avoid being buried too deep, which may cause the pipe to be unable to be pulled out. At the same time, the buried depth should not be too small to cause the steel cage to float or the conduit to be pulled out of the concrete surface to cause a broken pile accident. After the concrete pouring is completed, the casing and conduit are gradually removed. According to the buried depth of the conduit, 1 to 2 sections of the conduit are removed each time. The conduit should be rinsed immediately after removal for the next use; when the casing is lifted, slowly pull it up and shake it left and right so that concrete can flow into the space occupied by the casing. At the same time, pay attention to whether the steel cage floats. The buried depth of the casing should be controlled at about 2 meters. In order to ensure the quality of the designed pile top concrete, the concrete is poured to the pile 0.5m above the top elevation, this part of concrete is chiseled off before constructing the crown beam. After the pouring is completed, the casing and the conduit are pulled out. Technical personnel are assigned to be on duty throughout the pouring process and supervise the construction team to fill in the concrete pouring record. The retarding time of the pile concrete is determined according to the time of the single pile. The time of the single pile is directly related to the geological conditions, pile length, pile diameter and drilling rig capacity. Therefore, the retarding time of the pile concrete can be determined according to the following method. First, the time t required for the pile formation of a single pile is determined, and then it is calculated according to the following formula: T=3t+K, where: T=retarding time of the pile concrete, K=reserve time, generally 1.5t, t=time required for the formation of single piles of A and B piles, the verticality of the pile should be monitored and checked during the drilling process, and during the casing pressing process, 2 people are arranged to use hammer balls to detect the verticality of the casing during the pressing process from two mutually perpendicular directions, and any deviation is corrected at any time.

[0015] As a further technical solution of the present invention, in the step 2, the high-pressure jet grouting pile construction first uses manpower or machinery to level the site, dig a sewage pool and a sewage ditch, and make a slurry pool. According to the design requirements, the pile point is released by obvious marks, and the drilling rig is moved to the designed hole position by self-movement. The verticality is adjusted by the theodolite so that the drill bit is aligned with the pile point. To prevent the drill rod from tilting, the bottom weight of the drill rod can be increased, and a plumb line is used to check at any time during the drilling process. The inclination of the drill rod is not more than 0.5%, and the deviation between the drilling hole position and the designed hole position is not more than 50 mm. After the drilling rig is in place, a 0.5 MPa low-pressure water jet test is first carried out to check whether the nozzle is unobstructed and the pressure is normal. Move the debugged drilling rig to the designed hole position, and adjust the verticality so that the drill bit is aligned with the center of the designed pile position. After the water jet test, drilling can be started. The water jet pressure is increased from 0.5MPa to 1MPa to reduce friction and prevent nozzle clogging. After the first drill rod is drilled in, stop water jetting and wait for the pressure to drop. Then extend the drill rod and continue water jet drilling until the designed pile bottom position is drilled. Then use qualified 42.5 composite silicate cement and clean drinking water to prepare according to the selected mix ratio. The cement parameter is not less than 25%. According to the determined mix ratio, first add water into the bucket, then add cement, start the mixer to mix, and flow into the mud pool through the filter screen. Then use the mud pump to pump into the second filter screen and enter After the second filtration, the slurry flowing into the mud barrel is pressurized by a high-pressure pump and sent to the drilling rig for rotary spraying through a high-pressure pipe. The slurry pressure is greater than 3MPa, the water pressure is 25MPa, the slurry water-cement ratio is 0.8, the rotation speed is generally 10r / min, and the lifting speed is 10cm / min. After drilling to the designed elevation, unscrew the upper drill rod, put in a steel ball, block the water hole, and then install the drill rod to deliver high-pressure cement slurry to the drilling rig. After the slurry emerges from the bottom of the hole, the drill rod begins to rotate and lift, and rotary spraying is carried out from bottom to top. During the rotary spraying process, the amount of slurry should be controlled at 10-25%. When encountering special soil layers, such as gravel soil, in order to ensure the pile diameter and quality, re-spraying must be carried out, and the re-spraying height Not less than 500mm. During the rotation process, when the first drill rod is raised from the ground, stop grouting. After the pressure drops, quickly remove the drill rod. When it is lifted to the designed elevation of the pile top, restart the rotary jetting. When it is lifted to the designed elevation of the pile top, in order to avoid the slurry and soil being mixed in the mixer and shrinking due to the removal of the slurry, resulting in a concave hole on the top of the rotary jetting pile, low-pressure supplementary spraying is carried out. After the supplementary spraying is completed, raise the drill rod and drill bit for low-pressure water injection to flush the drill rod and nozzle, and then move the drilling rig. When encountering special circumstances, all pipelines and equipment must be cleaned. When a pile is completed after rotary jetting, the drilling rig can be removed to proceed to the next pile operation. The construction interval between two adjacent piles shall not be less than 2 days, and the spacing shall not be less than 2m.

[0016] As a further technical solution of the present invention, in the step 2, dewatering and drainage construction of the foundation pit is carried out, wherein the dewatering construction of the foundation pit firstly involves drilling the dewatering well, measuring and locating the well point, digging the wellhead, installing the protective tube, positioning the drilling rig, drilling, cleaning the hole, hanging the well pipe, backfilling the filter layer between the well pipe and the hole wall, washing the well, installing a water pump in the well pipe, installing the pumping control circuit, testing the water pumping, the normal operation of the dewatering well, pulling out the well pipe after dewatering, and sealing the well. A dewatering test is carried out before construction, and the layout, quantity, structural dewatering index, dewatering monitoring and other contents of the dewatering well points are adjusted to achieve the dewatering effect and ensure the foundation pit is well irrigated. The project is safe and the deformation of the foundation outside the pit is well controlled to ensure the safety of surrounding pipelines and buildings. After the dewatering well is constructed, one well is put into operation to reduce the groundwater level in time and maintain all-weather non-stop operation. The foundation pit excavation should be carried out two weeks after the pre-dewatering. After the pressure reduction well is completed, an overall depth reduction and pumping is required to verify whether it can meet the design requirements. When the foundation pit is excavated to the base, except for the reserved drainage outlet, the remaining pipe wells are immediately backfilled after being pulled out, and a cushion layer is applied. First, use a large-capacity water pump to pump water, and then use coarse sand to backfill the pipe well to the bottom elevation of the cushion layer, and use the same grade concrete as the cushion layer to fill the well pipe; at the same time, the following auxiliary or supplementary measures are taken Rescue measures: First, establish a dynamic groundwater monitoring network along the line, use the spare wells outside the pit as observation wells, and observe the daily monitoring data of groundwater level, monthly monitoring data of groundwater quality, daily drainage data of foundation pit, drainage sand content data, etc.; Second, establish a settlement monitoring network. Before the implementation of the precipitation project, according to the pumping influence range calculated in the precipitation design and the buildings within the range, set up settlement monitoring points. During the pumping period, continuous settlement monitoring should be carried out. If the accumulated settlement is close to the warning value, necessary measures should be taken in time. If it is found through settlement monitoring that the settlement of the building has reached a dangerous level, pumping must be stopped immediately to find out the specific cause of the settlement. When it is confirmed that it is caused by precipitation, recharging measures should be taken immediately. In the settlement area, the spare well outside the pit should be used for recharging. The distance between the recharging well and the precipitation well must be greater than 5.0m. The specific design of the recharging well point should be determined according to the specific settlement situation. Then, the foundation pit drainage construction should be carried out. Drainage ditches should be set around or in the middle of the excavated foundation pit. A collection well should be set every 15m to allow the seepage water in the foundation pit and the construction wastewater to flow into it. Then, it should be pumped into the surface sedimentation tank by water pumps and discharged to the municipal pipe network after being treated by sedimentation and other methods. The drainage ditch and collection well should be deepened while digging, and the ditch bottom should be kept at least 0.5m lower than the foundation pit bottom, and the collection well should be kept at least 0.5m, a 400×400 brick drainage ditch is set up on the ground around the foundation pit, and a 1000×500×500 sedimentation tank is set up at intervals of 20m. During the excavation process, the pit is kept dewatered to ensure that the groundwater is 1m below the excavation surface. The dewatering time lasts until the top plate is covered with soil. The foundation pit dewatering is carried out 15 to 20 days before the earthwork excavation, and the trial dewatering work is done. When the excavation reaches the construction bottom plate, a temporary drainage hole is set on the bottom plate. After the top plate is covered with soil and the internal paving layer is completed, the hole is sealed. 7 to 10 days before the foundation pit excavation, the outside of the foundation pit is dewatered to reduce the water level to 5m below the ground. A drainage hole is arranged every 200㎡. .

[0017] As a further technical solution of the present invention, in the step three, foundation pit excavation and support construction are carried out. During the foundation pit excavation and support, earth excavation should follow the principles of zoning, blocking, symmetry, balance and time limit. A comprehensive layered or step-by-step layered excavation method can be adopted. The layer thickness is not more than 2m. The temporary slope on the excavation surface during the excavation process is not more than 1:1.5. The unsupported exposure time is shortened as much as possible to effectively control the deformation of the support structure. The foundation pit is excavated using the "time and space effect" theory principle. The excavation should be carried out in layers. After the support is completed, the next layer can be excavated. Over-excavation is strictly prohibited. When the excavation approaches the base, the principle of rapid excavation and rapid bottom sealing should be followed. Key process control and preventive measures in the foundation pit excavation process should be well done, construction organization design and construction operation procedures should be formulated, and full preparations should be made to remove water from the foundation pit. Drainage equipment should be installed, conditions for excavation, transportation and abandonment of soil should be prepared, various monitoring points should be protected, and initial readings should be monitored. Excavation can only be carried out after the initial readings are obtained, and monitoring should be carried out at the frequency required by the design. Observation should be intensified according to the actual situation on site, and the stability of the foundation pit should be analyzed by dynamic conditions. During the excavation process, leakage on the retaining wall should be blocked in time to prevent small streams of quicksand from breaking through the support and developing into soil erosion, which will not only cause a large amount of ground subsidence, but will also cause the support structure to become unstable, resulting in serious catastrophic accidents. In order to level the pit bottom and prevent local over-excavation, the earthwork 30cm above the designed pit bottom elevation should be excavated and leveled manually, and the local excavated depressions should be filled with sand. At the same time, a sump must be set up to pump out the water at the bottom of the pit.

[0018] As a further technical solution of the present invention, in the step 4, the construction of reinforced concrete crown beam and reinforced concrete support beam is carried out. The process flow is leveling and compacting the earth under the support beam, measuring and laying out the lines, laying the tarpaulin isolation layer, steel bar binding, template installation, steel bar template acceptance, concrete pouring and maintenance. Before the construction of the retaining pile, a concrete guide wall is first set up. The outer guide wall is used as a retaining wall for excavation. Therefore, during construction, attention should be paid to protecting the integrity of the outer guide wall. After the retaining pile retaining structure is completed, the inner guide wall is dismantled and loaded together with the earth for transportation and disposal. The concrete debris and earth within the range of the wall top are cleaned and eliminated manually or by air compressor. and impurities, and rinse them with high-pressure water; the construction methods of reinforced concrete purlins and reinforced concrete supports are as follows: the excavation of the first layer of earthwork on the upper part and the construction of the first reinforced concrete purlin and support are carried out in layers and sections according to the aforementioned foundation pit excavation and support construction methods. According to the design elevation, the axis uses a level and the position of each reinforced concrete purlin and support is released according to the foundation pit retaining wall, and the base is cleaned manually to ensure the level of the foundation pit bottom. The support bottom formwork uses C20 concrete bottom formwork with a thickness of 15cm and a width 15cm wider than the width of the support beam. After the earthwork excavation and leveling are completed, the base is compacted and leveled with crushed stone. A 4cm thick wooden formwork is used on both sides to pour concrete. The concrete is compacted with a flat vibrator. The surface is pressed twice with a wooden wedge and then pressed with an iron plate. After the concrete bottom formwork is poured, it must be covered with straw bags and watered for 3 days. The steel bars can be tied only after the strength of the concrete bottom formwork reaches 50%. An isolation layer must be set on the surface of the concrete bottom formwork. Before tying the steel bars, steel pipe brackets are set up on both sides and one side of the support beam. After the steel bars are tied and formed, the steel pipe brackets are removed and the skeleton is placed on the bottom formwork. The crown beam, concrete support, and concrete corner brace are erected with a composite formwork. The support system uses 50×80 wooden squares, 48×3.5 short steel pipes, and M12 pull screws. The bolts and fasteners are connected to bear the force together. The surface of the formwork must be flat, the joints must be tight, and there must be no leakage. The straight edges and local unevenness must be repaired and corrected in time, otherwise they must not be used. The formwork must be coated with demoulding oil before supporting the formwork. The demoulding oil is clear engine oil. The formwork support uses Φ48 steel pipes with a length of 1.8m. The pipe is driven into the soil for not less than 0.6m, with a spacing of 80cm. It is connected by two longitudinal steel pipes. Before pouring, the position, elevation, cross-sectional dimensions of the formwork, the stability of the formwork and the support, and the joint conditions should be reviewed or checked. Commercial concrete is used, and commercial concrete is transported by a roller truck with a capacity of 6m 3 or 8m 3Transport to the site, and transport to each pouring point by automobile pump or fixed pump. Automobile pump uses a concrete pump truck with a wall length of 21m. Automobile pump or fixed pump is parked on the construction access road for pumping. Removal of crown beam, concrete support, concrete angle support formwork. Generally, after the final setting of concrete, the concrete strength can ensure that its surface and edges are not damaged by demoulding. The formwork can be removed when it is strong enough to ensure that its surface and edges are not damaged by demoulding. The demoulding must not be pried hard, and attention should be paid to the damage of the edges and corners. Concrete is maintained by watering and moisturizing, and the surface is covered with linen. The production water of the site water supply system is used. The maintenance time is generally 7 days. Pay attention to the protection of the finished product. Crown beam, concrete support, concrete angle support formwork The concrete strength of the support and concrete corner support must reach 95% before it can be subjected to force and the lower earth excavation can be carried out; the method of removing the concrete support of the foundation pit is mechanical cutting and breaking it, and the order of support removal is to remove the secondary support first, and then the top support. The support beam should be removed by removing the connecting rod first and then the main support. When removing each support beam, cutting should be started from the middle. When removing the support, the protection of the wall panel should be strengthened to prevent the support beam from damaging the top plate of the tunnel main structure. Protective measures such as laying wooden blocks on the top plate can be taken, and the construction waste after removal should be removed manually in time.

[0019] As a further technical solution of the present invention, in the step five, the main structure is constructed. First, the construction preparation work is carried out. After the foundation pit is excavated to the designed elevation, the trench is inspected as soon as possible, and the structure is measured and laid out. The formwork support system of the side wall and the top plate is designed and calculated, and a special plan for tunnel formwork is prepared. After being submitted to experts for demonstration and improvement and approval, the plan is organized for implementation. The material feed is arranged in advance according to the construction progress, and the structural construction sequence, construction schedule, construction methods and technical requirements are carefully explained to the work team and all management personnel; then the plain cushion layer is constructed. The cushion layer concrete is C20 and 20 cm thick. The cushion layer construction is carried out closely following the excavation surface to prevent the base from being exposed for too long, eliminate water accumulation in the foundation pit, remove the loose soil in the foundation pit, clean and level the top of the pull-out piles, silt and other debris. After the foundation pit is cleaned, the base is fully compacted with a tamping machine, and the bearing capacity of the foundation is measured, and the owner and engineer are reported in writing in a timely manner. When the cushion layer concrete is spread, according to the pre-buried The horizontal pile controls the elevation of the surface layer, and the concrete is vibrated with a flat vibrator. After the initial setting and before the final setting of the cushion concrete, the surface layer is calendered for the second time and fully cured to prevent looseness, sand and peeling. The thickness of the cushion layer is controlled according to the pre-buried elevation control piles, and the surface is closed and cured in time to ensure that there are no honeycombs, pits and cracks on the cushion surface. Then the bracket is arranged. The bracket used for the main structure frame concrete construction is a disc-type full-floor bracket. The bracket is arranged through calculation to ensure that the strength and stiffness meet the construction requirements. It is considered that each disc-type vertical pole can withstand 8 to 9 tons of vertical load. The calculation takes into account the side wall concrete pressure, the weight of the top plate concrete, the weight of the formwork, the construction load, the wind force acting on the formwork bracket and other possible loads. Therefore, the longitudinal and transverse spacing of the disc-type bracket is 60cm and 90cm, and it is encrypted to 60cm near the upper chamfer to strengthen the stiffness of the longitudinal and transverse beams of the top plate and the transverse and vertical belts of the side walls. The disc-type bracket has the characteristics of flexible disassembly, and no unloading device is provided during construction.Then the formwork construction is carried out. The outer formwork of the concrete project uses the side wall of the enclosure structure. Before the construction of the side wall, the wall surface of the enclosure structure should be trimmed and leveled first. The formwork consists of three parts: the bottom formwork, the side wall, and the top formwork. It is assembled on site. The construction formwork of the bottom plate and a section of the side wall uses a large steel formwork, which is processed into a frame with angle steel and channel steel. The bakelite board is connected to the frame as a whole and processed into large blocks according to the design drawings. It is assembled on site. At the same time, considering the turnover use, the formwork uses 2440×1220×15 plywood as the panel, 60mm×80mm square wood as the secondary rib, φ48*3.5mm steel pipe as the main rib, and the outer wall needs to be poured to the bottom plate when the bottom plate concrete is poured. 30cm above the armpit corner, there are 2 rows of vertical pre-embedded screws on the outer wall. The upper row is the tension screw, and the lower row of pre-embedded screws are welded to the main reinforcement of the structure. They do not penetrate the entire bottom plate to prevent the movement of the template. The longitudinal spacing of the screws is 600mm, and the vertical spacing is 500mm. The chamfered part of the inner side of the side wall adopts a special steel mold, the secondary ribs use 60*80 square wood, the main ribs are arranged vertically, and a steel pipe is set on the top for tying. The side wall formwork system of the main structure of the open-cut section adopts a single-sided formwork, which mainly uses the steel triangular truss and embedded parts as the support system of the formwork to fix the formwork firmly. The formwork panel adopts a 4.5m×1.5m×5mm overall large steel mold, and the surrounding The ribs are 75*8 steel plates, the vertical secondary ribs are 75*50 angle steels, and the horizontal ribs are connected with 70*6 steel plates. The spacing between the secondary back ribs is less than 300mm. The main back ribs on the vertical ribs are 10# double channel steel welded on the back ribs to increase the strength. The brackets use double 14# channel steel tripods with a spacing of 750mm. The top plate formwork system of the main structure of the open-cut section uses steel pipe scaffolding + top support + secondary rib square wood + main rib steel pipe support. The formwork uses 2440×1220×15mm plywood as the panel, and uses 8*8cm square wood @30cm and double-piece Φ48 steel pipe @30cm. Two secondary rib forms are used, 10# I-beam @80cm as the main rib, and the buckle type The brackets are used to set up full-floor scaffolding supports. According to the two forms of 48 and 60 buckle brackets, the horizontal spacing of the brackets is 90cm, and the vertical spacing is 60cm, 90cm and 120cm. The erection step distance is 1.5m. The template cuts are protected with edge sealing paint to reduce the generation of burrs or water swelling, loose deformation at the cuts. The incoming materials should have certificates and test reports. The wooden templates are processed on site. The woodworking processing team accurately arranges the templates according to the drawings. After processing and forming, the processing team first conducts self-inspection and promptly corrects any problems found; then the quality inspector conducts special inspections on the processing to control the allowable deviation of the template processing within the specified range;Before use, the installation team will conduct another handover inspection on the wooden processed products. Those that affect their use will be returned for repair immediately. Bottom ribs will be set at the joints of the top plate formwork, and plastic tape will be minimized. Sponge strips will be added to seal the vertical formwork joints. Cleaning ports will be set at appropriate positions on the top plate and the ends. Before pouring concrete, a vacuum cleaner will be prepared to clean up the debris in the formwork. During construction, attention should be paid to the appearance quality of the concrete. All joints should be tight and no slurry should be exposed. If necessary, thin sponge pads should be embedded in the joints or putty should be applied to eliminate gaps. Before erecting the formwork, the formwork should be polished, rust-removed, oiled, and tried out. When erecting the formwork, all embedded parts should be installed and fixed. Clean engine oil or a reliable quality release agent should be used as the formwork release agent. The demoulding time should be controlled, and test blocks for curing under the same conditions should be set up. Whether to demould or not should be decided according to the specifications. Special tools such as a flat shovel with an edge and a dry mop should be used to clean the formwork. It is forbidden to hit the formwork with a hammer. The formwork should be cleaned dry. No isolation agent shall be applied before cleaning. The templates that have not been cleaned, maintained, or coated with isolation agent cannot be used. The bottom tie rod and top tie rod of each vertical pole must be fully installed and ensure reliable connection. The exposed length of the adjustable screw rod shall not exceed 2 / 3 of the total length of the screw rod. Before the template enters the site, the template and the use position shall be numbered according to the project department's engineering arrangement and the division of flow sections. The templates shall be arranged in batches in an orderly manner to ensure the needs of on-site construction and avoid occupying more space on site. After the base waterproof coating is applied to meet the requirements, the bottom plate steel bar binding begins. The side wall and top plate steel bars shall be bound after the bottom plate concrete construction is completed and the inner mold and bottom mold are installed. Various joint steel bars shall be reserved according to the design. All steel bars shall be tested in advance according to the specifications, and laid out strictly according to the requirements of the design drawings. The binding and welding of steel bars shall meet the requirements of the construction specifications.Then the concrete is poured. Before pouring concrete, the concrete mix design and various material experiments are carefully done. Before concrete transportation, the equipment must be repaired to ensure that the machine is in good condition. The bottom slab concrete is poured first. The concrete pouring adopts the method of inclined layering and one-time to the top. The thickness of each layer is controlled at 30 to 40 cm. The pump truck starts pouring from the four corners on both sides of the foundation pit, allowing the concrete to flow naturally to form a certain slope, and then the middle partition wall and outer wall concrete pouring are carried out. For the tunnel concrete structure, the middle partition wall is poured first, and then the outer wall is poured. The "inclined layered construction method" is used to control the pouring height at one time, so that the material is discharged in layers, the layers are tamped, and the cycle is promoted as a whole. The thickness of each layer is preferably 30 cm. Two concrete pump trucks are used for pouring at the same time. The side walls and the middle wall on both sides of the frame are poured symmetrically at the same time. Then the top slab concrete is poured. The concrete pouring adopts The slope is layered and poured to the top at one time. The thickness of each layer is controlled at 30-40cm. The pump truck starts pouring from the four corners on both sides of the foundation pit, allowing the concrete to flow naturally to form a certain slope, and then the concrete is vibrated. The concrete is compacted by inserting vibration. The moving spacing of the vibrating rod shall not exceed 1.5 times its effective radius, and it shall be inserted into the lower concrete for 5-10cm. The concrete must be compacted without missing vibration, insufficient vibration, or excessive vibration. The fast insertion and slow withdrawal method is adopted, and the vibration points are evenly arranged. The construction joints and embedded parts must be vibrated more. The formwork, steel bars, water stop strips, and bottom plates are not touched during vibration. After the top plate concrete is vibrated and compacted, the surface slurry is smoothed, compacted, and pressed before final setting to ensure that the concrete surface does not crack. If there is too much moisture on the vibrated surface, the surface vacuum pump is used to absorb water and apply pressure multiple times, that is, a vacuum pump is used to connect a 15m piece. 2The vacuum absorbent pad absorbs the water on the surface of the concrete to ensure that the concrete surface does not crack. Finally, the concrete is cured. After the concrete is poured and initially set, it is watered to ensure that the concrete surface is always moist. At the same time, a geotextile is covered on the concrete surface to continue to keep the material moist. The curing water and materials must not cause adverse effects on the appearance quality of the concrete. The curing time is determined based on the on-site measured atmospheric humidity and temperature. For tunnel waterproofing construction, the self-waterproofing of the concrete structure should be designed first. The waterproof concrete should be configured by adjusting the mix ratio and adding admixtures and admixtures. The structural concrete impermeability grade, structural concrete water-cement ratio, and minimum amount of cementitious materials should be determined based on factors such as the strength of the concrete structure and the depth of structural burial. The top slab concrete and the side wall concrete cast together with the top slab should be added with appropriate amounts of high-quality fly ash, slag and other active materials and other anti-seepage measures. To reduce shrinkage due to drying and temperature difference, the self-waterproofing design of concrete structures should select appropriate materials according to the environmental conditions in which they are located to meet the requirements of the concrete's own impermeability, durability and crack resistance; then the waterproofing membrane construction should be carried out. The side wall / enclosure section uses 1.5mm thick pre-laid polymer waterproofing membrane, the bottom plate uses 1.5mm thick pre-laid polymer waterproofing membrane, and the top plate uses a flexible waterproof layer. The waterproofing construction progress is consistent with the main structure construction progress. After the foundation pit excavation cushion layer is completed, the bottom plate waterproofing membrane construction is carried out in each construction flow section. The construction of the bottom plate waterproofing membrane is controlled to be completed within 2 working days for each flow section. The construction of the side wall pre-laid polymer waterproofing membrane is completed before the construction of the tunnel side wall. Each flow section is completed within 5 days. The top plate single-component polyurethane waterproof coating is completed within 2 working days after the top plate construction is completed and the conditions are met. The 7cm thick C20 fine stone concrete protective layer is constructed immediately afterwards.

[0020] As a further technical solution of the present invention, in step six, backfilling is carried out. In the early stage of backfilling, 5-8t dump trucks are used to transport the purchased soil to the construction site, and the soil is spread manually with a bulldozer. The layer thickness is not more than 30cm. The two sides of the tunnel frame are backfilled according to the back of the bridge culvert and compacted with a 1-3t rammer. The density meets the design requirements. The top plate backfill is constructed according to the bridge upper backfill process. A roller is used to statically press the top plate within 50cm thick. If the thickness is greater than 50cm, a 10-15T dump truck can be used for soil. The bulldozer cooperates with the grader to spread the ground flat, and the roller vibrates and compacts it. The density should be not less than 95%. Only after one layer is filled and inspected to meet the requirements can the filling be continued and the next step of construction can be carried out. Then the construction of the top and side crash walls of the open section is carried out. When constructing the bottom plate, pay attention to pre-embedding some iron parts in order as reinforcement supports for the U-shaped retaining wall concrete and the crash wall. The crash wall on the top of the open retaining wall is constructed immediately after the retaining wall concrete reaches a certain strength. The formwork erection and concrete pouring of the open retaining wall and the crash wall are the same as those of the main structure of the tunnel.

[0021] As a further technical solution of the present invention, in the step six, electrical installation engineering is first carried out, including tunnel power supply and distribution, tunnel power distribution, tunnel lighting, lightning protection grounding and others, pump room and ancillary room lighting, tunnel management center, computer network system, closed-circuit television monitoring system, traffic video monitoring, electromechanical equipment automatic control system, fire alarm and linkage control system, wired broadcasting system, emergency telephone system, wireless communication system, UPS uninterruptible power supply system and other integrated pipelines; then the fan and control box in the tunnel are installed and debugged; finally, the decoration engineering, fire protection and landscape engineering are constructed.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: the method for constructing an open-cut tunnel group in an ecologically sensitive area first determines an open-cut tunnel as the first construction section of the tunnel group during the construction confirmation stage, and then starts construction of other open-cut tunnels in sequence according to the progress of pipeline relocation. The tunnels are constructed in parallel, and each tunnel is divided into a number of foundation pits according to design requirements. Two working faces are set up in each foundation pit, and a flow operation rhythm is formed between each process, forming a competition between working faces, formulating a reward and punishment incentive mechanism, and establishing a typical mechanism. Under the premise of ensuring the safety of the project, the construction of multiple tunnels is carried out at the same time, and the implementation of a standardized construction site and the timely and punctual realization of the construction progress goals are ensured, thereby improving the construction efficiency; by carrying out The dewatering and drainage construction of the foundation pit is carried out. Among them, the dewatering construction of the foundation pit first involves drilling the dewatering well, measuring and locating the well point, digging the wellhead, installing the casing, positioning the drilling rig, drilling, cleaning the hole, hanging the well pipe, backfilling the filter layer between the well pipe and the hole wall, washing the well, installing a water pump in the well pipe, installing the pumping control circuit, test pumping, the normal operation of the dewatering well, pulling out the well pipe after dewatering, and sealing the well. The dewatering test is carried out before construction, and the layout, number, structural dewatering indicators, dewatering monitoring and other contents of the dewatering well points are adjusted to achieve the dewatering effect and ensure the safety of the foundation pit project, and better control the deformation of the foundation outside the pit to ensure the safety of surrounding pipelines and buildings. After the dewatering well is constructed, one well is put into operation. In order to lower the groundwater level in time and maintain all-weather operation, the foundation pit excavation should be carried out two weeks after the pre-precipitation. After the pressure reduction well is completed, an overall depth reduction and pumping should be carried out to verify whether it can meet the design requirements. When the foundation pit is excavated to the base, except for the reserved drainage outlet, the remaining pipe wells are immediately backfilled after being pulled out, and a cushion layer is applied. First, use a large-capacity water pump to pump water, and then use coarse sand to backfill the pipe well to the bottom elevation of the cushion layer. Use concrete of the same grade as the cushion layer to fill the well pipe, and carry out tunnel waterproofing construction, design concrete structure self-waterproofing and waterproof membrane construction, and effectively ensure the construction quality of the main structure of the tunnel; by taking the following auxiliary or remedial measures: First, establish a dynamic groundwater monitoring network along the line, and use the spare wells outside the pit to serve as observation Well logging, observing daily monitoring data of groundwater level, monthly monitoring data of groundwater quality, daily drainage data of foundation pit, drainage sand content data, etc.; secondly, establishing a settlement monitoring network. Before the implementation of the precipitation project, settlement monitoring points should be arranged according to the pumping influence range calculated in the precipitation design and the buildings within the range. Continuous settlement monitoring should be carried out during the pumping period. If the accumulated settlement is close to the warning value, necessary measures should be taken in time. If the settlement monitoring finds that the settlement of the building has reached a dangerous level, pumping must be stopped immediately to find out the specific cause of the settlement. When it is confirmed that it is caused by precipitation, recharging measures should be taken immediately. In the settlement area, the spare well outside the pit should be used for recharging. The distance between the recharging well and the precipitation well must be greater than 5.0m, the specific design of the recharging well point should be determined according to the specific settlement situation. Through the monitoring data of foundation pit deformation under the condition of multi-storage excavation in urban areas, a set of advanced foundation pit safety management methods are summarized. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] Please refer to the attached Figure 1 , an embodiment provided by the present invention: a method for constructing an open-cut tunnel group in an ecologically sensitive area, comprising the following steps: step one: construction confirmation; step two: enclosure construction; step three: foundation pit excavation; step four: support construction; step five: main body construction; step six: ancillary project construction;

[0026] In the above step 1, the order of tunnel segment construction is confirmed, and corresponding traffic diversion is carried out. First, an in-depth investigation is conducted on the urban planning and traffic demand of the ecologically sensitive area to understand the geographical location, surrounding environment, traffic flow and other factors of the tunnel group. At the same time, the technical parameters such as the length, width, and burial depth of each tunnel are analyzed to provide a basis for determining the construction sequence. Based on the investigation and analysis results, each tunnel is divided into several construction sections. When dividing, it is necessary to consider factors such as the feasibility of the construction technology, the balance of construction difficulty, and the convenience of traffic diversion. Combined with urban planning and traffic needs, the principle of starting with the easy and then the difficult, and starting with the outside and then the inside is followed to determine the construction sequence of each open-cut tunnel and construction section to reduce interference and impact on traffic; during the construction period, temporary roads are set up to meet traffic needs. The setting of temporary roads should take into account parameters such as the width, length, and traffic capacity of the road to ensure smooth traffic. At the same time, open-cut tunnels and construction sections should be set up. Obvious traffic signs and markings are set up to guide vehicles and pedestrians to pass in an orderly manner. According to the traffic flow and road conditions during the construction period, the timing and phase of traffic lights are adjusted to improve the traffic capacity of the road. In addition, traffic warning signs and warning lights are set up during the construction period to remind vehicles and pedestrians to pay attention to safety. Detailed traffic diversion measures are formulated, including traffic control during the construction period, the deployment of traffic diversion personnel, and emergency traffic plans, etc., to ensure that during the construction period, the traffic order is in good order and reduce traffic congestion and traffic accidents. An open-cut tunnel is determined as the first construction section of the tunnel group. The other open-cut tunnels will start construction in sequence according to the progress of pipeline relocation. The tunnels will be constructed in parallel. According to the design requirements, each tunnel is divided into several foundation pits. Two working faces are opened in each foundation pit. A flow operation rhythm is formed between each process, forming a competition between working faces. A reward and punishment incentive mechanism is formulated and a typical mechanism is established.

[0027] In the above step 2, the tunnel retaining structure is constructed, and bored piles and bored interlocking piles are constructed first. The bored piles are all made of full casing plus rotary drilling rigs. The bored piles plus high-pressure rotary jet piles form a water-stop curtain. The adjacent single piles of the bored interlocking piles interlock with each other to form a pile wall. Among them, the bored piles first need to construct a reinforced concrete guide wall on the top of the pile. The guide wall is 3.5m wide and 35cm thick, and the material is C25 concrete. Then the center position of the pile is accurately determined as the control point for the positioning of the drilling rig. After the pile foundation is in place, 2.5 to 3m of soil is first taken to remove obstacles, and then the steel casing is sunk into the fully weathered rock layer using a puller to detect the verticality. If it is unqualified, it is corrected. If it is qualified, soil is taken downward until the designed bottom elevation of the hole is reached. Then a steel cage is made and hoisted by a crane. The designed elevation can be calculated from the casing top elevation. The correct elevation calculation must be ensured during installation. , the allowable error is ±10mm. When the steel cage is lowered, it is manually assisted to align the hole position, keep it vertical, place it gently and slowly, and generally use positive and reverse rotation to slowly sink it step by step to prevent collision. It should be fixed immediately after it reaches the designed elevation; if it is difficult to lower it, it should be stopped immediately, and the cause should be dealt with after it is found out. Then pour concrete. The reinforced piles use underwater C35 concrete, and the plain piles use super slow-setting C35 concrete. The concrete pouring conduit is connected by a screw buckle sleeve rubber sealing ring with an inner diameter of 25cm. After the connection is completed, it is checked in detail to ensure that the conduit is sealed and pressure-resistant. The conduit is slowly lowered into the hole by a crane. The bottom of the conduit should be 30 to 50cm higher than the bottom of the hole to ensure the discharge space at the lower outlet. The upper end of the conduit is connected to a concrete funnel, and the upper end of the conduit is sealed with a water stopper. Concrete flows into the funnel through the chute. When conditions are difficult, a crane can be used to lift it into the funnel through the hopper. 2m 3After the above concrete is poured, pull out the bottom cover of the funnel, pour concrete into the conduit, and keep pouring concrete continuously. After the pouring starts, the construction should be compact and continuous, and it is strictly forbidden to stop work in the middle. During the pouring process, pay attention to the rise and fall of the water level in the hole, measure the actual height of the concrete surface at any time and calculate the buried depth of the conduit to ensure that the bottom end of the conduit is buried 2 to 6 meters below the concrete surface. The conduit should avoid being buried too deep, which may cause the pipe to not be pulled out. At the same time, the buried depth should not be too small to cause the steel cage to float or the conduit to be pulled out of the concrete surface to cause a pile break accident. After the concrete pouring is completed, the casing and conduit are gradually removed. According to the buried depth of the conduit, 1 to 2 sections of the conduit are removed each time. The conduit should be rinsed immediately after removal for the next use; when the casing is lifted, slowly pull it up and shake it left and right so that concrete can flow into the space occupied by the casing. At the same time, pay attention to observe the steel bars. Whether the cage floats up, the buried depth of the casing should be controlled at about 2m. In order to ensure the quality of the designed pile top concrete, the concrete is poured to 0.5m above the pile top elevation, and this part of the concrete is chiseled off before the construction of the crown beam. After the pouring is completed, the casing and the guide tube are pulled out. During the pouring process, technical personnel are assigned to be on duty throughout the process and supervise the construction team to fill in the concrete pouring record. The retarding time of the pile concrete is determined according to the pile-forming time of the single pile. The pile-forming time of the single pile is directly related to the geological conditions, pile length, pile diameter and drilling rig capacity. Therefore, the retarding time of the pile concrete can be determined according to the following method. First, the time t required for the pile-forming of a single pile is determined, and then it is calculated according to the following formula: T=3t+K, where: T=retarding time of the pile concrete, K=reserve time, generally 1.5t, t=single pile forming time of A and B piles The time required for pile drilling, the verticality of the pile should be monitored and checked during the hole drilling process. During the casing pressing process, 2 people are arranged to use hammer balls to detect the verticality of the casing from two mutually perpendicular directions. If deviation is found, it should be corrected at any time. The high-pressure rotary jet pile construction first uses manpower or machinery to level the site, dig a sewage pool and sewage ditch, and make a slurry pool. According to the design requirements, use obvious signs to release the pile point, use the self-propelled drilling rig to move the drilling rig to the designed hole position, use the theodolite to adjust the verticality, and align the drill bit with the pile point. In order to prevent the drill rod from tilting, the bottom weight of the drill rod can be increased, and the plumb line hammer should be used to check at any time during the drilling process. The inclination of the drill rod is not more than 0.5%, and the deviation between the drilling hole position and the designed hole position is not more than 50mm. After the drilling rig is in place First, a 0.5MPa low-pressure water jet test is carried out to check whether the nozzle is unobstructed and the pressure is normal. The debugged drilling rig is moved to the designed hole position, and the verticality is adjusted to align the drill bit with the center of the designed pile position. After the water jet test, drilling can be started. The water jet pressure is increased from 0.5MPa to 1MPa to reduce friction and prevent nozzle blockage. After the first drill rod is drilled in, the water jet is stopped and the pressure drops. The drill rod is extended and the water jet drilling is continued until the designed pile bottom position is drilled. Then, qualified 42.5 composite silicate cement and clean drinking water are used to prepare according to the selected mix ratio. The cement parameter is not less than 25%. According to the determined mix ratio, water is first added to the bucket, and then cement is added. The mixer is started to mix and the mixture flows into the mud pool through the filter.The slurry is pumped into the second filter screen with a mud pump. After the second filtration, the slurry flowing into the mud barrel is pressurized by a high-pressure pump and sent to the drilling rig through a high-pressure pipe for rotary spraying. The slurry pressure is greater than 3MPa, the water pressure is 25MPa, the slurry water-cement ratio is 0.8, the rotation speed is generally 10r / min, and the lifting speed is 10cm / min. After drilling to the designed elevation, unscrew the upper drill rod, put in a steel ball, block the water hole, and then install the drill rod to deliver high-pressure cement slurry to the drilling rig. After the slurry emerges from the bottom of the hole, the drill rod begins to rotate and lift, and rotary spraying is carried out from bottom to top. The amount of slurry during rotary spraying should be controlled at 10-25%. When encountering special soil layers, such as gravel soil, in order to ensure the pile diameter and quality, re-spraying must be carried out, and the re-spraying height is not less than 50 0mm. During the rotation, when the first drill rod is raised from the ground, stop grouting. After the pressure drops, quickly remove the drill rod. When it is lifted to the designed elevation of the pile top, restart the jetting pile. When it is lifted to the designed elevation of the pile top, in order to avoid shrinkage due to the removal of the slurry after the slurry and soil are mixed in the mixer, resulting in a concave hole on the top of the jetting pile, low-pressure supplementary spraying is carried out. After the supplementary spraying is completed, the drill rod and drill bit are raised for low-pressure water injection to flush the drill rod and nozzle, and the drilling rig can be moved. When encountering special circumstances, all pipelines and equipment must be cleaned. When a pile is jetted, the drilling rig can be removed to carry out the next pile operation. The interval between the construction of two adjacent piles shall not be less than 2 days, and the spacing shall not be less than 2m. Dewatering and drainage construction of the foundation pit shall be carried out. Among them, the foundation pit dewatering construction shall be carried out first. The dewatering well is drilled and located according to the well point measurement, wellhead digging, casing installation, drilling rig positioning, drilling, hole cleaning, well pipe hanging, filter material layer between well pipe and hole wall backfilled, well washing, water pump installed in well pipe, pumping control circuit installed, test pumping, normal operation of dewatering well, well pipe pulling out after dewatering and well sealing. Dewatering test is carried out before construction, and the arrangement, quantity, structural dewatering index and dewatering monitoring of dewatering well points are adjusted to achieve dewatering effect and ensure the safety of foundation pit project, and better control the deformation of foundation outside the pit to ensure the safety of surrounding pipelines and buildings. After the dewatering well is constructed, one well is put into operation to reduce the groundwater level in time and maintain round-the-clock operation. Foundation pit excavation should be carried out two weeks after pre-dewatering. Depressurization well After the well construction is completed, an overall depth reduction and water pumping is required to verify whether it can meet the design requirements. When the foundation pit is excavated to the base, except for the reserved drainage outlet, the remaining pipe wells are immediately backfilled after being pulled out, and a cushion layer is applied. First, a large-capacity water pump is used to pump water, and then the pipe well is backfilled to the bottom elevation of the cushion layer with coarse sand, and the well pipe is filled with concrete of the same grade as the cushion layer; at the same time, the following auxiliary or remedial measures are taken: First, a groundwater dynamic monitoring network is established along the line, and the spare wells outside the pit are used as observation wells to observe the daily monitoring data of the groundwater level, the monthly monitoring data of the groundwater quality, the daily drainage data of the foundation pit, the drainage sand content data, etc.; second, a settlement monitoring network is established. Before the precipitation project is implemented, settlement monitoring points are arranged according to the pumping influence range calculated in the precipitation design and the buildings within the range.Continuous settlement monitoring should be carried out during the pumping period. If the accumulated settlement is close to the warning value, necessary measures should be taken in time. If it is found through settlement monitoring that the settlement of the building has reached a dangerous level, pumping must be stopped immediately to find out the specific cause of the settlement. When it is confirmed that it is caused by precipitation, recharge measures should be taken immediately. In the settlement area, the spare well outside the pit should be used for recharge. The distance between the recharge well and the precipitation well must be greater than 5.0m. The specific design of the recharge well point should be determined according to the specific settlement situation. Subsequently, foundation pit drainage construction should be carried out, and open drainage ditches should be set up around or in the middle of the excavated foundation pit. A collection well should be set up every 15m to allow the seepage water and construction wastewater in the foundation pit to merge into it, and then pumped into the surface sedimentation tank by water pump. After treatment by sedimentation and other methods, it can be discharged to the city. Government management network, deepen the drainage ditch and water collection well while digging, keep the ditch bottom no less than 0.5m below the foundation pit bottom, and the water collection well no less than 0.5m below the ditch bottom, set up a 400×400 brick drainage ditch on the ground around the foundation pit, and set up a 1000×500×500 sedimentation tank at intervals of 20m. Keep the pit dewatered during the excavation process to ensure that the groundwater is 1m below the excavation surface. The dewatering time lasts until the top plate is covered with soil. The foundation pit dewatering is carried out 15 to 20 days before the earthwork excavation, and the trial dewatering work is done. When excavating to the construction bottom plate, a temporary drainage hole is set on the bottom plate, and the hole is sealed after the top plate is covered with soil and the internal paving layer is completed. Dewater the outside of the foundation pit 7 to 10 days before the foundation pit excavation, and the water level is lowered to 5m below the ground. One drainage hole is arranged every 200㎡;,

[0028] In the above step three, the tunnel foundation pit is excavated, and the foundation pit excavation and support frame construction are carried out. During the foundation pit excavation and support, the earth excavation should follow the principles of zoning, block, symmetry, balance and time limit. The full layered or step-by-step layered excavation method can be adopted. The layer thickness is not more than 2m. The temporary slope on the excavation surface during the excavation process is not more than 1:1.5. The unsupported exposure time is shortened as much as possible to effectively control the deformation of the support structure. The foundation pit is excavated using the "time and space effect" theory. The excavation should be layered, and the next layer should be excavated after the support is completed. Over-excavation is strictly prohibited. When the excavation approaches the base, follow the principle of rapid excavation and rapid bottom sealing. Do a good job in key process control and preventive measures in the foundation pit excavation process, formulate construction organization design and construction operation procedures, and fully prepare drainage to remove water from the foundation pit. Equipment, prepare the conditions for excavation, transportation and abandonment of soil, protect various monitoring points, and monitor the initial readings. Only after the initial readings are obtained can excavation be carried out, and monitoring should be carried out at the frequency required by the design. In addition, observations should be intensified according to the actual situation on site, and the stability of the foundation pit should be analyzed by dynamic conditions. During the excavation process, leakage on the retaining wall should be blocked in time to prevent small streams of quicksand from breaking through the support and developing into soil erosion, which will not only cause a large amount of ground subsidence, but also cause the support structure to become unstable, resulting in serious catastrophic accidents. In order to make the pit bottom flat and prevent local over-excavation, the earthwork 30cm above the designed pit bottom elevation should be excavated and leveled manually, and the local excavated pits should be filled with sand. At the same time, a sump must be set up to remove the water at the bottom of the pit with a pump.

[0029] In the above step 4, the support structure engineering is constructed, and the reinforced concrete crown beam and reinforced concrete support beam are constructed. The process flow is leveling and compacting the earth under the support beam, measuring and laying out the lines, laying the tarpaulin isolation layer, steel bar binding, formwork installation, steel bar formwork acceptance, concrete pouring and maintenance. Before the construction of the retaining piles, a concrete guide wall is set up first. The outer guide wall is used as a retaining wall for excavation. Therefore, during construction, attention should be paid to protecting the integrity of the outer guide wall. After the retaining pile retaining structure is completed, the inner guide wall is removed and loaded together with the earth for transportation and disposal. The concrete debris, earth and impurities within the range of the wall top are cleaned and eliminated manually and with an air compressor. , rinse with high-pressure water; the construction methods of reinforced concrete purlins and reinforced concrete supports are as follows: the excavation of the first layer of earthwork on the upper part and the construction of the first reinforced concrete purlin and support are carried out in layers and sections according to the aforementioned foundation pit excavation and support construction methods. According to the design elevation, the axis uses a level and the position of each reinforced concrete purlin and support is released according to the foundation pit retaining wall, and the base is cleaned manually to ensure that the bottom of the foundation pit is level. The support bottom formwork uses C20 concrete bottom formwork with a thickness of 15cm and a width 15cm wider than the width of the support beam. After the earthwork excavation is completed, the base is compacted and leveled with crushed stone. Use a 4cm thick wooden formwork to pour concrete. The concrete is compacted with a flat vibrator. The surface is pressed twice with a wooden wedge and then polished with an iron plate. After the concrete bottom formwork is poured, it must be covered with straw bags and watered for 3 days. The steel bars can be tied only after the strength of the concrete bottom formwork reaches 50%. An isolation layer must be set on the surface of the concrete bottom formwork. Before tying the steel bars, set up steel pipe brackets on both sides and one side of the support beam. After the steel bars are tied and formed, remove the steel pipe brackets and place the skeleton on the bottom formwork. The crown beam, concrete support, and concrete corner brace are erected using a composite formwork. The support system uses 50×80 wooden squares, 48×3.5 short steel pipes, and M12 tension bolts. The template surface must be flat, the joints must be tight, and there must be no leakage. The straight edges and local unevenness must be repaired and corrected in time, otherwise they must not be used. The template must be coated with demoulding oil before supporting the template. The demoulding oil is clear engine oil. The template bracket uses Φ48 steel pipe, the length of the steel pipe is 1.8m, and it is not less than 0.6m into the soil. The spacing is 80cm, and it is connected by 2 longitudinal steel pipes. Before pouring, the position, elevation, cross-sectional dimensions of the template and the stability of the template and bracket, the joints, etc. should be reviewed or checked. Commercial concrete is used, and commercial concrete is transported by a roller truck with a capacity of 6m 3 or 8m 3Transport to the site, and transport to each pouring point by automobile pump or fixed pump. Automobile pump uses a concrete pump truck with a wall length of 21m. Automobile pump or fixed pump is parked on the construction access road for pumping. Removal of crown beam, concrete support, concrete angle support formwork. Generally, after the final setting of concrete, the concrete strength can ensure that its surface and edges are not damaged by demoulding. The formwork can be removed when it is strong enough to ensure that its surface and edges are not damaged by demoulding. The demoulding must not be pried hard, and attention should be paid to the damage of the edges and corners. Concrete is maintained by watering and moisturizing, and the surface is covered with linen. The production water of the site water supply system is used. The maintenance time is generally 7 days. Pay attention to the protection of the finished product. Crown beam, concrete support, concrete angle support formwork The concrete support and corner support can only be subjected to force when the concrete strength reaches 95%, and the lower earthwork can be excavated; the method of removing the concrete support of the foundation pit is to remove it by mechanical cutting. The order of support removal is to remove the secondary support first, and then remove the top support. When removing the support beam, the connecting rod should be removed first, and then the main support. When removing each support beam, the cutting should be started from the middle. When removing the support, the protection of the wall panel should be strengthened to prevent the support beam from damaging the top plate of the main structure of the tunnel. Protective measures such as laying wooden blocks on the top plate can be taken, and the construction waste after removal should be removed manually in time;

[0030] In the above step five, the main structure of the tunnel is constructed. For the main structure construction, the construction preparation work is carried out first. After the foundation pit is excavated to the designed elevation, the trench is inspected as soon as possible, and the structure is measured and laid out. The formwork support system of the side wall and the top plate is designed and calculated, and a special plan for tunnel formwork is prepared. After being submitted to experts for demonstration and improvement and approval, the plan is organized for implementation. The material feed is arranged in advance according to the construction progress, and the structural construction sequence, construction progress schedule, construction methods and technical requirements are carefully explained to the work team and all management personnel; then the plain cushion layer is constructed. The cushion layer concrete is C20, 20cm thick, and the cushion layer construction is carried out closely following the excavation surface to prevent the base from being exposed for too long, eliminate water accumulation in the foundation pit, remove the loose soil in the foundation pit, clean and level the top of the pull-out piles, silt and other debris. After the foundation pit is cleaned, the base is fully compacted with a tamping machine, and the bearing capacity of the foundation is measured, and the owner and engineer are reported in writing in a timely manner. When the cushion layer concrete is spread, according to the pre-buried water The elevation of the surface layer is controlled by flat piles, and the concrete is tamped with a flat vibrator. After the initial setting and before the final setting of the cushion concrete, the surface layer is calendered for the second time and fully cured to prevent looseness, sand and peeling. The thickness of the cushion layer is controlled by the pre-buried elevation control piles, and the surface is closed and cured in time to ensure that there are no honeycombs, pits and cracks on the cushion surface. Then the bracket is arranged. The bracket used for the main structure frame concrete construction is a disc-type full-floor bracket. The bracket is arranged through calculation to ensure that the strength and stiffness meet the construction requirements. It is considered that each disc-type vertical pole can withstand 8 to 9 tons of vertical load. The calculation takes into account the side wall concrete pressure, the weight of the top plate concrete, the weight of the formwork, the construction load, the wind force acting on the formwork bracket and other possible loads. Therefore, the longitudinal and transverse spacing of the disc-type bracket is 60cm and 90cm, and it is encrypted to 60cm near the upper chamfer to strengthen the stiffness of the longitudinal and transverse beams of the top plate and the transverse and vertical belts of the side walls. The disc-type bracket has the characteristics of flexible disassembly, and no unloading device is provided during construction.Then the formwork construction is carried out. The outer formwork of the concrete project uses the side wall of the enclosure structure. Before the construction of the side wall, the wall surface of the enclosure structure should be trimmed and leveled first. The formwork consists of three parts: the bottom formwork, the side wall, and the top formwork. It is assembled on site. The construction formwork of the bottom plate and a section of the side wall uses a large steel formwork, which is processed into a frame with angle steel and channel steel. The bakelite board is connected to the frame as a whole and processed into large blocks according to the design drawings. It is assembled on site. At the same time, considering the turnover use, the formwork uses 2440×1220×15 plywood as the panel, 60mm×80mm square wood as the secondary rib, φ48*3.5mm steel pipe as the main rib, and the outer wall needs to be poured to the bottom plate when the bottom plate concrete is poured. 30cm above the armpit corner, there are 2 rows of vertical pre-embedded screws on the outer wall. The upper row is the tension screw, and the lower row of pre-embedded screws are welded to the main reinforcement of the structure. They do not penetrate the entire bottom plate to prevent the movement of the template. The longitudinal spacing of the screws is 600mm, and the vertical spacing is 500mm. The chamfered part of the inner side of the side wall adopts a special steel mold, the secondary ribs use 60*80 square wood, the main ribs are arranged vertically, and a steel pipe is set on the top for tying. The side wall formwork system of the main structure of the open-cut section adopts a single-sided formwork, which mainly uses the steel triangular truss and embedded parts as the support system of the formwork to fix the formwork firmly. The formwork panel adopts a 4.5m×1.5m×5mm overall large steel mold, and the surrounding The ribs are 75*8 steel plates, the vertical secondary ribs are 75*50 angle steels, and the horizontal ribs are connected with 70*6 steel plates. The spacing between the secondary back ribs is less than 300mm. The main back ribs on the vertical ribs are 10# double channel steel welded on the back ribs to increase the strength. The brackets use double 14# channel steel tripods with a spacing of 750mm. The top plate formwork system of the main structure of the open-cut section uses steel pipe scaffolding + top support + secondary rib square wood + main rib steel pipe support. The formwork uses 2440×1220×15mm plywood as the panel, and uses 8*8cm square wood @30cm and double-piece Φ48 steel pipe @30cm. Two secondary rib forms are used, 10# I-beam @80cm as the main rib, and the buckle type The brackets are used to set up full-floor scaffolding supports. According to the two forms of 48 and 60 buckle brackets, the horizontal spacing of the brackets is 90cm, and the vertical spacing is 60cm, 90cm and 120cm. The erection step distance is 1.5m. The template cuts are protected with edge sealing paint to reduce the generation of burrs or water swelling, loose deformation at the cuts. The incoming materials should have certificates and test reports. The wooden templates are processed on site. The woodworking processing team accurately arranges the templates according to the drawings. After processing and forming, the processing team first conducts self-inspection and promptly corrects any problems found; then the quality inspector conducts special inspections on the processing to control the allowable deviation of the template processing within the specified range;Before use, the installation team will conduct another handover inspection on the wooden processed products. Those that affect their use will be returned for repair immediately. Bottom ribs will be set at the joints of the top plate formwork, and plastic tape will be minimized. Sponge strips will be added to seal the vertical formwork joints. Cleaning ports will be set at appropriate positions on the top plate and the ends. Before pouring concrete, a vacuum cleaner will be prepared to clean up the debris in the formwork. During construction, attention should be paid to the appearance quality of the concrete. All joints should be tight and no slurry should be exposed. If necessary, thin sponge pads should be embedded in the joints or putty should be applied to eliminate gaps. Before erecting the formwork, the formwork should be polished, rust-removed, oiled, and tried out. When erecting the formwork, all embedded parts should be installed and fixed. Clean engine oil or a reliable quality release agent should be used as the formwork release agent. The demoulding time should be controlled, and test blocks for curing under the same conditions should be set up. Whether to demould or not should be decided according to the specifications. Special tools such as a flat shovel with an edge and a dry mop should be used to clean the formwork. It is forbidden to hit the formwork with a hammer. The formwork should be cleaned dry. No isolation agent shall be applied before cleaning. The templates that have not been cleaned, maintained, or coated with isolation agent cannot be used. The bottom tie rod and top tie rod of each vertical pole must be fully installed and ensure reliable connection. The exposed length of the adjustable screw rod shall not exceed 2 / 3 of the total length of the screw rod. Before the template enters the site, the template and the use position shall be numbered according to the project department's engineering arrangement and the division of flow sections. The templates shall be arranged in batches in an orderly manner to ensure the needs of on-site construction and avoid occupying more space on site. After the base waterproof coating is applied to meet the requirements, the bottom plate steel bar binding begins. The side wall and top plate steel bars shall be bound after the bottom plate concrete construction is completed and the inner mold and bottom mold are installed. Various joint steel bars shall be reserved according to the design. All steel bars shall be tested in advance according to the specifications, and laid out strictly according to the requirements of the design drawings. The binding and welding of steel bars shall meet the requirements of the construction specifications.Then the concrete is poured. Before pouring concrete, the concrete mix design and various material experiments are carefully done. Before concrete transportation, the equipment must be repaired to ensure that the machine is in good condition. The bottom slab concrete is poured first. The concrete pouring adopts the method of inclined layering and one-time to the top. The thickness of each layer is controlled at 30 to 40 cm. The pump truck starts pouring from the four corners on both sides of the foundation pit, allowing the concrete to flow naturally to form a certain slope, and then the middle partition wall and outer wall concrete pouring are carried out. For the tunnel concrete structure, the middle partition wall is poured first, and then the outer wall is poured. The "inclined layered construction method" is used to control the pouring height at one time, so that the material is discharged in layers, the layers are tamped, and the cycle is promoted as a whole. The thickness of each layer is preferably 30 cm. Two concrete pump trucks are used for pouring at the same time. The side walls and the middle wall on both sides of the frame are poured symmetrically at the same time. Then the top slab concrete is poured. The concrete pouring adopts The slope is layered and poured to the top at one time. The thickness of each layer is controlled at 30-40cm. The pump truck starts pouring from the four corners on both sides of the foundation pit, allowing the concrete to flow naturally to form a certain slope, and then the concrete is vibrated. The concrete is compacted by inserting vibration. The moving spacing of the vibrating rod shall not exceed 1.5 times its effective radius, and it shall be inserted into the lower concrete for 5-10cm. The concrete must be compacted without missing vibration, insufficient vibration, or excessive vibration. The fast insertion and slow withdrawal method shall be adopted, and the vibration points shall be evenly arranged. The construction joints and embedded parts shall be vibrated more. The formwork, steel bars, water stop strips, and bottom plates shall not be touched during vibration. After the top plate concrete is vibrated and compacted, the surface slurry shall be smoothed, compacted, and pressed before final setting to ensure that the concrete surface does not crack. If there is too much moisture on the vibrated surface, the surface vacuum pump shall be used to absorb water and apply pressure multiple times, that is, a vacuum pump is used to connect a 15m piece. 2The vacuum absorbent pad absorbs the water on the surface of the concrete to ensure that the concrete surface does not crack. Finally, the concrete is cured. After the concrete is poured and initially set, it is watered to ensure that the concrete surface is always moist. At the same time, a geotextile is covered on the concrete surface to continue to keep the material moist. The curing water and materials must not cause adverse effects on the appearance quality of the concrete. The curing time is determined based on the on-site measured atmospheric humidity and temperature. For tunnel waterproofing construction, the self-waterproofing of the concrete structure should be designed first. The waterproof concrete should be configured by adjusting the mix ratio and adding admixtures and admixtures. The structural concrete impermeability grade, structural concrete water-cement ratio, and minimum amount of cementitious materials should be determined based on factors such as the strength of the concrete structure and the depth of structural burial. The top slab concrete and the side wall concrete cast together with the top slab should be added with appropriate amounts of high-quality fly ash, slag and other active materials and other anti-seepage measures. Reduce shrinkage and temperature difference shrinkage. The self-waterproofing design of concrete structures should select appropriate materials according to the environmental conditions to meet the requirements of concrete's own impermeability, durability and crack resistance. Then carry out waterproofing membrane construction. The side wall / enclosure section uses 1.5mm thick pre-laid polymer waterproofing membrane, the bottom plate uses 1.5mm thick pre-laid polymer waterproofing membrane, and the top plate uses a flexible waterproof layer. The waterproofing construction progress is consistent with the main structure construction progress. After the foundation pit excavation cushion layer is completed, the bottom plate waterproofing membrane construction of each construction flow section is carried out. The construction of the bottom plate waterproofing membrane is controlled to be completed within 2 working days for each flow section. The construction of the side wall pre-laid polymer waterproofing membrane is completed before the construction of the tunnel side wall. Each flow section is completed within 5 days. The top plate single-component polyurethane waterproof coating is completed within 2 working days after the top plate construction is completed and the conditions are met. The 7cm thick C20 fine stone concrete protective layer is constructed immediately afterwards.

[0031] In the sixth step above, earthwork is backfilled, and the rest of the structural engineering is constructed. Earthwork backfilling is carried out. In the early stage of backfilling, 5-8t dump trucks are used to transport the purchased earthwork to the construction site, and manual work is carried out with bulldozers for paving. The layer thickness is not more than 30cm. The two sides of the tunnel frame are backfilled according to the back of the bridge culvert, and compacted with 1-3t rammers. The density reaches the design requirements. The top plate backfill is constructed according to the bridge upper backfill process. A roller is used for static compaction within 50cm of the top plate. If the thickness is greater than 50cm, 10-15T dump trucks can be used for soil loading. The bulldozer cooperates with the grader to spread the soil flat, and the roller is vibrated and rolled. The density is not less than 95%. After one layer is filled and inspected to meet the requirements, the filling can be continued, and the next step of construction can be carried out. Subsequently, the top side anti-collision wall of the open section is constructed. When constructing the bottom plate, pay attention to the orderly pre-embedding Some iron parts are used as reinforcement supports for the U-shaped retaining wall concrete and the crash wall. The crash wall on the top of the open section retaining wall will be constructed immediately after the retaining wall concrete reaches a certain strength. The formwork erection and concrete pouring of the open section retaining wall and the crash wall are the same as the main structure of the tunnel. The electrical installation project is carried out first, including tunnel power supply and distribution, tunnel power distribution, tunnel lighting, lightning protection and grounding, etc., pump room and ancillary room lighting, tunnel management center, computer network system, closed-circuit television surveillance system, traffic video monitoring, electromechanical equipment automatic control system, fire alarm and linkage control system, wired broadcasting system, emergency telephone system, wireless communication system, UPS uninterruptible power supply system and other integrated pipelines; then the fan and control box in the tunnel are installed and debugged; finally, the decoration project, fire protection and landscape engineering are constructed.

[0032] Based on the above, the advantage of the present invention is that when the present invention is used, by first determining an open-cut tunnel as the first construction section of the tunnel group in the construction confirmation stage, the other open-cut tunnels start construction in sequence according to the progress of pipeline relocation, and the tunnels are constructed in parallel. Each tunnel is divided into a number of foundation pits according to design requirements, and each foundation pit opens two working faces. A flow operation rhythm is formed between each process, forming a competition between working faces, formulating a reward and punishment incentive mechanism, and establishing a typical mechanism. Under the premise of ensuring the safety of the project, the construction of multiple tunnels is carried out at the same time, and the implementation of standardized construction sites and the timely and punctual realization of construction progress goals are ensured, thereby improving construction efficiency; by carrying out dewatering and drainage construction of the foundation pit, among which the foundation pit dewatering construction first carries out a dewatering well The following procedures are followed for drilling, measuring and locating the well point, digging the wellhead, installing the casing, positioning the drilling rig, drilling, cleaning the hole, hanging and placing the well pipe, backfilling the filter layer between the well pipe and the hole wall, washing the well, installing a water pump in the well pipe, installing the pumping control circuit, test pumping, normal operation of the precipitation well, pulling out the well pipe after the precipitation is completed, and sealing the well. A precipitation test is carried out before construction, and adjustments are made to the layout, quantity, structural precipitation indicators, precipitation monitoring and other contents of the precipitation well points to achieve the precipitation effect and ensure the safety of the foundation pit project, as well as to better control the deformation of the foundation outside the pit and ensure the safety of the surrounding pipelines and buildings. After the precipitation well is constructed, one well is put into operation as soon as it is completed to reduce the groundwater level in time and maintain all-weather non-stop operation. The foundation pit should be excavated two weeks after the pre-precipitation. After the well construction is completed, it is necessary to do an overall depth reduction and pumping to verify whether it can meet the design requirements. When the foundation pit is excavated to the base, except for the reserved drainage outlet, the remaining pipe wells are immediately backfilled after being pulled out, and a cushion layer is applied. First, a large-capacity water pump is used to pump water, and then the pipe well is backfilled with coarse sand to the bottom elevation of the cushion layer. The well pipe is filled with concrete of the same grade as the cushion layer, and tunnel waterproofing construction is carried out. The concrete structure self-waterproofing and waterproof membrane construction are designed to effectively ensure the construction quality of the main structure of the tunnel; by taking the following auxiliary or remedial measures: First, establish a groundwater dynamic monitoring network along the line, use the spare wells outside the pit as observation wells, and observe the daily monitoring data of the groundwater level, the monthly monitoring data of the groundwater quality, the daily drainage data of the foundation pit, the drainage sand content data, etc.; second, establish a settlement monitoring Before the implementation of the precipitation project, settlement monitoring points shall be arranged according to the pumping influence range calculated in the precipitation design and the buildings within the range. Continuous settlement monitoring shall be carried out during the pumping period. If the accumulated settlement is close to the warning value, necessary measures shall be taken in time. If it is found through settlement monitoring that the settlement of the building has reached a dangerous level, pumping must be stopped immediately and the specific cause of the settlement shall be found out. When it is confirmed that it is caused by precipitation, recharge measures shall be taken immediately. Recharge shall be carried out using spare wells outside the pit in the settlement area. The distance between the recharge well and the precipitation well must be greater than 5.0m. The specific design of the recharge well point shall be determined according to the specific settlement situation. Through the monitoring data of foundation pit deformation under the condition of multi-warehouse excavation in urban areas, a set of advanced foundation pit safety management methods have been summarized.

[0033] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A method for constructing an open-cut tunnel group in an ecologically sensitive area, comprising the following steps: Step 1: Construction confirmation; Step 2: Enclosure construction; Step 3: Foundation pit excavation; Step 4: Support construction; Step 5: Main body construction; Step 6: Ancillary project construction; It is characterized by: In the above step 1, the order of tunnel segment construction is confirmed and corresponding traffic diversion is carried out; In the above step 2, constructing the tunnel enclosure structure; In the above step 3, excavation of the tunnel foundation pit is carried out; In the above step 4, the support structure engineering is constructed; In the above step 5, the main structure of the tunnel is constructed; In the above step six, the earthwork is backfilled and the remaining structural works are constructed.

2. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step 1, firstly, an in-depth investigation is conducted on the urban planning and traffic demand of the ecologically sensitive area to understand the geographical location, surrounding environment, traffic flow and other factors of the tunnel group, and at the same time, the technical parameters such as the length, width, and burial depth of each tunnel are analyzed to provide a basis for determining the construction sequence. Based on the investigation and analysis results, each tunnel is divided into several construction sections. When dividing, it is necessary to consider factors such as the feasibility of the construction technology, the balance of construction difficulty, and the convenience of traffic diversion. In combination with urban planning and traffic needs, the principle of starting with the easy and then the difficult, and starting with the outside and then the inside is followed to determine the construction sequence of each open-cut tunnel and construction section to reduce interference and impact on traffic. During the construction period, temporary roads are set up to meet traffic needs. The setting of temporary roads should take into account parameters such as the width, length, and traffic capacity of the road to ensure smooth traffic. At the same time, obvious traffic signs and markings need to be set up to guide traffic. Guide vehicles and pedestrians to pass in an orderly manner. According to the traffic flow and road conditions during the construction period, adjust the timing and phase of traffic lights to improve the traffic capacity of the road. In addition, it is necessary to set up traffic warning signs and warning lights during the construction period to remind vehicles and pedestrians to pay attention to safety. Detailed traffic diversion measures should be formulated, including traffic control during the construction period, the deployment of traffic diversion personnel, emergency traffic plans, etc., to ensure that during the construction period, the traffic order is in order and the occurrence of traffic congestion and traffic accidents is reduced; determine an open-cut tunnel as the first construction section of the tunnel group, and other open-cut tunnels will start construction in sequence according to the progress of pipeline relocation. The tunnels will be constructed in parallel. Each tunnel will be divided into several foundation pits according to the design requirements. Two working faces will be opened in each foundation pit. A flow operation rhythm will be formed between each process, forming a competition between working faces, and a reward and punishment incentive mechanism will be formulated and a typical mechanism will be established.

3. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step 2, bored piles and bored interlocking piles are first constructed. The bored piles are all made of full casing and rotary drilling rig. The bored piles are combined with high-pressure rotary jet piles to form a water-stop curtain. The adjacent single piles of the bored interlocking piles are interlocked with each other to form a pile wall. Among them, the bored piles first need to construct a reinforced concrete guide wall on the top of the pile. The guide wall is 3.5m wide and 35cm thick, and the material is C25 concrete. Then the center position of the pile is accurately determined as the control point for positioning the drilling rig. After the pile foundation is in place, 2.5 to 3m of soil is first taken to remove obstacles, and then a steel casing is sunk into the fully weathered rock layer using a puller to detect the verticality. If it is unqualified, it is corrected. If it is qualified, soil is taken downward until the designed hole bottom elevation is reached. Then a steel cage is made and hoisted by a crane. The designed elevation can be calculated from the casing top elevation. The elevation calculation must be correct during installation, and errors are allowed. The difference is ±10mm. When the steel cage is lowered, it is manually assisted to align the hole position, keep it vertical, put it gently and slowly, and generally use positive and reverse rotation to slowly sink it step by step to prevent collision. It should be fixed immediately after it reaches the designed elevation; if it is difficult to lower it, it should be stopped immediately, and the cause should be dealt with after it is found out. Then pour concrete. The reinforced piles use underwater C35 concrete, and the plain piles use super slow-setting C35 concrete. The concrete pouring conduit is connected by a screw buckle sleeve rubber sealing ring with an inner diameter of 25cm. After the connection is completed, it is checked in detail to ensure that the conduit is sealed and pressure-resistant. The conduit is slowly lowered into the hole by a crane. The bottom of the conduit should be 30 to 50cm higher than the bottom of the hole to ensure the discharge space at the lower outlet. The upper end of the conduit is connected to a concrete funnel, and the upper end of the conduit is sealed with a water stopper. Concrete flows into the funnel through the chute. When conditions are difficult, a crane can be used to lift it into the funnel through the hopper. 2m 3 After the above concrete is poured, pull out the bottom cover of the funnel, pour concrete into the conduit, and maintain continuous pouring of concrete. After the pouring starts, the construction should be compact and continuous, and it is strictly forbidden to stop work halfway. During the pouring process, pay attention to the rise and fall of the water level in the hole, measure the actual height of the concrete surface at any time and calculate the buried depth of the conduit to ensure that the bottom end of the conduit is buried 2 to 6 meters below the concrete surface. The conduit should avoid being buried too deep, which may cause the pipe to be unable to be pulled out. At the same time, the buried depth should not be too small to cause the steel cage to float or the conduit to be pulled out of the concrete surface to cause a broken pile accident. After the concrete pouring is completed, the casing and conduit are gradually removed. According to the buried depth of the conduit, 1 to 2 sections of the conduit are removed each time. The conduit should be rinsed immediately after removal for the next use; when the casing is lifted, slowly pull it up and shake it left and right so that concrete can flow into the space occupied by the casing. At the same time, pay attention to whether the steel cage floats. The buried depth of the casing should be controlled at about 2 meters. In order to ensure the quality of the designed pile top concrete, the concrete is poured to the pile 0.5m above the top elevation, this part of concrete is chiseled off before constructing the crown beam. After the pouring is completed, the casing and the conduit are pulled out. Technical personnel are assigned to be on duty throughout the pouring process and supervise the construction team to fill in the concrete pouring record. The retarding time of the pile concrete is determined according to the time of the single pile. The time of the single pile is directly related to the geological conditions, pile length, pile diameter and drilling rig capacity. Therefore, the retarding time of the pile concrete can be determined according to the following method. First, the time t required for the pile formation of a single pile is determined, and then it is calculated according to the following formula: T=3t+K, where: T=retarding time of the pile concrete, K=reserve time, generally 1.5t, t=time required for the formation of single piles of A and B piles, the verticality of the pile should be monitored and checked during the drilling process, and during the casing pressing process, 2 people are arranged to use hammer balls to detect the verticality of the casing during the pressing process from two mutually perpendicular directions, and any deviation is corrected at any time.

4. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step 2, the high-pressure jet grouting pile construction first uses manpower or machinery to level the site, dig a sewage pool and a sewage ditch, and make a slurry pool. According to the design requirements, the pile point is released by obvious signs, and the drilling rig is moved to the designed hole position by self-movement. The verticality is adjusted using a theodolite to align the drill bit with the pile point. To prevent the drill rod from tilting, the bottom weight of the drill rod can be increased, and a plumb line is used to check at any time during the drilling process. The inclination of the drill rod is not greater than 0.5%, and the deviation between the drill hole position and the designed hole position is not greater than 50mm. After the drilling rig is in place, a 0.5MPa low-pressure water jet test is first carried out to check whether the nozzle is unobstructed and the pressure is normal. The debugged drilling rig is moved to the designed hole position. To the designed hole position, and adjust the verticality so that the drill bit is aligned with the center of the designed pile position. After the water jet test, drilling can be started. The water jet pressure is increased from 0.5MPa to 1MPa to reduce friction and prevent nozzle clogging. After the first drill rod is drilled in, stop water jetting and wait for the pressure to drop. Then extend the drill rod and continue water jet drilling until the designed pile bottom position is drilled. Then use qualified 42.5 composite silicate cement and clean drinking water to prepare according to the selected mix ratio. The cement parameter is not less than 25%. According to the determined mix ratio, first add water into the bucket, then add cement, start the mixer to mix, and flow into the mud pool through the filter screen. Then use the mud pump to pump it into the second filter screen. After the second filtration The slurry flowing into the mud barrel is pressurized by a high-pressure pump and sent to the drilling rig through a high-pressure pipe for rotary spraying. The slurry pressure is greater than 3MPa, the water pressure is 25MPa, the slurry water-cement ratio is 0.8, the rotation speed is generally 10r / min, and the lifting speed is 10cm / min. After drilling to the designed elevation, unscrew the upper drill rod, put in a steel ball, block the water hole, and then install the drill rod to deliver high-pressure cement slurry to the drilling rig. After the slurry emerges from the bottom of the hole, the drill rod begins to rotate and lift, and rotary spraying is carried out from bottom to top. The amount of slurry during rotary spraying should be controlled at 10-25%. When encountering special soil layers, such as gravel soil, etc., in order to ensure the pile diameter and quality, re-spraying must be carried out, and the re-spraying height should not be less than 500mm. During the rotation, when the first drill rod is raised out of the ground, stop grouting. After the pressure drops, quickly remove the drill rod. When it is lifted to the designed elevation of the pile top, restart the jet grouting. When it is lifted to the designed elevation of the pile top, in order to avoid the slurry and soil being mixed in the mixer and shrinking due to the removal of the slurry, resulting in a concave hole on the top of the jet grouting pile, low-pressure supplementary spraying is carried out. After the supplementary spraying is completed, raise the drill rod and drill bit for low-pressure water injection to flush the drill rod and nozzle, and then move the drilling rig. When encountering special circumstances, all pipelines and equipment must be cleaned. When a pile is jetted, the drilling rig can be removed to proceed to the next pile. The construction interval between two adjacent piles shall not be less than 2 days, and the spacing shall not be less than 2m.

5. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the second step, the dewatering and drainage construction of the foundation pit is carried out. Among them, the dewatering construction of the foundation pit firstly involves drilling the dewatering well, measuring and locating the well point, digging the wellhead, installing the casing, positioning the drilling rig, drilling, cleaning the hole, hanging the well pipe, backfilling the filter layer between the well pipe and the hole wall, washing the well, installing a water pump in the well pipe, installing a pumping control circuit, testing water pumping, normal operation of the dewatering well, pulling out the well pipe after dewatering, and sealing the well. The dewatering test is carried out before the construction, and the layout, quantity, structural dewatering index, dewatering monitoring and other contents of the dewatering well points are adjusted to achieve the dewatering effect, ensure the safety of the foundation pit project, and better control The foundation outside the pit is deformed to ensure the safety of surrounding pipelines and buildings. After the construction of a dewatering well, one well is put into operation to lower the groundwater level in time and maintain all-weather non-stop operation. The excavation of the foundation pit should be carried out two weeks after the pre-dewatering. After the construction of the pressure-reducing well is completed, an overall depth reduction and pumping is required to verify whether it can meet the design requirements. When the foundation pit is excavated to the base, except for the reserved drainage outlet, the remaining pipe wells are immediately backfilled after being pulled out, and a cushion layer is applied. First, use a water pump to pump water with a large capacity, and then use coarse sand to backfill the pipe well to the bottom elevation of the cushion layer, and use concrete of the same grade as the cushion layer to fill the well pipe; at the same time, take the following auxiliary or remedial measures: First, Establish a dynamic groundwater monitoring network along the line, use the spare wells outside the pit as observation wells, and observe the daily monitoring data of groundwater level, monthly monitoring data of groundwater quality, daily drainage data of foundation pit, drainage sand content data, etc.; secondly, establish a settlement monitoring network. Before the implementation of the precipitation project, set up settlement monitoring points according to the pumping influence range calculated in the precipitation design and the buildings within the range. Continuous settlement monitoring should be carried out during the pumping period. If the accumulated settlement is close to the warning value, necessary measures should be taken in time. If it is found through settlement monitoring that the settlement of the building has reached a dangerous level, pumping must be stopped immediately to find out the specific cause of the settlement. When it is confirmed If it is caused by precipitation, recharging measures should be taken immediately. In the settlement area, the spare well outside the pit should be used for recharging. The distance between the recharging well and the precipitation well must be greater than 5.0m. The specific design of the recharging well point should be determined according to the specific settlement situation. Then, the foundation pit drainage construction should be carried out. Drainage ditches should be set around or in the middle of the excavated foundation pit. A collection well should be set every 15m to allow the seepage water in the foundation pit and the construction wastewater to flow into it. Then, it should be pumped into the surface sedimentation tank by water pumps and discharged to the municipal pipe network after being treated by sedimentation and other methods. The drainage ditch and collection well should be deepened while digging, and the ditch bottom should be kept at least 0.5m lower than the foundation pit bottom, and the collection well should be kept at least 0.5m, a 400×400 brick drainage ditch is set up on the ground around the foundation pit, and a 1000×500×500 sedimentation tank is set up at intervals of 20m. During the excavation process, the pit is kept dewatered to ensure that the groundwater is 1m below the excavation surface. The dewatering time lasts until the top plate is covered with soil. The foundation pit dewatering is carried out 15 to 20 days before the earthwork excavation, and the trial dewatering work is done. When the excavation reaches the construction bottom plate, a temporary drainage hole is set on the bottom plate. After the top plate is covered with soil and the internal paving layer is completed, the hole is sealed. 7 to 10 days before the foundation pit excavation, the outside of the foundation pit is dewatered to reduce the water level to 5m below the ground. A drainage hole is arranged every 200㎡. .

6. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step three, the foundation pit is excavated and the support frame is installed. During the foundation pit excavation and support, the earth excavation should follow the principles of zoning, block, symmetry, balance and time limit. The full layered or step-by-step layered excavation method can be adopted. The layer thickness is not more than 2m. The temporary slope on the excavation surface during the excavation process is not more than 1:1.

5. The unsupported exposure time is shortened as much as possible to effectively control the deformation of the support structure. The foundation pit is excavated using the "time and space effect" theory. The excavation should be carried out in layers. After the support is completed, the next layer can be excavated. Over-excavation is strictly prohibited. When the excavation approaches the base, the principle of rapid excavation and rapid bottom sealing should be followed. Key process control and preventive measures in the foundation pit excavation process should be well done. Construction organization design and construction operation procedures should be formulated, and drainage equipment for removing water from the foundation pit should be fully prepared. Prepare the conditions for excavation, transportation and abandonment, protect all kinds of monitoring points, and monitor the initial readings. Only after the initial readings are obtained can excavation be carried out, and monitoring should be carried out at the frequency required by the design. According to the actual situation on site, observation should be intensified to analyze the stability of the foundation pit by dynamic conditions. During the excavation process, any leakage on the retaining wall should be blocked in time to prevent small streams of quicksand from breaking through the support and developing into soil erosion, which will not only cause a large amount of ground subsidence, but also cause the support structure to become unstable, resulting in serious catastrophic accidents. In order to level the pit bottom and prevent local over-excavation, the earthwork 30cm above the designed pit bottom elevation should be excavated and leveled manually, and the local excavated depressions should be filled with sand. At the same time, a collection pit must be set up to remove the water at the bottom of the pit with a pump.

7. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step 4, the construction of reinforced concrete crown beam and reinforced concrete support beam is carried out. The process flow is leveling and compacting the earth under the support beam, measuring and laying out the lines, laying the tarpaulin isolation layer, reinforcing bar binding, template installation, reinforcement template acceptance, concrete pouring and maintenance. Before the construction of the retaining pile, a concrete guide wall is set up first. The outer guide wall is used as a retaining wall for excavation. Therefore, during construction, attention should be paid to protecting the integrity of the outer guide wall. After the retaining pile retaining structure is completed, the inner guide wall is removed and loaded together with the earth for transportation and disposal. The concrete debris, earth and impurities within the top range of the wall are cleaned and eliminated by manual labor and air compressors, and washed with high-pressure water. Clean; The construction methods of reinforced concrete purlins and reinforced concrete supports are as follows: The excavation of the first layer of earthwork and the construction of the first reinforced concrete purlin and support are carried out in layers and sections according to the aforementioned foundation pit excavation and support construction methods. According to the design elevation, the axis uses a level and the position of each reinforced concrete purlin and support is released according to the foundation pit retaining wall, and the base is cleaned manually to ensure the level of the foundation pit bottom. The support bottom formwork uses C20 concrete bottom formwork with a thickness of 15cm and a width 15cm wider than the width of the support beam. After the earthwork excavation is completed, the base is compacted and leveled with crushed stone. Both sides are leveled with 4c thick concrete. m shaped wooden formwork, pouring concrete, concrete is compacted with a flat vibrator, the surface is compressed twice with wooden wedges, and then the iron plate is pressed. After the concrete bottom formwork is poured, it must be covered with straw bags and watered for 3 days. The steel bars can be tied only after the strength of the concrete bottom formwork reaches 50%. An isolation layer must be set on the surface of the concrete bottom formwork. Before tying the steel bars, steel pipe brackets are set up on both sides and one side of the support beam. After the steel bars are tied and formed, the steel pipe brackets are removed and the skeleton is placed on the bottom formwork. The crown beam, concrete support, and concrete corner brace are erected with a composite formwork. The support system uses 50×80 wooden squares, 48×3.5 short steel pipes, M12 tension bolts and buckles The parts are connected and subjected to force together. The surface of the formwork must be flat, the joints must be tight, and there must be no leakage. The straight edges and local unevenness must be repaired and corrected in time, otherwise they must not be used. The formwork must be coated with demoulding oil before supporting the formwork. The demoulding oil is clear engine oil. The formwork bracket uses Φ48 steel pipe, the length of the steel pipe is 1.8m, and it is driven into the soil for not less than 0.6m, with a spacing of 80cm. It is connected by 2 longitudinal steel pipes. Before pouring, the position, elevation, cross-sectional dimensions of the formwork, the stability of the formwork and the bracket, the joint conditions, etc. should be reviewed or checked. Commercial concrete is used, and commercial concrete is transported by a roller truck with a capacity of 6m 3 or 8m 3 Transport to the site, and transport to each pouring point by automobile pump or fixed pump. Automobile pump uses a concrete pump truck with a wall length of 21m. Automobile pump or fixed pump is parked on the construction access road for pumping. Removal of crown beam, concrete support, concrete angle support formwork. Generally, after the final setting of concrete, the concrete strength can ensure that its surface and edges are not damaged by demoulding. The formwork can be removed when it is strong enough to ensure that its surface and edges are not damaged by demoulding. The demoulding must not be pried hard, and attention should be paid to the damage of the edges and corners. Concrete is maintained by watering and moisturizing, and the surface is covered with linen. The production water of the site water supply system is used. The maintenance time is generally 7 days. Pay attention to the protection of the finished product. Crown beam, concrete support, concrete angle support formwork The concrete strength of the support and concrete corner support must reach 95% before it can be subjected to force and the lower earth excavation can be carried out; the method of removing the concrete support of the foundation pit is mechanical cutting and breaking it, and the order of support removal is to remove the secondary support first, and then the top support. The support beam should be removed by removing the connecting rod first and then the main support. When removing each support beam, cutting should be started from the middle. When removing the support, the protection of the wall panel should be strengthened to prevent the support beam from damaging the top plate of the tunnel main structure. Protective measures such as laying wooden blocks on the top plate can be taken, and the construction waste after removal should be removed manually in time.

8. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step five, the main structure is constructed. First, the construction preparation work is carried out. After the foundation pit is excavated to the designed elevation, the trench is inspected as soon as possible, and the structure is measured and laid out. The formwork support system of the side wall and the top plate is designed and calculated, and a special plan for tunnel formwork is prepared. After being submitted to experts for demonstration and improvement and approval, the plan is organized for implementation. The material feed is arranged in advance according to the construction progress, and the structural construction sequence, construction schedule, construction methods and technical requirements are carefully explained to the work team and all management personnel; then the plain cushion layer is constructed. The cushion layer concrete is C20 and 20cm thick. The cushion layer construction is carried out closely following the excavation surface to prevent the base from being exposed for too long, eliminate water accumulation in the foundation pit, remove the loose soil in the foundation pit, clean and level the top of the pull-out piles, silt and other debris. After the foundation pit is cleaned, the base is fully compacted with a tamping machine, and the bearing capacity of the foundation is measured. The owner and engineer are reported in writing in a timely manner. When the cushion layer concrete is paved, the surface layer is controlled according to the pre-buried horizontal piles The concrete is vibrated with a flat vibrator. After the initial setting and before the final setting of the cushion concrete, the surface layer is calendered for the second time and fully cured to prevent looseness, sand and peeling. The cushion pouring thickness is controlled according to the pre-buried elevation control piles, and the surface is closed and cured in time to ensure that there are no honeycombs, pits and cracks on the cushion surface. Then the bracket is arranged. The bracket used for the main structure frame concrete construction is a disc-type full-floor bracket. The bracket is arranged through calculation to ensure that the strength and stiffness meet the construction requirements. It is considered that each disc-type vertical pole can withstand 8 to 9 tons of vertical load. The calculation takes into account the side wall concrete pressure, the weight of the top plate concrete, the weight of the formwork, the construction load, the wind force acting on the formwork bracket and other possible loads. Therefore, the longitudinal and transverse spacing of the disc-type bracket is 60cm and 90cm, and it is encrypted to 60cm near the upper chamfer to strengthen the stiffness of the longitudinal and transverse beams of the top plate and the transverse and vertical belts of the side walls. The disc-type bracket has the characteristics of flexible disassembly, and no unloading device is provided during construction.Then the formwork construction is carried out. The outer formwork of the concrete project uses the side wall of the enclosure structure. Before the construction of the side wall, the wall surface of the enclosure structure should be trimmed and leveled first. The formwork consists of three parts: the bottom formwork, the side wall, and the top formwork. It is assembled on site. The construction formwork of the bottom plate and a section of the side wall uses a large steel formwork, which is processed into a frame with angle steel and channel steel. The bakelite board is connected to the frame as a whole and processed into large blocks according to the design drawings. It is assembled on site. At the same time, considering the turnover use, the formwork uses 2440×1220×15 plywood as the panel, 60mm×80mm square wood as the secondary rib, φ48*3.5mm steel pipe as the main rib, and the outer wall needs to be poured to the bottom plate when the bottom plate concrete is poured. 30cm above the armpit corner, there are 2 rows of vertical pre-embedded screws on the outer wall. The upper row is the tension screw, and the lower row of pre-embedded screws are welded to the main reinforcement of the structure. They do not penetrate the entire bottom plate to prevent the movement of the template. The longitudinal spacing of the screws is 600mm, and the vertical spacing is 500mm. The chamfered part of the inner side of the side wall adopts a special steel mold, the secondary ribs use 60*80 square wood, the main ribs are arranged vertically, and a steel pipe is set on the top for tying. The side wall formwork system of the main structure of the open-cut section adopts a single-sided formwork, which mainly uses the steel triangular truss and embedded parts as the support system of the formwork to fix the formwork firmly. The formwork panel adopts a 4.5m×1.5m×5mm overall large steel mold, and the surrounding The ribs are 75*8 steel plates, the vertical secondary ribs are 75*50 angle steels, and the horizontal ribs are connected with 70*6 steel plates. The spacing between the secondary back ribs is less than 300mm. The main back ribs on the vertical ribs are 10# double channel steel welded on the back ribs to increase the strength. The brackets use double 14# channel steel tripods with a spacing of 750mm. The top plate formwork system of the main structure of the open-cut section uses steel pipe scaffolding + top support + secondary rib square wood + main rib steel pipe support. The formwork uses 2440×1220×15mm plywood as the panel, and uses 8*8cm square wood @30cm and double-piece Φ48 steel pipe @30cm. Two secondary rib forms are used, 10# I-beam @80cm as the main rib, and the buckle type The brackets are used to set up full-floor scaffolding supports. According to the two forms of 48 and 60 buckle brackets, the horizontal spacing of the brackets is 90cm, and the vertical spacing is 60cm, 90cm and 120cm. The erection step distance is 1.5m. The template cuts are protected with edge sealing paint to reduce the generation of burrs or water swelling, loose deformation at the cuts. The incoming materials should have certificates and test reports. The wooden templates are processed on site. The woodworking processing team accurately arranges the templates according to the drawings. After processing and forming, the processing team first conducts self-inspection and promptly corrects any problems found; then the quality inspector conducts special inspections on the processing to control the allowable deviation of the template processing within the specified range;Before use, the installation team will conduct another handover inspection on the wooden processed products. Those that affect their use will be returned for repair immediately. Bottom ribs will be set at the joints of the top plate formwork, and plastic tape will be minimized. Sponge strips will be added to seal the vertical formwork joints. Cleaning ports will be set at appropriate positions on the top plate and the ends. Before pouring concrete, a vacuum cleaner will be prepared to clean up the debris in the formwork. During construction, attention should be paid to the appearance quality of the concrete. All joints should be tight and no slurry should be exposed. If necessary, thin sponge pads should be embedded in the joints or putty should be applied to eliminate gaps. Before erecting the formwork, the formwork should be polished, rust-removed, oiled, and tried out. When erecting the formwork, all embedded parts should be installed and fixed. Clean engine oil or a reliable quality release agent should be used as the formwork release agent. The demoulding time should be controlled, and test blocks for curing under the same conditions should be set up. Whether to demould or not should be decided according to the specifications. Special tools such as a flat shovel with an edge and a dry mop should be used to clean the formwork. It is forbidden to hit the formwork with a hammer. The formwork should be cleaned dry. No isolation agent shall be applied before cleaning. The templates that have not been cleaned, maintained, or coated with isolation agent cannot be used. The bottom tie rod and top tie rod of each vertical pole must be fully installed and ensure reliable connection. The exposed length of the adjustable screw rod shall not exceed 2 / 3 of the total length of the screw rod. Before the template enters the site, the template and the use position shall be numbered according to the project department's engineering arrangement and the division of flow sections. The templates shall be arranged in batches in an orderly manner to ensure the needs of on-site construction and avoid occupying more space on site. After the base waterproof coating is applied to meet the requirements, the bottom plate steel bar binding begins. The side wall and top plate steel bars shall be bound after the bottom plate concrete construction is completed and the inner mold and bottom mold are installed. Various joint steel bars shall be reserved according to the design. All steel bars shall be tested in advance according to the specifications, and laid out strictly according to the requirements of the design drawings. The binding and welding of steel bars shall meet the requirements of the construction specifications.Then the concrete is poured. Before pouring concrete, the concrete mix ratio design and various material experiments are carefully done. Before concrete transportation, the equipment must be repaired to ensure that the machine is in good condition. The bottom slab concrete is poured first. The concrete pouring adopts the method of inclined layering and one-time to the top. The thickness of each layer is controlled at 30 to 40 cm. The pump truck starts pouring from the four corners on both sides of the foundation pit, allowing the concrete to flow naturally to form a certain slope, and then the middle partition wall and outer wall concrete pouring are carried out. For the tunnel concrete structure, the middle partition wall is poured first, and then the outer wall is poured. The "inclined layered construction method" is used to control the pouring height at one time, so that the material is discharged in layers, the layers are tamped, and the cycle is promoted as a whole. The thickness of each layer is preferably 30 cm. Two concrete pump trucks are used for pouring at the same time. The side walls and the middle wall on both sides of the frame are poured symmetrically at the same time. Then the top slab concrete is poured. The concrete pouring adopts The slope is layered and poured to the top at one time. The thickness of each layer is controlled at 30-40cm. The pump truck starts pouring from the four corners on both sides of the foundation pit, allowing the concrete to flow naturally to form a certain slope, and then the concrete is vibrated. The concrete is compacted by inserting vibration. The moving spacing of the vibrating rod shall not exceed 1.5 times its effective radius, and it shall be inserted into the lower concrete for 5-10cm. The concrete must be compacted without missing vibration, insufficient vibration, or excessive vibration. The fast insertion and slow withdrawal method shall be adopted, and the vibration points shall be evenly arranged. The construction joints and embedded parts shall be vibrated more. The formwork, steel bars, water stop strips, and bottom plates shall not be touched during vibration. After the top plate concrete is vibrated and compacted, the surface slurry shall be smoothed, compacted, and pressed before final setting to ensure that the concrete surface does not crack. If there is too much moisture on the vibrated surface, the surface vacuum pump shall be used to absorb water and apply pressure multiple times, that is, a vacuum pump is used to connect a 15m piece. 2 The vacuum absorbent pad absorbs the water on the surface of the concrete to ensure that the concrete surface does not crack. Finally, the concrete is cured. After the concrete is poured and initially set, it is watered to ensure that the concrete surface is always moist. At the same time, a geotextile is covered on the concrete surface to continue to keep the material moist. The curing water and materials must not cause adverse effects on the appearance quality of the concrete. The curing time is determined based on the on-site measured atmospheric humidity and temperature. For tunnel waterproofing construction, the self-waterproofing of the concrete structure should be designed first. The waterproof concrete should be configured by adjusting the mix ratio and adding admixtures and admixtures. The structural concrete impermeability grade, structural concrete water-cement ratio, and minimum amount of cementitious materials should be determined based on factors such as the strength of the concrete structure and the depth of structural burial. The top slab concrete and the side wall concrete cast together with the top slab should be added with appropriate amounts of high-quality fly ash, slag and other active materials and other anti-seepage measures. To reduce shrinkage due to drying and temperature difference, the self-waterproofing design of concrete structures should select appropriate materials according to the environmental conditions in which they are located to meet the requirements of the concrete's own impermeability, durability and crack resistance; then the waterproofing membrane construction should be carried out. The side wall / enclosure section uses 1.5mm thick pre-laid polymer waterproofing membrane, the bottom plate uses 1.5mm thick pre-laid polymer waterproofing membrane, and the top plate uses a flexible waterproof layer. The waterproofing construction progress is consistent with the main structure construction progress. After the foundation pit excavation cushion layer is completed, the bottom plate waterproofing membrane construction is carried out in each construction flow section. The construction of the bottom plate waterproofing membrane is controlled to be completed within 2 working days for each flow section. The construction of the side wall pre-laid polymer waterproofing membrane is completed before the construction of the tunnel side wall. Each flow section is completed within 5 days. The top plate single-component polyurethane waterproof coating is completed within 2 working days after the top plate construction is completed and the conditions are met. The 7cm thick C20 fine stone concrete protective layer is constructed immediately afterwards.

9. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step 6, backfilling is carried out. In the early stage of backfilling, 5-8t dump trucks are used to transport the purchased soil to the construction site, and manual work is carried out with bulldozers to spread the soil. The layer thickness is not more than 30cm. The two sides of the tunnel frame are backfilled according to the back of the bridge culvert and compacted with 1-3t rammers. The density meets the design requirements. The top plate backfill is constructed according to the bridge upper backfill process. A roller is used to statically press the top plate within 50cm thick. If the thickness is greater than 50cm, 10-15T dump trucks can be used to load the soil. Bulldozers are used to level the ground. The machine is used to spread the ground flat and the roller is used to vibrate and compact it. The density should not be less than 95%. Only after one layer is filled and inspected to meet the requirements can the filling be continued and the next step of construction can be carried out. Subsequently, the construction of the top and side crash walls of the open section is carried out. When constructing the bottom plate, pay attention to pre-embedding some iron parts in order as reinforcement supports for the U-shaped retaining wall concrete and the crash wall. The crash wall on the top of the open retaining wall is constructed immediately after the retaining wall concrete reaches a certain strength. The formwork erection and concrete pouring of the open retaining wall and the crash wall are the same as those of the main structure of the tunnel.

10. The method for constructing an open-cut tunnel group in an ecologically sensitive area according to claim 1, characterized in that: In the step six, electrical installation engineering is first carried out, including tunnel power supply and distribution, tunnel power distribution, tunnel lighting, lightning protection grounding and others, pump room and ancillary room lighting, tunnel management center, computer network system, closed-circuit television monitoring system, traffic video monitoring, electromechanical equipment automatic control system, fire alarm and linkage control system, wired broadcasting system, emergency telephone system, wireless communication system, UPS uninterruptible power supply system and other integrated pipelines; then the fan and control box in the tunnel are installed and debugged; finally, the decoration engineering, fire protection and landscape engineering are constructed.

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