Construction technology of double-track large-section split lining trolley for subway dark excavation section

Abstract

The invention discloses a construction process for a double-track large-section split lining trolley in a subway dark excavation section, including temporary support removal, surface treatment construction, waterproofing engineering construction, reinforcement engineering construction, support and dismantling of formwork and concrete pouring, second lining back pouring, construction joint and deformation joint treatment. The beneficial effects of the invention are: the second lining construction of the large section of the section is divided into three parts: an inverted arch, a side wall, and an arch for construction, which reduces the amount of temporary support structure demolition during each warehouse construction, reduces stratum disturbance, reduces material turnover and consumption, and makes full use of limited space for continuous operation. In the process of walking, mold closing and demolding, the safety of construction is improved. Compared with the overall formwork construction, during the concrete pouring process, the lining trolley can be installed with a flat vibrator for vibration, which improves the density of the concrete, reduces the assembly time in construction time, and has a great improvement in construction speed.

Description

Technical Field

[0001] The invention relates to a secondary lining construction process for a subway dark excavation area, in particular to a construction process for a double-line large-section split lining trolley for a subway dark excavation area, and belongs to the field of tunnel construction. Background Art

[0002] With the steady progress of China's urbanization, the population size of large cities, especially megacities, has increased year by year. However, as the size of cities continues to expand, traffic congestion has become one of the problems restricting urban economic development. Rail transit, represented by subways, has become an important means to solve the traffic congestion problem in megacities.

[0003] In the construction of subway sections, the large-section parking line section is difficult to control the settlement due to its large section. The timely closure of the second lining construction is particularly important. At present, the large-section second lining excavated by the existing construction method is limited by space and frequent process conversion. It is not feasible to use an integral lining trolley, and the construction method of scattered arch frames is generally adopted. According to the monitoring data of the excavation process, the length of the temporary dismantling support cannot meet the assembly line construction. In addition, the amount of temporary support structure removed during the construction of each warehouse is large, which disturbs the stratum more, increases the material turnover and consumption, and cannot make full use of the limited space for continuous operation. In the process of walking, mold assembly and demolding, the safety of the construction is explained. In terms of construction time, it takes more assembly time, resulting in the construction speed not being improved. Summary of the invention

[0004] The purpose of the present invention is to provide a construction process for a double-track large-section split lining trolley in a subway underground excavation section in order to solve the problem.

[0005] The present invention achieves the above-mentioned purpose through the following technical scheme: A construction process for a double-line large-section split lining trolley for a subway dark excavation section, comprising the following steps

[0006] Step 1: Dismantle temporary supports. According to the construction progress and overall construction organization, dismantle temporary inverts and temporary middle partitions. The temporary inverts and temporary middle partitions are dismantled in sequence according to the construction requirements. When dismantling temporary supports, first make a test section to observe the settlement of the arch crown. After the temporary supports of the CRD method and the double-side wall pilot method are dismantled, the arch crown settlement does not exceed 10mmn and reaches stability. The longitudinal dismantling length can be appropriately increased according to the monitoring data.

[0007] Step 2: Construction of base surface treatment. Initial support is closed into a ring. According to the monitoring value, the arch settlement tends to be stable. After the tunnel clearance meets the requirements through measurement and inspection, the base surface treatment is required before laying the waterproof board.

[0008] Step 3: Waterproofing construction: laying buffer layer and EVA waterproof board at deformation joints and construction joints;

[0009] Step 4: Construction of steel bar engineering: main bars and distribution bars are set in the secondary lining structure of the dark excavation area. The main bars are connected mechanically, and the distribution bars are connected by binding. During installation, attention should be paid to protecting the waterproof layer. Plastic caps should be worn on the steel bar joints to avoid damage to the waterproof board. After the steel bar is installed, the waterproof board should be carefully inspected and any damage should be repaired in time.

[0010] Step 5: Formwork support and concrete pouring, which includes formwork construction, trolley installation and operation, and concrete construction. First, the invert is constructed, and then the arch wall is constructed to form a secondary lining closure. The secondary lining inverts of all sections are poured in the form of local formwork + steel pipe support. The secondary lining arch wall is constructed with a combined steel formwork + curved steel arch frame + steel support system, and each formwork is supported by a trolley, and finally concrete is poured;

[0011] Step 6: Cast the back of the second lining, and grouting between the primary support and the second lining after the strength of the second lining concrete reaches more than 75% of the design strength; the second lining grouting pipe is buried, and the second lining grouting pipe should be pre-buried before the second lining is cast. If there is a grouting plate behind the second lining, grouting should be done using the grouting plate (see the interval waterproofing design drawing for details). Grouting uses DN32 steel welded pipes, one each for the vault and side wall, with a length of the second lining thickness + 200mm; the slurry material uses micro-expansive cement mortar, and the grouting pressure and specific ratio are determined based on on-site tests; the grouting equipment uses the initial support grouting equipment. The grouting pressure is determined based on actual conditions;

[0012] Step 7: Treatment of construction joints and deformation joints. Use 2cm thick wooden templates, wooden boards or high-strength foam boards to close the plugging templates. Use square wood to hold the templates and weld C22 steel bars to the longitudinal distribution bars to pull them inwards and fix them. Use square wood, steel pipes or wooden boards to support the top and strengthen them firmly. The angle of the support should not be greater than 45 degrees. Use cotton yarn to seal the gaps after closing the mold.

[0013] As a further solution of the present invention: the step 1 specifically includes the following steps:

[0014] Step 1: After the initial support surface treatment is completed, the temporary middle partition is broken according to the length of the interval secondary lining compartment, and the vertical middle partition at the invert is partially cut off in sections. The grid steel frame is retained between the vertical middle partitions. The vertical height is constructed according to the backfill concrete elevation of the invert of each section. The vertical temporary middle partition is buried in the invert concrete, and then the bottom plate and the side wall below the temporary invert and the invert waterproof layer are laid, steel bars are tied, and the second lining of the bottom plate is cast in the formwork, and the retained grid steel frame of the middle partition is cast in the invert concrete;

[0015] Step 2: Remove the temporary inverts of the side guide holes on both sides in sections, and remove the temporary middle partition according to the position of the trolley support crossbar. Then, treat the waterproof base surface of the side wall, lay the side wall waterproof layer, tie the steel bars, and place the trolley in place to support the formwork and cast the secondary lining side wall.

[0016] Step 3: Remove the temporary middle partition wall of the segmented upper guide tunnel, construct the top arch waterproof layer, tie the steel bars, support the formwork and cast the secondary lining top arch. The remaining temporary primary support will be removed after the secondary lining is formed into a ring and closed. During the removal of the vertical middle partition wall, vertical steel supports will be used to support the top if necessary based on the monitoring results.

[0017] As a further solution of the present invention: the step 2 specifically includes the following steps:

[0018] The first step is to block water in the primary support. Concentrated grouting is carried out at the location of local water leakage in the primary support. After the grouting is completed, cotton yarn is used to temporarily block the lower port of the grouting pipe to prevent the slurry from flowing out. After the grouting is completed, if there are still individual dripping and water flow, direct blocking and pipe blocking are adopted.

[0019] For direct plugging, when the water dripping or open water flow on the base surface is small and the water pressure is not high, the hole groove of the sprayed concrete is manually chiseled with the water outlet as the center. The hole groove has a diameter of about 2-4cm and a depth of about 3-5cm. After chiseling, the groove is rinsed clean with water, and then the leak-proof spirit is used to plug the groove, and it is squeezed around the groove wall to make it tightly combined with the groove wall. After 1-2 minutes, check whether there is leakage on the appearance. If there is leakage, re-apply it.

[0020] For the plugging of the lead pipe, it is used when the point leak is large and there is clear water flow. First, remove the loose layer around the leaking point manually to form a conical groove. After the groove is chiseled, clean the groove, insert the hose into the groove, seal the hose with fast-hardening cement mortar, let the water flow out through the hose, and plug the hose before laying the waterproof board.

[0021] The waterproof layer can be applied only when the primary support structure has been plugged to the point where there is no dripping and only a few wet stains on the inner surface of the primary support.

[0022] The second step is to pick up the bottom, which is done manually by using a shovel, bucket truck, or high-pressure air duct to blow it clean.

[0023] The third step is to deal with over-excavation and under-excavation. After cross-section inspection, if the under-excavation of the initial support is greater than 5cm, it needs to be dealt with, and if the under-excavation is less than 5cm, it is not dealt with. For under-excavation greater than 5cm, the arch is replaced and moved outward to meet the clearance requirements; for large-area over-excavation and the initial support surface is basically smooth, the secondary lining concrete is used for backfilling.

[0024] The fourth step is to spray the arch frame, where the arch frame is cut off, replaced, the arch frame reinforcement is exposed, and the concrete surface is obviously concave, spray concrete to make it smooth.

[0025] The fifth step is to cut off sharp objects protruding from the base surface. Metal components that pass through the base layer, such as steel bar heads and anchor rod heads, should be cut off and smoothed with mortar. Protruding bulges of concrete should be chiseled flat with a pneumatic pick to meet the clearance and roundness requirements.

[0026] The sixth step is to smooth the base surface. The concave and convex corners and edges of the base surface need to be smoothed into arcs with mortar, and the arc radius is 100mm.

[0027] As a further solution of the present invention: in the step 5, a double side wall pilot pit method is adopted, which specifically includes the following steps:

[0028] The first step is to break the temporary middle partition wall by jumping the compartment according to the length of the second lining compartment in the interval after the initial support surface treatment is completed. The vertical height is constructed according to the backfill concrete elevation of each section of the invert. It is advisable to bury the vertical temporary middle partition wall 10cm into the invert concrete. Then carry out the waterproofing construction of the invert. Use 1.5mm thick EVA plastic waterproof board + geotextile for full outsourcing treatment, and cast a 70mm thick C20 fine stone waterproof protective layer on the invert;

[0029] The second step is to tie the second lining steel bars of the invert, install the invert formwork, and pour the invert concrete. The construction joint is set 10cm below the track surface and is constructed using a small invert formwork;

[0030] The third step is to partially cut off the temporary inverts of the side guide holes on both sides in sections and break the temporary middle partition according to the position of the trolley support crossbar, then lay the side wall waterproof layer, tie the steel bars, support the formwork and cast the secondary lining side wall, with a casting length of 6m / bin;

[0031] Step 4: After the strength of the secondary lining of the side wall meets the specification requirements, remove the temporary middle partition of the upper guide hole, then lay the top arch waterproof layer, tie the steel bars, support the formwork and pour the top arch concrete. When using an integral trolley, combine the construction with the third step;

[0032] The fifth step is to remove all temporary arches and partition walls after the concrete strength reaches the designed strength, and the secondary lining is completed. For the construction of the arch wall secondary lining formwork, an integral steel formwork hydraulic lining trolley system is used.

[0033] As a further solution of the present invention: in the step 5, when installing and operating the trolley, specifically including:

[0034] The first step is to put the trolley in place and move it forward to the mileage to be lined. Repeat the action several times to relax the trolley structure and stop it at the correct lining position. Turn off the travel motor and drive wooden wedges or use car blockers at the travel wheels to prevent the trolley from slipping or the lining skeleton from being displaced by eccentric force, causing runaway or mold explosion. Apply release agent on the outer surface of the model plate, install the plug plate, and add necessary support.

[0035] Tighten the spiral legs under the bottom beam, ensure that the bottom plate falls on a solid foundation, remove the hinge pins on the side of the side mold support screw template, start the hydraulic oil pump, operate the lifting cylinder to rise to the designed arch elevation; operate the self-aligning cylinder to fine-tune the trolley to the correct position. If the cylinders move out of sync, you can lock the screw close to one cylinder, and continue to operate the operating valve to allow other cylinders in the same row to continue to extend. The screw can be used for micro-adjustment. After the side mold reaches the designed size, install all the side mold screws and ensure they are tightened.

[0036] After the trolley is in place, the power supply of the hydraulic oil pump must be turned off to avoid accidental operation of the valve group operating handle, which may cause deformation of the trolley structure or damage to the hydraulic cylinder.

[0037] The second step is demoulding preparation. After pouring, curing for the specified time, you can prepare for demoulding. Start the hydraulic oil pump, operate the side mold manual reversing valve handle to extend the cylinder slightly, loosen the screw, and remove all the screws of the side mold.

[0038] The third step is to remove the side mold by operating the side mold cylinder to retract the side mold and separate it from the formed concrete surface. When the cylinder retracts, it must be retracted in batches, and it is forbidden to force demolding at one time. The cylinder retraction stroke is 250mm to 300mm.

[0039] The fourth step is to remove the top mold and operate the main oil cylinder to retract the top mold and separate it from the forming concrete surface. The cylinder retraction stroke is 200mm to 250mm.

[0040] The fifth step is to retract the outriggers, rotate the spiral outriggers under the bottom beam, remove the wooden wedges or car blockers at the running wheels, operate the trolley forward to the next lining position, and start the next working cycle.

[0041] As a further solution of the present invention: in the step 5, when carrying out the concrete engineering construction, it specifically includes:

[0042] The main structural concrete of the section is C40P10 waterproof concrete, the internal components such as the middle partition wall are C40 concrete, the waterproof protective layer at the bottom of the structure is C20 fine stone concrete, and the backfill of the execution area arch is C30 plain concrete. During the concrete construction, a qualified concrete manufacturer is selected for pre-mixing, and then the concrete is transported to the construction site by concrete tankers for pouring.

[0043] Step 1: Preliminary preparation

[0044] (1) Carefully investigate and select mixing stations that have been reviewed for qualifications and issued enterprise grade certificates by the competent department of Beijing Municipal Construction Committee. The mixing station must have a sound management organization and quality assurance system.

[0045] (2) Sign a contract with the mixing station and put forward technical requirements in the contract. The contract clearly stipulates the obligations and responsibilities of both parties in terms of technology and quality.

[0046] The second step is the transportation and on-site acceptance of concrete

[0047] (1) Appoint a dedicated person to be responsible for the on-site acceptance of concrete quality and quantity. Concrete that does not meet the quality requirements of the contract shall not be used. Concrete that does not meet the quality requirements of the contract shall be rejected and returned.

[0048] (2) When the concrete is transported to the pouring site, its slump should be tested. Test pieces should be made according to regulations within 15 minutes after the concrete is transported to the pouring site. The production of on-site concrete slump and strength test pieces should be completed before handover and acceptance.

[0049] (3) When a concrete mixer truck is transporting concrete, the stirring speed should usually be controlled at a stirring speed of 2 to 4 r / min and rotated at least 30 times in addition.

[0050] (4) Reasonably arrange the pouring speed and transportation frequency of concrete. Ensure that the pouring is completed before the commercial concrete begins to set. After the concrete mixture is discharged from the mixer, it is transported to the paving site for paving and vibration operations. The maximum allowable time for the pouring to be completed is determined by the laboratory based on the initial setting time of cement and the construction temperature. A full-time quality and safety officer is assigned on site to conduct quality inspections on each truck of premixed concrete, including concrete grade, factory time, slump and segregation. Concrete that does not meet the requirements shall not be used.

[0051] (5) When the concrete mixture is transported to the pouring site, the temperature should not exceed 35°C and the minimum should not be lower than 10°C.

[0052] (6) Supervision is required at any time after the concrete is mixed out of the machine, and it is not allowed to add water to the mixture without authorization.

[0053] (7) When transporting concrete mixture, there should be no leakage and segregation should be prevented. If segregation or stratification occurs, the concrete mixture should be mixed again.

[0054] Step 3: Concrete pouring

[0055] (1) Before pouring concrete, the formwork, steel bars, embedded parts, reserved holes, construction joints, expansion joint waterstops, etc. should be inspected and debris in the formwork should be removed. Concrete can only be poured after the hidden acceptance is qualified.

[0056] (2) Concrete is constructed using a pumping process. The delivery pump pipe is connected to the working surface through a ground feed pipe or a shaft. The arch wall concrete of the interval structure should be poured symmetrically. If the height difference of the concrete surface on both sides of the formwork exceeds 0.5m, it needs to be adjusted to prevent the formwork from shifting due to the biased pressure on the surface, which will affect the quality of the project. At the same time, the concrete pouring speed should be controlled, preferably 2m per hour, to prevent accidents such as formwork running and bursting.

[0057] (3) During the concrete pouring process, the formwork, support, waterproof board, steel bar, embedded parts, reserved holes, etc. should be observed at all times and any problems found should be dealt with in a timely manner.

[0058] Step 4: Pouring of invert concrete

[0059] Before pouring concrete, the mold should be cleaned up. All kinds of debris, paper scraps, iron wire, soil and rocks in the mold should be cleaned up, and the accumulated water should be drained. Before pouring concrete, the formwork should be moistened to prevent pores from appearing on the base surface where the concrete meets the formwork.

[0060] The concrete pouring method is to use commercial concrete pump to deliver it into the mold, and use an inserted vibrator to vibrate the concrete in the mold. After the invert concrete construction is completed, it is covered and maintained according to the specifications.

[0061] Step 5: Pouring of arch concrete

[0062] Before pouring, clean up all kinds of debris, paper scraps, wire, soil and rocks in the formwork, moisten the concrete and formwork at the joints to prevent the formation of pores on the base surface where the concrete and formwork meet.

[0063] The side wall concrete is poured from both sides of the side wall at the same time, using a three-way pump pipe, and vibrating during the pouring process. The concrete vibration is observed through a small observation window reserved on the side wall formwork.

[0064] The top arch concrete is poured from the arch top pouring port to both sides, and vibrated with an attached vibrator. The pouring situation is observed through the plug template and the reserved observation hole (vent hole) until the arch concrete pouring is completed.

[0065] The beneficial effects of the present invention are:

[0066] 1. Lower risk: The three parts of the invert, side wall and arch are operated in parallel, making the large-section secondary lining construction more flexible, while reducing the amount of single primary support removal work, which is conducive to controlling surface settlement and primary support deformation;

[0067] 2. Short construction period: It reduces the number of times of dismantling, transporting and assembling the arch frame. After the trolley is assembled, the pre-laid trolley track slides to the next section of the secondary lining construction position, which is convenient and fast, and saves a significant amount of construction period. It has a great advantage in projects with tight construction period;

[0068] 3. Low material consumption: The use of loose-joined arch frames to construct the large-section secondary lining of the interval requires a lot of repetitive work such as dismantling, transporting, and assembling arch frames, which requires a lot of manual work. The use of large-section split lining trolleys will significantly reduce labor consumption;

[0069] 4. Good safety: The large-section second lining of the interval tunnel is constructed with a large-section split lining trolley, which reduces the number of dismantling, transportation and assembly, and will inevitably reduce the risk of safety accidents such as object impact in a limited space. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a schematic diagram of the construction process of the present invention. DETAILED DESCRIPTION

[0071] 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.

[0072] Embodiment 1

[0073] See also Figure 1 A construction process for a double-track large-section split lining trolley for a subway underground excavation section includes the following steps:

[0074] Step 1: Dismantle temporary supports. According to the construction progress and overall construction organization, dismantle temporary inverts and temporary middle partitions. The temporary inverts and temporary middle partitions are dismantled in sequence according to the construction requirements. When dismantling temporary supports, first make a test section to observe the settlement of the arch crown. After the temporary supports of the CRD method and the double-side wall pilot method are dismantled, the arch crown settlement does not exceed 10mmn and reaches stability. The longitudinal dismantling length can be appropriately increased according to the monitoring data.

[0075] Step 2: Construction of base surface treatment. Initial support is closed into a ring. According to the monitoring value, the arch settlement tends to be stable. After the tunnel clearance meets the requirements through measurement and inspection, the base surface treatment is required before laying the waterproof board.

[0076] Step 3: Waterproofing construction: laying buffer layer and EVA waterproof board at deformation joints and construction joints;

[0077] Step 4: Construction of steel bar engineering: main bars and distribution bars are set in the secondary lining structure of the dark excavation area. The main bars are connected mechanically, and the distribution bars are connected by binding. During installation, attention should be paid to protecting the waterproof layer. Plastic caps should be worn on the steel bar joints to avoid damage to the waterproof board. After the steel bar is installed, the waterproof board should be carefully inspected and any damage should be repaired in time.

[0078] Step 5: Formwork support and concrete pouring, which includes formwork construction, trolley installation and operation, and concrete construction. First, the invert is constructed, and then the arch wall is constructed to form a secondary lining closure. The secondary lining inverts of all sections are poured in the form of local formwork + steel pipe support. The secondary lining arch wall is constructed with a combined steel formwork + curved steel arch frame + steel support system, and each formwork is supported by a trolley, and finally concrete is poured;

[0079] Step 6: Cast the back of the second lining, and grouting between the primary support and the second lining after the strength of the second lining concrete reaches more than 75% of the design strength; the second lining grouting pipe is buried, and the second lining grouting pipe should be pre-buried before the second lining is cast. If there is a grouting plate behind the second lining, grouting should be done using the grouting plate (see the interval waterproofing design drawing for details). Grouting uses DN32 steel welded pipes, one each for the vault and side wall, with a length of the second lining thickness + 200mm; the slurry material uses micro-expansive cement mortar, and the grouting pressure and specific ratio are determined based on on-site tests; the grouting equipment uses the initial support grouting equipment. The grouting pressure is determined based on actual conditions;

[0080] Step 7: Treatment of construction joints and deformation joints. Use 2cm thick wooden templates, wooden boards or high-strength foam boards to close the plugging templates. Use square wood to hold the templates and weld C22 steel bars to the longitudinal distribution bars to pull them inwards and fix them. Use square wood, steel pipes or wooden boards to support the top and strengthen them firmly. The angle of the support should not be greater than 45 degrees. Use cotton yarn to seal the gaps after closing the mold.

[0081] In the embodiment of the present invention, the step 1 specifically includes the following steps:

[0082] Step 1: After the initial support surface treatment is completed, the temporary middle partition is broken according to the length of the interval secondary lining compartment, and the vertical middle partition at the invert is partially cut off in sections. The grid steel frame is retained between the vertical middle partitions. The vertical height is constructed according to the backfill concrete elevation of the invert of each section. The vertical temporary middle partition is buried in the invert concrete, and then the bottom plate and the side wall below the temporary invert and the invert waterproof layer are laid, steel bars are tied, and the second lining of the bottom plate is cast in the formwork, and the retained grid steel frame of the middle partition is cast in the invert concrete;

[0083] Step 2: Remove the temporary inverts of the side guide holes on both sides in sections, and remove the temporary middle partition according to the position of the trolley support crossbar. Then, treat the waterproof base surface of the side wall, lay the side wall waterproof layer, tie the steel bars, and place the trolley in place to support the formwork and cast the secondary lining side wall.

[0084] Step 3: Remove the temporary middle partition wall of the segmented upper guide tunnel, construct the top arch waterproof layer, tie the steel bars, support the formwork and cast the secondary lining top arch. The remaining temporary primary support will be removed after the secondary lining is formed into a ring and closed. During the removal of the vertical middle partition wall, vertical steel supports will be used to support the top if necessary based on the monitoring results.

[0085] In the embodiment of the present invention, the step 2 specifically includes the following steps:

[0086] The first step is to block water in the primary branch. Concentrated grouting is carried out at the location of local water leakage in the primary branch. After the grouting is completed, cotton yarn is used to temporarily block the lower port of the grouting pipe to prevent the slurry from flowing out. After the grouting is completed, if there are still individual dripping, streams and other scattered water phenomena, direct blocking and pipe blocking are adopted.

[0087] For direct plugging, when the water dripping or open water flow on the base surface is small and the water pressure is not high, the hole groove of the sprayed concrete is manually chiseled with the water outlet as the center. The hole groove has a diameter of about 2-4cm and a depth of about 3-5cm. After chiseling, the groove is rinsed clean with water, and then the leak-proof spirit is used to plug the groove, and it is squeezed around the groove wall to make it tightly combined with the groove wall. After 1-2 minutes, check whether there is leakage on the appearance. If there is leakage, re-apply it.

[0088] For the plugging of the lead pipe, it is used when the point leak is large and there is clear water flow. First, remove the loose layer around the leaking point manually to form a conical groove. After the groove is chiseled, clean the groove, insert the hose into the groove, seal the hose with fast-hardening cement mortar, let the water flow out through the hose, and plug the hose before laying the waterproof board.

[0089] The waterproof layer can be applied only when the primary support structure has been plugged to the point where there is no dripping and only a few wet stains on the inner surface of the primary support.

[0090] The second step is to pick up the bottom, which is done manually by using a shovel, bucket truck, or high-pressure air duct to blow it clean.

[0091] The third step is to deal with over-excavation and under-excavation. After cross-section inspection, if the under-excavation of the initial support is greater than 5cm, it needs to be dealt with, and if the under-excavation is less than 5cm, it is not dealt with. For under-excavation greater than 5cm, the arch is replaced and moved outward to meet the clearance requirements; for large-area over-excavation and the initial support surface is basically smooth, the secondary lining concrete is used for backfilling.

[0092] The fourth step is to spray the arch frame, where the arch frame is cut off, replaced, the arch frame reinforcement is exposed, and the concrete surface is obviously concave, spray concrete to make it smooth.

[0093] The fifth step is to cut off sharp objects protruding from the base surface. Metal components that pass through the base layer, such as steel bar heads, anchor rod heads, etc., should be cut off and smoothed with mortar. Protruding bulges of concrete should be chiseled flat with a pneumatic pick to meet the clearance and roundness requirements.

[0094] The sixth step is to smooth the base surface. The concave and convex corners and edges of the base surface need to be smoothed into arcs with mortar, and the arc radius is 100mm.

[0095] Embodiment 2

[0096] See also Figure 1A construction process for a double-track large-section split lining trolley for a subway underground excavation section includes the following steps:

[0097] Step 1: Dismantle temporary supports. According to the construction progress and overall construction organization, dismantle temporary inverts and temporary middle partitions. The temporary inverts and temporary middle partitions are dismantled in sequence according to the construction requirements. When dismantling temporary supports, first make a test section to observe the settlement of the arch crown. After the temporary supports of the CRD method and the double-side wall pilot method are dismantled, the arch crown settlement does not exceed 10mmn and reaches stability. The longitudinal dismantling length can be appropriately increased according to the monitoring data.

[0098] Step 2: Construction of base surface treatment. Initial support is closed into a ring. According to the monitoring value, the arch settlement tends to be stable. After the tunnel clearance meets the requirements through measurement and inspection, the base surface treatment is required before laying the waterproof board.

[0099] Step 3: Waterproofing construction: laying buffer layer and EVA waterproof board at deformation joints and construction joints;

[0100] Step 4: Construction of steel bar engineering: main bars and distribution bars are set in the secondary lining structure of the dark excavation area. The main bars are connected mechanically, and the distribution bars are connected by binding. During installation, attention should be paid to protecting the waterproof layer. Plastic caps should be worn on the steel bar joints to avoid damage to the waterproof board. After the steel bar is installed, the waterproof board should be carefully inspected and any damage should be repaired in time.

[0101] Step 5: Formwork support and concrete pouring, which includes formwork construction, trolley installation and operation, and concrete construction. First, the invert is constructed, and then the arch wall is constructed to form a secondary lining closure. The secondary lining inverts of all sections are poured in the form of local formwork + steel pipe support. The secondary lining arch wall is constructed with a combined steel formwork + curved steel arch frame + steel support system, and each formwork is supported by a trolley, and finally concrete is poured;

[0102] Step 6: Cast the back of the second lining, and grouting between the primary support and the second lining after the strength of the second lining concrete reaches more than 75% of the design strength; the second lining grouting pipe is buried, and the second lining grouting pipe should be pre-buried before the second lining is cast. If there is a grouting plate behind the second lining, grouting should be done using the grouting plate (see the interval waterproofing design drawing for details). Grouting uses DN32 steel welded pipes, one each for the vault and side wall, with a length of the second lining thickness + 200mm; the slurry material uses micro-expansive cement mortar, and the grouting pressure and specific ratio are determined based on on-site tests; the grouting equipment uses the initial support grouting equipment. The grouting pressure is determined based on actual conditions;

[0103] Step 7: Treatment of construction joints and deformation joints. Use 2cm thick wooden templates, wooden boards or high-strength foam boards to close the plugging templates. Use square wood to hold the templates and weld C22 steel bars to the longitudinal distribution bars to pull them inwards and fix them. Use square wood, steel pipes or wooden boards to support the top and strengthen them firmly. The angle of the support should not be greater than 45 degrees. Use cotton yarn to seal the gaps after closing the mold.

[0104] In the embodiment of the present invention, in the step 5, a double side wall pilot pit method is adopted, which specifically includes the following steps:

[0105] The first step is to break the temporary middle partition wall by jumping the compartment according to the length of the second lining compartment in the interval after the initial support surface treatment is completed. The vertical height is constructed according to the backfill concrete elevation of each section of the invert. It is advisable to bury the vertical temporary middle partition wall 10cm into the invert concrete. Then carry out the waterproofing construction of the invert. Use 1.5mm thick EVA plastic waterproof board + geotextile for full outsourcing treatment, and cast a 70mm thick C20 fine stone waterproof protective layer on the invert;

[0106] The second step is to tie the second lining steel bars of the invert, install the invert formwork, and pour the invert concrete. The construction joint is set 10cm below the track surface and is constructed using a small invert formwork;

[0107] The third step is to partially cut off the temporary inverts of the side guide holes on both sides in sections and break the temporary middle partition according to the position of the trolley support crossbar, then lay the side wall waterproof layer, tie the steel bars, support the formwork and cast the secondary lining side wall, with a casting length of 6m / bin;

[0108] Step 4: After the strength of the secondary lining of the side wall meets the specification requirements, remove the temporary middle partition of the upper guide hole, then lay the top arch waterproof layer, tie the steel bars, support the formwork and pour the top arch concrete. When using an integral trolley, combine the construction with the third step;

[0109] The fifth step is to remove all temporary arches and partition walls after the concrete strength reaches the designed strength, and the secondary lining is completed. For the construction of the arch wall secondary lining formwork, an integral steel formwork hydraulic lining trolley system is used.

[0110] In the embodiment of the present invention, in step 5, when installing and operating the trolley, specifically includes:

[0111] The first step is to put the trolley in place and move it forward to the mileage to be lined. Repeat the action several times to relax the trolley structure and stop it at the correct lining position. Turn off the travel motor and drive wooden wedges or use car blockers at the travel wheels to prevent the trolley from slipping or the lining skeleton from being displaced by eccentric force, causing runaway or mold explosion. Apply release agent on the outer surface of the model plate, install the plug plate, and add necessary support.

[0112] Tighten the spiral legs under the bottom beam, ensure that the bottom plate falls on a solid foundation, remove the hinge pins on the side of the side mold support screw template, start the hydraulic oil pump, operate the lifting cylinder to rise to the designed arch elevation; operate the self-aligning cylinder to fine-tune the trolley to the correct position. If the cylinders move out of sync, you can lock the screw close to one cylinder, and continue to operate the operating valve to allow other cylinders in the same row to continue to extend. The screw can be used for micro-adjustment. After the side mold reaches the designed size, install all the side mold screws and ensure they are tightened.

[0113] After the trolley is in place, the power supply of the hydraulic oil pump must be turned off to avoid accidental operation of the valve group operating handle, which may cause deformation of the trolley structure or damage to the hydraulic cylinder.

[0114] The second step is demoulding preparation. After pouring, curing for the specified time, you can prepare for demoulding. Start the hydraulic oil pump, operate the side mold manual reversing valve handle to extend the cylinder slightly, loosen the screw, and remove all the screws of the side mold.

[0115] The third step is to remove the side mold by operating the side mold cylinder to retract the side mold and separate it from the formed concrete surface. When the cylinder retracts, it must be retracted in batches, and it is forbidden to force demolding at one time. The cylinder retraction stroke is 250mm to 300mm.

[0116] The fourth step is to remove the top mold and operate the main oil cylinder to retract the top mold and separate it from the forming concrete surface. The cylinder retraction stroke is 200mm to 250mm.

[0117] The fifth step is to retract the outriggers, rotate the spiral outriggers under the bottom beam, remove the wooden wedges or car blockers at the running wheels, operate the trolley forward to the next lining position, and start the next working cycle.

[0118] In the embodiment of the present invention, in step 5, when performing concrete engineering construction, the steps specifically include:

[0119] The main structural concrete of the section is C40P10 waterproof concrete, the internal components such as the middle partition wall are C40 concrete, the waterproof protective layer at the bottom of the structure is C20 fine stone concrete, and the backfill of the execution area arch is C30 plain concrete. During the concrete construction, a qualified concrete manufacturer is selected for pre-mixing, and then the concrete is transported to the construction site by concrete tankers for pouring.

[0120] Step 1: Preliminary preparation

[0121] (1) Carefully investigate and select mixing stations that have been reviewed for qualifications and issued enterprise grade certificates by the competent department of Beijing Municipal Construction Committee. The mixing station must have a sound management organization and quality assurance system.

[0122] (2) Sign a contract with the mixing station and put forward technical requirements in the contract. The contract clearly stipulates the obligations and responsibilities of both parties in terms of technology and quality.

[0123] The second step is the transportation and on-site acceptance of concrete

[0124] (1) Appoint a dedicated person to be responsible for the on-site acceptance of concrete quality and quantity. Concrete that does not meet the quality requirements of the contract shall not be used. Concrete that does not meet the quality requirements of the contract shall be rejected and returned.

[0125] (2) When the concrete is transported to the pouring site, its slump should be tested. Test pieces should be made according to regulations within 15 minutes after the concrete is transported to the pouring site. The production of on-site concrete slump and strength test pieces should be completed before handover and acceptance.

[0126] (3) When a concrete mixer truck is transporting concrete, the stirring speed should usually be controlled at a stirring speed of 2 to 4 r / min and rotated at least 30 times in addition.

[0127] (4) Reasonably arrange the pouring speed and transportation frequency of concrete. Ensure that the pouring is completed before the commercial concrete begins to set. After the concrete mixture is discharged from the mixer, it is transported to the paving site for paving and vibration operations. The maximum allowable time for the pouring to be completed is determined by the laboratory based on the initial setting time of cement and the construction temperature. A full-time quality and safety officer is assigned on site to conduct quality inspections on each truck of premixed concrete, including concrete grade, factory time, slump and segregation. Concrete that does not meet the requirements shall not be used.

[0128] (5) When the concrete mixture is transported to the pouring site, the temperature should not exceed 35°C and the minimum should not be lower than 10°C.

[0129] (6) Supervision is required at any time after the concrete is mixed out of the machine, and it is not allowed to add water to the mixture without authorization.

[0130] (7) When transporting concrete mixture, there should be no leakage and segregation should be prevented. If segregation or stratification occurs, the concrete mixture should be mixed again.

[0131] Step 3: Concrete pouring

[0132] (1) Before pouring concrete, the formwork, steel bars, embedded parts, reserved holes, construction joints, expansion joint waterstops, etc. should be inspected and debris in the formwork should be removed. Concrete can only be poured after the hidden acceptance is qualified.

[0133] (2) Concrete is constructed using a pumping process. The delivery pump pipe is connected to the working surface through a ground feed pipe or a shaft. The arch wall concrete of the interval structure should be poured symmetrically. If the height difference of the concrete surface on both sides of the formwork exceeds 0.5m, it needs to be adjusted to prevent the formwork from shifting due to the biased pressure on the surface, which will affect the quality of the project. At the same time, the concrete pouring speed should be controlled, preferably 2m per hour, to prevent accidents such as formwork running and bursting.

[0134] (3) During the concrete pouring process, the formwork, support, waterproof board, steel bar, embedded parts, reserved holes, etc. should be observed at all times and any problems found should be dealt with in a timely manner.

[0135] Step 4: Pouring of invert concrete

[0136] Before pouring concrete, the mold should be cleaned up. All kinds of debris, paper scraps, iron wire, soil and rocks in the mold should be cleaned up, and the accumulated water should be drained. Before pouring concrete, the formwork should be moistened to prevent pores from appearing on the base surface where the concrete meets the formwork.

[0137] The concrete pouring method is to use commercial concrete pump to deliver it into the mold, and use an inserted vibrator to vibrate the concrete in the mold. After the invert concrete construction is completed, it is covered and maintained according to the specifications.

[0138] Step 5: Pouring of arch concrete

[0139] Before pouring, clean up all kinds of debris, paper scraps, wire, soil and rocks in the formwork, moisten the concrete and formwork at the joints to prevent the formation of pores on the base surface where the concrete and formwork meet.

[0140] The side wall concrete is poured from both sides of the side wall at the same time, using a three-way pump pipe, and vibrating during the pouring process. The concrete vibration is observed through a small observation window reserved on the side wall formwork.

[0141] The top arch concrete is poured from the arch top pouring port to both sides, and vibrated with an attached vibrator. The pouring situation is observed through the plug template and the reserved observation hole (vent hole) until the arch concrete pouring is completed.

[0142] Working principle: The secondary lining construction is carried out in the order of "invert first, then arch wall". First, the tunnel floor (invert) structure and partial backfill are constructed, then the side wall is constructed, and finally the arch top secondary lining is constructed. Later, according to the monitoring data during the actual support removal process, the arch and wall primary lining formation is considered to reduce construction joints and improve the self-waterproofing ability of the secondary lining. The longitudinal horizontal construction joint between the invert and the arch wall of the interval tunnel is set 100mm below the designed track surface elevation. The secondary lining arch wall adopts the longitudinal segmented construction method and is constructed at 6m / bin.

[0143] 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.

[0144] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. The construction process of the double-track large-section split lining trolley for subway underground excavation section is characterized by: The following steps are included Step 1: Dismantle temporary supports. According to the construction progress and overall construction organization, dismantle temporary inverts and temporary middle partitions. The temporary inverts and temporary middle partitions are dismantled in sequence according to the construction requirements. When dismantling temporary supports, first make a test section to observe the settlement of the arch crown. After the temporary supports of the CRD method and the double-side wall pilot method are dismantled, the arch crown settlement does not exceed 10mmn and reaches stability. The longitudinal dismantling length can be appropriately increased according to the monitoring data. Step 2: Construction of base surface treatment. Initial support is closed into a ring. According to the monitoring value, the arch settlement tends to be stable. After the tunnel clearance meets the requirements through measurement and inspection, the base surface treatment is required before laying the waterproof board. Step 3: Waterproofing construction: laying buffer layer and EVA waterproof board at deformation joints and construction joints; Step 4: Construction of steel bar engineering: main bars and distribution bars are set in the secondary lining structure of the dark excavation area. The main bars are connected mechanically, and the distribution bars are connected by binding. During installation, attention should be paid to protecting the waterproof layer. Plastic caps should be worn on the steel bar joints to avoid damage to the waterproof board. After the steel bar is installed, the waterproof board should be carefully inspected and any damage should be repaired in time. Step 5: Formwork support and concrete pouring, which includes formwork construction, trolley installation and operation, and concrete construction. First, the invert is constructed, and then the arch wall is constructed to form a secondary lining closure. The secondary lining inverts of all sections are poured in the form of local formwork + steel pipe support. The secondary lining arch wall is constructed with a combined steel formwork + curved steel arch frame + steel support system, and each formwork is supported by a trolley, and finally concrete is poured; Step 6: Cast the back of the secondary lining. Grouting between the primary support and the secondary lining is carried out after the strength of the secondary lining concrete reaches more than 75% of the design strength. The secondary lining grouting pipe is buried. The secondary lining grouting pipe should be pre-buried before the secondary lining is cast. If there is a grouting plate behind the secondary lining, use the grouting plate for grouting. The grouting adopts DN32 steel welded pipe, one pipe is arranged on the vault and the side wall, and the length is the thickness of the secondary lining + 200mm. The slurry material adopts micro-expansive cement mortar, and the grouting pressure and specific ratio are determined according to the field test. The grouting equipment adopts the initial support grouting equipment, and the grouting pressure is determined according to the actual situation. Step seven, construction joints and expansion joints are treated. The plugging formwork is closed with 2cm thick wooden formwork, wooden board or high-strength foam board. The formwork is formed with square wood on its back. C22 steel bars are welded to the longitudinal distribution reinforcement and fixed inside. Square wood, steel pipes or wooden boards are used to support the top with diagonal braces for reinforcement. The angle of the diagonal brace should not be greater than 45 degrees. After closing the formwork, the gap is sealed with cotton yarn.

2. The construction process of the large-section split lining trolley for double-track in a subway underground excavation section according to claim 1 is characterized in that: The step 1 specifically includes the following steps: Step 1: After the initial support surface treatment is completed, the temporary middle partition is broken according to the length of the interval secondary lining compartment, and the vertical middle partition at the invert is partially cut off in sections. The grid steel frame is retained between the vertical middle partitions. The vertical height is constructed according to the backfill concrete elevation of the invert of each section. The vertical temporary middle partition is buried in the invert concrete, and then the bottom plate and the side wall below the temporary invert and the invert waterproof layer are laid, steel bars are tied, and the second lining of the bottom plate is cast in the formwork, and the retained grid steel frame of the middle partition is cast in the invert concrete; Step 2: Remove the temporary inverts of the side guide holes on both sides in sections, and remove the temporary middle partition according to the position of the trolley support crossbar. Then, treat the waterproof base surface of the side wall, lay the side wall waterproof layer, tie the steel bars, and place the trolley in place to support the formwork and cast the secondary lining side wall. Step 3: Remove the temporary middle partition wall of the segmented upper guide tunnel, construct the top arch waterproof layer, tie the steel bars, support the formwork and cast the secondary lining top arch. The remaining temporary primary support will be removed after the secondary lining is formed into a ring and closed. During the removal of the vertical middle partition wall, vertical steel supports will be used to support the top if necessary based on the monitoring results.

3. The construction process of the large-section split lining trolley for double-track in a subway underground excavation section according to claim 1 is characterized in that: The step 2 specifically includes the following steps: The first step is to block water in the primary branch. Carry out centralized grouting at the location of local water leakage in the primary branch. After the grouting is completed, use cotton yarn to temporarily block the lower port of the grouting pipe to prevent the slurry from flowing out. After the grouting is completed, if there are still individual dripping and water flow, direct blocking and pipe blocking are adopted; For direct plugging, when the water dripping or open water flow on the base surface is small and the water pressure is not high, the water outlet point is taken as the center, and the hole groove of the sprayed concrete is manually chiseled. The diameter of the hole groove is about 2-4cm and the depth is about 3-5cm. After chiseling, the groove is rinsed clean with water, and then the leak-proof spirit is used to plug the groove, and it is squeezed around the groove wall to make it tightly combined with the groove wall. After 1-2 minutes, check whether there is leakage on the appearance. If there is leakage, re-apply it; For the plugging of the lead pipe, when the point leak is large and there is visible water flow, first use manual chiseling to remove the loose layer around the leaking point and chisel out a conical groove. After chiseling, clean the groove, insert a hose into the groove, seal the hose with quick-hardening cement mortar, let the water flow out through the hose, and plug the hose before laying the waterproof board; The waterproof layer can be applied only when the primary support structure has been plugged to the point where there is no dripping water on the inner surface of the primary support and only a few wet stains; The second step is to pick up the bottom, which is done by manually cleaning it with a shovel, bucket truck, and blowing it clean with a high-pressure air duct; The third step is to deal with over-excavation and under-excavation. After cross-section inspection, if the under-excavation of the initial support is greater than 5cm, it needs to be dealt with. If the under-excavation is less than 5cm, it is not dealt with. For under-excavation greater than 5cm, the arch is replaced and moved outward to meet the clearance requirements; for large-area over-excavation and the initial support surface is basically smooth, the secondary lining concrete is used for backfilling; The fourth step is to spray the arch frame, where the arch frame is cut off, replaced, the arch frame steel bars are exposed, and the concrete surface is obviously concave, spray the concrete to make it smooth; The fifth step is to cut off the sharp objects protruding from the base surface, cut off the metal components that penetrate the base layer and smooth them with mortar, and use a pneumatic pick to chisel the protruding bulges to meet the clearance and roundness requirements; The sixth step is to smooth the base surface. The concave and convex corners and edges of the base surface need to be smoothed into arcs with mortar, and the arc radius is 100mm.

4. The construction process of the double-track large-section split lining trolley for subway dark excavation section according to claim 1 is characterized by: In the step 5, a double sidewall pilot pit method is adopted, which specifically includes the following steps: The first step is to break the temporary middle partition wall by jumping the compartment according to the length of the second lining compartment in the interval after the treatment of the primary support surface is completed. The vertical height is constructed according to the backfill concrete elevation of each section of the invert. It is advisable to bury the vertical temporary middle partition wall 10cm into the invert concrete, and then carry out the invert waterproofing construction; use 1.5mm thick EVA plastic waterproof board + geotextile for full outsourcing treatment, and cast a 70mm thick C20 fine stone waterproof protective layer on the invert; The second step is to tie the second lining steel bars of the inverted arch, install the inverted arch formwork, pour the inverted arch concrete, set the construction joint 10cm below the track surface, and use the small inverted arch formwork for construction; The third step is to partially cut off the temporary inverts of the side guide holes on both sides in sections and break the temporary middle partition according to the position of the trolley support crossbar, then lay the side wall waterproof layer, tie the steel bars, support the formwork and cast the secondary lining side wall, with a casting length of 6m / bin; Step 4: After the strength of the secondary lining of the side wall meets the specification requirements, remove the temporary middle partition of the upper guide hole, then lay the top arch waterproof layer, tie the steel bars, support the formwork and pour the top arch concrete. When an integral trolley is used, the construction is combined with the third step; The fifth step is to remove all temporary arches and partition walls after the concrete strength reaches the designed strength, and the secondary lining is completed. For the construction of the arch wall secondary lining formwork, an integral steel formwork hydraulic lining trolley system is used.

5. The construction process of the double-track large-section split lining trolley for subway dark excavation section according to claim 1 is characterized by: In step 5, when installing and operating the trolley, the following steps are specifically performed: The first step is to put the trolley in place, move the trolley forward to the mileage to be lining, and repeat the movement several times to relax the trolley structure and stop it at the correct lining position. Turn off the travel motor, and drive wooden wedges or use car blockers at the travel wheels to prevent the car from slipping or the lining skeleton from being displaced by eccentric force, causing running and bursting of the mold; apply mold release agent on the outer surface of the model plate, install the plug plate, and add necessary support; Tighten the spiral legs under the bottom beam, ensure that the bottom plate falls on a solid foundation, remove the hinge pins on the side of the screw template supporting all side molds, start the hydraulic oil pump, operate the lifting cylinder to rise to the designed arch elevation; operate the self-aligning cylinder to fine-tune the trolley to the accurate position. If the cylinders move out of sync, you can lock the screw close to one cylinder, continue to operate the operating valve to make other cylinders in the same row continue to extend, and use the screw for micro-adjustment. After the side mold reaches the designed size, install all the side mold screws and ensure they are tightened; After the trolley is in place, the power supply of the hydraulic oil pump must be turned off to avoid accidental operation of the valve group operating handle, which may cause deformation of the trolley structure or damage to the hydraulic cylinder; The second step is demoulding preparation. After pouring, the demoulding can be prepared after the specified curing time. Start the hydraulic oil pump, operate the handle of the manual reversing valve of the side mold to extend the oil cylinder slightly, loosen the screw, and remove all the screws of the side mold. The third step is to operate the side mold cylinder to retract the side mold and separate it from the formed concrete surface. When the cylinder contracts, it must be contracted in batches. Do not force demolding at one time. The cylinder contraction stroke is 250mm to 300mm. The fourth step is to remove the top mold and operate the main oil cylinder to retract the top mold and separate it from the forming concrete surface. The cylinder retraction stroke is 200mm to 250mm. The fifth step is to retract the outriggers, rotate the spiral outriggers under the bottom beam, remove the wooden wedges or car blockers at the running wheels, operate the trolley forward to the next lining position, and start the next working cycle.

6. The construction process of the large-section split lining trolley for double-track in a subway underground excavation section according to claim 1 is characterized in that: In the step 5, when carrying out the concrete engineering construction, it specifically includes: The main structural concrete of the section is C40P10 waterproof concrete, the internal components of the middle partition wall are C40 concrete, the waterproof protective layer at the bottom of the structure is C20 fine stone concrete, and the backfill of the execution area arch is C30 plain concrete. During the concrete construction, a qualified concrete manufacturer is selected to pre-mix the concrete, and then the concrete tank truck is used to transport it to the construction site for pouring; Step 1: Preliminary preparation The second step is the transportation and on-site acceptance of concrete (1) Appoint a dedicated person to be responsible for the on-site acceptance of concrete quality and quantity. Concrete that does not meet the quality standards shall not be used. Concrete that does not meet the quality requirements of the contract shall be rejected and returned; (2) When the concrete is transported to the pouring site, its slump should be tested and test pieces should be made according to regulations within 15 minutes of the concrete being transported to the pouring site; the production of on-site concrete slump and strength test blocks should be completed before handover and acceptance; (3) When a concrete mixer truck is transporting concrete, the stirring speed should usually be controlled at 2 to 4 r / min, and the stirring speed should be rotated at least 30 times; (4) Rationally arrange the pouring speed and transportation frequency of concrete; ensure that pouring is completed before the commercial concrete begins to set; after the concrete mixture is discharged from the mixer, it is transported to the paving site for paving and vibration operations. The maximum allowable time for pouring completion is determined by the laboratory based on the initial setting time of cement and the construction temperature. A full-time quality and safety officer is assigned on site to conduct quality inspection on each truck of premixed concrete, including concrete grade, factory time, slump and segregation; (5) When the concrete mixture is transported to the pouring site, the temperature should not exceed 35°C and the lowest temperature should not be lower than 10°C; (6) At any time after the concrete is mixed out of the machine, supervision is required and it is not allowed to add water to the mixture without authorization; (7) When transporting concrete mixture, there should be no leakage and segregation should be prevented. If segregation or stratification occurs, the concrete mixture should be mixed again; Step 3: Concrete pouring (1) Before pouring concrete, the formwork, steel bars, embedded parts, reserved holes, construction joints, and deformation joint waterstops should be inspected and debris in the formwork should be removed. Concrete can only be poured after the concealed acceptance is qualified; (2) Concrete is constructed by pumping technology. The delivery pump pipe is connected to the working surface through the ground feed pipe or the shaft mouth. The arch wall concrete of the interval structure should be poured symmetrically. If the height difference of the concrete surface on both sides of the formwork exceeds 0.5m, it needs to be adjusted to prevent the formwork from shifting due to the bias pressure on the surface, which will affect the quality of the project. At the same time, the concrete pouring speed should be controlled, preferably 2m per hour, to prevent the occurrence of formwork running and bursting accidents; (3) During the concrete pouring process, the formwork, support, waterproof board, steel bar, embedded parts and reserved holes should be observed at any time, and any problems found should be dealt with promptly; Step 4: Pouring of invert concrete Before pouring concrete, the mold should be cleaned up to remove all debris, paper scraps, iron wire, soil and rocks, and the accumulated water should be drained. The formwork should be moistened before pouring concrete to prevent pores from appearing on the surface where the concrete meets the formwork. The concrete pouring method is to use commercial concrete pump to deliver it into the mold, and use an inserted vibrator to vibrate the concrete in the mold. After the invert concrete construction is completed, it is covered and maintained according to the specifications. Step 5: Pouring of arch concrete Before pouring, clean up all kinds of debris, paper scraps, iron wire, soil and rocks in the formwork, and moisten the concrete and formwork at the joint to prevent pores from appearing on the surface where the concrete and formwork meet; The side wall concrete is poured simultaneously from both sides of the side wall, using a three-way pump pipe, and vibrated during the pouring process; a small observation window is reserved on the side wall formwork to observe the concrete vibration; The top arch concrete is poured from the arch top pouring port to both sides, and vibrated by an attached vibrator. The pouring situation is observed through the plug template and the reserved observation hole until the arch concrete pouring is completed.

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