Construction process of underground diaphragm wall in sensitive area

Abstract

The invention relates to a construction technology for an underground diaphragm wall in a sensitive area. The construction technology comprises the following steps that S1, construction preparation is conducted, and a site is arranged; sa2, setting a slurry system; sb2, measuring and setting out; sa3, slurry is prepared; sb3, guide wall construction; sa4, storing the slurry; sb4, reinforcing the foundation; sa5, recycling and separating the slurry; sb5, grooving excavation and inspection are carried out; sa6, slurry regeneration is carried out; sb6, wall brushing and hole sweeping are conducted on the connector; sc1, manufacturing a reinforcement cage platform; sa7, slurry discarding is carried out; sb7, tank bottom treatment; sc2, manufacturing a steel bottom plate and a reinforcement cage; s8, hoisting the reinforcement cage; s9, hoisting the joint box; s10, a guide pipe is installed; s11, concrete pouring is conducted; s12, the connector box is pulled out; in Sb4, in foundation reinforcement, reinforcing holes are vertically punched downwards in one side of the guide wall at equal intervals, slurry is sprayed to the position under the guide wall in a covering mode in the reinforcing holes in the direction towards the guide wall in a 150-degree rotary spraying mode, and the depth of the reinforcing holes is larger than that of the underground continuous wall. Guniting reinforcement is conducted on the foundation before construction, the grooving quality is improved, and meanwhile the settlement risk is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of underground continuous wall construction, and in particular to a construction process of underground continuous wall in a sensitive area. Background Art

[0002] Underground continuous wall is a deep foundation structure widely used in construction projects, especially in the fields of subway tunnels, basement pit enclosures of high-rise buildings, etc. It is often used as a reliable foundation pit support method to reduce the impact of the surrounding environment on the building and ensure the quality and safety of the construction project.

[0003] However, during the construction process, the higher the building to be built, the more stringent the building requirements, and generally the deeper the foundation to be built, and the depth of the underground continuous wall will also increase accordingly. Especially when the depth of the underground continuous wall is more than 40 meters, the deeper the depth, the greater the probability of encountering a geological foundation with a high groundwater content in the region. In southern China or tropical and subtropical areas of Southeast Asia, it is more common to have abundant groundwater at around 50 meters. At the same time, the weight of the supporting steel cage is relatively large. When poured in sections, the weight of a 10-meter-wide steel cage will reach more than 80 tons. When the water content is high, the soil is soft. During the construction of the underground continuous wall, the steel cage sometimes settles under the action of gravity, thus affecting the continuity and stability of the underground continuous wall. Summary of the invention

[0004] In order to reduce the settlement that occurs during the construction of underground continuous walls when the groundwater content is high, the present application provides a construction process for underground continuous walls in sensitive areas.

[0005] The application provides a sensitive area underground continuous wall construction process using the following technical solutions: A construction process for underground continuous wall in sensitive areas, comprising the following steps: S1. Construction preparation and site layout; Sa2. Mud system setting; Sb2. Measurement and setting out; Sc1. Steel cage platform production; Sa3. Mud preparation; Sb3. Guide wall construction; Sa4. Mud storage; Sb4. Foundation reinforcement; Sa5. Mud regeneration; Sb5. Trench excavation and inspection; Sa6. Mud recovery and separation; Sb6. Joint wall brushing and hole sweeping; Sa7. Mud disposal; Sb7. Trench bottom treatment; Sc2. Steel bottom plate and steel cage production; S8. Steel base plate hoisting; S9. Lifting of steel cage; S10.Joint box hoisting; S11.Conduit installation; S12. Concrete pouring; S13. Pull out the connector box; In the Sb4. foundation reinforcement, reinforcement holes are first drilled vertically downward at equal intervals on one side of the guide wall, and mud is sprayed in the reinforcement holes in a 150° rotary spraying manner toward the guide wall to the bottom of the guide wall, and the depth of the reinforcement holes is greater than the depth of the underground continuous wall.

[0006] By adopting the above technical solution, an underground continuous wall construction process suitable for geological conditions with high water content is realized. On the basis of the traditional construction process, the technical solution in this application separately sets up a foundation reinforcement step, which reinforces the foundation by spraying mud, strengthens the foundation density at the construction location, especially at the underground continuous wall location, and improves the foundation stability during concrete pouring, thereby reducing the situation where the quality of the underground continuous wall project is affected by loose geological foundation due to high underground water content.

[0007] Optionally, during the foundation reinforcement of Sb4., a verticality test is performed after the reinforcement hole is drilled. If the verticality deviation exceeds 1 / 500, correction is performed. After the drilling is completed, the MJS main machine porous pipe is inserted into the hole with a lifting time of 25 minutes per meter, a mud flow rate of 90 to 110 L / min, a mud pressure of 40 MPa, and a main air pressure of 0.7 MPa to form a central injection.

[0008] By adopting the above technical solution, the verticality of the reinforced hole and the injection intensity are guaranteed, thereby ensuring that the position directly below the guide wall, the underground continuous wall and the position below can be covered and reinforced within the injection range.

[0009] Optionally, in the construction of the guide wall of Sb3., the guide wall adopts the "┓┏" type, the 800mm thick underground continuous wall adopts the guide wall with a net width of 840mm, the guide wall axis and the guide wall net distance allowable deviation of ±10mm, the inner side wall unevenness of the guide wall is less than 5mm, and the guide wall top surface unevenness is less than 30mm; during the construction of the guide wall, first excavate the guide wall, tie the guide wall steel bars, erect the formwork, and pour the guide wall concrete; after the guide wall formwork is removed, immediately use two 100*100@2000mm square timbers to support the guide wall to prevent the guide wall from moving inwards; when the concrete strength of the guide wall reaches 70% of the design strength, the Sb5 can be carried out.

[0010] By adopting the above technical solution, the guide wall adopts a "┓┏" type design, controls the guide wall axis and net distance deviation within ±10mm, and supports the inside of the guide wall by wooden formwork support and clay backfill, thereby reducing the collapse of the guide wall. When the concrete strength reaches 70% of the design standard, the grooving process of step Sb5 can be carried out, which can improve the construction efficiency to a certain extent while ensuring the quality.

[0011] Optionally, in the trenching excavation and inspection of Sb5, the soil layer trench is excavated by a trenching machine, and the trenching is carried out in the order of first the two sides and then the middle. Mud is added after the trench is formed, the depth is measured after the trench is formed, and the vertical accuracy and axial trench width are measured by an ultrasonic measuring instrument.

[0012] By adopting the above technical solution, the situation of trench collapse is reduced and the smooth insertion of the steel cage is ensured.

[0013] Optionally, during the Sb5. trench excavation and inspection, after the trench excavation is completed, a reinforcement groove is dug on both sides of the bottom of the trench along the length direction, and during the S8 steel bottom plate hoisting, the steel bottom plate is placed at the bottom of the trench along the length direction of the trench, and at the same time, both sides of the steel bottom plate extend into the reinforcement grooves on both sides of the trench respectively.

[0014] By adopting the above technical scheme, the reinforced groove set at the bottom of the trench can further increase the stress-bearing area of ​​the bottom of the underground continuous wall, that is, increase the bearing area of ​​the foundation at the bottom of the trench, thereby strengthening the bearing capacity of the underground soil and reducing the settlement of the concrete and steel cage of the underground continuous wall to a certain extent.

[0015] Optionally, the width of the steel bottom plate is equal to the width of the groove plus twice the width of the reinforcement groove, and the depth of the reinforcement groove is not less than the width of the steel bottom plate.

[0016] By adopting the above technical solution, the steel bottom plate can expand the bottom area of ​​the underground continuous wall, and can also make the steel bottom plate more convenient to be placed at the bottom of the trench.

[0017] Optionally, at least four pairs of steel bar hooks are fixedly connected to each steel bottom plate, and the bent portions at the tops of the hooks in the same pair are arranged facing each other and overlapped with each other; two pairs of the four pairs of hooks form a group, and the groups of hooks are evenly arranged in the length direction of the steel bottom plate; the two pairs of hooks in the same group are symmetrically fixed at the positions on both sides of the length direction of the steel bottom plate; The height of the hook is not greater than the width of the groove; The maximum spacing between the hooks in the same group is no greater than the width of the groove; Two bottom wall bars are fixed at the bottom of the steel cage along the length direction of the groove, and each of the bottom wall bars corresponds to a hook on one side of the steel bottom plate. When the steel cage is lowered into the groove, the bottom wall bars are pressed into the hooking area of ​​the corresponding hook.

[0018] By adopting the above technical solution, after the steel bottom plate is placed at the bottom of the groove, when the steel cage is hoisted and lowered, the bottom wall reinforcement of the steel cage can be pressed to the corresponding hook bending part under the action of its own gravity, causing the steel hook to deform and finally enter the corresponding hooking area. The hooking connection between the bottom wall reinforcement and the steel hook improves the integrity and stability of the underground continuous wall and the steel bottom plate, which enhances the buoyancy of the underground continuous wall after forming. On the one hand, it can reduce the settlement of the underground continuous wall. On the other hand, the part of the reinforced groove is connected with the foundation, which also limits the floating of the building foundation to a certain extent. Especially after the concrete solidifies, the steel cage of the underground continuous wall and the steel bottom plate can communicate and transmit force through the steel bars, further improving the stability of the building foundation.

[0019] Optionally, two opposite side walls of the vertical groove of the H-shaped steel away from the steel cage are vertically provided with slide grooves, a bottom sealing box is slidably installed in the slide groove, a clearance groove is provided at the bottom of the slide groove, the inner cavity of the slide groove passes through the H-shaped steel through the clearance groove and is connected with the reinforcement grooves on both sides of the groove, and the depth of the clearance groove is greater than the depth of the reinforcement groove; Blocking holes are provided at positions corresponding to the give-way grooves on both sides of the bottom sealing box, and a blocking steel plate is slidably connected in the blocking hole. A hydraulic cylinder for pushing the blocking steel plate is provided in the bottom sealing box; When the steel cage is lowered to the bottom of the groove, the hydraulic cylinder is driven to push the blocking steel plates out of the blocking holes, and then pass through the makeshift groove and insert into the inner wall of the reinforcement groove until the blocking steel plates are out of the bottom sealing box and are clamped in the makeshift groove, and then the bottom sealing box is pulled out of the slide.

[0020] Through the above technical scheme, the reinforcement groove is sealed by using a sealing steel plate, and the sealing steel plate is inserted into the inner wall of the reinforcement groove and connected to the H-shaped steel, which can minimize the bypass during concrete pouring and reduce the situation where the steel cage cannot be lowered into place due to concrete bypass in adjacent grooves.

[0021] Optionally, the steel bottom plate is an arc-shaped plate, which is bent along the width direction and has an opening arranged downward.

[0022] Through the above technical solutions, the bearing capacity of the steel bottom plate is improved to a certain extent.

[0023] Optionally, in the preparation of Sa3. mud, the mud includes bentonite, CMC and soda ash, and the weight ratio of each component is water: bentonite: CMC: soda ash = 100: (8-10): (0.1-0.3): (0.3-0.4); the preparation process is that after the mixer is rotated with water, bentonite is evenly added, and then CMC, soda ash and water are taken out, and after fully stirring, they are poured into the bentonite aqueous solution in the mixer and stirred evenly, and then flowed into the slurry storage tank after stirring for 24 hours before testing, and the test is carried out. The indicators are: the relative density of mud applied to clay soil layer is 1.04-1.05g / cm3, the viscosity is 20-24S, and the sand content is less than 3%; the relative density of mud applied to sandy soil layer is 1.06-1.08g / cm3, the viscosity is 25-30S, and the sand content is less than 4%. The common detection indicators of the two are: colloid rate greater than 95%, water loss in 30 minutes is less than 30mL, mud skin thickness is 1-3mm, pH value is 8-9, initial shear force is 2-3Pa, and final shear force is 5-10Pa.

[0024] By adopting the above technical solution, the performance of the mud can be effectively improved. The preparation process ensures the full dissolution and uniform dispersion of each component, thereby improving its stability and applicability in use.

[0025] Optionally, in the Sa5. mud recovery and separation, the mud is located at different positions in the groove wall and has different degrees of contamination. During the groove bottom excavation construction, mud is taken out at different depths in the groove, and the relative density, viscosity, sand content and pH value are tested. When the test is qualified, the mud is recycled to the gravity sedimentation tank. When the test is unqualified, the mud is restored to use after regeneration treatment. The regeneration treatment includes using bentonite to increase the stability value, using CMC to increase the viscosity, using soda ash to increase the pH value, using water to reduce the viscosity, using bentonite to increase the relative density, using water to reduce the relative density, using bentonite and CMC to increase the static shear force, using water to reduce the static shear force, using bentonite and CMC to reduce the water loss, and using bentonite and CMC to increase the colloid rate.

[0026] By adopting the above technical solution, mud can be classified and treated according to the degree of contamination at different locations, which can effectively improve the utilization rate of mud and reduce resource waste. By sampling and testing the mud at different depths in the tank wall and treating the mud according to the test results, the quality of the mud is ensured to meet the construction requirements, while reducing the cost increase caused by blind abandonment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a flow chart of a construction process of underground continuous wall in a sensitive area in an embodiment of the present application; Figure 2 It is a schematic diagram of the internal structure of the groove and the reinforcement groove in the embodiment of the present application; Figure 3It is a schematic diagram of the layout positions of the reinforcement holes in the foundation reinforcement stage in the embodiment of the present application; Figure 4 This is a schematic diagram of the structural position of the steel bottom plate in the embodiment of the present application; Figure 5 Schematic diagram of the lower structure of the steel cage in the embodiment of the present application; Figure 6 It is a cross-sectional view of the matching structure of the H-shaped steel bottom and the bottom sealing box in the embodiment of the present application.

[0028] Explanation of the reference numerals in the accompanying drawings: 1. existing building; 2. guide wall; 21. wooden square; 3. reinforcement hole; 4. groove; 5. reinforcement groove; 6. steel bottom plate; 61. middle area; 611. tooth groove; 612. block; 62. reinforcement area; 63. steel bar hook; 631. bending part; 632. hooking area; 7. steel bar cage; 71. supporting truss; 72. shear bar; 73. reinforcement bar; 74. bottom wall bar; 75. H-shaped steel; 751. slide; 752. bottom box; 753. give way groove; 754. blocking steel plate; 756. hydraulic cylinder. DETAILED DESCRIPTION

[0029] The following is combined with Figure 1-6 This application is described in further detail.

[0030] The present application embodiment discloses a construction process of underground continuous wall in sensitive area. In this application, sensitive area refers to an area with a large number of built buildings around the construction area, such as subway stations, residential buildings, etc., and a high water content of deep groundwater. With the development of urbanization, urban projects are becoming more and more common. During the construction process, it is necessary to consider the impact of construction on surrounding buildings and minimize the scope of the construction area; at the same time, due to geological conditions, a more stable underground foundation needs to be built when building high-rise buildings to improve the stability of the entire building. Especially in areas with abundant groundwater and soft soil, the construction difficulty and risk control difficulty will increase significantly, and when the underground continuous wall exceeds a depth of 40 meters, it is more common to encounter abundant groundwater. Taking the above factors into consideration, this construction process reinforces the foundation and underground continuous wall to ensure that the impact of construction activities on the construction area is minimized, while ensuring the construction quality and stability of the underground continuous wall, laying the foundation for subsequent foundation pit excavation and main structure construction.

[0031] Reference Figure 1 The construction process of underground continuous wall in sensitive areas includes the following steps: S1. Construction preparation and site layout; The large-scale mechanical equipment (such as MJS main machine, trenching machine, etc.) used in underground continuous wall construction has a large deadweight, large working load, large equipment and frequent movement, so it is necessary to add construction access roads. The construction access roads are mainly located in the foundation pit. There are old building foundations in the foundation pit. Before adding construction access roads, obstacle clearance construction is required. After obstacle clearance, the backfill needs to be compacted layer by layer, and the thickness of each layer shall not exceed 30cm. After compaction, 30cm thick C30 concrete is paved.

[0032] Sa2. Mud system settings; A comprehensive mud pool is set up on site, each mud pool is equipped with a mud machine for simultaneous construction of two continuous walls. The mud pool is divided into a mixing pool, a slurry storage pool, a gravity sedimentation pool, a waste slurry pool and a soil collection pit.

[0033] Sa3. Mud preparation; The mud includes bentonite, CMC and soda ash, and the weight ratio of each component is Water: bentonite: CMC: soda ash = 100: (8-10): (0.1-0.3): (0.3-0.4); Under the condition of high underground water content in deep layers, the relative density of the injected mud is high. The preparation process is as follows: after the mixer is rotated with water, bentonite is evenly added, and then CMC, soda ash and water are taken out, fully stirred, poured into the bentonite aqueous solution in the mixer and stirred evenly, and then flowed into the slurry storage tank to be dissolved and swollen for 24 hours before use.

[0034] The properties of the prepared mud are shown in Table 1.

[0035] Table 1 Mud performance data Sa4. Mud storage; To prevent the mud from being contaminated, a cover plate is added to the top of the guide wall when pouring concrete to prevent concrete from falling into the trench; after the trench is excavated, a grab is used to clear the soil and debris at the bottom of the trench to reduce the amount of low-quality mud floating on the surface; when pouring concrete, low-quality mud within a few meters below the top of the wall should be pumped into a waste slurry pool.

[0036] Sa5. Mud recovery and separation; In areas with abundant groundwater, the mud is polluted to different degrees at different locations in the trench wall. During the trench bottom excavation, the mud at different depths in the trench is taken out to test the relative density, viscosity, sand content and pH value. If the test is qualified, it is recycled to the gravity sedimentation tank. If the test is unqualified, it is regenerated and then reused.

[0037] The relative density can be measured by using a mud relative density meter. The viscosity can be measured by using a standard funnel viscometer for construction sites. The sand content can be measured by using a sand content meter for construction sites.

[0038] The pH value test method can be used to measure the potential difference of the mud using a pH meter or pH electrode to directly read the pH value. The stability value test method: put the mud into the stability cylinder, let it stand for 24 hours, and then measure the density difference between the upper and lower layers of the mud column to determine the stability of the mud.

[0039] In addition, the static shear force, colloid rate, water loss and mud skin thickness were tested.

[0040] The force required to make the static mud start to flow and destroy the mesh structure per unit area is called static shear force. The force measured after 1 minute of static is the initial shear force, and the force measured after 10 minutes of static is the final shear force. The test method can be carried out using a surface shear force gauge or a static shear force gauge.

[0041] The colloid rate, also known as the stability rate, refers to the performance of the soil particles in the mud to maintain a suspended state. The test method of the colloid rate is to put 100ml of mud into a clean measuring cup, cover it with a glass plate, and let it stand for 24 hours. The mud on the top of the measuring cup may be clarified into transparent water, and there may be sediment at the bottom of the measuring cup. 100-(water + sediment) volume is equal to the colloid rate.

[0042] Water loss and mud skin thickness: a 120mm×120mm filter paper can be placed on a horizontal glass plate, a circle with a diameter of 30mm can be drawn in the center, and 2ml of mud can be dropped in the center of the circle. After 30 minutes, the average radius of the wet circle minus the average radius of the mud cake (mm) is the water loss. The calculated result (mm) represents the water loss, unit: ml / min. The thickness of the mud cake (mm) measured on the filter paper is the mud skin thickness. The flatter and thinner the mud skin is, the higher the mud quality is.

[0043] Sa6. Mud regeneration; The mud regeneration treatment is carried out by combining gravity sedimentation mechanical treatment and chemical treatment. The mud recovered from the tank is removed by a vibrating screen to remove the larger soil residues, and then gravity sedimentation is carried out. Then the smaller soil residues are separated by a cyclone. If it still does not meet the use index, it is added with additives for chemical treatment. The treatment rules are shown in Table 2.

[0044] Table 2 Chemical slurry preparation methods Sa7. Mud disposal; Waste slurry is generally produced at the last stage of concrete pouring. Since the slurry has the longest contact time with concrete and is seriously contaminated by cement, the viscosity and relative density of the slurry may have exceeded the standard and it is difficult to separate and purify it to restore its performance. This part of the slurry is first temporarily stored in a waste slurry pool, and then transported out of the site after slurry filtration.

[0045] Sb2. Measurement and setting out; The coordinates and elevations are calibrated. The underground continuous wall construction area adopts an 800mm thick underground continuous wall, and a concrete guide wall is set on the upper part of the underground continuous wall. The positions of the reinforcement holes are marked at equal intervals on the side of the underground continuous wall close to the existing building. In this embodiment, the axis of the reinforcement hole is 800mm away from the central axis of the guide wall, and the spacing between adjacent reinforcement holes is 2000mm.

[0046] Sb3.Guide wall construction; Reference Figure 2 , a guide wall 2 is set at the top area of ​​the underground continuous wall. The guide wall 2 adopts the "┓┏" type, and the 800mm thick underground continuous wall adopts the guide wall 2 with a net width of 840mm. The axis of the guide wall 2 coincides with the axis of the underground continuous wall. When constructing the guide wall 2, first excavate the guide wall 2, tie the guide wall steel bars, set up the formwork, and pour the guide wall concrete; after the guide wall is demolded, two 100*100@2000mm square timbers 21 are immediately used to support the guide wall 2, and the guide wall 2 is backfilled with clay to prevent the guide wall 2 from moving inward. When the concrete strength of the guide wall 2 reaches 70% of the design strength, Sb5 can be carried out.

[0047] Sb4. Foundation reinforcement; Reference Figure 3 , a drilling machine is used to drill vertically downward at the position of the reinforcement hole 3, with a hole diameter of 200mm; after the hole is formed, the verticality is tested, and if the verticality deviation exceeds 1 / 500, it is corrected. If it cannot be corrected, it is backfilled and re-drilled; after the reinforcement hole is drilled, the MJS host porous pipe is deeply inserted into the hole, and a 150° rotary spraying process is used to horizontally spray one side of the guide wall to strengthen the foundation density and improve the foundation stability at the underground continuous wall. In this embodiment, the spraying range is 1600mm-2000mm, and the specific rotary spraying parameters are shown in Table 3 to achieve the effect of covering spray reinforcement of the foundation.

[0048] Table 3 Main technical parameters of 150° rotary spraying Serial number Parameter Item Numeric unit 1 Water-cement ratio 1 2 Lifting time per meter 25 min 3 Mud flow rate 90～110 L / min 4 Mud pressure 40 MPa 5 Main air pressure 0.7 MPa 6 Cutting water pressure 10～25 MPa Sb5. Trench excavation and inspection; A slotting machine is used to dig a slot 4 vertically downward along the guide wall 2 at the position of the underground continuous wall. If the slot 4 is a straight slot, the slotting sequence is first the two sides and then the middle. If the slot 4 is a special-shaped slot, the sequence is first the short side and then the long side. After the slot 4 is dug, mud is added in time to maintain the stability of the mud liquid level in the guide wall 2. The allowable deviation of the verticality of the slot 4 is 1 / 500. After the slot 4 is constructed, an ultrasonic measuring instrument is used to measure the vertical accuracy and axial width of the slot 4 to ensure that the steel cage 7 is smoothly inserted.

[0049] After the trench 4 is excavated, a reinforcement groove 5 is dug at both sides of the bottom of the trench 4 along the length direction, so that the trench 4 and the reinforcement groove 5 at the location of the underground continuous wall are in an inverted "T" shape as a whole. The provision of the reinforcement groove 5 can increase the force-bearing area at the bottom of the underground continuous wall and reduce the pressure at the bottom of the trench to a certain extent. To a certain extent, the settlement of the underground continuous wall under its own gravity can be reduced.

[0050] Sb6. Brush the joint wall and sweep the hole; During the construction of trenching 4, a layer of mud is often attached to the old joints, which will affect the quality of the trench wall joints and cause water leakage at the joints. The joints must be brushed. The joints are brushed with steel bottom plate brushes and wire brushes. The steel bottom plate brush is installed on the grab bucket of the trenching machine. The grab bucket moves up and down in the vertical direction to drive the steel bottom plate brush to scrape the joints. The wire brush uses its own guide plate to allow the brush to be close to the joints during the brushing process.

[0051] Sb7.Trough bottom treatment; Since the mud has a certain specific gravity and viscosity, it takes some time for the soil residue to sink to the bottom of the trough in the mud. Therefore, the bottom cleaning by sedimentation method should be started after a certain period of time after the troughing is completed. The hydraulic grab of the troughing machine is used to directly dig out the sediment at the bottom of the trough.

[0052] Sc1. Fabrication of steel cage platform; A steel cage assembly pedestal was set up on site. The platform was welded with channel steel, and the bottom layer of the platform was welded with C28 steel bars for legs. The platform was leveled with a level, and the four corners of the steel cage platform were all right angles.

[0053] Sc2. Production of steel base plate and steel cage; Reference Figure 2 and Figure 4 , a steel bottom plate 6 is installed at the bottom of the underground continuous wall. The width of the steel bottom plate 6 is equal to or slightly less than the width of the groove 4 plus twice the width of the reinforcement groove 5. In order to facilitate the installation of the steel bottom plate 6 at the bottom of the groove 4 and the position of the reinforcement groove 5, the depth of the reinforcement groove 5 is not less than the width of the steel bottom plate 6. In this embodiment, the depth of the reinforcement groove 5 is 1700mm, and the width of the reinforcement groove 5 is 300mm. The length of the steel bottom plate 6 is cut according to the length of the groove 4, and the width is 1400mm.

[0054] The steel bottom plate 6 is divided into a middle area 61 at the width position corresponding to the groove 4 along the parallel length direction, and the positions on both sides of the middle area 61 corresponding to the reinforcement groove 5 are divided into reinforcement areas 62. At least four pairs of steel bar hooks 63 are fixedly connected to the upper surface of the middle area 61 of each steel bottom plate 6, and the end of the steel bar hook 63 away from the fixed position is a bending portion 631. The bending portions of two steel bar hooks in the same pair of steel bar hooks 63 are close to each other and overlap each other, and form a hooking area 632 with the steel bottom plate.

[0055] Reference Figure 4 In this embodiment, there are 8 steel bar hooks 63, two of which are used as a pair, and two pairs are used as a group to be fixed on the steel base plate 6. The two groups of hooks are evenly arranged in the length direction of the steel base plate 6; the two pairs of steel bar hooks 63 in the same group are symmetrically fixed on the two sides of the middle area 61 of the steel base plate 6, and the height of the steel bar hooks 63 is lower than the width of the groove. In this embodiment, the height of the hook is set to 500mm, and the maximum spacing between the four steel bar hooks 63 in the same group is not greater than the width of the groove 4.

[0056] In this embodiment, the steel bottom plate 6 is a flat plate. In other embodiments, the steel bottom plate can be replaced by an arc-shaped plate with an arc in the width direction, the opening of the steel bottom plate is placed downward, and the steel bar hook is fixed to the raised side of the steel bottom plate. The arc-shaped plate with the opening downward can have a better bearing capacity and further improve the anti-settlement ability of the underground continuous wall.

[0057] like Figure 5 As shown, the steel cage 7 is fixed by welding. In order to improve the integrity and structural stability of the steel cage 7, a support truss 71 is welded inside the steel cage 7, reinforcement welding is performed on both sides of the steel truss 71, and then stirrups, lifting rings, lifting point reinforcements, steel cage reinforcements, hanging bars, etc. are welded until the steel cage is formed.

[0058] In order to ensure the overall stress performance of the steel cage, multiple groups of "X"-shaped shear bars 72 are welded on the front and rear positive facades of the steel cage, and four "L"-shaped reinforcement bars 73 of the same model are welded and reinforced at the intersection. The "X" shape ensures that the shear bars 72 are continuous, and the "X"-shaped shear bars 72 are set at 45°.

[0059] In order to improve the integrity and stability of the steel bottom plate 6 and the steel cage 7, two rows of bottom wall bars 74 are symmetrically welded on both sides of the bottom of the steel cage 6 along the length direction of the groove 4. Each row of bottom wall bars 74 is arranged in sequence from bottom to top, and each row of bottom steel bars 74 corresponds to the steel hook 63 on one side of the steel bottom plate 6. When the steel cage 7 is lowered into the groove 4, the bottom wall bars 74 are pressed into the hook area 632, and the bent portion 631 of the steel hook 63 is hooked in the interval of the bottom wall bars 74. In this way, the gap between the steel cage 7 and the steel bottom plate 6 is further reduced, and they are more closely connected. When the underground continuous wall is subjected to buoyancy or pressure after solidification, the steel bottom plate 6 and the steel cage 7 can transmit the force through the steel hook 63 and the bottom wall bars 74, reducing the tension and pressure on the concrete structure of the underground continuous wall, and improving the integrity and stability of the underground continuous wall.

[0060] In order to make the bottom wall reinforcement 74 of the steel cage 7 enter the hooking area 632 more smoothly, the length of the bending portion 631 of the steel hook 63 is not less than 200 mm, and the angle between the bending portion and the horizontal plane is not greater than 50°.

[0061] The underground continuous wall adopts the sound wave transmission method to detect the wall structure quality, so it is necessary to pre-embed the sound detection pipe in the trench 4. When the wall quality determined by the sound wave transmission method is unqualified, the core drilling method should be used for verification. The installation of the sound detection pipe follows the "W" type layout.

[0062] In this embodiment, the casting is carried out in sections, and the H-shaped steel 75 is used in the trough 4 to separate the trough sections of the trough 4. The H-shaped steel 75 is vertically welded to one end of the steel cage 7 along the length direction of the trough 4, and one end of the steel cage 7 extends into the vertical groove on one side of the H-shaped steel 75. When the steel cage 7 is manufactured, the H-shaped steel 75 is welded to the steel cage 7 to form a whole, and is lowered into the trough 4 together when the cage is lowered.

[0063] Reference Figure 6 In the vertical groove of the H-shaped steel 75 away from the steel cage 7, two opposite inner walls are vertically provided with slide grooves 751, and a bottom sealing box 752 is slidably connected in the slide groove 751. A clearance groove 753 is provided at the bottom of the slide groove 751, and the inner cavity of the slide groove 751 is connected to the reinforcement grooves 5 on both sides of the groove 4 through the clearance groove 753 through the H-shaped steel 75, and the height of the clearance groove 753 is greater than the height of the reinforcement groove 5.

[0064] Sealing holes are provided at positions corresponding to the clearance grooves 753 on both sides of the bottom sealing box 752, and a sealing steel plate 754 is slidably placed in the sealing hole. A plurality of annular sealing rubbers are fixed to the vertical section of the sealing steel plate 754, and the sealing steel plate 754 is fixed in the sealing hole by extrusion of the sealing rubber. Two groups of hydraulic cylinders 756 for pushing the sealing steel plates are provided in the bottom sealing box 752 in a one-to-one correspondence, and the piston rods of the hydraulic cylinders 756 are in contact with the bottom sealing steel plates 754. When the bottom sealing box 52 is lowered to the bottom of the groove 4 along the slide groove 751, the hydraulic cylinder 756 is started. After the piston rod pushes the sealing steel plate 754 out of the sealing hole, it passes through the clearance groove 753 and is inserted into the inner wall of the reinforcing groove 5, separating the reinforcing grooves 5 of different groove sections on the front and rear sides of the H-shaped steel 75. At the same time, the sealing rubber of the blocking steel plate 754 near the bottom sealing box 752 is squeezed into the clearance groove 753, thereby increasing the sealing performance to a certain extent and reducing the bypass of concrete. At this time, the blocking steel plate 754 is separated from the bottom sealing box 752 and clamped in the clearance groove 753, and finally the bottom sealing box 752 is pulled out of the slide groove 751, and the groove section into which the steel cage 7 is placed is poured.

[0065] In order to maximize the moving stroke of the blocking steel plate 754, the blocking holes on both sides of the bottom box 752 are staggered. Further, in order to strengthen the bypass flow during the pouring of concrete between adjacent slot sections, an iron sheet is welded between the inner side wall of the H-shaped steel 75 opening toward the steel cage 7 and the steel cage 7.

[0066] S8. Steel base plate hoisting; During hoisting, four hooks are respectively hooked in the hooking areas 632 of the four pairs of steel bar hooks 63. During hoisting, the steel bottom plate 6 is erected along the width direction and tilted down into the groove 4. When the steel bottom plate 6 is lowered to the bottom of the groove, the steel bottom plate 6 is straightened by adjusting the hooks in the hooking area 632.

[0067] After the steel bottom plate 6 is placed at the bottom of the trench along the length direction of the trench 4, the reinforcement areas 632 on both sides of the steel bottom plate 6 extend into the reinforcement grooves 5 on both sides of the trench 4. The steel bottom plate 6 as a whole can support the structure of the underground continuous wall, improve the stability of the internal structure of the trench 4, and reduce the settlement of the steel cage 7 after the steel cage 7 is hoisted to a certain extent.

[0068] S9. Lifting of steel cage; The horizontal hanging points of the steel cage adopt a 10-point hanging scheme, with 4 main hanging points (2 longitudinal points and 2 transverse points) and 6 auxiliary hanging points (3 longitudinal points and 2 transverse points).

[0069] The steel cage is hoisted by two cranes of 200T and 100T at the same time. The hoist and two lifting ropes hoist the steel cage from the ground to a certain height, then lift the main hoisting rope and lower the auxiliary hoisting rope. When it is vertical, the main crane is used to lower the steel cage inward. When the steel cage is lowered to the bottom of the groove, the bottom wall reinforcement of the steel cage is pressed into the corresponding hook of the steel bottom plate.

[0070] Furthermore, in order to reduce the situation where the steel bars slide on the steel bottom plate 6 and cause the steel bottom plate 6 and the steel cage 7 to be skewed relative to each other, at least two tooth grooves 611 are provided on the upper surface of the middle area of ​​the steel bottom plate 6 along the length direction, wherein at least one tooth groove 611 is provided in the middle of each pair of steel hooks 63, and the bottom wall reinforcement 74 at the bottom of the steel cage 7 is clamped in the tooth groove 611. A plurality of clamping blocks 612 are evenly provided on the bottom wall of the tooth groove 611, and the height of the clamping blocks 612 is not higher than the depth of the tooth groove 611. After the bottom end of the steel cage 7 extends into the tooth groove 611, the movement space will be restricted by the tooth groove 611. Especially when the steel bottom plate 6 is an arc-shaped steel plate, the upper surface of the steel bottom plate is relatively smooth, and the provision of the tooth groove 611 can greatly reduce the sliding deviation of the steel cage 7.

[0071] S10.Joint box hoisting; After the steel cage is lowered into place, the joint box is lowered on the side of the H-shaped steel 75 away from the steel cage 7 to support the H-shaped steel 75, and the H-shaped steel 75 separates the slot 4 into different slot sections and casts them in sections to prevent the H-shaped steel 75 from deforming and shifting during the concrete pouring process, and to prevent bypass. After the joint box is spliced ​​into the designed length at the slot mouth, it is lowered to the bottom of the slot. After the joint box is lowered into place, the continuous wall concrete is poured in time.

[0072] S11.Conduit installation; Use a rack to lower the catheter to the specified depth according to the depth of the trench. The catheter should be 30 to 50 cm away from the bottom of the trench. A bladder is placed in the catheter to isolate the mud.

[0073] S12. Concrete pouring; In addition to the above-mentioned joint box before pouring, sandbag filling can also be used to assist in preventing concrete from bypassing. The sandbag filling adopts the steps of detection, trial filling, small amounts and multiple times, and layered compaction. The sandbags are filled to the top of the concrete pouring to prevent concrete from bypassing from above.

[0074] The concrete used is commercial underwater concrete with a compressive strength of C35 and a water-resistance grade of P6.

[0075] Concrete is poured by unloading concrete tank trucks directly into the discharge hopper, and then poured underwater through the lifting conduit. Double conduits are used for concrete pouring, and the maximum distance between conduits shall not exceed 4m. The joints are first assembled into 2-3 sections on the ground, and then hoisted into the slot hole by the derrick winch. The distance from the lower end of the conduit to the bottom of the slot is generally 300-500mm.

[0076] During the pouring process, the concrete pipe should be buried 2 to 6 meters in the concrete, and the pipe should be lifted as the pouring progresses.

[0077] S13. Pull out the connector box.

[0078] When the concrete in the trough has been poured for 3 hours, start to move the joint box, then lift it every three hours and observe the sinking of the protective box. 6 to 8 hours after the concrete pouring is completed, that is, after the concrete has finally set, pull out all the joint boxes at once and clean and clear them in time.

[0079] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A construction process for underground continuous walls in sensitive areas, used in scenes with abundant groundwater and many sensitive buildings, characterized in that: The following steps are involved: S1. Construction preparation and site layout; Sa2. Mud system setting; Sb2. Measurement and setting out; Sc1. Steel cage platform production; Sa3. Mud preparation; Sb3. Guide wall (2) construction; Sa4. Mud storage; Sb4. Foundation reinforcement; Sa5. Mud regeneration; Sb5. Trench excavation and inspection; Sa6. Mud recovery and separation; Sb6. Joint wall brushing and hole sweeping; Sa7. Slurry disposal; Sb7. Tank bottom treatment; Sc2. Steel bottom plate (6), steel cage (7) production; S8. Steel base plate (6) hoisting; S9. Lifting of steel cage (7); S10.Joint box hoisting; S11.Conduit installation; S12. Concrete pouring; S13. Pull out the connector box; In the Sb4. foundation reinforcement, reinforcement holes (3) are first drilled vertically downward at equal intervals on one side of the guide wall (2), and mud is sprayed in the reinforcement holes (3) in a 150° rotary spraying manner in the direction of the guide wall (2) to the bottom of the guide wall (2), and the depth of the reinforcement holes (3) is greater than the depth of the underground continuous wall.

2. The construction process of underground continuous wall in sensitive area according to claim 1 is characterized in that: When the foundation is reinforced as described in Sb4., the verticality of the reinforcement hole (3) is checked after it is drilled. If the verticality deviation exceeds 1 / 500, it is corrected. After the drilling is completed, the MJS main machine porous pipe is inserted into the hole with a lifting time of 25 minutes per meter, a mud flow rate of 90~110L / min, a mud pressure of 40MPa, and a main air pressure of 0.7MPa to form a central injection.

3. The construction process of underground continuous wall in sensitive area according to claim 2 is characterized in that: In the construction of the guide wall (2) described in Sb3, the guide wall (2) adopts a "┓┏" type. When the guide wall (2) is constructed, the guide wall (2) area is first excavated, the guide wall (2) steel bars are tied, the formwork is erected, and the guide wall (2) concrete is poured; after the guide wall (2) formwork is erected, a plurality of square timbers are placed between the guide wall (2) formworks for support, and the position of the underground continuous wall in the guide wall (2) is backfilled with clay soil. When the concrete strength of the guide wall (2) reaches 70% of the design strength, the described Sb5 can be carried out.

4. The construction process of underground continuous wall in sensitive area according to claim 1 is characterized in that: In the trenching excavation and inspection of Sb5, a trenching machine is used to dig the corresponding trench (4) along the guide wall (2). The trenching (4) is formed in the order of first the two sides and then the middle. After the trench (4) is formed, mud is added. After the trench (4) is formed, the depth is measured, and the vertical accuracy and axial width of the trench (4) are measured using an ultrasonic measuring instrument.

5. The construction process of underground continuous wall in sensitive area according to claim 1 is characterized in that: In the Sb5. trench excavation and inspection, after the trench (4) is excavated, a reinforcement groove (5) is excavated on both sides of the bottom of the trench (4) along the length direction; in the S8 steel bottom plate hoisting, the steel bottom plate (6) is placed at the bottom of the trench (4) along the length direction of the trench (4), and at the same time, the two sides of the steel bottom plate (6) are respectively extended into the reinforcement grooves (5) on both sides of the trench (4).

6. The construction process of underground continuous wall in sensitive area according to claim 5 is characterized in that: In the production of the steel bottom plate and the steel cage, the width of the steel bottom plate (6) is equal to the width of the groove (4) plus twice the width of the reinforcing groove (5), and the depth of the reinforcing groove (5) is not less than the width of the steel bottom plate (6).

7. The construction process of underground continuous wall in sensitive area according to claim 5, characterized in that: In the production of the steel bottom plate (6) and the steel cage (7), at least four pairs of steel hooks (63) are fixedly connected to the upper surface of each steel bottom plate (6), and the bent portions (631) in the same pair of steel hooks (63) are arranged opposite to each other and cross-overlapped to form a hooking area (632); two pairs of the four pairs of steel hooks (63) form a group, and the two groups of steel hooks (63) are evenly arranged in the length direction of the steel bottom plate (6); the two pairs of steel hooks (63) in the same group are symmetrically fixed at the positions on both sides of the length direction of the steel bottom plate (6); The height of the steel bar hook (63) is not greater than the width of the groove (4); The maximum spacing between any two of the steel bar hooks (63) in the same group is no greater than the width of the groove (4); two rows of bottom wall bars (74) are fixedly arranged at the bottom of the steel bar cage (7) along the length direction of the groove (4), and the two rows of bottom wall bars (74) are arranged vertically at intervals; each row of the bottom wall bars (74) corresponds to a steel bar hook (63) on one side of the steel bottom plate (6), and when the steel bar cage (7) is lowered into the groove (4), part of the bottom wall bars (74) are pressed into the hooking area (632) of the corresponding steel bar hook (63).

8. The construction process of underground continuous wall in sensitive area according to claim 7 is characterized in that: An H-shaped steel (75) is vertically welded to one end of the steel cage (7), and one end of the steel cage (7) extends into a vertical groove on one side of the H-shaped steel (75). Two opposite side walls of the vertical groove of the H-shaped steel (75) facing away from the steel cage (7) are vertically provided with sliding grooves (751), a bottom sealing box (752) is slidably installed in the sliding groove (751), a clearance groove (753) is provided at the bottom of the sliding groove (751), and the inner cavity of the sliding groove (751) passes through the H-shaped steel (75) through the clearance groove (753) and is connected to the reinforcement grooves (5) on both sides of the groove (4), and the depth of the clearance groove (753) is greater than the depth of the reinforcement groove (5); Blocking holes are provided at positions corresponding to the clearance grooves (753) on both sides of the bottom sealing box (752), and a blocking steel plate (754) is slidably connected in the blocking hole. A hydraulic cylinder (756) for pushing the blocking steel plate (754) is provided in the bottom sealing box (752); When the steel cage (7) is lowered to the bottom of the groove (4), the hydraulic cylinder (756) is driven to push the blocking steel plates (754) to extend out of the blocking holes, and then pass through the clearance groove (753) and insert into the inner wall of the reinforcement groove (5) until the blocking steel plates (754) are out of the bottom sealing box (752) and are engaged in the clearance groove (753), and then the bottom sealing box (752) is pulled out of the slide groove (751).

9. The construction process of underground continuous wall in sensitive area according to claim 1, characterized in that: Said Sa3. In the mud preparation, the mud includes bentonite, CMC and soda ash, and the weight ratio of each component is water: bentonite: CMC: soda ash = 100: (8-10): (0.1-0.3): (0.3-0.4); The preparation process is as follows: after the mixer is rotated with water, bentonite is evenly added, and then CMC, soda ash and water are taken out, and after being fully stirred, they are poured into the bentonite aqueous solution in the mixer and stirred evenly. After stirring, the mixture flows into the slurry storage tank and is tested after being dissolved for 24 hours. The relative density of the mud in the clay layer is 1.04~1.05g / cm3, the viscosity is 20~24S, and the sand content is less than 3%. The relative density of the mud applied to the sandy soil layer is 1.06~1.08g / cm3, the viscosity is 25~30S, and the sand content is less than 4%. The common detection indicators of the two are a colloid rate greater than 95%, a water loss of less than 30mL in 30min, a mud skin thickness of 1~3mm, a pH value of 8~9, an initial shear force of 2~3Pa, and a final shear force of 5~10Pa.

10. The construction process of underground continuous wall in sensitive area according to claim 1, characterized in that: In the Sa5. mud recovery and separation, mud at different depths in the trench is taken out during the trench bottom excavation construction, and the relative density, viscosity, sand content and pH value are tested. When the test is qualified, the mud is recovered to the gravity sedimentation tank. When the test is unqualified, it is restored to use after regeneration treatment. The regeneration treatment includes using bentonite to increase the stability value, using CMC to increase the viscosity, using soda ash to increase the pH value, using water to reduce the viscosity, using bentonite to increase the relative density, using water to reduce the relative density, using bentonite and CMC to increase the static shear force, using water to reduce the static shear force, using bentonite and CMC to reduce the water loss, and using bentonite and CMC to increase the colloid rate.

Images