Backfilling construction method for narrow fat groove of ultra-deep foundation pit
By using a combined backfill method of plain concrete and gravel grouting in a narrow fertilizer tank of ultra-deep foundation pit, combined with the fixing technology of hidden drainage systems and waterproof protection plates, the operation difficulty and bearing capacity of the traditional backfill method are solved. Leakage problem achieves cost-effective backfill effect and waterproof performance.
Patent Information
- Application Number
- CN202411552619.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-01
- Publication Date
- 2025-01-07
AI Technical Summary
In the narrow fertilizer trough of ultra-deep foundation pit, the traditional backfill method has problems such as difficult operation, insufficient bearing capacity, high cost and leakage of the basement side wall, and the waterproof protective plate and grouted steel pipe are easily damaged.
Using a combination of backfill of plain concrete and gravel grouting, a hidden drainage system is set up, and the waterproof protection plate and grouting steel pipe are fixed with non-cured rubber asphalt and super glue to ensure backfill density and waterproof performance, and to reserve holes and vibration compact machinery to improve the compactness of gravel.
It reduces the backfill cost, meets the anti-flood and impermeability requirements of the foundation, avoids the fall off of the waterproof protective plate and the damage of the grouted steel pipe, solves the problem of surface water and pressure-bearing water retention, and improves the backfill density and bearing capacity.
Smart Images
Figure CN119266249A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of building construction, and in particular to a backfill construction method for a narrow fertilizer trench in an ultra-deep foundation pit. Background Art
[0002] With the rapid development of my country's economy and the acceleration of urbanization, urban land is becoming increasingly scarce, land prices are gradually rising, and land utilization is getting higher and higher. The scale of urban ground and underground space development is getting larger and larger, with basements up to several floors. The depth of the basement outer wall and the foundation pit edge, i.e., the fertilizer trough, is deep and extremely narrow. The fertilizer trough is often equipped with foundation pit support structures such as replacement support plates. Therefore, the selection of fertilizer trough backfill materials and construction methods have become a major difficulty in on-site construction.
[0003] For ultra-deep and narrow fertilizer troughs, traditional plain soil backfilling is difficult to operate, the backfill density cannot be guaranteed, and the waterproof protection board and waterproof membrane are easily damaged during the backfilling process, and its bearing capacity cannot meet the requirements; the cost of using foam concrete backfilling is relatively low, but due to its light weight and low compressive strength, it cannot meet the bearing capacity requirements; when plain concrete backfilling is used, the cost is too high and the economy is poor. After comparing technical and economic options, under the premise of meeting the requirements of anti-floating and anti-seepage, the backfilling method using a combination of plain concrete and crushed stone grouting structure not only reduces the cost but also meets the requirements of foundation bearing capacity. Summary of the invention
[0004] Based on the deficiencies in the above-mentioned prior art, the technical problem to be solved by the present invention is to provide a construction method for backfilling narrow fertilizer troughs in ultra-deep foundation pits, which solves the problem of damage to waterproof membranes, waterproof protection plates, grouting steel pipes, and precipitation well casings during gravel backfilling. A hidden drainage system is set in the backfill structure to solve the problem of retention of surface water and pressurized water in the fertilizer troughs of ultra-deep foundation pits, and solves a series of problems such as the difficulty of operation, insufficient bearing capacity, high cost, and leakage of basement side walls of traditional backfilling methods.
[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical measures:
[0006] A method for backfilling a narrow fertilizer trough in an ultra-deep foundation pit comprises the following steps:
[0007] S1. After the basement structure is completed, the base is treated and the basement exterior wall waterproofing is carried out to ensure that the base is clean and dry; first, two coats of 2mm thick non-curing rubber asphalt are applied to the corners and an additional layer of 300mm width is laid, and then two coats of 2mm thick non-curing rubber asphalt are applied to the large surface and waterproofing membrane is laid;
[0008] S2. Layout and position the waterproof protection board and grouting steel pipe in advance, determine the installation position of the waterproof protection board, waterproof protection board nails and grouting steel pipe adhesive buckle on one side of the basement outer wall, and determine the installation position of the grouting steel pipe nail buckle and the casing of the dewatering well on one side of the underground continuous wall; the grouting steel pipe adhesive buckle is used to fix the grouting steel pipe and prevent the waterproof protection board from falling off. The number of waterproof protection board nails is not less than 6 per square meter, and waterproof protection board nails or grouting steel pipe adhesive buckles must be installed at the junction of the waterproof protection board; after positioning is completed, use strong glue to stick the waterproof protection board nails and grouting steel pipe adhesive buckle, and set one grouting steel pipe adhesive buckle every 600mm to ensure that the waterproof protection board nails and grouting steel pipe adhesive buckle are firmly pasted, and install the waterproof protection board;
[0009] S3. Pour the backfill concrete of the bottom fertilizer trough to the bottom of the replacement support plate at the negative second floor slab. The backfill concrete of the fertilizer trough is C20 plain concrete, which is poured in layers and sections. To ensure that the concrete at the bottom of the replacement support plate is poured densely, a hole with a diameter of 300 mm is reserved in the middle of the replacement support plate during construction. During the pouring of the backfill concrete of the fertilizer trough, the concrete at the bottom of the replacement support plate is poured from the reserved hole. During the pouring process, a vibrating rod is inserted into the reserved hole to ensure that the concrete is dense. A concrete test block is reserved during pouring;
[0010] S4. Drainage ditches and water collection wells are set up on one side of the underground continuous wall, and a water collection well is installed. A water collection well is set up every 40 meters. The slope of the drainage ditch from the outer wall of the basement to the underground continuous wall is adjusted to 5%, and the slope of the drainage ditch to the water collection wells on both sides is 3%; Use a level to determine the elevation of the fertilizer trough backfill concrete pouring, set up the formwork for the drainage ditch and the precipitation well, pour concrete, and remove the formwork after the concrete strength reaches 75%. Reserve concrete test blocks during pouring;
[0011] S5. Install the grouting steel pipe and the casing of the drainage well according to the layout. The bottom of the grouting steel pipe is the top of the fertilizer trough backfill concrete. The grouting steel pipe is continuously set at intervals of 2m on both sides of the basement outer wall and the underground continuous wall. The casing of the drainage well is installed along with the position of the water collection well; install the grouting steel pipe on one side of the basement outer wall, tighten the screws and nuts to make the grouting steel pipe firmly installed, and ensure that it will not fall off during the gravel backfill process; install the grouting steel pipe on one side of the underground continuous wall, first nail the grouting steel pipe nail buckle into the underground continuous wall, at an interval of 600mm, install the grouting steel pipe, and tighten the screws and nuts to make the grouting steel pipe firmly installed; install the drainage well casing, first nail the drainage well casing buckle into the underground continuous wall, at an interval of 1m, install the drainage well casing, tighten the screws and nuts to make the drainage well casing firmly installed, and the pipe openings of all grouting steel pipes and drainage well casings are higher than the top plate;
[0012] S6. The crushed stones required for backfilling the fertilizer trough are processed into the required particle size using the concrete fragments removed from the support in the foundation pit support system. The crushed stones are first backfilled to the bottom of the replacement support plate belt at the negative first floor slab. To ensure that the bottom of the replacement support plate belt is backfilled densely, a hole with a diameter of 300mm is reserved in the middle during the construction of the replacement support plate belt. After the bottom of the replacement support plate belt is backfilled from the reserved hole, a vibration compacting machine is used to compact the crushed stones at the bottom of the replacement support plate belt. The crushed stones are continued to be backfilled so that the top surface elevation of the crushed stones is 350mm lower than the natural ground. A vibration compacting machine is used to compact the surface of the crushed stones in the fertilizer trough.
[0013] S7. To ensure the quality of grouting and the compactness of crushed stone grouting, a top plate with a thickness of 350mm is set on the top of the crushed stone. Double-layer bidirectional steel bars are laid and C25 concrete is poured. The top plate has a slope of 3% from the outer wall of the basement to the natural ground, and the surface of the top plate is flush with the natural ground.
[0014] S8. Grouting starts when the strength of the top plate reaches 75%. Grouting is stopped when grout comes out from the plate seams or overflow holes of the top plate. The grouting sequence is plane interval grouting.
[0015] S9. Install the water pump for the precipitation well. The water pump is a high-lift automatic submersible pump. The water pump is installed in the casing of the precipitation well. When the water level reaches a certain height, it will automatically pump water to the municipal drainage pipe. The fertilizer tank backfill construction is completed;
[0016] S10. After the reserved concrete test block reaches 28 days old, a compressive strength test shall be carried out. The compressive strength assessment value shall be qualified if it reaches 20MPa. The foundation static load test shall be carried out 28 days after the completion of the crushed stone grouting construction. The number of test points shall be no less than 3 points, evenly distributed in the backfill area, and the bearing capacity characteristic value shall be based on the design requirements.
[0017] Furthermore, in step S1, the lap width of the long side of the waterproof membrane should be ≥80mm, the lap width of the short side should be ≥100mm, and the joints of the waterproof membrane should be staggered by no less than 500mm to avoid overlapping of multiple layers of joints and uneven laying of the membrane, ensuring that the waterproof layer forms an overall waterproof system.
[0018] Preferably, the grouting steel pipe is a steel pipe with a diameter of φ32mm and a wall thickness of 2.5mm; the precipitation well casing is a steel pipe with a diameter of φ200mm and a wall thickness of 2.5mm.
[0019] Preferably, in step S8, cement is P.O42.5, the parameter is 20%, the grouting water-cement ratio is controlled between 0.45 and 0.55, the grouting breakthrough pressure is 2.0 MPa, the normal grouting pressure is 0.2 to 0.3 MPa, and the termination pressure is controlled at 0.5 MPa in principle.
[0020] Furthermore, in step S8, the pipe openings of the grouting steel pipe and the dewatering well casing exceed the top plate by 300 mm.
[0021] From the above, after the basement structure construction is completed, the base is treated and the basement exterior wall waterproofing construction is carried out → After gluing the waterproof protection board nails and grouting steel pipe clips, install the waterproof protection board → Pour the bottom fertilizer trough backfill concrete (reserve test blocks) → Install the grouting steel pipe clips and precipitation well casing clips on one side of the underground continuous wall → Install the grouting steel pipes and precipitation well casings on both sides → Backfill the fertilizer trough with gravel to the designed elevation → Tie the steel bars of the fertilizer trough top plate and pour concrete → Grout the gravel backfill part → Install the precipitation well water pump → Compressive strength test and foundation static load test.
[0022] Compared with the existing traditional methods, the beneficial effects and advantages of the ultra-deep foundation pit narrow fertilizer trough backfill construction method of the present invention are:
[0023] 1. The traditional concrete backfill method is too expensive. Due to the deep foundation pit and the average width of 1.2m, the earth backfill is difficult to compact, and its deadweight cannot meet the anti-floating bearing capacity requirements. Foam concrete is relatively cheap and easy to construct, but its deadweight is light and cannot meet the anti-floating bearing capacity requirements. Therefore, a combined backfill method of C20 plain concrete backfilling the third negative layer and crushed stone plus grouting for the second and first negative layers is selected. The required crushed stone is processed into the required particle size using the concrete fragments supported by the foundation pit support system. This not only reduces the cost but also meets the anti-floating bearing capacity requirements.
[0024] 2. The traditional waterproof protection board is easy to fall off during the backfilling process. This application invents a method for fixing the waterproof protection board, which uses strong glue to fix the waterproof protection board nails. Before construction, the waterproof protection board and the waterproof protection board nails are arranged, which solves the problem of the waterproof protection board falling off.
[0025] 3. The backfilling method of crushed stone plus grouting requires burying the grouting pipe in advance. The present application invents a grouting steel pipe clip for fixing the grouting steel pipe without damaging the waterproof membrane.
[0026] 4. As the foundation pit is deep and the fertilizer tank is 17.65m deep, the pressure of the pressurized water is large, and there is pressurized water and surface water in the fertilizer tank, a hidden drainage system is set up. A through drainage ditch with a slope of 3% is set up near the underground continuous wall at the junction of plain concrete and crushed stone grouting, and water collection wells are evenly set up. At the same time, drainage equipment is installed in the water collection wells to carry out organized drainage, solving the problem of surface water and pressurized water retention.
[0027] 5. In order to ensure that the lower part of the fertilizer trough's supporting plate belt is backfilled densely, a through hole is reserved in the middle of the supporting plate belt as a transportation channel for the backfill material, while ensuring structural safety. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the drawings of the embodiment are briefly introduced below.
[0029] Figure 1 It is a schematic diagram of the structure of the waterproof protection plate, the waterproof protection plate nails and the grouting steel pipe adhesive buckle;
[0030] Figure 2 This is a structural schematic diagram of the grouting pipe and the casing of the dewatering well on one side of the underground continuous wall;
[0031] Figure 3 This is a schematic diagram of the water source in the fertilizer tank;
[0032] Figure 4 Schematic diagram for setting up drainage ditches and precipitation wells;
[0033] Figure 5 This is a schematic diagram of the completion of the concrete pouring of the negative third layer fertilizer trough and a large-scale drawing of the drainage ditch and precipitation well;
[0034] Figure 6 This is a schematic diagram of the installation of grouting pipes and dewatering well casings;
[0035] Figure 7 Complete schematic diagram for gravel backfill;
[0036] Figure 8 This is a schematic diagram of the completion of the top plate reinforcement binding;
[0037] Fig. 9 This is a schematic diagram of the completion of the fertilizer tank backfill construction.
[0038] In the figure: 1- waterproof protection plate; 2- waterproof protection plate nails; 3- grouting steel pipe; 4- grouting steel pipe adhesive buckle; 5- grouting steel pipe nail buckle; 6- replacement support plate belt; 7- dewatering well casing; 8- dewatering well casing buckle; 9- steel bars; 10- top plate. DETAILED DESCRIPTION
[0039] like Figure 1-Figure 9 As shown, the ultra-deep foundation pit narrow fertilizer trough backfill construction method of the present invention comprises the following steps:
[0040] Step 1: After the basement structure is completed, the base is treated and the basement exterior wall waterproofing is carried out to ensure that the base is clean and dry. First, apply two layers of 2mm thick non-curing rubber asphalt on the corners and lay an additional layer with a width of 300mm. Then apply two layers of 2mm thick non-curing rubber asphalt on the large surface and lay waterproof membrane. The long side overlap width of the waterproof membrane should be ≥80mm, and the short side overlap width should be ≥100mm. The joints of the waterproof membrane should be staggered by no less than 500mm to avoid overlapping of multiple joints and uneven laying of the membrane, ensuring that the waterproof layer forms an overall waterproof system.
[0041] Step 2: Arrange and position the waterproof protection board 1 and the grouting steel pipe 3 in advance. The thickness of the waterproof protection board 1 is generally 50 mm. Determine the installation position of the waterproof protection board 1, the waterproof protection board nails 2 and the grouting steel pipe adhesive buckle 4 on one side of the basement outer wall. For details, see Figure 1 , determine the installation position of the grouting steel pipe nail buckle 5 and the drainage well casing 7 on one side of the underground continuous wall, see Figure 2 . The grouting steel pipe adhesive buckle 4 is used to fix the grouting steel pipe 3 and prevent the waterproof protection plate 1 from falling off. The number of waterproof protection plate nails 2 is no less than 6 per square meter, and the waterproof protection plate nails 2 or grouting steel pipe adhesive buckles 4 need to be installed at the intersection of the waterproof protection plate 1. After positioning is completed, use strong glue to stick the waterproof protection plate nails 2 and the grouting steel pipe adhesive buckle 4. The grouting steel pipe adhesive buckle 4 is set every 600mm to ensure that the waterproof protection plate nails 2 and the grouting steel pipe adhesive buckle 4 are firmly pasted, and then install the waterproof protection plate 1.
[0042] Step 3: pour the bottom fertilizer tank backfill concrete to the bottom of the replacement support plate belt 6 at the negative second floor slab. The fertilizer tank backfill concrete is C20 plain concrete, which is poured in layers and sections. To ensure that the concrete at the bottom of the replacement support plate belt 6 is poured densely, a hole with a diameter of 300mm is reserved in the middle of the replacement support plate belt 6 during construction. For details, see Figure 2 A large-scale drawing of the middle replacement support plate belt 6. During the pouring of the fertilizer trough backfill concrete, the concrete at the bottom of the replacement support plate belt 6 is poured from the reserved holes. During the pouring process, a vibrating rod is inserted into the reserved hole to ensure that the concrete is dense, and a concrete test block is reserved during pouring.
[0043] Step 4: Due to the deep depth of the foundation pit, the depth of the fertilizer tank is 17.65m, the pressure of the pressurized water is relatively large, and there is pressurized water and surface water in the fertilizer tank. Figure 3 Therefore, drainage ditches (200mm*200mm) and water collection wells (200mm*200mm*400mm deep) are set on one side of the underground continuous wall and a water pump is installed. A water collection well is set every 40 meters. The drainage ditch is sloped from the outer wall of the basement to the underground continuous wall with a slope of 5%. The drainage ditch is sloped to the water collection wells on both sides with a slope of 3%. For details, see Figure 4 Use a level to determine the elevation of the fertilizer tank backfill concrete pouring, set up the formwork for the drainage ditch and precipitation well, pour the concrete, and remove the formwork after the concrete strength reaches 75%. Figure 5 , reserve concrete test blocks during pouring.
[0044] Step 5: Install the grouting steel pipe 3 and the dewatering well casing 7 according to the layout. Figure 6The grouting steel pipe 3 is a steel pipe with a diameter of φ32mm and a wall thickness of 2.5mm. The bottom of the grouting steel pipe 3 is the top of the fertilizer trough backfill concrete. The grouting steel pipe 3 is continuously arranged at intervals of 2m on both sides of the basement outer wall and the underground continuous wall. The precipitation well casing 7 is a steel pipe with a diameter of φ200mm and a wall thickness of 2.5mm. The precipitation well casing 7 is installed along with the position of the water collection well. Install the grouting steel pipe 3 on one side of the basement outer wall, tighten the screws and nuts to ensure that the grouting steel pipe 3 is firmly installed to ensure that it will not fall off during the gravel backfilling process; install the grouting steel pipe 3 on one side of the underground continuous wall, first nail the grouting steel pipe nail buckle 5 into the underground continuous wall, at an interval of 600mm, install the grouting steel pipe 3, tighten the screws and nuts to ensure that the grouting steel pipe 3 is firmly installed; install the precipitation well casing 7, first nail the precipitation well casing buckle 8 into the underground continuous wall, at an interval of 1m, install the precipitation well casing 7, tighten the screws and nuts to ensure that the precipitation well casing 7 is firmly installed, and the pipe openings of all grouting steel pipes 3 and precipitation well casings 7 are higher than the top plate 10, and the height exceeding the top plate 10 is 300mm.
[0045] Step 6: The crushed stones required for fertilizer tank backfill are processed into the required particle size using the concrete fragments removed from the support in the foundation pit support system. The crushed stone particle size is ≤25mm. The crushed stones are first backfilled to the bottom of the replacement support plate belt 6 at the negative first floor slab. To ensure that the bottom of the replacement support plate belt 6 is backfilled densely, a hole with a diameter of 300mm is reserved in the middle during the construction of the replacement support plate belt 6. After the bottom of the replacement support plate belt 6 is backfilled from the reserved hole, a vibration compacting machine is used to compact the crushed stones at the bottom of the replacement support plate belt 6, and the crushed stones are continued to be backfilled so that the top surface elevation of the crushed stones is 350mm lower than the natural ground. For details, see Figure 7 , use vibration compaction machinery to compact the surface of the gravel in the fertilizer trough.
[0046] Step 7: To ensure the quality of grouting and the compactness of the crushed stone, a top plate 10 is set on the top of the crushed stone. The thickness of the top plate 10 is 350mm. Double-layer bidirectional steel bars 9 are laid. The steel bars 9 are made of steel mesh with a diameter of 12@250. For details, see Figure 8 , pour C25 concrete, set a 3% slope on the top plate 10 from the outer wall of the basement to the natural ground, and the surface of the top plate 10 is flush with the natural ground.
[0047] Step 8, grouting starts after the strength of the top plate 10 reaches 75%. P.O42.5 cement is used, the parameter is 20%, the grouting water-cement ratio is controlled between 0.45 and 0.55, the grouting breakthrough pressure is about 2.0 MPa, the normal grouting pressure is about 0.2 to 0.3 MPa, and the termination pressure is controlled at 0.5 MPa in principle. Grouting is terminated when grout comes out of the plate seams or overflow holes of the top plate 10. The grouting sequence is plane interval grouting.
[0048] Step 9: Install the water pump for the precipitation well. The water pump is a high-lift automatic submersible pump. The water pump is installed in the casing of the precipitation well. When the water level reaches a certain height, it will automatically pump water to the municipal drainage pipe. The fertilizer tank backfill construction is completed. For details, see Fig. 9 .
[0049] Step 10: After the reserved concrete test block reaches 28 days old, a compressive strength test is carried out. The compressive strength assessment value is qualified when it reaches 20MPa. After the gravel and grouting construction is completed, a foundation static load test is carried out 28 days later. The number of test points shall be no less than 3 points, evenly distributed in the backfill area, and the bearing capacity characteristic value shall be based on the design requirements.
[0050] The above description is only a specific implementation of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be understood by anyone familiar with the technology within the technical scope disclosed by the present invention should be included in the scope of the present invention.
Claims
1. A method for backfilling a narrow fertilizer trough in an ultra-deep foundation pit, characterized in that: The following steps are involved: S1. After the basement structure is completed, the basement should be treated and the basement exterior wall waterproofing should be carried out to ensure that the basement is clean and dry; first, two coats of non-curing rubber asphalt should be applied to the corners and an additional layer should be laid, and then two coats of non-curing rubber asphalt should be applied to the large surface and waterproofing membrane should be laid; S2, the waterproof protection plate (1) and the grouting steel pipe (3) are arranged and positioned in advance, and the installation positions of the waterproof protection plate (1), the waterproof protection plate nails (2) and the grouting steel pipe adhesive buckle (4) on one side of the basement outer wall are determined, and the installation positions of the grouting steel pipe nail buckle (5) and the dewatering well casing (7) on one side of the underground continuous wall are determined; the grouting steel pipe adhesive buckle (4) is used to fix the grouting steel pipe (3) and prevent the waterproof protection plate (1) from falling off. The number of waterproof protection plate nails (2) is not less than 6 per square meter, and the waterproof protection plate nails (2) or grouting steel pipe adhesive buckle (4) need to be installed at the intersection of the waterproof protection plate (1); after the positioning is completed, the waterproof protection plate nails (2) and the grouting steel pipe adhesive buckle (4) are glued with strong glue, and the grouting steel pipe adhesive buckle (4) is set every 600mm to ensure that the waterproof protection plate nails (2) and the grouting steel pipe adhesive buckle (4) are firmly glued, and the waterproof protection plate (1) is installed; S3, pouring the backfill concrete of the bottom fertilizer trough to the bottom of the replacement support plate belt (6) at the negative second floor slab. The backfill concrete of the fertilizer trough is C20 plain concrete, which is poured in layers and sections. In order to ensure that the concrete at the bottom of the replacement support plate belt (6) is poured densely, a hole with a diameter of 300 mm is reserved in the middle of the replacement support plate belt (6) during the construction of the replacement support plate belt (6). During the pouring of the backfill concrete of the fertilizer trough, the concrete at the bottom of the replacement support plate belt (6) is poured from the reserved hole. During the pouring process, a vibrating rod is inserted into the reserved hole to ensure that the concrete is dense. During the pouring process, a concrete test block is reserved; S4. Drainage ditches and water collection wells are set up on one side of the underground continuous wall, and a water collection well is installed. A water collection well is set up every 40 meters. The slope of the drainage ditch from the outer wall of the basement to the underground continuous wall is adjusted to 5%, and the slope of the drainage ditch to the water collection wells on both sides is 3%; Use a level to determine the elevation of the fertilizer trough backfill concrete pouring, set up the formwork for the drainage ditch and the precipitation well, pour concrete, and remove the formwork after the concrete strength reaches 75%. Reserve concrete test blocks during pouring; S5. Install the grouting steel pipe (3) and the drainage well casing (7) according to the layout. The bottom of the grouting steel pipe (3) is the top of the fertilizer trough backfill concrete. The grouting steel pipe (3) is continuously installed at intervals of 2m on both sides of the basement outer wall and the underground continuous wall. The drainage well casing (7) is installed along with the water collection well position; install the grouting steel pipe (3) on one side of the basement outer wall, tighten the screws and nuts to ensure that the grouting steel pipe (3) is firmly installed to ensure that it will not fall off during the gravel backfill process; install the grouting steel pipe (3) on one side of the underground continuous wall. ), first nail the grouting steel pipe nail buckle (5) into the underground continuous wall at an interval of 600mm, install the grouting steel pipe (3), and tighten the screws and nuts to make the grouting steel pipe (3) firmly installed; installation of the precipitation well casing (7), first nail the precipitation well casing buckle (8) into the underground continuous wall at an interval of 1m, install the precipitation well casing (7), and tighten the screws and nuts to make the precipitation well casing (7) firmly installed, and the pipe openings of all grouting steel pipes (3) and precipitation well casings (7) are higher than the top plate (10); S6. The crushed stones required for backfilling the fertilizer trough are processed into the required particle size using the concrete fragments removed from the support in the foundation pit support system. The crushed stones are first backfilled to the bottom of the replacement support plate belt (6) at the negative first floor slab. To ensure that the bottom of the replacement support plate belt (6) is backfilled densely, a hole with a diameter of 300 mm is reserved in the middle during the construction of the replacement support plate belt (6). After the bottom of the replacement support plate belt (6) is backfilled from the reserved hole, a vibration compacting machine is used to compact the crushed stones at the bottom of the replacement support plate belt (6). The crushed stones are continued to be backfilled so that the top surface elevation of the crushed stones is 350 mm lower than the natural ground. The surface of the crushed stones in the fertilizer trough is compacted by a vibration compacting machine. S7. A top plate (10) is set on the top of the gravel, double-layer bidirectional steel bars (9) are laid, and C25 concrete is poured. The top plate (10) is set with a slope of 3% from the outer wall of the basement to the natural ground, and the surface of the top plate (10) is flush with the natural ground; S8, grouting starts after the strength of the top plate (10) reaches 75%, and grouting is stopped when grout is seen from the plate seams or overflow holes of the top plate (10). The grouting sequence is plane interval grouting; S9. Install the water pump for the precipitation well. The water pump is a high-lift automatic submersible pump. The water pump is installed in the casing of the precipitation well. When the water level reaches a certain height, it will automatically pump water to the municipal drainage pipe. The fertilizer tank backfill construction is completed; S10. After the reserved concrete test block reaches 28 days old, a compressive strength test shall be carried out. The compressive strength assessment value shall be qualified if it reaches 20MPa. The foundation static load test shall be carried out 28 days after the completion of the crushed stone grouting construction. The number of test points shall be no less than 3 points, evenly distributed in the backfill area, and the bearing capacity characteristic value shall be based on the design requirements.
2. The method for backfilling a narrow fertilizer trough in an ultra-deep foundation pit according to claim 1 is characterized in that: In step S1, the overlap width of the long side of the waterproof membrane should be ≥80mm, the overlap width of the short side should be ≥100mm, and the joints of the waterproof membrane should be staggered by no less than 500mm to avoid overlapping of multiple layers of joints and uneven laying of the membrane, ensuring that the waterproof layer forms an overall waterproof system.
3. The method for backfilling a narrow fertilizer trough in an ultra-deep foundation pit according to claim 1 is characterized in that: The grouting steel pipe (3) is a steel pipe with a diameter of φ32 mm and a wall thickness of 2.5 mm; the precipitation well casing (7) is a steel pipe with a diameter of φ200 mm and a wall thickness of 2.5 mm.
4. The method for backfilling a narrow fertilizer trough in an ultra-deep foundation pit according to claim 1 is characterized in that: In step S8, cement P.O42.5 is used, the parameter is 20%, the grouting water-cement ratio is controlled between 0.45 and 0.55, the grouting breakthrough pressure is 2.0 MPa, the normal grouting pressure is 0.2 to 0.3 MPa, and the termination pressure is controlled at 0.5 MPa in principle.
5. The method for backfilling a narrow fertilizer trough in an ultra-deep foundation pit according to claim 1 is characterized in that: In step S8, the pipe openings of the grouting steel pipe (3) and the dewatering well casing (7) exceed the top plate (10) by 300 mm.