A method for constructing foundation pit retaining walls and a water control structure for foundation pit retaining walls.

Abstract

This invention relates to a construction method for foundation pit retaining walls and a water control structure for foundation pit retaining walls. The construction method includes the following steps: excavating a retaining wall pre-embedded trench at the boundary of the foundation pit to be excavated; after the excavation of the retaining wall pre-embedded trench is completed, sinking several sand-free permeable retaining walls into the retaining wall pre-embedded trench to form a retaining structure surrounding the area of ​​the foundation pit to be excavated; within the retaining structure, excavating the foundation pit from the top elevation to the bottom elevation to form a foundation pit enclosed by the retaining structure. The advantages of this invention are: it can control groundwater around the foundation pit more quickly and effectively. Compared with traditional processes, it can avoid continuous groundwater seepage causing quicksand and slope collapse, ensure the quality of foundation pit slope formation, avoid the risk of secondary water leakage after the retaining wall is removed, and balance foundation pit formation and long-term water control. At the same time, the prefabricated retaining walls can be recycled and reused after dismantling, reducing one-time material input, simplifying construction procedures, and controlling project costs.

Description

Technical Field

[0001] This invention belongs to the field of foundation pit support construction technology, specifically relating to a foundation pit support construction method and a foundation pit support water control structure. Background Technology

[0002] Groundwater control is a common technical challenge in underground civil engineering construction during foundation pit excavation. Currently, three common treatment methods are lightweight well points, perimeter manholes, and sheet piles for water sealing. Well points and manholes can quickly drain groundwater, while sheet piles can temporarily seal seepage and meet the needs of short-term excavation operations.

[0003] However, all three conventional treatment methods mentioned above have significant shortcomings in actual construction. Lightweight wellpoint dewatering and perimeter well dewatering are both methods of internal groundwater extraction. Even if groundwater within the pit area is pre-drained, during the subsequent excavation phase, the surrounding aquifers will continue to replenish the groundwater laterally. Residual groundwater within the soil will continuously seep out from the excavation slope, and this seepage disturbance can easily induce quicksand and slope collapse, making it impossible to stably maintain the designed slope shape of the pit and delaying the construction period. Sheet piles only rely on physical barriers to block water; they cannot release the groundwater pressure accumulated in the soil surrounding the pit sidewalls. After the sheet piles are removed, the previously confined and pressurized groundwater loses its restraint and is highly susceptible to seepage again, posing a seepage hazard to subsequent structural construction.

[0004] In summary, existing dewatering and water-stopping technologies either fail to prevent the continuous seepage of groundwater in the later stages, which can easily lead to slope instability, or they can only temporarily isolate water without releasing the external water and soil pressure. Neither of these technologies can meet the construction requirements of both foundation pit formation and long-term water control. Summary of the Invention

[0005] This invention provides a method for constructing foundation pit retaining walls and a water control structure for foundation pit retaining walls, which can solve the problem in the prior art that it is difficult to simultaneously meet the construction requirements of foundation pit formation and long-term water control.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for constructing a foundation pit retaining structure, comprising the following steps: Excavate retaining wall pre-embedded trenches at the boundary of the foundation pit to be excavated. After the excavation of the retaining wall pre-embedded trenches is completed, sink several sand-free permeable retaining walls into the retaining wall pre-embedded trenches to form a retaining structure surrounding the foundation pit area to be excavated. Within the retaining structure, the foundation pit is excavated from the top elevation to the bottom elevation, forming a foundation pit enclosed by the retaining structure. During the excavation process, support rods are installed between the sand-free permeable retaining walls to prevent the retaining structure from collapsing. After the groundwater outside the foundation pit seeps into the foundation pit through the retaining structure, the water in the foundation pit is continuously pumped out and drained until the seepage around the pit is lower than the construction allowable limit. The retaining structure is removed, and the foundation pit is sloped to form a slope surface, thus completing the construction of the foundation pit.

[0007] Preferably, the method further includes: after sinking the sand-free permeable retaining wall into the pre-embedded trench of the retaining wall, filling the pre-embedded trench of the retaining wall and the outside of the sand-free permeable retaining wall with filter material; the filter material is a fragmented material with a water permeability not less than that of the sand-free permeable retaining wall.

[0008] Preferably, the sand-free permeable retaining wall includes a straight retaining wall and a corner retaining wall; the straight retaining wall is a straight rectangular plate; the corner retaining wall is an L-shaped rectangular plate, and the straight retaining wall and the corner retaining wall are spliced ​​together to form a complete enclosure outline.

[0009] Preferably, it further includes: providing connectors between adjacent sand-free permeable retaining walls to splice and fix adjacent sand-free permeable retaining walls.

[0010] Preferably, the connecting member is an I-beam, and two adjacent sand-free permeable retaining walls are respectively fixedly connected to the grooves formed on both sides of the web of the I-beam.

[0011] Preferably, it further includes: fixing a bracket to the inner side of the sand-free permeable retaining wall at the position of the I-beam flange corresponding to the connector; the support rod is fixedly installed on the bracket.

[0012] Preferably, the bracket is a right-angled triangle structure and is connected to the support rod and the I-beam through the two right-angled sides respectively.

[0013] This invention also discloses a water control structure for foundation pit protection, comprising several sand-free permeable retaining walls, which are connected end to end to form a retaining structure adapted to the size of the foundation pit; a connector is provided between any two adjacent sand-free permeable retaining walls, and each connector is used to splice and fix the sand-free permeable retaining walls; a support rod is provided between the sand-free permeable retaining walls, and the support rod is used to support the retaining structure to prevent it from collapsing.

[0014] Preferably, the connecting member is an I-beam, and two adjacent sand-free permeable retaining walls are respectively fixedly connected to the grooves formed on both sides of the web of the I-beam.

[0015] Compared to existing technologies, this invention pre-embeds sand-free permeable retaining walls around the foundation pit. The perforated pores within the walls allow groundwater to seep directionally into the pit, while continuous pumping gradually releases groundwater pressure from the surrounding strata. Once the pressure is fully released, the retaining walls are removed, and slope trimming is carried out. The core logic is to increase the permeable surface area, effectively turning the entire foundation pit into a large well, enabling faster and more effective control of groundwater around the pit. Compared to traditional methods, this avoids continuous groundwater seepage that could cause quicksand and slope collapse, ensuring the quality of the foundation pit slope formation, mitigating the risk of secondary water leakage after the retaining walls are removed, and balancing foundation pit formation with long-term water control. Furthermore, the prefabricated retaining walls can be recycled and reused after dismantling, reducing one-time material costs, meeting green construction requirements, simplifying construction procedures, and controlling project costs. Attached Figure Description

[0016] Figure 1 This is a flowchart of the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure at the foundation pit of the present invention; Figure 3 This is a top view of the foundation pit of the present invention; Figure 4 This is a schematic diagram of the straight plate retaining wall of the present invention; Figure 5 This is a schematic diagram of the corner retaining wall of the present invention; Figure 6 This is a schematic diagram of the sand-free permeable retaining wall splicing structure of the present invention; Figure 7 This is a schematic diagram of the support rod installation structure of the present invention.

[0017] In the diagram: 1. Sand-free permeable retaining wall; 101. Straight slab retaining wall; 1011. Sand-free permeable slab; 1012. Steel mesh; 1013. Structural steel reinforcement; 1014. Lifting hook; 102. Corner retaining wall; 2. Foundation pit; 3. Top elevation of pit; 4. Bottom elevation of pit; 5. Groundwater level; 6. Embedded trench for retaining wall; 7. Slope of pit; 8. Connecting parts; 9. Supporting rods; 10. Bracket. Detailed Implementation

[0018] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] like Figures 1 to 3 As shown, the present invention provides a method for constructing a foundation pit retaining structure, comprising the following steps: Excavate a retaining wall pre-embedded trench 6 at the boundary of the foundation pit 2 to be excavated. After the excavation of the retaining wall pre-embedded trench 6 is completed, sink several sand-free permeable retaining walls 1 into the retaining wall pre-embedded trench 6 to form a retaining structure surrounding the foundation pit area to be excavated. Within the retaining structure, the foundation pit 2 is excavated from the top elevation 3 to the bottom elevation 4, forming the foundation pit 2 enclosed by the retaining structure. During the excavation process, support rods 9 are installed between the sand-free permeable retaining walls 1 to prevent the retaining structure from collapsing; After the groundwater outside the foundation pit 2 seeps into the foundation pit 2 through the retaining structure, the water in the foundation pit 2 is continuously pumped out and drained until the seepage around the pit is lower than the construction allowable limit. The retaining structure is removed, and the slope of the foundation pit 2 is repaired to form the pit slope 7, thus completing the construction of the foundation pit 2.

[0020] This invention also provides a foundation pit retaining structure for water control, comprising several sand-free permeable retaining walls 1, which are connected end-to-end to form a retaining structure adapted to the size of the foundation pit; a connector 8 is provided between any two adjacent sand-free permeable retaining walls 1, and each connector 8 is used to splice and fix the sand-free permeable retaining wall 1; a support rod 9 is provided between the sand-free permeable retaining walls 1, and the support rod 9 is used to support the retaining structure to prevent it from collapsing. The connector 8 is an I-beam, and two adjacent sand-free permeable retaining walls 1 are respectively fixedly connected to the grooves formed on both sides of the web of the I-beam.

[0021] Specifically, foundation pit 2 can be the pit excavated for foundation construction, or it can be a localized sinking area during foundation pit construction, such as elevator shaft pits, sump pits, structural slab drop pits, etc. It is the core construction element for groundwater control and shaping in this invention. When setting it up, the excavation boundary and depth must be strictly determined according to the design elevation to ensure precise connection with the main foundation pit construction system. It should be noted that foundation pit 2 must be excavated only after the sand-free permeable retaining wall 1 retaining system is formed to avoid water seepage, quicksand, and slope collapse problems caused by early excavation.

[0022] The retaining wall pre-embedded trench 6 is a dedicated installation reference trench for the sand-free permeable retaining wall 1. Its main function is to precisely define the layout position, burial depth, and installation range of the sand-free permeable retaining wall 1, providing a working basis for the sinking and installation of the retaining wall and the orderly enclosure layout. During installation, it must be excavated along the outer contour line of the foundation pit 2, ensuring the trench line is straight and its direction conforms to the contour of the foundation pit enclosure. It should be noted that after the trench excavation is completed, the bottom of the trench must be flat and free of protruding debris to prevent the retaining wall from tilting or becoming suspended after sinking, ensuring the stability of the overall enclosure structure. The retaining wall pre-embedded trench 6 should be at least 0.5 meters deeper than the foundation pit 2, so that the bottom of the sand-free permeable retaining wall 1 is lower than the bottom elevation 4 of the foundation pit 2, thus constraining the bottom of the sand-free permeable retaining wall 1 and, together with the support rods 9, ensuring the stability of the sand-free permeable retaining wall 1 after the foundation pit 2 is excavated.

[0023] The sand-free permeable retaining wall 1 is the core water control and retaining component of this invention. It serves a dual function of lateral soil retention and water permeability, both enclosing the soil around the foundation pit 2 and preventing soil collapse during excavation, while also using its permeability to evenly guide groundwater from the outer strata into the pit, thus slowly releasing the surrounding soil and water pressure. The main body of this component is a sand-free permeable slab 1011, made of sand-free concrete. It relies on the natural interconnected pores between the aggregates to form permeable channels, while also possessing sufficient compressive strength to resist lateral soil pressure. The permeable slab 1011 is internally reinforced with steel mesh 1012 and structural steel bars 1013. The steel mesh 1012, with a specification of 40×70×2.0mm, is evenly laid inside the slab to improve the overall integrity and crack resistance of the retaining wall, preventing the permeable slab from cracking under stress and the pores from deforming and becoming clogged. The structural steel bars 1013 are made of Ф12 or Ф14 steel bars, neatly arranged at 0.5m intervals, further strengthening the vertical and lateral load-bearing capacity of the retaining wall and ensuring the structural stability of the deep-buried support. During installation, the upper end of the structural steel bars 1013 extends out of the permeable slab 1011 and is bent to form a lifting hook 1014, specifically used for the overall lifting, placement, and subsequent extraction and recovery of the retaining wall, greatly improving the ease of construction. It should be noted that after the permeable slab 1 is sunk and installed, it must form a complete closed loop of enclosure without gaps or breaks to prevent localized seepage dead zones. This component can be adapted to various structural forms such as straight plates and corners according to the outline of the foundation pit 2, and is suitable for foundation pit layouts of different specifications such as square and rectangular.

[0024] Support members 9 are temporary internal support components used during excavation. They are mainly used to provide lateral support and restraint to the inner sand-free permeable retaining wall 1, counteracting the lateral earth pressure generated by the outer soil, preventing deformation, displacement, and overturning of the retaining wall, and ensuring the overall stability of the retaining structure throughout the excavation process. They must be installed synchronously with the top-down excavation progress of the foundation pit 2, with support provided as excavation progresses. The spacing should be matched to the excavation depth: when the pit depth is less than 3 meters, only one layer of support members 9 is installed at a depth of 0.5 meters; when the pit depth is greater than 3 meters, one layer of support members 9 is installed every 2.5 to 3 meters along the depth direction. It should be noted that the support members 9 must be firmly attached to the inner side of the retaining wall, with uniform force distribution, ensuring the continuity and reliability of the overall support system and adapting to the support force requirements of different excavation depths.

[0025] Slope 7 of the pit body is the final structural slope after the completion of the foundation pit 2 construction. It is formed by extending and trimming outward at a 45-degree angle, which can regulate the shape of the foundation pit, stabilize the loose soil on the pit side, and provide a flat, dense, stable and reliable construction base for subsequent slope bedding layer pouring, waterproofing paving, protective layer construction and structural base slab construction, ensuring the quality of subsequent underground structure construction. The slope trimming work should be carried out only after the groundwater pressure has been completely released and the sand-free permeable retaining wall 1 has been completely removed. It should be noted that the slope trimming process must strictly adhere to the designed 45-degree slope to ensure a flat slope and dense soil, avoiding the potential risks of soil loosening, secondary seepage and collapse later.

[0026] In order to achieve the purpose of filtering and intercepting groundwater, preventing silt and fine impurities from clogging the sand-free permeable retaining wall, and ensuring the continuous smooth flow of groundwater seepage channels, preferably, the method further includes: after the sand-free permeable retaining wall 1 is sunk into the retaining wall pre-embedded trench 6, filling the pre-embedded trench 6 and the outside of the sand-free permeable retaining wall with filter material; the filter material is a fragmented material with a water permeability not less than that of the sand-free permeable retaining wall 1.

[0027] Specifically, after the sand-free permeable retaining wall 1 is sunk into the pre-embedded trench 6, filter media is filled in. The fragmented filter media can physically filter the flowing groundwater, effectively intercepting impurities such as silt and fine soil particles carried in the water, preventing impurities from entering the interconnecting pores of the sand-free permeable retaining wall and causing blockage, ensuring that the retaining wall maintains good permeability performance for a long time. At the same time, the permeability of the filter media is no less than that of the sand-free permeable retaining wall, and the gaps between its particles can form a smooth seepage path, without blocking the normal flow of groundwater. It can continuously guide groundwater from the outer strata into the foundation pit to release water pressure, effectively solving the problems of poor groundwater drainage, slope seepage, and secondary leakage in traditional processes. The filter media is filled inside the pre-embedded trench 6 and outside the sand-free permeable retaining wall 1. Its core purpose is to filter groundwater, intercept silt and fine particulate impurities in the water, and prevent impurities from accumulating and clogging the permeable pores of the sand-free permeable retaining wall. The selected materials should be hard, fragmented materials such as crushed stone and pebbles, and the overall permeability should be no less than that of a sand-free permeable retaining wall. Layered backfilling should be used during construction to ensure uniform distribution of the filter media. It is important to note that materials that are easily migrated with water flow, such as silt and fine sand, should not be used as filter media to prevent the filter media itself from being carried into the retaining wall pores by the water flow.

[0028] like Figures 4 to 5 As shown, in order to achieve complete protection of foundation pits with different shapes and avoid seepage and slope collapse caused by gaps in the protection, preferably, the sand-free permeable retaining wall 1 includes a straight retaining wall 101 and a corner retaining wall 102; the straight retaining wall 101 is a straight rectangular plate; the corner retaining wall 102 is an L-shaped rectangular plate, and the straight retaining wall 101 and the corner retaining wall 102 are spliced ​​together to form a complete protection outline.

[0029] Specifically, the combination of straight retaining walls and corner retaining walls can flexibly adapt to various conventional foundation pit outlines such as squares and rectangles. It can quickly form a continuous and uninterrupted closed retaining system, completely eliminating dead corners in the retaining structure, effectively preventing the collapse of the surrounding soil, and ensuring that groundwater seeps evenly along the retaining wall, avoiding localized concentrated seepage, thus strengthening the soil retention and water guiding effects from a structural perspective.

[0030] Straight retaining wall 101 is a fundamental component forming the main retaining structure, primarily used for soil retention and water permeability along the straight sections of the foundation pit. The material is consistent with the overall no-fines permeable retaining wall, constructed using no-fines concrete, and is a straight rectangular plate structure. During installation, it must be arranged sequentially along the straight boundary of the foundation pit to ensure a straight line. It is important to note that the ends of straight retaining wall 101 must precisely align with adjacent components, without any misalignment or gaps. This component is a standard, universal structure and can be cut or customized to different sizes according to the length of the straight section of the foundation pit. Corner retaining wall 102 is used for connecting retaining structures at the corners of the foundation pit, achieving a smooth transition between adjacent straight retaining walls 101 and ensuring a complete closed retaining contour. The material is also no-fines concrete, with an overall design of an L-shaped rectangular plate structure, suitable for right-angle corner conditions in foundation pits. During installation, it must be precisely positioned at the corner of the foundation pit, with both sides connecting with straight retaining walls 101. It should be noted that the thickness and height of the corner retaining wall 102 must be consistent with those of the straight retaining wall 101 to ensure that the stress and water permeability of the enclosure system are consistent.

[0031] like Figure 3 and Figure 6 As shown, in order to achieve a firm connection at the joint of the retaining wall and prevent excessive gaps from causing water inrush, quicksand, and slope instability, it is preferred to further include: setting a connector 8 between adjacent sand-free permeable retaining walls 1 to splice and fix the adjacent sand-free permeable retaining walls 1.

[0032] Specifically, installing connectors at the joints of the sand-free permeable retaining wall panels for locking and fixing effectively reduces the gaps between the panels, significantly improving the overall integrity and lateral displacement resistance of the entire retaining structure. This prevents the retaining wall panels from shifting due to soil lateral pressure, avoids the joints becoming channels for concentrated groundwater seepage and soil particle loss, and ensures that groundwater on the outside is guided through the retaining wall body in an orderly manner, continuously mitigating the risks of quicksand and slope collapse. Connector 8 is a locking component between adjacent sand-free permeable retaining walls 1. Its main function is to position and tie adjacent retaining wall panels, ensuring a firm and sealed joint. It must be installed one by one at each retaining wall joint node, ensuring complete coverage. It should be noted that after installation, connector 8 must not obstruct the permeable area of ​​the sand-free permeable retaining wall 1 or hinder normal groundwater seepage. This component can be selected from various connection structures such as steel profiles and fasteners, depending on the site conditions.

[0033] like Figure 3 and Figure 6 As shown, in order to ensure that the connector has sufficient structural strength and reliable fixing effect, and to avoid the failure of the connector and the recurrence of water seepage problems, preferably, the connector 8 is an I-beam, and the two adjacent sand-free permeable retaining walls 1 are respectively fixedly connected in the grooves formed on both sides of the web of the I-beam.

[0034] Specifically, I-beams are selected as the splicing connectors. They possess high structural strength and excellent bending and shear resistance, enabling them to withstand long-term lateral soil pressure. The fixing method, using grooves on both sides of the web for interlocking, offers high positioning accuracy and convenient assembly / disassembly. This method firmly restrains the retaining wall panels on both sides, preventing displacement and deformation, while ensuring unobstructed water permeability at the splicing joints, thus balancing structural stability and water control. Connector 8, also made of I-beams, utilizes the natural grooves on both sides of the I-beam's web for interlocking and positioning of the retaining wall, primarily serving to connect and fix the two sand-free permeable retaining walls 1. Standard hot-rolled I-beams are preferred, with specifications matched to the retaining wall thickness. During installation, the ends of two adjacent sand-free permeable retaining wall 1 panels are embedded into the grooves on both sides of the I-beam to ensure a tight connection. It is important to note that the height of the I-beam must match the height of the sand-free permeable retaining wall 1 to avoid vertical misalignment. This structure is the preferred implementation method for retaining wall splicing, offering superior stability compared to ordinary snap-fit ​​and binding structures.

[0035] like Figure 7 As shown, in order to achieve stable erection of the support rods and prevent the rods from slipping and shifting, causing deformation of the retaining wall and blockage of the permeable pores, preferably, it also includes: fixing a bracket 10 on the inner side of the sand-free permeable retaining wall 1, corresponding to the I-beam flange position of the connector 8; the support rod 9 is fixedly installed on the bracket 10.

[0036] Specifically, brackets are installed at the flange positions of the I-beams as dedicated bases for the support members. This allows for precise positioning of the support members, ensuring that lateral support forces are evenly distributed throughout the entire sand-free permeable retaining wall. This prevents localized stress concentration that could lead to retaining wall deformation and blockage of permeable channels, guaranteeing the retaining wall's normal soil-retaining and water-guiding functions. It also simplifies the installation process of the support members and improves the efficiency of the support system erection. Bracket 10 is a dedicated support for the support member 9, primarily used to support and fix the support member 9, transferring the support load to the connector 8 and the sand-free permeable retaining wall 1. During installation, it is uniformly installed on the inner side of the sand-free permeable retaining wall 1, at the flange positions of the I-beams, and is deployed synchronously with the support points. It is important to note that the connection between bracket 10 and the I-beam flange must be secure, without any looseness or gaps. The dimensions and plate thickness of this component can be adjusted according to the size of the support load.

[0037] like Figure 7 As shown, in order to achieve high structural stability and connection strength of the bracket and avoid the failure of the support system leading to the collapse of the retaining wall and the collapse of the pit, the bracket 10 is preferably a right-angled triangle structure and is connected to the support rod 9 and the I-beam through the two right-angled sides respectively.

[0038] Specifically, by utilizing the inherent geometric stability of the right-angled triangle structure, the load-bearing capacity and deformation resistance of the bracket are greatly improved; the two right-angled sides are rigidly connected to the I-beams and support members respectively, with high node connection strength and clear force transmission path, which can effectively disperse lateral earth pressure, ensure that the support system remains effective throughout the entire excavation cycle, and prevent the instability of the retaining structure and slope collapse caused by support failure.

[0039] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for constructing a foundation pit retaining structure, characterized in that, Includes the following steps: Excavate retaining wall pre-embedded trenches at the boundary of the foundation pit to be excavated. After the excavation of the retaining wall pre-embedded trenches is completed, sink several sand-free permeable retaining walls into the retaining wall pre-embedded trenches to form a retaining structure surrounding the foundation pit area to be excavated. Within the retaining structure, the foundation pit is excavated from the top elevation to the bottom elevation, forming a foundation pit enclosed by the retaining structure. During the excavation process, support rods are installed between the sand-free permeable retaining walls to prevent the retaining structure from collapsing. After the groundwater outside the foundation pit seeps into the foundation pit through the retaining structure, the water in the foundation pit is continuously pumped out and drained until the seepage around the pit is lower than the construction allowable limit. The retaining structure is removed, and the foundation pit is sloped to form a slope surface, thus completing the construction of the foundation pit.

2. The method for constructing foundation pit support according to claim 1, characterized in that, Also includes: After the sand-free permeable retaining wall is sunk into the pre-embedded trench of the retaining wall, filter material is filled into the pre-embedded trench of the retaining wall and the outside of the sand-free permeable retaining wall. The filter media is made of fragmented material with a water permeability no less than that of a sand-free permeable retaining wall.

3. The method for constructing foundation pit support according to claim 1, characterized in that: The sand-free permeable retaining wall includes a straight retaining wall and a corner retaining wall; the straight retaining wall is a straight rectangular plate; the corner retaining wall is an L-shaped rectangular plate, and the straight retaining wall and the corner retaining wall are spliced ​​together to form a complete enclosure outline.

4. The method for constructing foundation pit support according to claim 3, characterized in that, Also includes: Connectors are installed between adjacent sand-free permeable retaining walls to splice and fix the adjacent sand-free permeable retaining walls.

5. The method for constructing foundation pit support according to claim 4, characterized in that: The connector is an I-beam, and two adjacent sand-free permeable retaining walls are fixedly connected to the grooves formed on both sides of the web of the I-beam.

6. The method for constructing foundation pit retaining walls according to claim 5, characterized in that, Also includes: A bracket is fixedly connected to the inner side of the sand-free permeable retaining wall at the position of the I-beam flange corresponding to the connecting piece; the support rod is fixedly installed on the bracket.

7. The method for constructing foundation pit support according to claim 6, characterized in that: The bracket is a right-angled triangle structure, and is connected to the support rod and the I-beam through the two right-angled sides respectively.

8. A water control structure for foundation pit retaining walls, characterized in that, It includes several sand-free permeable retaining walls, which are connected end to end to form a retaining structure adapted to the size of the foundation pit; a connector is provided between any two adjacent sand-free permeable retaining walls, and each connector is used to splice and fix the sand-free permeable retaining walls; a support rod is provided between the sand-free permeable retaining walls, and the support rod is used to support the retaining structure to prevent it from collapsing.

9. The foundation pit retaining water control structure according to claim 8, characterized in that, The connector is an I-beam, and two adjacent sand-free permeable retaining walls are fixedly connected to the grooves formed on both sides of the web of the I-beam.

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