Water leakage stoppage structure for composite cofferdam of foundation pit in subsidence area

Abstract

The utility model discloses a subsidence area foundation pit composite cofferdam leakage water plugging structure. The subsidence area foundation pit composite cofferdam leakage water plugging structure comprises a steel sheet pile, an inner composite filling body and an outer composite filling body. The steel sheet piles are downwards driven into the sludge silty clay layer and transversely extend in the length direction of the composite cofferdam so that the subsidence area can be divided into an inner leaking stoppage treatment area and an outer leaking stoppage treatment area, and the two transverse sides of the steel sheet piles are further in sealed connection with the existing cement mixing piles correspondingly. And the inner composite filling body is filled in the inner closed filling area, so that the composite cofferdam, the inner composite filling body and the steel sheet piles are connected to form an integrated transverse water leakage plugging structure. The outer leaking stoppage processing area is filled with the outer composite filling body, so that the outer composite filling body and the transverse water leakage leaking stoppage structure are connected to form a whole leaking stoppage structure of an integrated structure. By means of the structure, the technical problems that in a humid environment, the electric shock risk of welding operation is high, the water leakage plugging effect is poor, the cement double-grout grouting cost is high, and the clay bearing capacity is low and the lateral supporting force is small in the liquefied state can be effectively solved.

Description

Technical Field

[0001] This utility model relates to the field of seepage plugging technology for foundation pit cofferdams, and in particular, to a seepage plugging structure for composite cofferdams in foundation pits in settlement zones. Background Technology

[0002] In a bridge project in the Guangdong Delta Plain, the No. 7 main pier foundation traverses a clay layer, a silty clay layer, a medium sand layer, a silty sand layer, and a silty clay layer, and sits atop the silty clay layer. During the foundation construction, sheet piles were driven into the silty clay layer at a depth of 18m, with the top of the sheet piles extending 0.5m above the top of the soil layer outside the foundation pit. A row of cement-mixed piles, 0.60m wide and 8.0m long, was constructed outside the sheet piles, with the tops of the cement-mixed piles flush with the surface of the soil layer outside the foundation pit, abutting against the outer side of the sheet piles. A 0.20m thick concrete pavement and a concrete drainage ditch were then poured at the top of the cement-mixed piles and the top of the soil layer outside the foundation pit, forming a composite cofferdam for the foundation pit. However, due to reasons such as encountering boulders during sheet pile driving, the sheet pile cofferdam forming an "S" shape after driving, or severe deformation of the locking mechanism after repeated use of sheet piles, the sheet pile locking mechanisms may become loose or disengaged. In addition, the cement mixing piles may not be tightly interlocked, resulting in gaps between the piles and forming seepage points. This causes groundwater outside the cofferdam of the foundation pit to seep into the foundation pit through the seepage points, resulting in water accumulation in the foundation pit and affecting the construction of the foundation pit. Alternatively, construction wastewater in the foundation pit may seep out of the foundation pit into the nearby river through the seepage points, polluting the river water quality.

[0003] When the excavation of the foundation pit reached the medium sand layer and the underlying silty sand and silty clay layers, the groundwater pressure caused water leakage and sand inrush in the well-permeable medium sand and silty sand layers, resulting in soil erosion on the outer wall of the foundation pit covering an area of ​​1-3 m². 2 The funnel-shaped subsidence area and the voids in the existing concrete ground pose a significant safety hazard to the construction of the bridge abutment.

[0004] Commonly used methods for plugging water leakage include: filling the gaps at the leakage points of steel sheet piles and reinforcing them with welded steel plates; sprinkling cement mortar on the outside of the steel sheet piles; injecting cement grout on the outside of the steel sheet piles; and backfilling clay in the funnel-shaped settlement area. These methods have technical defects such as: high risk of electric shock during welding operations in humid environments; poor water leakage plugging effect; high cost of cement grout injection; and low bearing capacity and weak lateral support of clay in a liquefied state. The above-mentioned water leakage plugging methods can no longer meet the construction requirements for water leakage plugging of composite cofferdams in foundation pits in large-area funnel-shaped settlement areas.

[0005] Therefore, in the construction of bridge abutment foundation pits, how to develop a foundation pit cofferdam seepage plugging structure that is simple to construct, quick to plug leaks, economical, reasonable, safe and feasible is an urgent problem to be solved for the safe construction of bridge abutments. Utility Model Content

[0006] This utility model provides a seepage plugging structure for a composite cofferdam in a subsidence area foundation pit, which solves the technical problems of existing plugging methods, such as high risk of electric shock during welding operations in humid environments, poor seepage plugging effect, high cost of cement double grout injection, low bearing capacity of clay in liquefied state, and small lateral support force.

[0007] The technical solution adopted in this utility model is as follows:

[0008] A seepage plugging structure for a composite cofferdam in a subsidence area includes: sheet piles, an inner composite filler, and an outer composite filler, all installed in the subsidence area outside the composite cofferdam. The sheet piles are driven vertically downwards through the subsidence area into the underlying silty clay layer. The sheet piles extend laterally along the length of one side of the composite cofferdam to divide the subsidence area into an inner and outer seepage plugging area, arranged sequentially. The sheet piles are also sealed on both sides to existing cement mixing piles located on the outer side of the composite cofferdam, forming a circumferentially closed inner filler area. The inner composite filler is filled within the inner closed filler area, connecting the composite cofferdam, the inner composite filler, and the sheet piles to form an integrated seepage plugging structure. The outer composite filler is filled within the outer seepage plugging area, connecting the outer composite filler and the integrated seepage plugging structure to form a unified seepage plugging structure.

[0009] Furthermore, the sheet piles are arranged parallel to and spaced apart from the existing cement mixing piles, and the lateral sides of the sheet piles extend to the non-settled area outside the settlement area, and gradually bend inward to seal and connect with the existing cement mixing piles.

[0010] Furthermore, the sheet pile includes multiple first pile bodies and second pile bodies, and two third pile bodies; the multiple first pile bodies are arranged sequentially and alternately in the transverse direction, and the multiple second pile bodies are arranged sequentially and alternately in the transverse direction between two adjacent first pile bodies and outside the outermost first pile body, and the sequentially arranged second pile bodies and first pile bodies are transversely sealed and connected to form a whole; the two third pile bodies are respectively arranged on the outermost side in the transverse direction, and one side of the third pile body is sealed and connected to the adjacent second pile body, and the other side of the third pile body is sealed and connected to the existing cement mixing pile.

[0011] Furthermore, the first, second, and third piles have the same structure, each including a U-shaped steel sheet pile body and two locking buckles connected to both sides of the open end of the steel sheet pile body; the openings of the first and second piles face opposite directions and are sequentially sealed and connected by the corresponding two locking buckles; the opening of the third pile is inclined towards the existing cement mixing pile, so that the locking buckle on one side of it is sealed and fastened to the locking buckle on the outer side of the adjacent second pile, and its opposite side is sealed and welded to the existing cement mixing pile.

[0012] Furthermore, the upper end of the sheet pile is flush with the upper end of the existing sheet pile.

[0013] Furthermore, the seepage plugging structure of the composite cofferdam for the foundation pit in the settlement area also includes two driving guide rods for positioning and guiding the driving of steel sheet piles, and multiple sets of fasteners for limiting the driving guide rods; the two driving guide rods are arranged parallel to each other and spaced apart, and each driving guide rod is supported at both ends on the existing concrete ground in the non-settled area after crossing the settlement area laterally; the fasteners are located at both ends of the driving guide rods to limit the lateral movement of the driving guide rods.

[0014] Furthermore, the internal composite filling body includes lime-gravel clay body, fine sand body and mud body; along the transverse direction of the sheet pile, the lime-gravel clay body fills the middle part, the fine sand body fills the transverse sides of the lime-gravel clay body, and the mud body fills the non-settled area outside the fine sand body, and the lime-gravel clay body, fine sand body and mud body extend vertically downward into the silty clay layer.

[0015] Furthermore, the outer composite filler is a lime-clay body, which extends vertically downward into the silty clay layer.

[0016] Furthermore, the upper ends of both the inner and outer composite fillers are flush with the surface of the soil layer outside the foundation pit.

[0017] Furthermore, the leakage plugging structure of the composite cofferdam for the subsidence area also includes a concrete floor cast on the existing cement mixing piles, inner composite filler, outer composite filler, and the top of the soil layer outside the foundation pit, as well as a drainage ditch constructed on the concrete floor; the concrete floor is flush with the existing cement mixing piles and the existing concrete floor at the top of the soil layer outside the foundation pit in the composite cofferdam.

[0018] This utility model has the following beneficial effects:

[0019] In the leakage plugging structure of the utility model, through the arrangement of steel sheet piles, firstly, the funnel-shaped subsidence area is divided into an internal leakage plugging treatment area and an external leakage plugging treatment area. The internal leakage plugging treatment area and the composite cofferdam of the pile cap foundation pit enclose an internal leakage plugging treatment area similar to a "mouth" shape, which is convenient for leakage plugging construction in the leakage-prone areas of the subsidence area. Secondly, when filling the funnel-shaped subsidence area, the steel sheet piles play a role as a skeleton, and together with the internal composite filling body and the external filling composite body, they form an integral high-strength leakage plugging structure for water seepage. Moreover, the backfill also pushes against the composite cofferdam and the soil layer outside the foundation pit, thereby increasing the lateral support force on the outside of the composite cofferdam. Thirdly, when filling the funnel-shaped subsidence area, the steel sheet piles play a role in water stop, and together with the internal composite filling body and the external composite filling body, they form a multi-layer water stop filling body with alternating flexible, semi-rigid and rigid layers arranged in sequence from the outside to the inside of the pile cap foundation pit: semi-rigid external composite filling body → flexible steel sheet pile → semi-rigid internal composite filling body → rigid existing cement mixing pile → flexible existing steel sheet pile, which jointly resists the groundwater outside the composite cofferdam from seeping into the inside of the composite cofferdam in the horizontal, vertical and up-and-down directions centered on the water seepage point. At the same time, it also resists the construction sewage inside the composite cofferdam from seeping out to the outside of the composite cofferdam near the river and polluting the river water quality.

[0020] On the other hand, in the leakage plugging structure of the utility model, at a certain position outside the composite cofferdam, a layer of steel sheet piles is arranged to abut against the existing cement mixing piles to enclose an internal leakage plugging treatment area similar to a "mouth" shape. And in the internal leakage plugging treatment area, a horizontally arranged internal composite filling body is filled to form a horizontal filling layer. At the same time, in the external leakage plugging treatment area, an externally extended external composite filling body is filled to form a longitudinal filling layer. And at the bottom of the outside of the composite cofferdam, the bottoms of the horizontal filling layer and the longitudinal filling layer are both embedded in the silty clay layer. And at the top of the filling material, the soil layer outside the foundation pit and the existing cement mixing piles, concrete is backfilled to form a concrete ground and a concrete drainage ditch, thereby forming an integral leakage plugging structure for water seepage. It can achieve leakage plugging for groundwater and surface water outside the composite cofferdam in the horizontal, vertical and up-and-down directions centered on the water seepage point, and the leakage plugging effect is good. Therefore, the leakage plugging structure of this new type does not need to carry out construction such as filling and welding reinforcement at the water seepage point of the steel sheet pile, spreading cement sand powder outside the steel sheet pile, injecting cement double slurry outside the steel sheet pile, and backfilling clay in the funnel-shaped subsidence area, etc., and can effectively solve the technical problems of high risk of electric shock during welding operation in a humid environment, poor leakage plugging effect for water seepage, high cost of cement double slurry grouting, low bearing capacity of clay in a liquefied state and small lateral support force.

[0021] In addition to the purposes, features and advantages described above, the utility model has other purposes, features and advantages. The following will refer to the drawings to further elaborate on the utility model in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0023] Figure 1 This is a top view schematic diagram of the leakage plugging structure of the composite cofferdam for foundation pit in the subsidence area according to a preferred embodiment of this utility model.

[0024] Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure along the middle I-I direction.

[0025] Legend:

[0026] 1. Foundation pit; 2. Existing sheet piles; 3. Existing cement mixing piles; 4. Existing concrete floor; 5. Soil layer outside the foundation pit; 6. Leakage point; 7. Sheet piles; 701. First pile body; 702. Second pile body; 703. Third pile body; 8. Settlement zone; 9. Limestone-clay body; 10. Fine sand body; 11. Mud body; 12. Limestone-clay body; 13. Silt-silty clay layer; 14. Concrete floor. Detailed Implementation

[0027] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered below.

[0028] Reference Figure 1-2 A preferred embodiment of this utility model provides a seepage-stopping structure for a composite cofferdam in a subsidence area, comprising: sheet piles 7, an inner composite filler, and an outer composite filler, all arranged within the subsidence area 8 outside the composite cofferdam. The sheet piles 7 are driven vertically downwards through the subsidence area 8 into the underlying silty clay layer 13. The sheet piles 7 extend laterally along the length of one side of the composite cofferdam, dividing the subsidence area 8 into an inner and outer seepage-stopping treatment area arranged sequentially. The sheet piles 7 are also sealed on both sides of an existing cement mixing pile 3 located on the outer side of the composite cofferdam, forming a circumferentially closed inner filler area. The inner composite filler fills the inner closed filler area, connecting the composite cofferdam, the inner composite filler, and the sheet piles 7 to form an integrated transverse seepage-stopping structure. The outer composite filler fills the outer seepage-stopping area, connecting the outer composite filler with the transverse seepage-stopping structure to form an integrated seepage-stopping structure.

[0029] In the leakage plugging structure of the utility model, through the arrangement of the steel sheet pile 7, firstly, the funnel-shaped subsidence area 8 is divided into an internal leakage plugging treatment area and an external leakage plugging treatment area, and the internal leakage plugging treatment area and the composite cofferdam of the bearing platform foundation pit 1 are enclosed to form an internal leakage plugging treatment area similar to a "mouth" shape, which is convenient for leakage plugging construction in the leakage water of the subsidence area 8 by dividing the area; secondly, when filling the funnel-shaped subsidence area 8, the steel sheet pile 7 plays a role as a framework, and together with the internal composite filling body and the external filling composite body, they form a high-strength overall leakage plugging structure for leakage water, and at the same time, it also squeezes and pushes the composite cofferdam and the soil layer 5 outside the foundation pit, thereby increasing the lateral support force on the outside of the composite cofferdam; thirdly, when filling the funnel-shaped subsidence area 8, the steel sheet pile 7 plays a role in water stop, and together with the internal composite filling body and the external composite filling body, they form a multi-layer water stop filling body arranged in sequence from the outside of the bearing platform foundation pit 1 towards the inside of the bearing platform foundation pit 1: semi-rigid external composite filling body → flexible steel sheet pile 7 → semi-rigid internal composite filling body → rigid existing cement mixing pile 3 → flexible existing steel sheet pile 2, with flexible, semi-rigid and rigid alternately arranged, which jointly resists the groundwater outside the composite cofferdam from infiltrating into the inside of the composite cofferdam in the horizontal, vertical and up-and-down directions centered on the leakage water point 6, and at the same time, it also resists the construction sewage inside the composite cofferdam from seeping out of the composite cofferdam and polluting the water quality of the adjacent river.

[0030] On the other hand, in the leakage plugging structure of the utility model, at a certain position outside the composite cofferdam, a layer of steel sheet pile 7 is arranged to abut against the existing cement mixing pile 3 to enclose an internal leakage plugging treatment area similar to a "mouth" shape, and a horizontally arranged internal composite filling body is filled in the internal leakage plugging treatment area to form a horizontal filling layer. At the same time, an externally extended external composite filling body is filled in the external leakage plugging treatment area to form a longitudinal filling layer. At the bottom of the outside of the composite cofferdam, the bottoms of the horizontal filling layer and the longitudinal filling layer are embedded in the silty clay layer 13, and at the top of the filling material, the soil layer outside the foundation pit and the existing cement mixing pile, concrete is backfilled to form a concrete ground 14 and a concrete drainage ditch, thereby forming an overall leakage plugging structure for leakage water. It can achieve leakage plugging for groundwater and surface water outside the composite cofferdam in the horizontal, vertical and up-and-down directions centered on the leakage water point 6, and the leakage plugging effect is good. Therefore, the leakage plugging structure of this new type does not need to carry out construction such as stuffing and welding reinforcement at the leakage water point of the steel sheet pile, sprinkling cement sand powder outside the steel sheet pile, injecting cement double slurry outside the steel sheet pile, and backfilling clay in the funnel-shaped subsidence area, etc., and can effectively solve the technical problems of high risk of electric shock during welding operation in a humid environment, poor leakage plugging effect for leakage water, high cost of cement double slurry grouting, low bearing capacity of clay in a liquefied state and small lateral support force.

[0031] Optionally, as Figure 1As shown in the figure, the steel sheet piles 7 are arranged in parallel intervals relative to the existing cement mixing piles 3, preventing the steel sheet piles 7 from presenting a "S" shape horizontally, thereby causing the connection between the pile bodies in the steel sheet piles 7 to be inconsistent or disconnected, and further resulting in water leakage at the joints of the steel sheet piles 7. Moreover, the two lateral sides of the steel sheet piles 7 respectively extend to the non-subsided areas outside the subsidence area 8 and are gradually bent inward to be hermetically connected to the existing cement mixing piles 3; in this alternative solution, the steel sheet piles 7 are inserted and extended horizontally to the non-subsided areas by 3-5 m on the left and right, thereby further improving the overall stability of the water leakage plugging structure and expanding the plugging range.

[0032] In this alternative solution, as Figure 1 shown in the figure, the steel sheet piles 7 include multiple first pile bodies 701, second pile bodies 702, and two third pile bodies 703. The multiple first pile bodies 701 are arranged at intervals in sequence horizontally, the multiple second pile bodies 702 are arranged horizontally between two adjacent first pile bodies 701 and outside the outermost first pile body 701 in sequence, and the second pile bodies 702 and the first pile bodies 701 arranged at intervals are hermetically connected into a whole horizontally. The two third pile bodies 703 are respectively arranged at the outermost sides horizontally, and one side of the third pile body 703 is hermetically connected to the adjacent second pile body 702, and the other side of the third pile body 703 is hermetically connected to the existing cement mixing pile 3.

[0033] In a specific embodiment of this alternative solution, as Figure 1 shown in the figure, the first pile body 701, the second pile body 702, and the third pile body 703 have the same structure, all including a steel sheet pile body with a "U" - shaped cross - section and two lock catches connected to both sides of the open end of the steel sheet pile body; further, the steel sheet piles adopt PU600×210×18 mm steel sheet piles with the material Q355P and a length of 18 m. The steel sheet piles are composed of a web, a flange, and a lock catch. Among them: one end of the flange is welded to the lock catch, and the other end is welded to any one end of the web to form a "U" shape. The lock catch end is set away from the web, and the opening direction of the steel sheet pile is opposite to the opening direction of the lock catch. The quality of the steel sheet piles meets the requirements of the "Hot - rolled steel sheet piles" (GB / T20933) standard. For piles with damage or inconsistent lock catches, the deformation must be corrected to make the dimensions correct and the lock openings smooth without bending. The quality inspection standard for smooth lock openings is that a 1 - m - long pile body is used to sleeve each group of steel sheet piles 7, and those that can pass smoothly are judged as qualified; the anti - "U - shaped protrusion" design of the lock catches on both outer sides of each steel sheet pile body is used to interlock adjacent pile bodies to form an interlocking structure, forming a watertight structure when the pile bodies are interlocked, thereby increasing the strength of the steel sheet pile 7 cofferdam structure. Further, as Figure 1 shown in the figure, the opening directions of the first pile body 701 and the second pile body 702 are opposite, and they are hermetically connected in sequence through the corresponding two lock catches; the opening of the third pile body 703 is inclined towards the existing cement mixing pile 3 so that the lock catch on one side of it is hermetically buckled to the lock catch on the outer side edge of the adjacent second pile body 702, and the opposite other side is hermetically welded to the existing cement mixing pile 3.

[0034] Preferably, the upper end of the sheet pile 7 is flush with the upper end of the existing sheet pile 2, so that the sheet pile 7 can be directly removed without breaking the concrete ground 14 and the concrete drainage ditch after the foundation pit 1 project is completed.

[0035] Preferably, not shown in the figure, the seepage plugging structure of the composite cofferdam in the settlement area also includes two driving guide rods for positioning and guiding the driving of the sheet piles 7, and multiple sets of fasteners for limiting the driving guide rods. The two driving guide rods are arranged parallel to each other and spaced apart, and each driving guide rod crosses the settlement area 8 laterally and is supported at both ends on the existing concrete ground 4 in the non-settled area. Fasteners are located at both ends of the driving guide rods to limit the lateral movement of the driving guide rods. In specific operation, starting 200mm from the outside of the existing cement mixing pile 3, on the existing concrete ground 4 of the non-settled area on both sides of the settlement zone 8, the first and second [200×75×9mm channel steels] are installed in parallel front and back, so that the lower leg ends of the first and second channel steels are placed on the existing concrete ground 4, and the waist ends of the first and second channel steels are perpendicular to the existing concrete ground 4, with a distance of 460mm between the two waist ends facing each other; then, two φ20mm expansion bolts are drilled and inserted into the existing concrete ground 4 on both sides of each channel steel, close to the channel steel, to ensure that the channel steel is stable and does not shift laterally; after the channel steels are installed, the first and second channel steels span across the top surface of the funnel-shaped settlement zone 8, thus forming the guide frame for driving the sheet pile 7. After the guide frame for driving the sheet pile 7 is installed, it is ensured that the sheet pile 7 is straight laterally after being driven, so that the sheet pile 7 is tightly locked and there are no gaps for water seepage.

[0036] Optionally, such as Figure 1-2 As shown, the inner composite filling body includes lime-gravel clay body 9, fine sand body 10, and mud body 11. Along the transverse direction of the sheet pile 7, the lime-gravel clay body 9 fills the middle, the fine sand body 10 fills the transverse sides of the lime-gravel clay body 9, and the mud body 11 fills the non-settled area outside the fine sand body 10. The lime-gravel clay body 9, fine sand body 10, and mud body 11 extend vertically downward into the silty clay layer 13. In this optional scheme, the transverse seepage plugging structure is as follows: In the inner plugging treatment area in the middle of the outer side of the composite cofferdam, with the seepage point 6 as the center, lime-gravel clay body 9, fine sand body 10 and mud body 11 are filled horizontally side by side to form a transverse filling layer, which prevents the free transverse flow of groundwater outside the composite cofferdam. The water seeps into the foundation pit 1 through the transverse filling layer and the seepage point 6, thereby achieving the transverse seepage plugging of groundwater outside the composite cofferdam with the seepage point 6 as the center.

[0037] Optionally, such as Figure 1-2As shown, the outer composite filler is a lime-clay body 12, which extends vertically downward into the silty clay layer 13. In this optional scheme, the longitudinal seepage plugging structure is as follows: in the outer plugging treatment area outside the composite cofferdam, lime-clay body 12 is filled to form a longitudinal filling layer, preventing the longitudinal free flow of groundwater outside the composite cofferdam. The longitudinal filling layer seeps into the inner plugging treatment area, thereby achieving longitudinal seepage plugging of groundwater outside the composite cofferdam, centered on the seepage point 6.

[0038] Preferably, the upper ends of both the inner and outer composite fillers are flush with the surface of the outer soil layer 5 of the foundation pit, which facilitates the subsequent construction of the concrete floor and drainage ditch.

[0039] Preferably, the leakage plugging structure of the composite cofferdam for the subsidence area also includes a concrete floor 14 cast on top of the existing cement mixing piles 3, the inner composite filler, the outer composite filler, and the outer soil layer 5 of the foundation pit, as well as a drainage ditch constructed on the concrete floor. The concrete floor 14 is flush with the existing concrete floor 4 at the top of the existing cement mixing piles 3 and the outer soil layer 5 of the foundation pit in the composite cofferdam. In this preferred embodiment, the leakage plugging structure in the vertical direction is as follows: at the bottom of the outer side of the composite cofferdam, the bottom ends of both the transverse filling layer and the longitudinal filling layer are embedded 250-400mm into the silty clay layer 13; on the top surface of the transverse filling layer, the longitudinal filling layer, the existing cement mixing pile 3, and the soil layer 5 outside the foundation pit at the top of the outer side of the composite cofferdam, a concrete floor 14 and a concrete drainage ditch are poured to prevent the free flow of groundwater and surface water in the vertical direction outside the composite cofferdam. The water seeps into the inner side of the composite cofferdam through the transverse filling layer, the longitudinal filling layer, the concrete floor 14, and the leakage point 6, thereby plugging the vertical leakage of groundwater and surface water outside the composite cofferdam, centered on the leakage point 6.

[0040] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A leakage plugging structure for a composite cofferdam in a subsidence area foundation pit, characterized in that, include: Sheet piles (7), inner composite filler and outer composite filler are installed in the settlement area (8) outside the composite cofferdam; After the steel sheet pile (7) is driven vertically downward through the settlement area (8), it is driven into the silty clay layer (13) below. The steel sheet pile (7) is laid horizontally along the length of one side of the composite cofferdam to divide the settlement area (8) into an inner leak-stopping treatment area and an outer leak-stopping treatment area set in sequence. The steel sheet pile (7) is also sealed on both sides of the horizontal direction to connect the existing cement mixing pile (3) located on the outer side of the composite cofferdam, so that the inner leak-stopping treatment area forms a circumferentially closed inner closed filling area. The inner composite filler is filled in the inner closed filling area so that the composite cofferdam, the inner composite filler and the steel sheet pile (7) are connected to form an integrated transverse seepage plugging structure; The external composite filler is filled into the external leak-stopping treatment area so that the external composite filler is connected with the transverse leakage-stopping structure to form an integral leakage-stopping structure.

2. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 1, characterized in that, The sheet piles (7) are arranged parallel to the existing cement mixing piles (3) and the two sides of the sheet piles (7) extend to the unsettled area outside the settlement area (8) and gradually bend inward to seal with the existing cement mixing piles (3).

3. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 2, characterized in that, The sheet pile (7) includes multiple first pile bodies (701) and second pile bodies (702), and two third pile bodies (703); Multiple first piles (701) are arranged in a horizontally spaced manner, and multiple second piles (702) are arranged in a horizontally spaced manner between two adjacent first piles (701) and outside the outermost first pile (701). The second piles (702) and the first piles (701) arranged in a horizontally spaced manner are connected in a horizontally sealed manner to form a whole. Two third pile bodies (703) are located on the outermost side in the transverse direction, and one side of the third pile body (703) is sealed to the adjacent second pile body (702), while the other side of the third pile body (703) is sealed to the existing cement mixing pile (3).

4. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 3, characterized in that, The first pile body (701), the second pile body (702) and the third pile body (703) have the same structure. They all include a steel sheet pile body with a "U" shaped cross section and two locking buckles connected to the two sides of the open end of the steel sheet pile body. The openings of the first pile (701) and the second pile (702) face opposite directions and are sequentially sealed and connected by two corresponding latches; The opening of the third pile body (703) is tilted toward the existing cement mixing pile (3) so that the lock on one side of it is sealed and fastened to the lock on the outer side of the adjacent second pile body (702), and its opposite side is sealed and welded to the existing cement mixing pile (3).

5. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 1, characterized in that, The upper end of the sheet pile (7) is flush with the upper end of the existing sheet pile (2).

6. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 1, characterized in that, The seepage plugging structure of the composite cofferdam for the foundation pit in the subsidence area also includes two driving guide rods for positioning and guiding the driving of steel sheet piles (7), and multiple sets of fasteners for limiting the driving guide rods; Two guide rods are set in parallel at intervals, and each guide rod crosses the settlement area (8) laterally and its two ends are supported on the existing concrete ground (4) of the non-settled area. Fasteners are located at both ends of the insertion guide rod to restrict the lateral movement of the insertion guide rod.

7. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 1, characterized in that, The internal composite filler includes limestone-clay body (9), fine sand body (10) and mud body (11); Along the transverse direction of the sheet pile (7), lime-gravel clay body (9) fills the middle, fine sand body (10) fills the transverse sides of the lime-gravel clay body (9), and mud body (11) fills the unsettled area outside the fine sand body (10). The lime-gravel clay body (9), fine sand body (10) and mud body (11) extend vertically downward into the silty clay layer (13).

8. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 1, characterized in that, The outer composite filler is a lime-clay body (12), which extends vertically downward into the silty clay layer (13).

9. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 1, characterized in that, The upper ends of both the inner and outer composite fillers are flush with the surface of the outer soil layer (5) of the foundation pit.

10. The seepage plugging structure for the composite cofferdam of the foundation pit in the subsidence area according to claim 9, characterized in that, The seepage plugging structure of the composite cofferdam for the foundation pit in the subsidence area also includes a concrete ground (14) cast on top of the existing cement mixing pile (3), inner composite filler, outer composite filler, and outer soil layer (5) of the foundation pit, and a drainage ditch constructed on the concrete ground. The concrete ground (14) is flush with the existing concrete ground (4) on top of the existing cement mixing piles (3) and the soil layer (5) outside the foundation pit in the composite cofferdam.

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