Deep foundation pit supporting combined structure of sand-filled steel pipe pile and construction method of deep foundation pit supporting combined structure

Abstract

The invention belongs to the technical field of sand filling steel pipe piles, and particularly relates to a deep foundation pit supporting combined structure of sand filling steel pipe piles and a construction method of the deep foundation pit supporting combined structure. Comprising sand-filled steel pipe piles; a plurality of sand-filled steel pipe piles are vertically arranged, the sand-filled steel pipe piles and the Larsen steel sheet piles are mutually connected through seaming, the sand-filled steel pipe piles and the Larsen steel sheet piles are arranged side by side, and the sand-filled steel pipe piles are provided with crown beams in a connected mode. The sand-filled steel pipe pile serves as a stiffening structure, the overall flexural rigidity can be remarkably improved, the steel plate pile forms a continuous soil and water retaining wall through locking opening meshing, the combined supporting structure is adopted for soft stratums such as mucky soil, soil lateral pressure can be effectively resisted, and meanwhile the good water stopping effect is achieved. According to the combined supporting structure, through dual protection of the sand filling steel pipe piles and the steel sheet piles, the overall strength and stability are improved, and safety in the construction process is ensured.

Description

Technical Field

[0001] This invention belongs to the technical field of sand-filled steel pipe piles, specifically the deep foundation pit support combination structure of sand-filled steel pipe piles and its construction method. Background Technology

[0002] Deep foundation pit construction faces complex conditions such as soft soil layers, high groundwater levels, protection of adjacent buildings and structures, and "construction and operation at the same time" (such as half of the highway is open to traffic). This places stringent requirements on the stability, deformation resistance, ease of construction, and economy of the support structure.

[0003] Deep foundation pit support methods mainly include soil nailing walls, anchor bolts (cables), shotcrete spraying, diaphragm walls, sheet (pipe) piles, SWM (surface-work maneuver) methods, and combinations of one or more of these methods. In construction scenarios such as highway reconstruction and expansion, municipal road construction, and building construction, the surrounding environment of deep foundation pits excavated for the construction of structures is complex. Often, there are important buildings, underground pipelines, and other objects requiring protection around the foundation pit. Especially in highway reconstruction and expansion projects, it is generally impossible to completely close the entire width of the foundation pit for construction; instead, a construction organization form of half-width operation and half-width closure is adopted. The traffic load on the side of the foundation pit that allows traffic is large, and the construction period is tight. In addition, some deep foundation pits have complex geological and hydrogeological conditions. While existing support methods such as diaphragm wall support, cast-in-place piles, and SWM methods have good water-stopping effects, they are difficult to construct, have long construction periods, high economic costs, and are prone to borehole collapse, affecting the surrounding environment.

[0004] Against this backdrop, the deep foundation pit support combination structure of sand-filled steel pipe piles and steel sheet piles exhibits significant adaptability and superiority compared to other support methods, particularly excelling in highway reconstruction and expansion projects. Unlike other support methods, sand-filled steel pipe piles and steel sheet piles do not have these limitations, making them more suitable for foundation pit support under various complex geological and environmental conditions. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies and solve at least one of the problems mentioned in the background art, a deep foundation pit support composite structure of sand-filled steel pipe piles is proposed.

[0006] The technical solution adopted by this invention to solve its technical problem is: A deep foundation pit support composite structure using sand-filled steel pipe piles includes sand-filled steel pipe piles; several sand-filled steel pipe piles are arranged vertically, and the structure also includes several Larssen steel sheet piles interconnected by interlocking joints. The sand-filled steel pipe piles and the Larssen steel sheet piles are arranged side by side, and a capping beam is provided on each sand-filled steel pipe pile.

[0007] As one embodiment of the present invention, it includes sand-filled steel pipe piles; a plurality of sand-filled steel pipe piles are arranged vertically, a connecting mechanism is provided on one side of the surface of the sand-filled steel pipe piles, and fixing components are provided on both sides of the connecting mechanism; a docking component is provided on the side of the surface of the sand-filled steel pipe piles away from the first arc-shaped ring, and a positioning component is provided on the side of the first connecting plate near the docking component; a support component is provided on the side of the docking component away from the sand-filled steel pipe piles; the connecting mechanism includes a first arc-shaped ring, a first connecting plate, and an anti-slip protrusion, a plurality of first arc-shaped rings are arranged, and the plurality of first arc-shaped rings are longitudinally movably connected to the surface of the sand-filled steel pipe piles, one side of the first arc-shaped ring is fixedly installed with the first connecting plate, and the inner wall of the first arc-shaped ring is fixedly installed with the anti-slip protrusion; the cooperative use of the first arc-shaped ring, the first connecting plate, and the anti-slip protrusion enables rapid docking with the second arc-shaped ring and the third connecting plate, thereby enabling alignment and fixation to be completed in a short time during installation.

[0008] Preferably, the fixing component includes a second connecting plate and fixing bolts. The second connecting plate is fixedly installed on the side of the first arc-shaped ring away from the first connecting plate. Two sets of the second connecting plates are provided, and the two sets of the second connecting plates are fitted together. The two sets of the second connecting plates are threadedly connected to each other by fixing bolts. In this scheme, the cooperation between the second connecting plate and the fixing bolts can connect the first arc-shaped ring and the second arc-shaped ring to each other, so as to speed up the construction progress and also make the anti-slip protrusion firmly grip the sand-filled steel pipe pile to prevent shaking.

[0009] Preferably, the docking assembly includes a second arc-shaped ring and a third connecting plate. Several second arc-shaped rings are provided, and these rings are longitudinally and movably connected to the side of the sand-filled steel pipe pile surface away from the first arc-shaped ring. The side of the second arc-shaped ring closest to the first connecting plate is fixedly installed with the third connecting plate, and the side of the second arc-shaped ring away from the third connecting plate is fixedly installed with another set of second connecting plates. In this design, the combined use of the second arc-shaped ring and the third connecting plate provides stable support for the support assembly and allows for rapid installation of the support assembly to both sides of the sand-filled steel pipe pile. It also has a disassembly function, improving portability.

[0010] Preferably, the positioning component includes a plug and a through hole. The plug is fixedly installed on the side of the first connecting plate near the third connecting plate, and the through hole is opened on the side of the third connecting plate near the first connecting plate. The plug is movably inserted into the inner wall of the third connecting plate through the opening of the through hole. In this solution, the cooperation of the plug and the through hole can facilitate the user to position the device during installation, ensuring that the first arc ring and the second arc ring can fit perfectly together, thereby improving the stability of the assembly.

[0011] Preferably, the support assembly includes a first sheet pile and a second sheet pile. Several first sheet piles and several second sheet piles are provided. The first sheet piles are welded laterally to the side of the second arc-shaped ring away from the sand-filled steel pipe pile. The second sheet piles are also welded laterally to the side of the second arc-shaped ring away from the sand-filled steel pipe pile. The first sheet piles are inclined. In this scheme, the combined use of the first and second sheet piles can enhance the support strength of the sand-filled steel pipe pile and can be used in combination with the sand-filled steel pipe pile to achieve both support and protection.

[0012] Preferably, a circular steel plate is movably connected to the top of the inner wall of the sand-filled steel pipe pile. In this design, the circular steel plate can compact the sand after the user has finished filling the sand, thereby preventing air from appearing in the sand and ensuring that the sand inside the sand-filled steel pipe pile can completely fill and cover the inner wall of the sand-filled steel pipe pile.

[0013] The construction method of deep foundation pit support composite structure using sand-filled steel pipe piles includes the following steps: Steel pipe piles are continuously drilled longitudinally along a certain range around the proposed deep foundation pit and embedded, with the anchorage depth of the steel pipe piles into the soil not less than 0.8 times the depth of the foundation pit. A reinforced concrete cap beam is installed on top of the sand-filled steel pipe pile. The width of the cap beam is 10-20cm wider than the diameter of the steel pipe pile, and the height is higher than the top of the steel pipe pile. The cap beam extends to both ends and is 1m wider than the steel pipe pile, thus completely enclosing the sand-filled steel pipe pile. The sand-filled steel pipe piles and Larssen steel sheet piles are arranged side by side with the same length. The Larssen steel sheet piles are connected by interlocking method, and the anchorage depth of the Larssen steel sheet piles into the soil is not less than 0.8 times the depth of the foundation pit. The beneficial effects of this invention are as follows: 1. Construction adaptability and safety This combined support structure enables phased excavation and support, meeting the special requirements of "construction while traffic is open." For soft strata such as silty soil, this combined support structure effectively resists lateral soil pressure and provides good water-stopping properties. Through the dual protection of sand-filled steel pipe piles and steel sheet piles, the combined support structure improves overall strength and stability, ensuring safety during construction.

[0014] 2. Synergistic effect of composite support system Sand-filled steel pipe piles, as stiffening structures, can significantly improve the overall bending stiffness. Steel sheet piles form a continuous retaining wall through interlocking joints. The combination of the two has both anti-lateral deformation and water-stopping functions, making it suitable for deep foundation pit projects near existing access roads.

[0015] 3. Convenient construction Steel pipe piles can be driven into the ground using a rotary drilling rig of the appropriate diameter for rapid hole formation, minimizing the impact on vehicle side vibration, simplifying operation, reducing construction difficulty, and significantly improving work efficiency. 4. Economic efficiency Compared to other support methods, the combined support method of sand-filled steel pipe piles and steel sheet piles is more economical. Sand-filled steel pipe piles can be recycled and reused, reducing material costs by approximately 40% and significantly lowering overall project costs. 5. Advantages of green construction and environmental protection Compared to other support methods, this combined structure has significant environmental advantages, greatly reducing construction noise. Since most of the materials in this combined structure can be recycled and reused, it reduces the amount of construction waste compared to traditional concrete support. In addition, it can also avoid the pollution of water bodies by mud. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of the deep foundation pit support combination structure of the sand-filled steel pipe pile of the present invention; Figure 2 This is a front perspective view of Embodiment 1 of the present invention; Figure 3 This is an exploded view of the docking component and the positioning component in Embodiment 1 of the present invention; Figure 4 This is a partial structural schematic diagram of the support component in Embodiment 1 of the present invention; Figure 5 This is a partial structural schematic diagram of the first arc-shaped ring in Embodiment 1 of the present invention; Figure 6 This is a schematic diagram of the fit between the sand-filled steel pipe pile and the circular steel plate in Embodiment 1 of the present invention; Figure 7 This is a partial structural schematic diagram of the connecting mechanism in Embodiment 1 of the present invention; Figure 8 This is a schematic diagram of the support combination structure in Embodiment 2 of the present invention.

[0018] Legend: 1. Sand-filled steel pipe pile; 2. Connecting mechanism; 21. First arc-shaped ring; 22. First connecting plate; 23. Anti-slip protrusion; 3. Fixing component; 31. Second connecting plate; 32. Fixing bolt; 4. Butt joint component; 41. Second arc-shaped ring; 42. Third connecting plate; 5. Positioning component; 51. Insert block; 52. Through hole; 6. Support component; 61. First steel sheet pile; 62. Second steel sheet pile; 70. Circular steel plate; 101. Crown beam; 102. Larssen steel sheet pile; 200. Horizontal brace; 201. Diagonal bracing tie beam. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] See Figure 1 As shown, the present invention provides a deep foundation pit support combination structure of sand-filled steel pipe piles, including sand-filled steel pipe piles 1; the sand-filled steel pipe piles 1 are provided in a plurality of columns, which are arranged vertically, and also include a plurality of Larssen steel sheet piles 101 connected to each other by interlocking joints. The sand-filled steel pipe piles and the plurality of Larssen steel sheet piles are arranged side by side, and a capping beam 101 is provided on the sand-filled steel pipe piles.

[0021] The construction method of deep foundation pit support composite structure using sand-filled steel pipe piles includes the following steps: (1) Drill steel pipe piles continuously in a certain range around the perimeter of the deep foundation pit to be excavated. The anchorage depth of the steel pipe piles into the soil shall not be less than 0.8 times the depth of the foundation pit. There is no need to consider the influence of soil geology on the construction of the pipe piles. After the steel pipe piles are driven, the inside of the pipes shall be filled with sand. The inside of the pipes shall be compacted by using a long-arm excavator with an extended drill bit (with a circular ramming plate welded to the end).

[0022] (2) A reinforced concrete cap beam is installed on the top of the sand-filled steel pipe pile. The width of the cap beam is 10-20cm wider than the diameter of the steel pipe pile, and the height is higher than the top of the steel pipe pile. The cap beam extends to both ends and is 1m wider than the steel pipe pile, thus fully wrapping the sand-filled steel pipe pile. After the cap beam is completed, Larssen steel sheet piles are driven on the outside of the cap beam and back against the steel pipe pile system to form a strong combined support system.

[0023] (3) The sand-filled steel pipe piles and Larssen steel sheet piles are arranged side by side with the same length. The Larssen steel sheet piles are connected by interlocking method. The anchorage depth of the Larssen steel sheet piles into the soil is not less than 0.8 times the depth of the foundation pit.

[0024] After the support structure is completed, excavation and backfilling of the foundation pit and construction of related structures can be carried out quickly. After construction is completed, the Larssen sheet piles and steel pipe piles can be extracted for reuse. This combined support system is mainly used in foundation pit support construction for deep pits or near accessible roads, including highway reconstruction and expansion, municipal road construction, and building construction. During construction, attention should be paid to determining parameters such as the pile length of the steel pipe piles and sheet piles according to the depth of the planned excavation pit.

[0025] The supporting structure used as temporary support in existing culverts can be implemented in the following two ways: Example

[0026] like Figures 2 to 7 As shown, in the case of existing culverts, a supporting structure can also be used as temporary support. The deep foundation pit support combination structure of the sand-filled steel pipe piles described in this embodiment includes sand-filled steel pipe piles 1; several sand-filled steel pipe piles 1 are arranged vertically; a connecting mechanism 2 is provided on one side of the surface of the sand-filled steel pipe pile 1, and fixing components 3 are provided on both sides of the connecting mechanism 2; a docking component 4 is provided on the side of the surface of the sand-filled steel pipe pile 1 away from the first arc-shaped ring 21, and a positioning component 5 is provided on the side of the first connecting plate 22 near the docking component 4; a support component 6 is provided on the side of the docking component 4 away from the sand-filled steel pipe pile 1; the connecting mechanism... The 2 includes a first arc-shaped ring 21, a first connecting plate 22, and anti-slip protrusions 23. Several first arc-shaped rings 21 are provided, and these rings are longitudinally and movably connected to the surface of the sand-filled steel pipe pile 1. One side of each first arc-shaped ring 21 is fixedly installed to the first connecting plate 22, and the inner wall of each first arc-shaped ring 21 is fixedly installed to the anti-slip protrusions 23. The fixing assembly 3 includes a second connecting plate 31 and fixing bolts 32. The second connecting plate 31 is fixedly installed on the side of the first arc-shaped ring 21 away from the first connecting plate 22. Two sets of second connecting plates 31 are provided, and the two sets of second connecting plates 31 are fitted together. The two sets of second connecting plates 31 are connected by a fixing bolt. The fixing bolts 32 are threaded together. The mating assembly 4 includes a second arc-shaped ring 41 and a third connecting plate 42. Several second arc-shaped rings 41 are provided, and these rings are longitudinally movably connected to the side of the sand-filled steel pipe pile 1 away from the first arc-shaped ring 21. The side of the second arc-shaped ring 41 near the first connecting plate 22 is fixedly installed with the third connecting plate 42, and the side of the second arc-shaped ring 41 away from the third connecting plate 42 is fixedly installed with another set of second connecting plates 31. The positioning assembly 5 includes a plug 51 and a through hole 52. The plug 51 is fixedly installed on the side of the first connecting plate 22 near the third connecting plate 42, and the through hole 52 is open. Located on the side of the third connecting plate 42 near the first connecting plate 22, the insert block 51 is movably inserted into the inner wall of the third connecting plate 42 through the opening of the through hole 52. The support component 6 includes a first steel sheet pile 61 and a second steel sheet pile 62. Several first steel sheet piles 61 and several second steel sheet piles 62 are provided. Several first steel sheet piles 61 are horizontally welded to the side of the second arc-shaped ring 41 away from the sand-filled steel pipe pile 1. Several second steel sheet piles 62 are horizontally welded to the side of the several second arc-shaped ring 41 away from the sand-filled steel pipe pile 1. The first steel sheet piles 61 are inclined. A circular steel plate 70 is movably connected to the top of the inner wall of the sand-filled steel pipe pile 1.

[0027] like Figures 2 to 7As shown, the cooperation of the first arc-shaped ring 21, the first connecting plate 22, and the anti-slip protrusion 23 enables rapid docking with the second arc-shaped ring 41 and the third connecting plate 42, allowing for quick alignment and fixation during installation. The cooperation of the second connecting plate 31 and the fixing bolt 32 connects the first arc-shaped ring 21 and the second arc-shaped ring 41 together, accelerating the construction progress and ensuring that the anti-slip protrusion 23 firmly grips the sand-filled steel pipe pile 1, preventing shaking. The cooperation of the second arc-shaped ring 41 and the third connecting plate 42 provides stable support for the support component 6 and allows for the rapid installation of the support component 6 onto both sides of the sand-filled steel pipe pile 1. It also has a disassembly function, which improves portability. The use of the insert block 51 and the through hole 52 makes it easy for users to position during installation, ensuring that the first arc ring 21 and the second arc ring 41 can fit perfectly, thereby improving the stability after assembly. The use of the first steel sheet pile 61 and the second steel sheet pile 62 can strengthen the support strength of the sand-filled steel pipe pile 1, and can be used in combination with the sand-filled steel pipe pile 1 to achieve both support and protection. The circular steel plate 70 can compact the gravel after the user has filled the sand, thereby preventing air from appearing in the gravel and ensuring that the gravel inside the sand-filled steel pipe pile 1 can completely fill and cover the inner wall of the sand-filled steel pipe pile 1.

[0028] During operation, multiple sets of sand-filled steel pipe piles 1 are first inserted into the foundation in sequence. Then, sand and gravel are poured into the interior of each pile. Next, the user aligns a circular steel plate 70 with the top of the pile and installs it onto the inner wall of the pile, allowing the plate to compact the sand and gravel inside. Then, the user places the first arc-shaped ring 21 onto one side of the pile surface, followed by the connection of the second arc-shaped ring 41 to the first ring 21. During this connection, the insertion... Block 51 is aligned with through hole 52, allowing the insert block 51 to be inserted into the third connecting plate 42, so that the first arc ring 21 and the second arc ring 41 can be accurately aligned. At that time, the user needs to fix the two sets of second connecting plates 31 with fixing bolts 32. After the third connecting plate 42 is installed, it can be used. During use, the anti-slip protrusion 23 can prevent the first arc ring 21 and the second arc ring 41 from sliding freely on the surface of the sand-filled steel pipe pile 1. At the same time, the mutual support of the first steel sheet pile 61 and the second steel sheet pile 62 can greatly improve the stability of the foundation.

[0029] The arrangement of the first arc-shaped ring, the first connecting plate, the anti-slip protrusion, the second connecting plate, and the fixing bolts enables the first arc-shaped ring, the first connecting plate, and the anti-slip protrusion to quickly connect with the second arc-shaped ring and the third connecting plate. This allows for alignment and fixation to be completed quickly during installation. The second connecting plate and the fixing bolts connect the first and second arc-shaped rings to each other, accelerating the construction progress. They also ensure that the anti-slip protrusions firmly grip the sand-filled steel pipe pile, preventing wobbling.

[0030] The design of the second arc-shaped ring, the third connecting plate, the insert block, and the through hole allows the second arc-shaped ring and the third connecting plate to work together to provide stable support for the support assembly. This also enables the support assembly to be quickly installed on both sides of the sand-filled steel pipe pile. Furthermore, it allows for disassembly, improving portability. The insert block and through hole facilitate positioning during installation, ensuring a perfect fit between the first and second arc-shaped rings, thereby enhancing the stability of the assembled structure. Example

[0031] See Figure 8 As shown, in the backfill area at the top of the existing culvert, double-section I20b steel tie beams are welded to the sand-filled steel pipe piles on both sides of the culvert to provide temporary support for the backfill at the top of the culvert. The steel tie beams are divided into horizontal bracing 200 and diagonal bracing 201. The horizontal bracing beams are set at a spacing of 1m, and the diagonal bracing beams are connected to the three horizontal bracing beams by welding.

[0032] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A deep foundation pit support composite structure using sand-filled steel pipe piles, comprising sand-filled steel pipe piles (1); characterized in that: The sand-filled steel pipe pile (1) is provided in several columns, and the sand-filled steel pipe pile (1) is arranged vertically. It also includes several Larssen steel sheet piles that are connected to each other through interlocking joints. The sand-filled steel pipe pile (1) and the several Larssen steel sheet piles are arranged side by side. A cap beam is provided on the sand-filled steel pipe pile (1).

2. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 1, characterized in that: A connecting mechanism (2) is provided on one side of the surface of the sand-filled steel pipe pile (1), and a fixing component (3) is provided on both sides of the connecting mechanism (2). The connecting mechanism (2) includes a first arc ring (21), a first connecting plate (22), and an anti-slip protrusion (23). The first arc ring (21) is provided with several of them. The several first arc rings (21) are longitudinally and movably connected to the surface of the sand-filled steel pipe pile (1). One side of the first arc ring (21) is fixedly installed with the first connecting plate (22), and the inner wall of the first arc ring (21) is fixedly installed with the anti-slip protrusion (23). The fixing component (3) includes a second connecting plate (31) and a fixing bolt (32). The second connecting plate (31) is fixedly installed on the side of the first arc ring (21) away from the first connecting plate (22). There are two sets of the second connecting plates (31). The two sets of the second connecting plates (31) are attached to each other and the two sets of the second connecting plates (31) are threadedly connected to each other by the fixing bolt (32).

3. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 2, characterized in that: A docking assembly (4) is provided on the side of the surface of the sand-filled steel pipe pile (1) away from the first arc ring (21), and a positioning assembly (5) is provided on the side of the first connecting plate (22) close to the docking assembly (4).

4. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 3, characterized in that: The docking assembly (4) is provided with a support assembly (6) on the side away from the sand-filled steel pipe pile (1).

5. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 4, characterized in that: The docking assembly (4) includes a second arc-shaped ring (41) and a third connecting plate (42). The second arc-shaped ring (41) is provided with several of them. The several second arc-shaped rings (41) are longitudinally and movably connected to the side of the sand-filled steel pipe pile (1) away from the first arc-shaped ring (21). The side of the second arc-shaped ring (41) close to the first connecting plate (22) is fixedly installed with the third connecting plate (42). The side of the second arc-shaped ring (41) away from the third connecting plate (42) is fixedly installed with another set of second connecting plates (31).

6. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 5, characterized in that: The positioning component (5) includes a plug (51) and a through hole (52). The plug (51) is fixedly installed on the side of the first connecting plate (22) near the third connecting plate (42). The through hole (52) is opened on the side of the third connecting plate (42) near the first connecting plate (22). The plug (51) is movably inserted into the inner wall of the third connecting plate (42) through the opening of the through hole (52).

7. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 6, characterized in that: The support assembly (6) includes a first sheet pile (61) and a second sheet pile (62). Each of the first sheet pile (61) and the second sheet pile (62) has several piles. Several first sheet piles (61) are welded laterally to the side of the second arc ring (41) away from the sand-filled steel pipe pile (1). Several second sheet piles (62) are welded laterally to the side of the several second arc rings (41) away from the sand-filled steel pipe pile (1). The first sheet piles (61) are in an inclined position.

8. The deep foundation pit support composite structure of sand-filled steel pipe piles according to claim 7, characterized in that: A circular steel plate (70) is movably connected to the top of the inner wall of the sand-filled steel pipe pile (1).

9. A construction method for a combined structure for deep foundation pit support using sand-filled steel pipe piles, characterized in that: Includes the following steps: (1) Drill steel pipe piles continuously in the longitudinal direction along a certain range around the proposed deep foundation pit, and the anchorage depth of the steel pipe piles into the soil shall not be less than 0.8 times the depth of the foundation pit. (2) A reinforced concrete cap beam is installed on the top of the sand-filled steel pipe pile. The width of the cap beam is 10-20cm wider than the diameter of the steel pipe pile, and the height is higher than the top of the steel pipe pile. The cap beam extends to both ends and is 1m wider than the steel pipe pile, so as to fully wrap the sand-filled steel pipe pile. (3) The sand-filled steel pipe piles and Larssen steel sheet piles are arranged side by side with the same length. The Larssen steel sheet piles are connected by interlocking method. The anchorage depth of the Larssen steel sheet piles into the soil is not less than 0.8 times the depth of the foundation pit.

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