A foundation pit double-row pile retaining structure and a construction method thereof

Abstract

This invention discloses a double-row pile retaining structure for foundation pits and its construction method, aiming to provide a double-row pile retaining structure for foundation pits with good deformation control, strong resistance to earth pressure, and high stability. A double-row pile retaining structure for foundation pits includes: a front row of piles, which are set in the soil; a front row of pile capping beam, with the top of the front row of piles connected to the front row of pile capping beam; a rear row of piles, which are set in the soil, with the front row of piles located between the rear row of piles and the foundation pit; a rear row of pile capping beam, with the top of the rear row of piles connected to the rear row of pile capping beam; a tie beam, connecting the front row of pile capping beam and the rear row of pile capping beam; and lapped steel sections, which are inserted into the soil, the lapped steel sections are inclined, the lower end of the lapped steel sections is connected to the rear row of piles, and the upper end of the lapped steel sections is connected to the tie beam or the front row of pile capping beam.

Description

Technical Field

[0001] This invention relates to the field of foundation pit support technology, specifically to a double-row pile retaining structure for foundation pits and its construction method. Background Technology

[0002] Foundation pit support typically involves installing concrete piles within the soil along the pit's sidewalls. When the site soil quality is poor, deformation control requirements are high, or the excavation depth is deep, internal bracing is usually installed to ensure the safety and stability of the foundation pit and control its deformation. For the construction of large-area foundation pits, which have large areas and long perimeters, if an internal bracing retaining structure is used, the internal bracing needs to span the entire length of the pit, resulting in inconvenient construction, high project costs, weakened rigidity due to excessive length, and unclear socio-economic benefits, failing to meet green and environmental protection goals.

[0003] Traditional double-row pile retaining structures are convenient to construct and relatively inexpensive, and are commonly used in the support of single-story basement foundation pits. However, the two rows of piles in a traditional double-row pile retaining structure are parallel to each other, making it essentially a cantilever retaining structure with poor deformation control. Under high earth pressure, traditional double-row piles are prone to deformation, which is detrimental to the protection of surrounding municipal roads and pipelines, and is unsuitable for projects with high environmental protection requirements. In projects with weak soil or high deformation control requirements, the soil between the double-row piles is conventionally reinforced and improved using processes such as mixing, jet grouting, and injection to obtain stronger overall rigidity, thereby increasing the stability of the foundation pit and its resistance to deformation. However, the quality of large-area soil reinforcement is difficult to control, and it consumes a large amount of cement resources, which is detrimental to environmental protection.

[0004] Therefore, there is an urgent need for a double-row pile retaining structure and its construction method that has good deformation control, strong resistance to earth pressure, and high stability. Summary of the Invention

[0005] The purpose of this invention is to provide a double-row pile retaining structure for foundation pits with good deformation control, strong resistance to earth pressure, and high stability, as well as its construction method.

[0006] The technical solution of this invention is:

[0007] A double-row pile retaining structure for foundation pits includes:

[0008] Front row of piles, which are set in the soil.

[0009] The top of the front row of piles is connected to the capping beam of the front row of piles;

[0010] The rear row of piles is set in the soil, and the front row of piles is located between the rear row of piles and the foundation pit;

[0011] The top of the rear piles is connected to the rear pile cap beam;

[0012] Tie beams connect the front pile cap beams and the rear pile cap beams;

[0013] The lapped steel sections are inserted into the soil at an angle. The lower ends of the lapped steel sections connect to the rear piles, while the upper ends connect to the tie beams or the front pile cap beams. This scheme integrates the front piles, front pile cap beams, and rear piles and cap beams into a single unit using lapped steel sections and tie beams. Furthermore, the lapped steel sections, the connected rear piles, and the tie beams form a triangular arrangement, effectively enhancing the stability and deformation resistance of the double-row pile retaining structure in the foundation pit. This design exhibits good deformation control, strong resistance to earth pressure, and high stability, thereby improving the overall horizontal level of the retaining structure and ensuring the safety of the foundation pit.

[0014] Preferably, the rear row of piles includes a reinforcing cage, with several lower connecting reinforcing bars on the lower end face of the lapped steel section, which are inserted into the reinforcing cage of the rear row of piles. This ensures the stability and reliability of the connection between the lower end of the lapped steel section and the rear row of piles, preventing the lower end of the lapped steel section from separating and detaching from the rear row of piles during use, thus preventing the piles from functioning effectively.

[0015] Preferably, a grouting pipe is fixed to the lapped steel section. The lapped steel section is inserted into the soil before the concrete of the rear pile solidifies, and the lower connecting steel bar is inserted into the concrete of the rear pile. The lower end of the grouting pipe is close to or inserted into the concrete of the rear pile. After the lower connecting steel bar is inserted into the concrete of the rear pile, grout is injected through the grouting pipe to reinforce the connection between the lapped steel section and the rear pile. This further improves the integrity, connection stability, and reliability of the lower connecting steel bar and the rear pile, and further avoids the problem of the lower end of the lapped steel section separating from the rear pile during the use of double-row piles.

[0016] Preferably, the lower end face of the lapped steel section is a concave arc surface, and the curvature of the concave arc surface matches the curvature of the reinforcing cage of the rear pile. In this way, after the lower connecting reinforcing bar of the lapped steel section is inserted into the concrete of the rear pile, the lower end face of the lapped steel section can be tightly pressed against the reinforcing cage of the rear pile, which helps to improve the stability and reliability of the connection between the lower end of the lapped steel section and the rear pile.

[0017] Preferably, the upper end of the lapped steel section is provided with several upper connecting steel bars, which are anchored into the tie beam or the capping beam of the front row of piles. This ensures the stability and reliability of the connection between the upper end of the lapped steel section and the tie beam or the capping beam of the front row of piles, and avoids the problem that the upper end of the lapped steel section may separate from the tie beam or the capping beam of the front row of piles during use, thus rendering it ineffective.

[0018] Preferably, a guiding device is also included. This guiding device is fixed to the ground surface and close to the front row of piles. The guiding device includes a guide steel sleeve with inclined inner holes. During the insertion of the overlapping steel section into the soil, the guide steel sleeve guides the overlapping steel section. Thus, during the insertion of the overlapping steel section into the soil, the guide steel sleeve can guide the insertion direction, ensuring that the insertion position and angle meet the requirements, and avoiding the problem of the lower end of the overlapping steel section failing to connect with the rear row of piles due to incorrect insertion position.

[0019] Preferably, the guiding device also includes a bottom steel sleeve box, which is pressed into the soil. The guide steel sleeve is located above the bottom steel sleeve box, and the guide steel sleeve is connected to the bottom steel sleeve box by steel ribs. This increases the stability of the guiding device, thereby ensuring the accuracy of the steel section insertion position and angle.

[0020] Preferably, the system also includes a fixed steel section, with the front row of piles comprising a reinforcing cage. The fixed steel section is welded to the reinforcing cage of the front row of piles, and the bottom steel sleeve is welded to the fixed steel section. This further increases the stability of the guiding device, thereby ensuring the accuracy of the steel section insertion position and angle.

[0021] As a preferred embodiment, the overlapping steel section, the rear piles connected to the overlapping steel section, and the tie beam are arranged in a triangular pattern.

[0022] A construction method for a double-row pile retaining structure for foundation pits includes the following steps:

[0023] A. Construction of the front row of piles, drilling of the holes for the front row of piles, lowering the steel cage for the front row of piles, and pouring concrete until the front row of piles is completed.

[0024] After the construction of the rear piles, the holes for the rear piles are formed, the steel cages for the rear piles are lowered, and concrete is poured until the rear piles are completed.

[0025] B, lapped steel section insertion, several lower connecting steel bars on the lower end face of the lapped steel section, and grouting pipes fixed on the lapped steel section;

[0026] Before the concrete of the rear piles solidifies, the lapped steel section is inserted into the soil at a set angle until the lower connecting steel bar at the lower end of the lapped steel section is inserted into the steel cage of the rear pile; the lower end of the grouting pipe is close to or inserted into the concrete of the rear pile.

[0027] C. Concrete grout is injected into the connection between the lapped steel and the rear piles through the grouting pipe to reinforce the connection between the lapped steel and the rear piles.

[0028] D. Cut off the portion of the upper end of the lapped steel that extends into the front pile cap beam or tie beam; then weld several connecting steel bars to the upper end face of the lapped steel.

[0029] E. Construct the reinforcing cages for the front and rear pile cap beams and tie beams, extending the upper connecting steel bars into the front pile cap beam or tie beam. Next, pour concrete for the front and rear pile cap beams and tie beams to form the front and rear pile cap beams and tie beams, and then integrate the upper connecting steel bars of the lapped steel section with the tie beam or front pile cap beam. In this way, the front piles, front pile cap beam, and rear piles and tie beams are connected as a whole through the lapped steel section and tie beam. The lapped steel section and the rear piles and tie beam connected to it form a triangular distribution, effectively improving the stability and deformation resistance of the double-row pile retaining structure in this foundation pit design. It exhibits good deformation control, strong resistance to earth pressure, and high stability, thereby improving the overall level of the retaining structure and ensuring the safety of the foundation pit.

[0030] The beneficial effects of this invention are:

[0031] Firstly, by using overlapping steel sections and tie beams, the front row of piles, the front row of pile cap beams, and the rear row of piles and the rear row of pile cap beams are connected as a whole. Furthermore, the overlapping steel sections and the rear row of piles and tie beams connected to the overlapping steel sections are arranged in a triangular distribution, which effectively improves the stability and deformation resistance of the double-row pile retaining structure of the foundation pit in this scheme. It has good deformation control effect, strong soil pressure resistance and high stability, thereby improving the overall level of the retaining structure and ensuring the safety of the foundation pit.

[0032] Secondly, ensure the stability and reliability of the connection between the lower end of the lapped steel section and the rear pile, to avoid the problem of the lower end of the lapped steel section separating from the rear pile and failing to function properly during the use of double-row piles; ensure the stability and reliability of the connection between the upper end of the lapped steel section and the tie beam or the capping beam of the front pile, to avoid the problem of the upper end of the lapped steel section separating from the tie beam or the capping beam of the front pile and failing to function properly during the use of double-row piles.

[0033] Third, during the process of inserting the lapped steel into the soil, the insertion direction of the lapped steel can be guided by the guide steel sleeve to ensure that the insertion position and angle of the lapped steel meet the requirements, thus avoiding the problem that the lower end of the lapped steel cannot be connected to the rear pile due to incorrect insertion position. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a plan view of a double-row pile retaining structure for foundation pits according to the present invention.

[0035] Figure 2 This is a three-dimensional structural diagram of a double-row pile retaining structure for foundation pits according to the present invention.

[0036] Figure 3 This is a three-dimensional structural diagram of an overlapping steel section of a double-row pile retaining structure for foundation pits according to the present invention.

[0037] Figure 4 This is a schematic diagram of a structure for connecting the lapped steel section and the rear piles in a double-row pile retaining structure for foundation pits according to the present invention.

[0038] Figure 5 This is a schematic diagram of a guiding device for a double-row pile retaining structure in a foundation pit according to the present invention.

[0039] Figure 6 This is a schematic diagram of a structure after the front and rear rows of piles are constructed in a construction method for a double-row pile retaining structure in a foundation pit according to the present invention.

[0040] Figure 7 This is a schematic diagram of a structure in the process of inserting overlapping steel into the soil in a construction method for a double-row pile retaining structure for foundation pits according to the present invention.

[0041] Figure 8 This is a schematic diagram of a structure after the lapped steel section is inserted into place in a construction method for a double-row pile retaining structure in a foundation pit according to the present invention.

[0042] In the picture:

[0043] 1. Lap-joint steel section, 1.1. Concave arc surface, 1.2. Lower connecting steel bar, 1.3. Upper connecting steel bar, 1.4. Grouting pipe;

[0044] Front pile 2;

[0045] Rear pile 3;

[0046] Front row of pile cap beam 4;

[0047] Rear pile cap beam 5;

[0048] Tie beam 6;

[0049] 7. Soil within the foundation pit;

[0050] 8. Soil outside the foundation pit;

[0051] Guide device 9, guide steel sleeve 9.1, bottom steel sleeve box 9.2, steel rib plate 9.3;

[0052] Fixed steel section 10. Detailed Implementation

[0053] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0054] Specific Implementation Example 1, such as Figure 1 , Figure 2As shown, a double-row pile retaining structure for a foundation pit includes a front row of piles 2, a rear row of piles 3, a front row pile capping beam 4, a rear row pile capping beam 5, a tie beam 6, and lapped steel sections 1. The front row of piles and the rear row of piles are both located within the soil. In this embodiment, the front row of piles is located at the boundary between the soil 7 inside the foundation pit and the soil 8 outside the foundation pit, while the rear row of piles is located within the soil 8 outside the foundation pit. The front row of piles is positioned between the rear row of piles and the foundation pit. The front and rear rows of piles are parallel. The top of the front row of piles is connected to the front row pile capping beam. The top of the rear row of piles is connected to the rear row pile capping beam. The tie beam connects the front and rear row pile capping beams. The lapped steel sections are inserted into the soil. The lapped steel sections are distributed at an angle. The lower end of the lapped steel sections is connected to the rear row of piles, and the upper end of the lapped steel sections is connected to the tie beam or the front row pile capping beam.

[0055] In this embodiment, the double-row pile retaining structure for the foundation pit connects the front row of piles, the front row of pile cap beam, and the rear row of piles and the rear row of pile cap beam into one unit through overlapping steel sections and tie beams. Furthermore, the overlapping steel sections and the rear row of piles and tie beams connected to the overlapping steel sections are arranged in a triangular distribution, thereby effectively improving the stability and deformation resistance of the double-row pile retaining structure for the foundation pit. It has good deformation control, strong resistance to earth pressure, and high stability, thereby improving the overall level of the retaining structure and ensuring the safety of the foundation pit.

[0056] Specifically, such as Figure 1 , Figure 2 As shown, the front row of piles 2 are reinforced concrete piles, including a reinforcing cage and concrete piles. There are several front row piles, distributed sequentially along the edge of the foundation pit. The top of each front row pile is connected to the front row pile capping beam 4. The rear row of piles 3 are reinforced concrete piles, including a reinforcing cage and concrete piles. There are several rear row piles, distributed sequentially along the edge of the foundation pit. The top of each rear row pile is connected to the rear row pile capping beam 5. The front row pile capping beam is a reinforced concrete pile, including a reinforcing cage and concrete beam. The rear row pile capping beam is a reinforced concrete pile, including a reinforcing cage and concrete beam. The tie beam 6 is a reinforced concrete pile, including a reinforcing cage and concrete beam. There are several tie beams. The tie beams are distributed between the front row pile capping beam and the rear row pile capping beam. There are also several lapped steel sections 1. In this embodiment, the lapped steel section is an H-beam; however, the lapped steel section can also be square steel, round steel pipe, or other types of steel. The overlapping steel sections, the rear piles connected to the overlapping steel sections, and the tie beams are arranged in a triangular pattern.

[0057] Furthermore, such as Figure 3 , Figure 4As shown, the lower end face of the lapped steel section 1 is provided with several lower connecting steel bars 1.2, which are inserted into the reinforcing cage of the rear pile 3. This ensures the stability and reliability of the connection between the lower end of the lapped steel section and the rear pile, preventing the lower end of the lapped steel section from separating from the rear pile during use and thus failing to function. In this embodiment, the lower connecting steel bars extend along the length of the lapped steel section, and each lower connecting steel bar is located within the reinforcing cage of the rear pile. None of the lower connecting steel bars extend beyond the outside of the reinforcing cage of the rear pile.

[0058] Furthermore, such as Figure 3 As shown, the lower end face of the lapped steel section is a concave arc surface 1.1, and the curvature of the concave arc surface matches the curvature of the reinforcing cage of the rear pile. The lower end face of the lapped steel section abuts against the outer wall of the reinforcing cage of the rear pile. In this way, after the lower connecting reinforcing bar of the lapped steel section is inserted into the concrete of the rear pile, the lower end face of the lapped steel section can be tightly pressed against the reinforcing cage of the rear pile, which helps to improve the stability and reliability of the connection between the lower end of the lapped steel section and the rear pile.

[0059] Furthermore, such as Figure 1 , Figure 3 As shown, the upper end face of the lapped steel section is provided with several upper connecting steel bars 1.3, which are anchored into the tie beam or the front pile cap beam. In this embodiment, the upper connecting steel bars of the lapped steel section are inserted into the steel cage of the tie beam or the front pile cap beam. This ensures the stability and reliability of the connection between the upper end of the lapped steel section and the tie beam or the front pile cap beam, avoiding the problem of the upper end of the lapped steel section separating from the tie beam or the front pile cap beam during the use of double-row piles, thus failing to perform its function. In actual construction, before the construction of the tie beam, the front pile cap beam and the rear pile cap beam, the portion of the upper end of the lapped steel section that extends into the front pile cap beam or tie beam is cut off; then, several upper connecting steel bars are welded to the upper end face of the lapped steel section.

[0060] Furthermore, such as Figure 3 As shown, a grouting conduit 1.4 is fixed to the lapped steel section. The lapped steel section is inserted into the soil before the concrete of the rear pile solidifies, and the lower connecting steel bar is inserted into the concrete of the rear pile. The lower end of the grouting conduit is close to or inserted into the concrete of the rear pile. After the lower connecting steel bar is inserted into the concrete of the rear pile, grout is injected through the grouting conduit to reinforce the connection between the lapped steel section and the rear pile. This further improves the integrity, connection stability, and reliability of the lower connecting steel bar and the rear pile, and further avoids the problem of the lower end of the lapped steel section separating from the rear pile during the use of double-row piles. In this embodiment, the lower end of the grouting conduit extends to the outside of the lower end of the lapped steel section. The length direction of the grouting conduit is parallel to that of the lapped steel section.

[0061] Furthermore, such as Figure 5 , Figure 7As shown, a double-row pile retaining structure for foundation pits also includes a guiding device 9. The guiding device is fixed to the ground surface and close to the front row of piles. The guiding device includes a guiding steel sleeve 9.1. The guiding steel sleeve has openings at both ends, and the inner diameter of the guiding steel sleeve is adapted to the cross-sectional dimensions of the overlapping steel. The inner diameter of the guiding steel sleeve is inclined. The inclination angle of the inner diameter of the guiding steel sleeve is consistent with the inclination angle of the overlapping steel. The guiding steel sleeve guides the overlapping steel during the insertion of the overlapping steel into the soil. Grease is applied to the inner wall of the inner diameter of the guiding steel sleeve to reduce the friction when the overlapping steel is inserted. In this way, during the insertion of the overlapping steel into the soil, the insertion direction of the overlapping steel can be guided by the guiding steel sleeve to ensure that the insertion position and angle of the overlapping steel meet the requirements, avoiding the problem that the lower end of the overlapping steel cannot be connected to the rear row of piles due to incorrect steel insertion position.

[0062] The guiding device also includes a bottom steel sleeve 9.2. The bottom steel sleeve is pressed into the soil, and the guide steel sleeve is located above the bottom steel sleeve. The guide steel sleeve and the bottom steel sleeve are connected by steel ribs 9.3. This increases the stability of the guiding device, thereby ensuring the accuracy of the steel section insertion position and angle.

[0063] Furthermore, such as Figure 7 As shown, a double-row pile retaining structure for foundation pits also includes a fixed steel section 10. The fixed steel section is welded to the reinforcing cage of the front row of piles. The bottom steel sleeve is welded to the fixed steel section. This further increases the stability of the guiding device, thereby ensuring the accuracy of the steel section insertion position and angle.

[0064] Specific embodiment two, such as Figure 1 , Figure 2 As shown, a construction method for a double-row pile retaining structure for foundation pits is described. The specific structure of the double-row pile retaining structure for foundation pits in this embodiment is referred to in Specific Embodiment 1.

[0065] A construction method for a double-row pile retaining structure for foundation pits includes the following steps:

[0066] A, such as Figure 6 As shown, the construction of the first row of piles 2 is carried out. Holes are formed for the first row of piles, the steel cages for the first row of piles are lowered, and concrete is poured until the first row of piles is completed.

[0067] After constructing the third row of piles, drill holes for the piles, lower the steel cages for the piles, and pour concrete until the piles are completed.

[0068] In this embodiment, the front row of piles is constructed first, followed by the rear row of piles. This facilitates the insertion of the lower connecting steel bars of the subsequent lapped steel sections into the steel cage of the rear row of piles.

[0069] B, Lap-joint steel insertion 1, before the concrete of the rear pile solidifies, insert the lap-joint steel into the soil at a set angle until the lower connecting steel bar at the lower end of the lap-joint steel is inserted into the steel cage of the rear pile, and the lower end of the grouting pipe is close to or inserted into the concrete of the rear pile.

[0070] Next, the earthwork is excavated to the bottom elevation of the capping beam (i.e., excavated to the bottom elevation of the capping beam of the front row of piles and the capping beam of the rear row of piles).

[0071] C. Concrete grout is injected into the connection between the lapped steel and the rear piles through the grouting pipe to reinforce the connection between the lapped steel and the rear piles.

[0072] D. Cut off the portion of the lapped steel section that extends into the front pile cap beam or tie beam; then weld several connecting steel bars to the upper end face of the lapped steel section.

[0073] E, such as Figure 1 As shown, the steel reinforcement cages for the front and rear pile cap beams and tie beams are constructed, with the upper connecting steel bars extending into the front pile cap beam or tie beam. Next, concrete is poured for the front and rear pile cap beams and tie beams, forming the front and rear pile cap beams and tie beams. The upper connecting steel bars of the lapped steel section are then integrated with the tie beam or front pile cap beam. In this way, the front piles, front pile cap beam, and rear piles are connected as a whole by the lapped steel section and tie beam. The lapped steel section and the rear piles and tie beam connected to it form a triangular distribution, effectively improving the stability and deformation resistance of the double-row pile retaining structure in this foundation pit design. It exhibits good deformation control, strong resistance to earth pressure, and high stability, thereby improving the overall level of the retaining structure and ensuring the safety of the foundation pit.

[0074] Furthermore, step A1 is included between step A and step B. For example... Figure 7 As shown, step A1 includes placing the guide device, using static pressure to press the bottom steel sleeve into the soil, then chiseling out the reinforcing cage of the front row of piles, welding the fixed steel section to the reinforcing cage of the front row of piles, and welding the bottom steel sleeve to the fixed steel section to fix and install the guide device; then, grease is applied to the inside of the guide steel sleeve. Next, during the insertion of the lapped steel section in step B, the insertion direction of the lapped steel section can be guided by the guide steel sleeve (the lapped steel section is inserted into the guide steel sleeve), ensuring that the insertion position and angle of the lapped steel section meet the requirements, so that the lower connecting steel bar at the lower end of the lapped steel section is inserted into the reinforcing cage of the rear row of piles, avoiding the problem of the lower end of the lapped steel section failing to connect with the rear row of piles due to incorrect steel section insertion position.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A double-row pile retaining structure for foundation pits, characterized in that, include: The front row of piles is set within the soil. The top of the front row of piles is connected to the capping beam of the front row of piles; The rear row of piles is set in the soil, and the front row of piles is located between the rear row of piles and the foundation pit; The top of the rear piles is connected to the rear pile cap beam; Tie beams connect the front pile cap beams and the rear pile cap beams; The lapped steel section is inserted into the soil. The lapped steel section is distributed at an angle. The lower end of the lapped steel section is connected to the rear pile, and the upper end of the lapped steel section is connected to the tie beam or the front pile cap beam. The guiding device is fixed on the ground surface and close to the front row of piles. The guiding device includes a guide steel sleeve and a bottom steel sleeve box. The inner hole of the guide steel sleeve is inclined. The guide steel sleeve guides the overlapping steel during the process of inserting the overlapping steel into the soil. The bottom steel sleeve box is pressed into the soil. The guide steel sleeve is located above the bottom steel sleeve box. The guide steel sleeve and the bottom steel sleeve box are connected by steel ribs.

2. The double-row pile retaining structure for foundation pits according to claim 1, characterized in that, The rear pile includes a reinforcing cage, and the lower end face of the lapped steel section is provided with several lower connecting steel bars, which are inserted into the reinforcing cage of the rear pile.

3. The double-row pile retaining structure for foundation pits according to claim 2, characterized in that, A grouting pipe is fixed on the lapped steel section. The lapped steel section is inserted into the soil before the concrete of the rear pile solidifies, and the lower connecting steel bar is inserted into the concrete of the rear pile. The lower end of the grouting pipe is close to or inserted into the concrete of the rear pile. After the lower connecting steel bar is inserted into the concrete of the rear pile, grouting is injected through the grouting pipe to reinforce the connection between the lapped steel section and the rear pile.

4. A double-row pile retaining structure for foundation pits according to claim 2 or 3, characterized in that, The lower end face of the lapped steel section is a concave arc surface, and the curvature of the concave arc surface matches the curvature of the reinforcing cage of the rear pile.

5. A double-row pile retaining structure for foundation pits according to claim 1, 2, or 3, characterized in that, The upper end face of the lapped steel section is provided with several upper connecting steel bars, which are anchored into the tie beam or the front pile cap beam.

6. A double-row pile retaining structure for foundation pits according to claim 1, 2, or 3, characterized in that, It also includes fixed steel sections, and the front row of piles includes a steel reinforcement cage, with the fixed steel sections welded to the steel reinforcement cage of the front row of piles.

7. A double-row pile retaining structure for foundation pits according to claim 6, characterized in that, The bottom steel casing is welded to the fixed steel frame.

8. A double-row pile retaining structure for foundation pits according to claim 1, 2, or 3, characterized in that, The overlapping steel section, the rear piles connected to the overlapping steel section, and the tie beam are arranged in a triangular pattern.

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