A deep foundation pit multi-row pile construction method

Abstract

The application relates to a deep foundation pit multi-row pile construction method, which comprises the following steps: S1, constructing a water-stopping curtain pile group, a first row of piles and a second row of piles; S2, excavating a first layer of earthwork and constructing a first prestressed anchor rod and a first row of pile crown beams; S3, constructing a second prestressed anchor rod, a first row of pile waist beams, a second row of pile crown beams and connecting beams; S4, installing a steel structure support assembly; and S5, vertically excavating downwards along the second row of piles to the bottom of the foundation pit. The application can reduce the inclination of the foundation pit and the settlement influence of the environment near the edge of the foundation pit.

Description

Technical Field

[0001] This application relates to the field of foundation pit support, and in particular to a method for constructing multi-row piles for deep foundation pits. Background Technology

[0002] When excavating deep foundation pits, especially large deep foundation pits for high-speed railway stations, the surrounding environment can be easily affected, such as causing settlement of existing railways and affecting track smoothness. Therefore, double-row pile cantilever support is often used to protect the foundation pit soil and reduce the lateral tilting of the foundation pit soil.

[0003] However, the applicable depth of double-row pile cantilever support is limited. When the depth of the foundation pit is large, the support capacity of double-row piles is poor and the ability to resist the lateral tilting of the foundation pit soil is weak. Summary of the Invention

[0004] In order to improve the support effect of deep foundation pits and reduce the impact on the surrounding environment, this application provides a method for constructing multi-row piles for deep foundation pits.

[0005] This application provides a method for constructing multi-row piles in deep foundation pits, which adopts the following technical solution:

[0006] A method for constructing multi-row piles in deep foundation pits includes the following steps:

[0007] S1. Mark out the outer perimeter and inner perimeter of the foundation pit, and construct a water-stop curtain pile group in the area between the outer perimeter and inner perimeter of the foundation pit. The plane where the top of the water-stop curtain pile group is located is set as a secondary horizontal plane. Construct the first row of piles on the side of the outer perimeter of the foundation pit away from the water-stop curtain pile group, and construct the second row of piles on the side of the inner perimeter of the foundation pit away from the water-stop curtain pile group. The top of the first row of piles is provided with a half pile part, and the lowest point of the half pile part is located in the primary horizontal plane. The plane where the top of the second row of piles is located is located in the secondary horizontal plane.

[0008] S2. Excavate the first layer of soil to the first horizontal plane, and construct the first prestressed anchor rod on the side wall of the first layer of soil. The exposed end of the first prestressed anchor rod is located between two adjacent half piles. Then, construct the first row of pile cap beams. The first row of pile cap beams is located at the inner right angle of the half pile. Then, use the first row of pile cap beams as the load-bearing foundation to apply prestress to the first prestressed anchor rod.

[0009] S3. Excavate the second layer of soil to the secondary horizontal plane, exposing the top of the second row of piles. Construct the second prestressed anchor rod, with the exposed end of the second prestressed anchor rod located between the tops of two adjacent piles in the second row. Then, integrally cast the first row of pile waist beam, the second row of pile cap beam, and the connecting beam. The first row of pile waist beam is located at the waist of the first row of piles, the second row of pile cap beam is located at the top of the second row of piles, and the connecting beam connects the first row of pile waist beam and the second row of pile cap beam. The opposing surfaces of the first row of pile cap beam and the second row of pile cap beam are parallel. Then, using the second row of pile cap beam as the load-bearing foundation, apply prestress to the second prestressed anchor rod.

[0010] S4. Install steel structure support components between the first row of pile cap beams and the second row of pile cap beams. The steel structure support components are respectively abutted and fixed on the opposite surfaces of the first row of pile cap beams and the second row of pile cap beams.

[0011] S5. Excavate vertically downwards along the second row of piles to the bottom of the foundation pit.

[0012] By adopting the above technical solution, firstly, compared with the traditional double-row pile cap beam connection structure, the first row pile waist beam, the second row pile cap beam, the connecting beam and the steel structure support components of this application constitute a spatial support structure, and together with the half pile part, to provide strong support for the soil above the foundation pit, thereby indirectly increasing the overall foundation pit depth that the first row pile and the second row pile can support, that is, the anti-tilting ability of deep foundation pit soil is stronger, thus meeting the requirements of deep foundation pit support and reducing the impact on the surrounding area of ​​the foundation pit.

[0013] Secondly, by setting up a water-stop curtain pile group, it is possible not only to reduce the precipitation of the soil around the foundation pit to maintain water pressure and reduce the settlement of the surrounding soil, but also to reinforce the soil near the outer perimeter and inner perimeter of the foundation pit, thereby improving the anchorage strength of the first and second rows of piles and thus improving the support strength of the foundation pit.

[0014] Thirdly, by setting the first prestressed anchor rod and the second prestressed anchor rod, the deformation range of the first row of piles and the second row of piles can be controlled by prestressing, thereby improving the positional accuracy and anchoring effect of the first row of piles and the second row of piles.

[0015] Optionally, a semi-circular first pressure plate is installed on the horizontal surface of the half pile, and a vertical plate is installed on the vertical surface of the half pile. The vertical plate and the first pressure plate are integrally formed and connected. A first embedded bar is fixed through the first pressure plate. The lower end of the first embedded bar extends into the concrete of the first row of piles, and the upper end of the first embedded bar is located in the capping beam of the first row of piles.

[0016] By adopting the above technical solution, the first pressure plate and the vertical plate can serve as part of the template to facilitate the casting and forming of the pile body and half pile of the first row of piles. Secondly, by setting the first embedded reinforcement, the connection strength between the first row of pile cap beam and the first row of piles can be improved, thereby improving the force transmission effect.

[0017] Optionally, a circular second pressure plate is installed on the top of the second row of piles, and a second embedded bar is fixed through the second pressure plate. The lower end of the second embedded bar extends into the concrete of the second row of piles, and the upper end of the second embedded bar is located in the capping beam of the second row of piles.

[0018] By adopting the above technical solution, by setting a second pressure plate, which can serve as part of the template, it is possible to cast and shape the pile body of the second row of piles. Secondly, by setting a second embedded reinforcement bar, the connection strength between the second row of pile cap beam and the second row of piles can be improved, thereby improving the force transmission effect.

[0019] Optionally, the steel structure support assembly includes multiple first connecting seats, second connecting seats, and steel pipes, wherein each of the first and second connecting seats is fixed with a rotating shaft, and both ends of the steel pipe are hinged to the rotating shafts of the first and second connecting seats respectively; each of the first connecting seats is arranged at intervals along the length direction of the second row of pile cap beams, and the first connecting seats are fixedly connected to the second row of pile cap beams by first expansion bolts; each of the second connecting seats is arranged at intervals along the length direction of the first row of pile cap beams, and the second connecting seats are fixedly connected to the first row of pile cap beams by second expansion bolts.

[0020] By adopting the above technical solution, firstly, by setting up a first connecting seat, a second connecting seat, and a steel pipe, and using their hinged connection, the positions of adjacent first connecting seats can be adjusted, and the inclination angle of the steel pipe can be changed, thereby adapting to the different distances between the first row of pile cap beams and the second row of pile cap beams. This facilitates the improvement of the installation accuracy of the steel structure support components, thereby ensuring the accuracy of force transmission and the support effect.

[0021] Secondly, when the lateral pressure of the first row of piles is applied to the second connecting seat and steel pipe through the first row of pile cap beam, the pressure direction is the axial direction of the steel pipe due to the cross-inclined arrangement of the steel pipes. Therefore, the pressure components of the two adjacent steel pipes cancel each other out, thereby indirectly improving the support strength of the steel structure support component and thus improving the anti-tilting ability.

[0022] Optionally, in step S3, inclined trenches are excavated on both sides of the top of the second row of piles, extending along the arrangement direction of the second row of piles. Then, the soil between adjacent piles of the second row of piles and the soil in the gap between the top of the second row of piles and the second pressure plate are removed to form the lower half of the area to be poured. Then, triangular steel reinforcement groups are placed in the inclined trenches, and formwork is erected. The formwork is closed to form the upper half of the area to be poured. Then, concrete is injected into the upper half of the area to be poured and the lower half of the area to be poured to form the cap beam of the second row of piles.

[0023] By adopting the above technical solution, the lower half of the area to be poured is formed by excavating inclined trenches and hollowing out the soil, and by coordinating with triangular steel reinforcement groups, a second row of reinforced concrete pile cap beams with a large cross section is formed, thereby greatly improving the structural strength of the second row of pile cap beams.

[0024] Furthermore, part of the concrete of the second row of pile cap beam is embedded into the top of the second row of piles, thus greatly improving the connection strength between the second row of pile cap beam and the second row of piles.

[0025] Optionally, the steel structure support assembly includes two guide rails, multiple first connecting seats, second connecting seats, and steel pipes. The two guide rails are respectively disposed on the opposite surfaces of the first row of pile cap beams and the second row of pile cap beams, and the guide rails extend along the length direction of the second row of pile cap beams. The first connecting seats and the second connecting seats are slidably connected to the two guide rails, and each of the first connecting seats and the second connecting seat is fixed with a rotating shaft. The two ends of the steel pipe are respectively hinged to the rotating shafts of the first connecting seats and the second connecting seats. A first steel strand is fixedly connected between two adjacent first connecting seats, and the first steel strand is in a taut state.

[0026] By adopting the above technical solution, by setting the first steel strand, the prestress of the first steel strand in the tensioned state is used to force the two first connecting seats to move closer to each other. The prestress of the first steel strand can be applied to the second connecting seat through the steel pipe, so that the second connecting seat is forced to abut more tightly against the guide rail. That is, the prestress of the first steel strand is converted into a force perpendicular to the inner surface of the two guide rails. This force is the prestress, which effectively copes with the lateral pressure of the first row of piles, thereby indirectly improving the support strength of the steel structure support component.

[0027] Optionally, a hooked steel bar is fixed to the back of the guide rail of the first row of pile cap beams. The hooked steel bar is anchored into the first row of pile cap beams. A detachable side stop is provided on one side of the guide rail of the first row of pile cap beams. The side stop is used to restrict the second connecting seat from detaching from the guide rail. A back plate is provided on the back of the guide rail of the second row of pile cap beams. The back plate is fixedly connected to the second row of pile cap beams. The guide rail and the back plate are slidably connected along the width direction of the guide rail. In step S4, the first connecting seat is installed on the guide rail. Then, the first connecting seats at both ends are tensioned and moved to tighten the first steel strand. Then, the guide rail is slid along the width direction of the guide rail so that the steel pipe is located between the opposite surfaces of the first row of pile cap beams and the second row of pile cap beams. The second connecting seat enters the guide rail along the side of the guide rail of the first row of pile cap beams without the side stop. Then, the tension of the first connecting seat is released. The prestress of the first steel strand forces the adjacent first connecting seats to move closer to each other. The second connecting seat is tightly abutted against the inside of the guide rail of the first row of pile cap beams. Then, the side stop is fixed to prevent the second connecting seat from detaching from the guide rail.

[0028] By adopting the above technical solution, by setting side stops and guide rails that can slide along their own width direction, the first connection at the beginning and end positions is tightened, and the first steel strand is pre-tensioned so that the width of the steel structure support component is less than the distance between the first row of pile cap beams and the second row of pile cap beams. This allows the steel structure support component to enter between the first row of pile cap beams and the second row of pile cap beams when the guide rails slide along the width direction. Then, the side stops are used to restrict the position of the steel structure support component, so as to facilitate the tensioning and subsequent installation of the steel structure support component.

[0029] Optionally, multiple force transmission plates are arranged at intervals inside the guide rail of the second row of pile cap beams. The force transmission plates are slidably connected to the guide rail and are located between two adjacent first connecting seats. Both sides of the force transmission plate in the length direction are provided with first guide surfaces. A second steel strand is fixedly connected between two adjacent force transmission plates. The second steel strand is in a taut state. The two sides of the first connecting seat in the sliding direction are provided with second guide surfaces, which are in contact with the first guide surfaces. The guide rail is fixed with a top-pressing bolt. The end of the top-pressing bolt abuts against the first connecting seat to force the first connecting seat to move closer to the force transmission plate.

[0030] By adopting the above technical solution, when the lateral pressure of the first row of piles is applied sequentially to the second connecting seat, steel pipe, first connecting seat and force transmission plate through the first row of pile cap beam, the lateral pressure will be transformed into a force that forces the first steel strand and the second steel strand to be further tensioned through the cooperation of the first guide surface and the second guide surface. The prestress of the first steel strand and the second steel strand effectively resists this force, so as to effectively cope with the lateral pressure of the first row of piles, thereby indirectly improving the support strength of the steel structure support component.

[0031] Optionally, a PTFE membrane is laid on the inner surface of the guide rail located on the second row of pile cap beams. The PTFE membrane is partially bonded to the inner surface of the guide rail, and the bonded part extends along the length of the guide rail. Lubricating oil is injected into the PTFE membrane and the inner surface of the guide rail. Rounded corners are provided on both sides of the sliding direction of the first connecting seat.

[0032] By adopting the above technical solution, firstly, the PTFE membrane has high strength and low surface roughness, which can improve the smoothness of the sliding of the first connecting seat, thereby increasing the ease with which it can resist the lateral pressure of the first row of piles due to the displacement of the first connecting seat, and thus improving the force transmission effect and support effect.

[0033] Secondly, by adding lubricating oil, not only can the lubrication between the PTFE membrane and the guide rail be increased, but the lubricating oil can also overflow after the PTFE membrane is accidentally damaged due to excessive tilting pressure, so as to further improve the lubrication effect and cope with the situation of excessive tilting pressure.

[0034] Optionally, the angle between the first prestressed anchor rod and the vertical plane is 30 degrees, the angle between the second prestressed anchor rod and the vertical plane is 60 degrees, and the angle between the support direction of the steel structure support assembly and the vertical plane is 60 degrees.

[0035] By adopting the above technical solutions and setting various angles, the force transmission effect of steel structure support components can be effectively improved.

[0036] In summary, this application includes at least one of the following beneficial technical effects:

[0037] 1. By setting up a spatial support structure consisting of a first row of pile waist beams, a second row of pile cap beams, connecting beams, and steel structure support components, and in conjunction with half piles, the soil above the foundation pit is strongly supported, thereby indirectly increasing the overall support depth of the foundation pit for the first and second rows of piles. Furthermore, the water-stop curtain pile group can not only reduce the precipitation and settlement of the soil around the foundation pit, but also reinforce the soil near the outer perimeter and inner perimeter of the foundation pit, thereby increasing the anchorage strength of the first and second rows of piles and improving the support strength for the foundation pit soil, so as to reduce the impact on the perimeter of the foundation pit.

[0038] 2. By excavating inclined trenches, hollowing out the soil, and coordinating with triangular steel reinforcement groups, a second row of reinforced concrete pile cap beams with large cross sections are formed, thereby greatly improving the structural strength and connection strength of the second row of pile cap beams;

[0039] 3. By setting the first steel strand and the second steel strand, when the lateral pressure of the first row of piles forces the first connecting seat to move along the vertical guide rail direction and is applied to the force transmission plate through the first connecting seat, the lateral pressure is transformed into a force that forces the first steel strand and the second steel strand to be further tensioned through the cooperation of the first guide surface and the second guide surface. The prestress of the first steel strand and the second steel strand effectively resists this force, so as to effectively cope with the lateral pressure of the first row of piles, thereby indirectly improving the support strength of the steel structure support component. Attached Figure Description

[0040] Figure 1 This is a flowchart of the construction method in Example 1.

[0041] Figure 2 This is a schematic diagram of step S1 in Example 1.

[0042] Figure 3 This is a structural schematic diagram of step S3 in Example 1.

[0043] Figure 4 This is a schematic diagram of step S4 in Example 1.

[0044] Figure 5 This is a schematic diagram of the steel structure support component of Example 1.

[0045] Figure 6 This is a cross-sectional view of the second row of pile cap beams in Example 2.

[0046] Figure 7 This is a cross-sectional view of the guide rail on the first row of pile cap beams in Example 3.

[0047] Figure 8 This is a schematic diagram of the guide rail on the second row of pile cap beams in Example 3.

[0048] Figure 9 This is a schematic diagram of the steel structure support component of Example 3.

[0049] Figure 10 This is a schematic diagram of the first steel strand in Example 3.

[0050] Figure 11 This is a cross-sectional view of the first connecting seat in Embodiment 4.

[0051] Figure 12 This is a schematic diagram of the steel structure support component of Example 5.

[0052] Figure 13 yes Figure 12 A magnified view of a portion of point A in the middle.

[0053] Figure 14 This is a schematic diagram of the guide rail on the second row of pile cap beams in Example 5.

[0054] Explanation of reference numerals in the attached drawings: 1. First row of piles; 2. Second row of piles; 3. Steel structure support assembly; 10. Water-stop curtain pile group; 110. Outer perimeter of the foundation pit; 120. Inner perimeter of the foundation pit; 111. Waist beam of the first row of piles; 112. Connecting beam; 11. Half pile; 12. Vertical plate; 13. First pressure plate; 14. First embedded reinforcement; 15. First prestressed anchor; 16. First row of pile cap beam; 21. Second pressure plate; 22. Second embedded reinforcement; 23. Second row of pile cap beam; 231. Inclined groove; 232. Horizontal reinforcement; 233. Reinforcing ring; 24. Second prestressed anchor; 31. First connecting seat; 311. Rotating shaft; 312. Base plate; 313. 314. Side plate; 315. Rounded corner; 316. Second guide surface; 32. Second connecting seat; 33. Steel pipe; 337. First expansion bolt; 338. Second expansion bolt; 339. Third expansion bolt; 300. Fourth expansion bolt; 310. Fifth expansion bolt; 331. Sixth expansion bolt; 32. Guide rail; 331. Side guard; 342. Back plate; 343. Dovetail groove; 344. Dovetail block; 345. Hooked steel bar; 346. Strip hole; 347. Top pressure bolt; 36. First steel strand; 361. First screw; 37. Force transmission plate; 38. First guide surface; 39. Second steel strand; 30. Second screw. Detailed Implementation

[0055] The following is in conjunction with the appendix Figure 1-14 This application will be described in further detail.

[0056] Embodiment 1 of this application discloses a method for constructing multi-row piles in deep foundation pits.

[0057] Reference Figure 1 The construction method for multiple rows of piles in deep foundation pits includes the following steps:

[0058] S1, such as Figure 2 As shown, the outer perimeter 110 and inner perimeter 120 of the foundation pit are marked out, and a water-stopping curtain pile group 10 is constructed in the area between the outer perimeter 110 and the inner perimeter 120. The plane where the top of the piles of the water-stopping curtain pile group 10 is located is set as a secondary horizontal plane, that is, there is a section of empty pile area from the top surface of the piles of the water-stopping curtain pile group 10 to the ground surface. The water-stopping curtain pile group 10 can not only reduce the precipitation of the soil around the foundation pit to maintain water pressure and reduce the settlement of the surrounding soil, but also reinforce the soil near the outer perimeter 110 and the inner perimeter 120 of the foundation pit.

[0059] The first row of piles 1 is constructed on the side of the outer perimeter 110 of the foundation pit away from the water-stop curtain pile group 10. The first row of piles 1 is a reinforced concrete cast-in-place pile. The top of the pile of the first row of piles 1 is provided with a half pile part 11. The specific forming method of the half pile part 11 is as follows: before pouring, a semi-circular first pressure plate 13 is installed on the horizontal surface of the half pile part 11, and a vertical plate 12 is installed on the vertical surface of the half pile part 11. The vertical plate 12 and the first pressure plate 13 are integrally formed and connected. The first pressure plate 13 has grouting holes (not shown in the figure). The first pressure plate 13 and the vertical plate 12 are part of the template to facilitate the casting and forming of the pile body and half pile part 11 of the first row of piles 1. Furthermore, a first embedded bar 14 is also fixed through the first pressure plate 13. The lower end of the first embedded bar 14 extends into the concrete of the first row of piles 1 to strengthen the connection strength of the first pressure plate 13. The upper end of the first embedded bar 14 is higher than the first pressure plate 13.

[0060] The plane where the first pressure plate 13 on the half pile 11 is located is set as the primary horizontal plane, which is higher than the secondary horizontal plane.

[0061] A second row of piles 2 is constructed on the side of the perimeter 120 of the foundation pit away from the water-stop curtain pile group 10. The second row of piles 2 is a reinforced concrete cast-in-place pile, and the plane where the top of the second row of piles 2 is located is in a secondary horizontal plane. Specifically, before pouring, a circular second pressure plate 21 is installed on the top of the second row of piles 2. The second pressure plate 21 has grouting holes (not shown in the figure). The plane where the second pressure plate 21 is located is a secondary horizontal plane. The second pressure plate 21 acts as part of the template to facilitate the formation of the pile body of the second row of piles 2.

[0062] Furthermore, a second embedded bar 22 is fixed through the second pressure plate 21. The lower end of the second embedded bar 22 extends into the concrete of the second row of piles 2 to strengthen the connection strength of the second pressure plate 21. The upper end of the second embedded bar 22 is higher than the second pressure plate 21.

[0063] S2, such as Figure 3 As shown, the first layer of soil is excavated to the first horizontal plane. The first prestressed anchor rod 15 is constructed on the side wall of the first layer of soil. The angle between the first prestressed anchor rod 15 and the vertical plane is 30 degrees. The exposed end of the first prestressed anchor rod 15 is located between two adjacent half piles 11. Then, the first row of pile cap beams 16 is constructed. The first row of pile cap beams 16 is located at the inner right angle of the half pile 11. The first row of pile cap beams 16 has an inclined surface, and the angle between the inclined surface and the vertical plane is 30 degrees. When pouring the first row of pile cap beams 16, the upper end of the first embedded reinforcement 14 is anchored into the concrete of the first row of pile cap beams 16, thereby improving the connection strength between the first row of pile cap beams 16 and the first row of piles 1. After the first row of pile cap beams 16 has been cured to 80% of the design strength, the first row of pile cap beams 16 is used as the load-bearing foundation to apply prestress to the first prestressed anchor rod 15.

[0064] S3. Excavate the second layer of soil to the secondary horizontal plane, exposing the tops of the second row of piles 2 and the tops of the water-stop curtain pile group 10. Then, construct the second prestressed anchor rod 24. The angle between the second prestressed anchor rod 24 and the vertical plane is 60 degrees. The second prestressed anchor rod 24 passes through the water-stop curtain pile group 10. The exposed end of the second prestressed anchor rod 24 is located between two adjacent pile tops of the second row of piles 2. Then, integrally cast the first row of pile waist beam 111 and the second row of pile waist beam 111. The pile cap beam 23 and the connecting beam 112 are provided. The first row of pile waist beam 111 is located at the waist of the first row of piles 1, the second row of pile cap beam 23 is located at the top of the second row of piles 2, and the connecting beam 112 connects the first row of pile waist beam 111 and the second row of pile cap beam 23. The second row of pile cap beam 23 has an inclined surface with an angle of 30 degrees between the inclined surface and the vertical surface. That is, the inclined surface of the second row of pile cap beam 23 and the inclined surface of the first row of pile cap beam 16 form opposite surfaces and are parallel to each other.

[0065] Furthermore, in order to strengthen the connection strength of the first row of pile waist beam 111, steel bars can be pre-embedded in the waist of the first row of piles 1, and the other end of the steel bars is anchored into the concrete of the first row of pile waist beam 111.

[0066] When the second row of pile cap beam 23 is poured, the upper end of the second embedded bar 22 is anchored into the concrete of the second row of pile cap beam 23, thereby improving the connection strength between the second row of pile cap beam 23 and the second row of piles 2.

[0067] After the second row of pile cap beam 23 has been cured to 80% of its design strength, prestress is applied to the second prestressed anchor rod 24 using the second row of pile cap beam 23 as the load-bearing foundation.

[0068] S4, such as Figure 4 As shown, a steel structure support component 3 is installed between the first row of pile cap beam 16 and the second row of pile cap beam 23. The steel structure support component 3 is respectively abutted and fixed on the opposite surfaces of the first row of pile cap beam 16 and the second row of pile cap beam 23, and the angle between the support direction of the steel structure support component 3 and the vertical plane is 60 degrees.

[0069] like Figure 5 As shown, the steel structure support component 3 includes multiple first connecting seats 31, second connecting seats 32 and steel pipes 33. Each first connecting seat 31 is arranged at intervals along the length direction of the second row of pile cap beams 23, and each second connecting seat 32 is arranged at intervals along the length direction of the first row of pile cap beams 16. The first connecting seats 31 and the second connecting seats 32 are staggered.

[0070] The first connecting seat 31 and the second connecting seat 32 each include a base plate 312 and two side plates 313. A rotating shaft 311 is fixed between the two side plates 313 of the first connecting seat 31 and the second connecting seat 32. The two ends of the steel pipe 33 are respectively hinged to the rotating shaft 311 of the first connecting seat 31 and the second connecting seat 32, and one end of the two steel pipes 33 is simultaneously hinged to a rotating shaft 311.

[0071] During installation, the first connecting seat 31, the second connecting seat 32, and the steel pipe 33 are placed in the area between the first row of pile cap beams 16 and the second row of pile cap beams 23, ensuring that the base plate 312 of the first connecting seat 31 abuts against the inclined surface of the second row of pile cap beams 23. Then, the position of the first connecting seat 31 is adjusted, and the position of the second connecting seat 32 is adjusted by swinging the steel pipe 33, so that the second connecting seat 32 abuts against the inclined surface of the first row of pile cap beams 16. Then, the first connecting seat 31 is fixedly connected to the second row of pile cap beams 23 by the first expansion bolt 331, and the second connecting seat 32 is fixedly connected to the first row of pile cap beams 16 by the second expansion bolt 332, thereby completing the installation of the steel structure support component 3.

[0072] S5. Excavate vertically downwards along the second row of piles 2 to the bottom of the foundation pit.

[0073] The implementation principle of Example 1 is as follows: First, the first row of pile waist beam 111, the second row of pile cap beam 23, the connecting beam 112 and the steel structure support component 3 are used to form a spatial support structure, and in conjunction with the half pile part 11, to provide strong support for the soil above the foundation pit, thereby indirectly increasing the overall foundation pit depth that the first row of piles 1 and the second row of piles 2 can support, thus meeting the requirements of deep foundation pit support and reducing the impact on the surrounding area of ​​the foundation pit.

[0074] Furthermore, the construction of the water-stop curtain pile group 10 can reinforce the soil near the outer perimeter 110 and inner perimeter 120 of the foundation pit, thereby improving the anchorage strength of the first row of piles 1 and the second row of piles 2, and thus improving the support strength of the foundation pit, further meeting the requirements of deep foundation pit support, so as to reduce the impact on the perimeter of the foundation pit.

[0075] Example 2

[0076] The difference between Example 2 and Example 1 is that, as Figure 6 As shown, in step S1, the pouring height of the second row of piles 2 is controlled so that the top of the second row of piles 2 is lower than the second pressure plate 21, that is, there is a gap between the second pressure plate 21 and the top of the second row of piles 2.

[0077] In step S3, inclined grooves 231 are excavated on both sides of the top of the second row of piles 2. The inclined grooves 231 extend along the arrangement direction of the second row of piles 2. Then, the soil between adjacent piles of the second row of piles 2 and the soil in the gap between the top of the second row of piles 2 and the second pressure plate 21 are removed to form the lower half of the area to be poured. Then, triangular steel reinforcement groups are placed in the inclined grooves 231. The triangular steel reinforcement groups include three horizontal bars 232. The three horizontal bars 232 are fixedly connected by steel reinforcement rings 233. Then, a formwork is erected and enclosed to form the upper half of the area to be poured. Then, concrete is injected into the upper half of the area to be poured and the lower half of the area to be poured to form the second row of pile cap beam 23. This forms a large-section reinforced concrete second row of pile cap beam 23, which greatly improves the structural strength of the second row of pile cap beam 23. Furthermore, part of the concrete of the second row of pile cap beam 23 is embedded into the top of the second row of piles 2, thus greatly improving the connection strength between the second row of pile cap beam 23 and the second row of piles 2.

[0078] Example 3

[0079] The difference between Example 3 and Example 1 is that, as Figure 7 As shown, the steel structure support component 3 also includes two guide rails 34, which are respectively set on the opposite surfaces of the first row of pile cap beams 16 and the second row of pile cap beams 23. The guide rails 34 extend along the length of the first row of pile cap beams 16 and the second row of pile cap beams 23. Specifically, a hooked steel bar 345 is fixed to the back of the guide rail 34 located on the first row of pile cap beams 16. The hooked steel bar 345 is anchored into the first row of pile cap beams 16, that is, the guide rail 34 is fixedly connected to the first row of pile cap beams 16. The second connecting seat 32 is slidably connected to the guide rail 34. Furthermore, one side of the guide rail 34 has a detachable side stop 341, that is, it is detachably connected by bolts. The side stop 341, as part of the guide rail 34, can assist the sliding of the second connecting seat 32 and at the same time restrict the second connecting seat 32 from disengaging from the guide rail 34.

[0080] like Figure 8As shown, a back plate 342 is provided on the back of the guide rail 34 located on the second row of pile cap beam 23. The first connecting seat 31 is slidably connected to the guide rail 34. The back plate 342 is fixedly connected to the second row of pile cap beam 23. The surface of the back plate 342 is provided with a dovetail groove 343 that runs through it along its own width direction. A dovetail block 344 extending along its own width direction is fixed on the back of the guide rail 34. The dovetail block 344 and the dovetail groove 343 slide and engage, so that the guide rail 34 and the back plate 342 slide and connect along the width direction of the guide rail 34.

[0081] like Figure 9 , Figure 10 As shown, a first steel strand 36 is fixedly connected between two adjacent first connecting seats 31. The first steel strand 36 is in a taut state. The specific fixed connection method can be that the bottom plate 312 of the first connecting seat 31 is provided with a first threaded hole on both sides, and a first screw 361 is fixed to the end of the first steel strand 36. The first screw 361 is threadedly engaged with the first threaded hole.

[0082] During installation, the first connecting seat 31 is installed onto the guide rail 34. Then, the first connecting seats 31 at both ends are tensioned and moved simultaneously in opposite directions to tighten each of the first steel strands 36. This tension is maintained, and the guide rail 34 is slid along its width, causing the first connecting seat 31, the second connecting seat 32, and the steel pipe 33 to move into the area between the opposite faces of the first row of pile cap beams 16 and the second row of pile cap beams 23. At the same time, the second connecting seat 32 enters the guide rail 34 through the side of the guide rail 34 without the side guard 341. Then, the tension of the first connecting seat 31 is released, and the prestress of the first steel strands 36 forces the adjacent first connecting seats 31 to move closer to each other. The swing of the steel pipe 33 forces the second connecting seat 32 to press tightly against the inside of the guide rail 34 of the first row of pile cap beams 16. At this time, the first steel strands 36 still have a large prestress. Then, the side guard 341 is fixed to prevent the second connecting seat 32 from detaching from the guide rail 34.

[0083] To ensure the stability of the connection, the following steps can be performed: a strip hole 346 extending along the length of the guide rail 34 is pre-set on the guide rail 34; the first connecting seat 31 at the first position is fixedly connected to the second row of pile cap beam 23 by the third expansion bolt 333; and the second connecting seat 32 at the last position is fixedly connected to the first row of pile cap beam 16 by the fourth expansion bolt 334. The third expansion bolt 333 and the fourth expansion bolt 334 pass through the strip hole 346 respectively.

[0084] The implementation principle of Example 3 is as follows: the prestress of the first steel strand 36 under tension is used to force the two first connecting seats 31 to move closer to each other, so that the prestress of the first steel strand 36 can be applied to the second connecting seat 32 through the steel pipe 33, so that the second connecting seat 32 is forced to abut more tightly against the guide rail 34. This force also forces the first connecting seat 31 to abut more tightly against the guide rail 34. That is, the prestress of the first steel strand 36 is converted into a force perpendicular to the inner surface of the two guide rails 34, so as to effectively cope with the lateral pressure of the first row of piles 1, thereby indirectly improving the support strength of the steel structure support component 3.

[0085] Example 4

[0086] The difference between Example 4 and Example 3 is that, as Figure 11 As shown, the base plate 312 of the first connecting seat 31 has rounded corners 314 on both sides along its sliding direction.

[0087] A PTFE membrane (not shown in the figure) is laid on the inner surface of the guide rail 34 located on the second row of pile cap beam 23. The PTFE membrane is partially bonded to the inner surface of the guide rail 34, and the bonded part extends along the length of the guide rail 34. Lubricating oil is injected into the PTFE membrane and the inner surface of the guide rail 34, and the lubricating oil is located in the gap between two adjacent bonded parts.

[0088] The PTFE membrane has high strength and low surface roughness, which can improve the smoothness of the sliding of the first connecting seat 31, thereby improving the ease with which the first connecting seat 31 slides to resist the lateral pressure of the first row of piles 1, and thus improving the force transmission effect and support effect.

[0089] Example 5

[0090] The difference between Example 5 and Example 3 is that, as Figure 12 , Figure 13 As shown, multiple force transmission plates 37 are arranged at intervals inside the guide rail 34 of the second row of pile cap beam 23. The force transmission plates 37 are slidably connected to the guide rail 34. The force transmission plates 37 are located between two adjacent first connecting seats 31, and the force transmission plates 37 are closer to the bottom plate 312 of the guide rail 34 than the first connecting seats 31. Both sides of the force transmission plates 37 in the length direction are provided with first guide surfaces 371. A second steel strand 38 is fixedly connected to two adjacent force transmission plates 37. The second steel strand 38 is in a taut state. Specifically, the force transmission plates 37 are provided with second threaded holes on both sides. The end of the second steel strand 38 is fixed with a second screw 381, and the second screw 381 is threadedly engaged with the second threaded hole.

[0091] The base plate 312 of the first connecting seat 31 is provided with a second guide surface 315 on both sides along the sliding direction, and the second guide surface 315 is in contact with the first guide surface 371.

[0092] During installation, first tension the force transmission plates 37 located at the first and last positions to tighten the second steel strands 38. Then, use the fifth expansion bolt 335 to fix the force transmission plate 37 located at the first position, while keeping the force transmission plate 37 located at the last position in the same position. Then, place the first connecting seat 31 into the guide rail 34 and tension the first connecting seat 31 located at the first and last positions to tighten the first steel strands 36. The first connecting seat 31 is placed exactly between two adjacent force transmission plates 37, so that the second guide surface 315 fits against the first guide surface 371. At this time, the second connecting seat 32 is tightly abutted against the inner wall of another guide rail 34, and the second connecting seat 32 located at the last position is fixed to the first row of pile cap beams 16 by the sixth expansion bolt 336.

[0093] Then tighten the top bolt 347 on the guide rail 34 (see...) Figure 14 The end of the top-pressing bolt 347 presses against the first connecting seat 31 to force the first connecting seat 31 to move closer to the force transmission plate 37, so as to finally limit the first connecting seat 31.

[0094] The implementation principle of Example 5 is as follows: When the lateral pressure of the first row of piles 1 is applied sequentially to the second connecting seat 32, steel pipe 33, first connecting seat 31 and force transmission plate 37 through the first row of pile cap beam 16, the lateral pressure will be transformed into a force that forces the two adjacent first connecting seats 31 to separate and the two adjacent force transmission plates 37 to separate through the cooperation of the first guide surface 371 and the second guide surface 315. That is, the force will force the first steel strand 36 and the second steel strand 38 to be further tensioned. The prestress of the first steel strand 36 and the second steel strand 38 is opposite to the force. Therefore, the prestress of the first steel strand 36 and the second steel strand 38 effectively resists the force, so as to effectively cope with the lateral pressure of the first row of piles 1, thereby indirectly improving the support strength of the steel structure support component 3.

[0095] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for constructing multi-row piles in deep foundation pits, characterized in that: Includes the following steps: S1. Mark out the outer perimeter (110) and inner perimeter (120) of the foundation pit, and construct a water-stopping curtain pile group (10) in the area between the outer perimeter (110) and inner perimeter (120). The plane where the top of the water-stopping curtain pile group (10) is located is set as a secondary horizontal plane. Construct the first row of piles (1) on the side of the outer perimeter (110) away from the water-stopping curtain pile group (10), and construct the second row of piles (2) on the side of the inner perimeter (120) away from the water-stopping curtain pile group (10). The top of the first row of piles (1) is provided with a half pile part (11). The lowest point of the half pile part (11) is located in the primary horizontal plane. The plane where the top of the second row of piles (2) is located is located in the secondary horizontal plane. S2. Excavate the first layer of soil to the first horizontal plane, and construct the first prestressed anchor rod (15) on the side wall of the first layer of soil. The exposed end of the first prestressed anchor rod (15) is located between two adjacent half piles (11). Then construct the first row of pile cap beams (16). The first row of pile cap beams (16) is located at the inner right angle of the half pile (11). Then, using the first row of pile cap beams (16) as the load-bearing foundation, apply prestress to the first prestressed anchor rod (15). S3. Excavate the second layer of soil to the secondary horizontal plane, expose the top of the second row of piles (2), construct the second prestressed anchor rod (24), the exposed end of the second prestressed anchor rod (24) is located between the tops of two adjacent piles of the second row of piles (2), and then cast the first row of pile waist beam (111), the second row of pile crown beam (23) and the connecting beam (112) in one piece, wherein the first row of pile waist beam (111) is located at the waist of the first row of piles (1), the second row of pile crown beam (23) is located at the top of the second row of piles (2), and the connecting beam (112) connects the first row of pile waist beam (111) and the second row of pile crown beam (23), and the opposite faces of the first row of pile crown beam (16) and the second row of pile crown beam (23) are parallel; then, using the second row of pile crown beam (23) as the load-bearing foundation, apply prestress to the second prestressed anchor rod (24); S4. Install steel structure support components (3) between the first row of pile cap beams (16) and the second row of pile cap beams (23). The steel structure support components (3) are respectively abutted and fixed on the opposite surfaces of the first row of pile cap beams (16) and the second row of pile cap beams (23). S5. Excavate vertically downwards along the second row of piles (2) to the bottom of the foundation pit; The steel structure support assembly (3) includes two guide rails (34), multiple first connecting seats (31), second connecting seats (32), and steel pipes (33). The two guide rails (34) are respectively set on the opposite surfaces of the first row of pile cap beams (16) and the second row of pile cap beams (23). The guide rails (34) extend along the length of the second row of pile cap beams (23). The first connecting seats (31) and the second connecting seats (32) are slidably connected to the two guide rails (34). The first connecting seats (31) and the second connecting seats (32) are both fixed with rotating shafts (311). The two ends of the steel pipe (33) are hinged to the rotating shafts (311) of the first connecting seats (31) and the second connecting seats (32). A first steel strand (36) is fixedly connected between two adjacent first connecting seats (31). The first steel strand (36) is in a taut state. Multiple force transmission plates (37) are arranged at intervals in the guide rail (34) of the second row of pile cap beam (23). The force transmission plates (37) are slidably connected to the guide rail (34). The force transmission plates (37) are located between two adjacent first connecting seats (31). The two sides of the length direction of the force transmission plates (37) are provided with first guide surfaces (371). A second steel strand (38) is fixedly connected between two adjacent force transmission plates (37). The second steel strand (38) is in a taut state. The two sides of the first connecting seat (31) along the sliding direction are provided with second guide surfaces (315). The second guide surfaces (315) are in contact with the first guide surfaces (371). The guide rail (34) is fixed with a top-pressing bolt (347). The end of the top-pressing bolt (347) presses against the first connecting seat (31) to force the first connecting seat (31) to move closer to the force transmission plate (37).

2. The method for constructing multi-row piles in deep foundation pits according to claim 1, characterized in that: A semi-circular first pressure plate (13) is installed on the horizontal surface of the half pile (11), and a vertical plate (12) is installed on the vertical surface of the half pile (11). The vertical plate (12) and the first pressure plate (13) are integrally formed and connected. A first embedded bar (14) is fixed through the first pressure plate (13). The lower end of the first embedded bar (14) extends into the concrete of the first row of piles (1), and the upper end of the first embedded bar (14) is located in the first row of pile cap beam (16).

3. The method for constructing multi-row piles in deep foundation pits according to claim 1, characterized in that: The top of the second row of piles (2) is equipped with a circular second pressure plate (21), and a second embedded bar (22) is fixed through the second pressure plate (21). The lower end of the second embedded bar (22) extends into the concrete of the second row of piles (2), and the upper end of the second embedded bar (22) is located in the second row of pile cap beam (23).

4. The method for constructing multi-row piles in deep foundation pits according to claim 1, characterized in that: The steel structure support assembly (3) includes multiple first connecting seats (31), second connecting seats (32) and steel pipes (33), wherein the first connecting seats (31) and the second connecting seats (32) are both fixed with rotating shafts (311), and the two ends of the steel pipes (33) are respectively hinged to the rotating shafts (311) of the first connecting seats (31) and the second connecting seats (32); each first connecting seat (31) is arranged at intervals along the length direction of the second row of pile cap beams (23), and the first connecting seats (31) are fixedly connected to the second row of pile cap beams (23) by first expansion bolts (331); each second connecting seat (32) is arranged at intervals along the length direction of the first row of pile cap beams (16), and the second connecting seats (32) are fixedly connected to the first row of pile cap beams (16) by second expansion bolts (332).

5. The method for constructing multi-row piles in deep foundation pits according to claim 3, characterized in that: In step S3, inclined grooves (231) are excavated on both sides of the top of the second row of piles (2). The inclined grooves (231) extend along the arrangement direction of the second row of piles (2). Then, the soil between adjacent piles of the second row of piles (2) and the soil in the gap between the top of the second row of piles (2) and the second pressure plate (21) are removed to form the lower half of the area to be poured. Then, triangular steel bars are placed in the inclined grooves (231), and formwork is erected. The formwork is closed to form the upper half of the area to be poured. Then, concrete is injected into the upper half of the area to be poured and the lower half of the area to be poured to form the second row of pile cap beam (23).

6. The method for constructing multi-row piles in deep foundation pits according to claim 1, characterized in that: A hooked steel bar (345) is fixed on the back of the guide rail (34) located on the first row of pile cap beams (16). The hooked steel bar (345) is anchored into the first row of pile cap beams (16). A detachable side stop (341) is provided on one side of the guide rail (34) located on the first row of pile cap beams (16). The side stop (341) is used to restrict the second connecting seat (32) from disengaging from the guide rail (34). A back plate (342) is provided on the back of the guide rail (34) located on the second row of pile cap beams (23). The back plate (342) is fixedly connected to the second row of pile cap beams (23). The guide rail (34) and the back plate (342) are slidably connected along the width direction of the guide rail (34). In step S4, the first connecting seat (31) is installed on the guide rail (34), and then the first connecting seat is tensioned and moved. The first connecting seat (31) is used to tighten the first steel strand (36), and then the guide rail (34) is slid along the width direction of the guide rail (34) so ​​that the steel pipe (33) is located between the opposite surfaces of the first row of pile cap beam (16) and the second row of pile cap beam (23), and the second connecting seat (32) enters the guide rail (34) without side guards (341) along the side of the guide rail (34) of the first row of pile cap beam (16). Then the tension of the first connecting seat (31) is released, and the prestress of the first steel strand (36) forces the adjacent first connecting seats (31) to move closer to each other. The second connecting seat (32) is tightly abutted against the inside of the guide rail (34) of the first row of pile cap beam (16). Then the side guards (341) are fixed to prevent the second connecting seat (32) from detaching from the guide rail (34).

7. The method for constructing multi-row piles in deep foundation pits according to claim 1, characterized in that: A PTFE membrane is laid on the inner surface of the guide rail (34) located on the second row of pile cap beam (23). The PTFE membrane is partially bonded to the inner surface of the guide rail (34). The bonded part extends along the length of the guide rail (34). Lubricating oil is injected into the PTFE membrane and the inner surface of the guide rail (34). Rounded corners (314) are provided on both sides of the sliding direction of the first connecting seat (31).

8. The method for constructing multi-row piles in deep foundation pits according to claim 1, characterized in that: The first prestressed anchor rod (15) has an angle of 30 degrees with the vertical plane, the second prestressed anchor rod (24) has an angle of 60 degrees with the vertical plane, and the support direction of the steel structure support assembly (3) has an angle of 60 degrees with the vertical plane.

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