Vertical anchoring type reinforced double-row pile support and construction method thereof

Abstract

The invention relates to the technical field of underground engineering foundation pit support, and discloses a vertical anchoring type reinforced double-row pile support, the structure is mainly composed of front-row support piles, rear-row support piles, vertical anchor cables, a coupling beam, a coping concrete plate and a crown beam, the anchor cables are perpendicular to the ground and arranged between the rear-row support piles or in the rear-row support piles in a driving mode; a cavity needs to be reserved when the vertical anchor cables are driven into the top beam between the piles, PVC pipes need to be embedded in the piles when the vertical anchor cables are driven into the piles, anchor heads of the vertical anchor cables are anchored on the top beam and form a whole with the top beam, an adjusting well is arranged on the left side of the back-row supporting piles, two rectangular plates are fixedly connected to the inner wall of the adjusting well, and a bearing is fixedly connected to the inner wall of each rectangular plate. The inner ring of each bearing is fixedly connected with a rotating shaft; a steel frame supporting body structure is not needed, and the supporting structure is a cantilever type supporting structure and has good adaptability.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering foundation pit support, in particular to a vertical anchor-type reinforced double-row pile support. Background Art

[0002] The double-row pile support structure is a commonly used form of foundation pit support. It consists of two parallel rows of reinforced concrete piles, a crown beam, a connecting beam between the tops of the front and rear rows of piles, and a concrete slab to form a portal-like spatial structure.

[0003] The overall rigidity of cantilever double-row piles is low, and they are only suitable for foundation pits with a depth of less than 10m. It is difficult to meet the safety stability and displacement control requirements of foundation pits with a depth of more than 10m. Therefore, for foundation pits with a depth of more than 10m, additional support or lateral anchor systems are required. For deep foundation pits with large plane dimensions, if an internal support system is used, the cost is relatively high due to the long support length, low rigidity, excessive horizontal displacement and long construction period. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a vertical anchor-type reinforced double-row pile support, which has the advantages of increasing the support stiffness of the double-row piles without adding supports and improving the application scope of the double-row pile support system.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a vertical anchor-pull reinforced double-row pile support, comprising a front row support pile, a rear row support pile, a vertical anchor cable, a top concrete slab, a connecting beam, a crown beam and an adjustable anchor cable; characterized in that: the vertical anchor cable is perpendicular to the ground and is driven between the rear row support piles or in the rear row support piles, and the vertical anchor cable is anchored on the crown beam through an anchor to form a whole with the crown beam; The adjustable anchor cable is fixed in the adjustment well through an anchor plate and an anchor sheet. The adjustment well is arranged at the rear side of the rear row support piles. The inner wall of the adjustment well is fixedly connected with a vertical plate and two rectangular plates. The vertical plate is inserted into the soil layer of the adjustment well. The two rectangular plates are welded to the upper and lower ends of the vertical plate. The anchor plate and the anchor sheet fix the adjustable anchor cable to the vertical plate. The inner wall of each rectangular plate is fixedly connected with a bearing. The inner ring of each bearing is fixedly connected with a rotating shaft. The ends of the two rotating shafts close to each other are fixedly connected with a rotating cylinder. After the adjustable anchor cable is anchored, its The remaining anchor cable segment at the tail end is rolled up on the rotating drum; a locking piece is fixedly connected to the right side surface of the front row supporting pile, and the adjustable anchor cable passes through the front row supporting pile and is fixed to the front end of the front row supporting pile through the locking piece; the top end of the rotating shaft is fixedly connected to a rotating handle, the inner wall of the rotating handle is threadedly connected to a threaded shaft, the top end of the threaded shaft is fixedly connected to a rotating plate, and the bottom end of the threaded shaft is fixedly connected to a clamping shaft; the clamping shaft is clamped into the mounting hole of the upper rectangular plate through the self-rotation of the threaded shaft, and the upper rectangular plate is provided with at least four mounting holes.

[0006] The adjustable anchor cable is a flexible steel strand.

[0007] The upper rectangular plate is provided with eight mounting holes, wherein the central angle of the arcs of adjacent mounting holes with the rotating shaft as the center is 45°.

[0008] The anchor cable is driven vertically into the ground between or in the rear row of supporting piles.

[0009] The vertical anchor cable anchor head is anchored on the crown beam. The vertical anchor cable is tensioned by prestressing, and the secondary grouting and tensioning are completed.

[0010] The adjustable anchor cable is provided with a stress sensor, and the stress sensor is connected to the mobile terminal through communication.

[0011] When the soil pressure changes, the stress sensor receives the stress change. When the stress value exceeds 5% and not more than 10% of the limit load of the adjustable anchor cable, the anchor plate (72) can be removed and the rotating handle can be rotated forward by one hole position by external power to tighten it. After tightening, the anchor plate can be installed to re-anchor it. When the stress value exceeds 10% and not more than 20% of the limit load of the adjustable anchor cable, the anchor plate (72) can be removed and the rotating handle can be rotated backward by one hole position by external power to loosen it. After loosening, the anchor plate can be installed to re-anchor it. When the stress value exceeds 20% of the limit load of the adjustable anchor cable, the foundation pit soil layer enters a damage warning mode, and the construction personnel are reminded to repair and inspect the foundation pit and leave in time to ensure the safety of the personnel.

[0012] At the same time, a construction method for vertical anchor-type reinforced double-row pile support is provided, which comprises the following steps: Step (1): Determine the depth of the foundation pit, the surrounding environment level and the safety level of the foundation pit based on the project's architectural, structural and hydrogeological data; establish a two-dimensional cantilever double-row pile model based on the Lizheng software, and preliminarily determine the diameter, spacing and embedding depth of the support piles; Step (2): Establish a finite element model of double-row piles, vertical anchor cables and adjustable anchor cables using the three-dimensional Midas finite element software. Finally, determine the diameter, spacing, reinforcement and embedding depth of the support piles, and determine the length and spacing parameters of the vertical anchor cables and adjustable anchor cables based on the displacement and bending moment of the support structure. Step (3): To construct double-row piles, first position the pile driver, lay out and position the holes according to the hole position calculated in the previous stage, install the pile driver, and move it to the designed pile position for construction. First, start the mixer to reach the designed depth and then complete the drilling. Then, install the steel cage and pour concrete. After completing the construction of one pile, proceed to the construction of the next pile body. Finally, complete the pouring of the front row support piles and the rear row support piles. According to the design requirements, construct the cap beam and the connecting beam on the front row support piles and the rear row support piles to complete the construction of the double-row piles. Step (4): constructing vertical anchor cables. According to the requirements of the vertical anchor cable position, the vertical anchor cables are driven vertically to the ground between the rear support piles or in the rear support piles. The vertical anchor cable anchor heads are anchored on the crown beam and form an integral body with the crown beam. Step (5): construct the adjustable anchor cable, first construct the adjustment well, and install the vertical plate and two rectangular plates, then drill and install the adjustable anchor cable, one end of the adjustable anchor cable is fixed to the locking piece of the front support pile, and the other end is fixed to the vertical plate through the anchor plate and the anchor sheet, the adjustable anchor cable (7) is provided with a stress sensor, and the stress sensor is connected to the mobile terminal through communication; when the soil pressure changes, the stress sensor receives the stress change, and when its stress value exceeds 5% and not more than 10% of the limit load of the adjustable anchor cable, the adjustable anchor cable can be removed by removing the anchor sheet and passing The handle is rotated forward one hole position by external power and tightened, and then the anchor plate is installed to re-anchor after tightening; when the stress value exceeds 10% and not more than 20% of the adjustable anchor cable's ultimate load, the anchor plate can be removed and the handle is rotated reversely one hole position by external power to loosen it, and then the anchor plate can be installed to re-anchor after loosening; when the stress value exceeds 20% of the adjustable anchor cable's ultimate load, the foundation pit soil layer enters the damage warning mode, and the construction personnel are reminded to repair and inspect the foundation pit and leave in time to ensure personnel safety.

[0013] The construction sequence of vertical anchor cables is as follows: (1) drilling anchor cable holes; (2) making anchor cable bodies; (3) placing anchor cable bodies; (4) using air compressors to clean anchor cable holes and perform grouting; and (5) tensioning and locking anchor cables.

[0014] The anchor cable is made of high-strength, low-relaxation steel strand. When making the anchor cable, the length above the ground should be increased by 1.5m as the tensioning section.

[0015] The drilling rig drills vertically between or in the bored piles to the designed depth. The water-cement ratio of the first grouting is 0.50-0.60 (grouting pressure 0.50MPa), and the second grouting is 0.8~0.9 (the compressive strength of the grouting body is not less than 3MPa).

[0016] Tension locking can only be carried out after the concrete strength of the grouting body and crown beam reaches 75% of the design strength (for no less than 12 days).

[0017] Before locking the anchor cable, tension it to 1.2 times the pull-out force, maintain it for 15 minutes, then unload it to zero, and then tension it again to the locking load for locking. The tensioning load classification and observation time of the anchor cable should comply with the specifications.

[0018] After the grouting body reaches 28 days of age, the anchor tension acceptance test shall be carried out in accordance with the specification. The number of tests shall be 5% of the number of anchors and shall not be less than 6.

[0019] Compared with the prior art, the present invention provides a vertical anchor-type reinforced double-row pile support, which has the following beneficial effects: (1) It does not require a support system and is a cantilever support structure. It is very adaptable to foundation pit projects with large plane dimensions, strict displacement requirements, and where lateral anchor cable support is not possible; (2) Vertical anchor cables and adjustable anchor cables improve the overall rigidity of the support structure, enhance the support structure's ability to resist bending, overturning, and water and soil pressure outside the pit, and can effectively control the deformation of the foundation pit; (3) The adjustable anchor cable setting can effectively adjust the tension and looseness according to the changes in the dynamic soil load, thus ensuring the safety of foundation pit support and personnel.

[0020] (4) The scope of application is wider, and the applicable depth can be expanded from the maximum depth of 10m to the maximum depth of 14m. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the cross section of the vertical anchor-type reinforced double-row pile support; Figure 2 This is a schematic diagram of the regulating well and adjustable anchor cable; Figure 3 It is a plane schematic diagram of the clamping shaft; Figure 4 Schematic diagram of vertical anchor cable installation.

[0022] Figure 5 It is a schematic diagram of the plan view of the reinforced double-row pile support system with vertical anchor cables driven into the piles; Figure 6 It is a schematic diagram of the plan view of the reinforced double-row pile support system with vertical anchor cables driven between piles; In the figure: 1. crown beam; 2. top concrete slab; 3. front support piles; 4. connecting beam; 5. rear support piles; 6. vertical anchor cable; 7. adjustable anchor cable; 71. anchor plate; 72. anchor sheet; 8. anchor; 9. locking piece; 10. vertical plate; 11. adjusting well; 12. rotating cylinder; 13. bearing; 14. rectangular plate; 15. mounting hole; 16. rotating handle; 17. threaded shaft; 18. rotating plate; 19. clamping shaft; 20. rotating shaft. DETAILED DESCRIPTION

[0023] In order to better understand the purpose, structure and function of the present invention, a vertical anchor-type reinforced double-row pile support of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0024] See also Figure 1-6 The present invention: a vertical anchor-pull reinforced double-row pile support, comprising a front row support pile 3, a rear row support pile 5, a vertical anchor cable 6, a top concrete slab 2, a connecting beam 4, a crown beam 1 and an adjustable anchor cable 7; characterized in that: the vertical anchor cable 6 is perpendicular to the ground and is driven between the rear row support piles 5 or in the rear row support piles, and the vertical anchor cable 6 is anchored on the crown beam 1 through an anchor 8 to form a whole with the crown beam 1; The adjustable anchor cable 7 is fixed in the regulating well 11 through the anchor plate 71 and the anchor sheet 72. The regulating well 11 is arranged at the rear side of the rear row support piles 5. The inner wall of the regulating well 11 is fixedly connected with a vertical plate 10 and two rectangular plates 14. The vertical plate is inserted into the soil layer of the regulating well. The two rectangular plates are welded to the upper and lower ends of the vertical plate. The anchor plate and the anchor sheet fix the adjustable anchor cable to the vertical plate. The inner wall of each rectangular plate 14 is fixedly connected with a bearing 13. The inner ring of each bearing 13 is fixedly connected with a rotating shaft 20. The ends of the two rotating shafts 20 close to each other are fixedly connected with a rotating cylinder 12. After the adjustable anchor cable is anchored, The remaining anchor cable segment at its tail end is rolled on the rotating drum; the right side surface of the front row supporting pile 3 is fixedly connected with a locking piece 9, and the adjustable anchor cable 7 passes through the front row supporting pile 3 and is fixed to the front end of the front row supporting pile through the locking piece 9; the top end of the rotating shaft 20 is fixedly connected with a rotating handle 16, the inner wall of the rotating handle 16 is threadedly connected with a threaded shaft 17, the top end of the threaded shaft 17 is fixedly connected with a rotating plate 18, and the bottom end of the threaded shaft 17 is fixedly connected with a clamping shaft 19; the clamping shaft 19 is fixed in the mounting hole 15 of the upper rectangular plate through the self-rotation clamping of the threaded shaft, and the upper rectangular plate is provided with at least four mounting holes.

[0025] The adjustable anchor cable 7 is a flexible steel strand.

[0026] The upper rectangular plate is provided with eight mounting holes, wherein the central angle of the arcs of adjacent mounting holes with the rotating shaft 20 as the center is 45°.

[0027] The vertical anchor cable 6 is driven vertically on the ground between the rear row supporting piles 5 or in the rear row supporting piles.

[0028] The anchor head of the vertical anchor cable 6 is anchored on the crown beam (1).

[0029] The vertical anchor cable 6 is tensioned by prestressing, and secondary grouting and tensioning are completed.

[0030] The adjustable anchor cable 7 is provided with a stress sensor, and the stress sensor is connected to the mobile terminal via communication.

[0031] When the soil pressure changes, the stress sensor receives the stress change. When the stress value exceeds 5% and is not greater than 10% of the adjustable anchor cable's ultimate load, the anchor plate 72 can be removed and the rotating handle can be rotated forward one hole position by external power to tighten it. After tightening, the anchor plate can be installed to re-anchor it; when the stress value exceeds 10% and is not greater than 20% of the adjustable anchor cable's ultimate load, the anchor plate 72 can be removed and the rotating handle can be rotated reversely one hole position by external power to loosen it. After loosening, the anchor plate can be installed to re-anchor it; when the stress value exceeds 20% of the adjustable anchor cable's ultimate load, the foundation pit soil layer enters a damage warning mode, and the construction personnel are reminded to repair and inspect the foundation pit and leave in time to ensure personnel safety.

[0032] The embodiment also provides a construction method for vertical anchor-type reinforced double-row pile support, comprising the following steps: Step (1): Determine the depth of the foundation pit, the surrounding environment level and the safety level of the foundation pit based on the project's architectural, structural and hydrogeological data; establish a two-dimensional cantilever double-row pile model based on the Lizheng software, and preliminarily determine the diameter, spacing and embedding depth of the support piles; Step (2): Establish a finite element model of double-row piles, vertical anchor cables and adjustable anchor cables using the three-dimensional Midas finite element software. Finally, determine the diameter, spacing, reinforcement and embedding depth of the support piles, and determine the length and spacing parameters of the vertical anchor cables and adjustable anchor cables based on the displacement and bending moment of the support structure. Step (3): To construct double-row piles, first position the pile driver, lay out and position the holes according to the hole position calculated in the previous stage, install the pile driver, and move it to the designed pile position for construction. First, start the mixer to reach the designed depth and then complete the drilling. Then, install the steel cage and pour concrete. After completing the construction of one pile, proceed to the construction of the next pile body. Finally, complete the pouring of the front row support piles and the rear row support piles. According to the design requirements, construct the cap beam and the connecting beam on the front row support piles and the rear row support piles to complete the construction of the double-row piles. Step (4): constructing vertical anchor cables. According to the requirements of the vertical anchor cable position, the vertical anchor cables are driven vertically to the ground between the rear support piles or in the rear support piles. The vertical anchor cable anchor heads are anchored on the crown beam and form an integral body with the crown beam. Step (5): construct the adjustable anchor cable, first construct the adjustment well, and install the vertical plate and two rectangular plates, then drill and install the adjustable anchor cable, one end of the adjustable anchor cable is fixed to the locking piece of the front support pile, and the other end is fixed to the vertical plate through the anchor plate and the anchor sheet, the adjustable anchor cable (7) is provided with a stress sensor, and the stress sensor is connected to the mobile terminal through communication; when the soil pressure changes, the stress sensor receives the stress change, and when its stress value exceeds 5% and not more than 10% of the limit load of the adjustable anchor cable, the adjustable anchor cable can be removed by removing the anchor sheet and passing The handle is rotated forward one hole position by external power and tightened, and then the anchor plate is installed to re-anchor after tightening; when the stress value exceeds 10% and not more than 20% of the adjustable anchor cable's ultimate load, the anchor plate can be removed and the handle is rotated reversely one hole position by external power to loosen it, and then the anchor plate can be installed to re-anchor after loosening; when the stress value exceeds 20% of the adjustable anchor cable's ultimate load, the foundation pit soil layer enters the damage warning mode, and the construction personnel are reminded to repair and inspect the foundation pit and leave in time to ensure personnel safety.

[0033] The anchor sheets and anchor plates used in the present application are conventional components in the prior art. During the loosening and tightening operations, the installation dimensions of the adjustment well may be considered to perform prestressing and tightening of the anchor sheets and anchor sheets.

[0034] The embodiment also provides a simulation test comparison of a vertical anchor-type reinforced double-row pile support in foundation pit support, with a foundation pit depth of 7.35m, front and rear rows of ∅1200@1400mm cast-in-place piles, a cast-in-place pile embedding depth of 17.0m, and a 1.1m×0.8m crown beam of the front and rear rows of cast-in-place piles; ∅150 holes are drilled between the rear row of cast-in-place piles, 4x7∅5@1200mm vertical anchor cables, and a vertical anchor cable length of 25m; 8x5∅5@1200mm adjustable anchor cables, and a vertical anchor cable length of 38m.

[0035] According to the calculation of the theory, the maximum horizontal displacement of the double-row pile (without vertical anchor) support system of this section is 50.39mm; according to the finite element calculation, the maximum horizontal displacement of the double-row pile + vertical anchor support system of this section is 31.63mm; according to the finite element calculation, the maximum horizontal displacement of the double-row pile + vertical anchor support system + adjustable anchor support system of this section is 21.63mm. At present, the foundation pit has been backfilled, and the monitoring report shows that the maximum horizontal displacement is 18.37mm, indicating that the vertical anchor and adjustable anchor effectively increase the stiffness of the double-row pile support system and effectively control the displacement of the foundation pit.

[0036] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A vertical anchor-type reinforced double-row pile support, comprising a front row of support piles (3), a rear row of support piles (5), a vertical anchor cable (6), a top concrete slab (2), a connecting beam (4), a crown beam (1) and an adjustable anchor cable (7); characterized in that: The vertical anchor cable (6) is installed perpendicular to the ground between the rear support piles (5) or in the rear support piles. The vertical anchor cable (6) is anchored to the crown beam (1) through an anchor (8) and forms an integral body with the crown beam (1). The adjustable anchor cable (7) is fixed in the regulating well (11) through an anchor plate (71) and an anchor sheet (72); the regulating well (11) is arranged at the rear side of the rear row support piles (5); the inner wall of the regulating well (11) is fixedly connected to a vertical plate (10) and two rectangular plates (14); the vertical plate is inserted into the soil layer of the regulating well; the two rectangular plates are welded to the upper and lower ends of the vertical plate; the anchor plate and the anchor sheet fix the adjustable anchor cable to the vertical plate; the inner wall of each rectangular plate (14) is fixedly connected to a bearing (13); the inner ring of each bearing (13) is fixedly connected to a rotating shaft (20); the ends of the two rotating shafts (20) close to each other are fixedly connected to a rotating cylinder (12); after the adjustable anchor cable is anchored, The remaining anchor cable section at the tail end is rolled onto the rotating drum; a locking piece (9) is fixedly connected to the right side surface of the front row supporting pile (3); the adjustable anchor cable (7) passes through the front row supporting pile (3) and is fixed to the front end of the front row supporting pile through the locking piece (9); the top end of the rotating shaft (20) is fixedly connected to a rotating handle (16); the inner wall of the rotating handle (16) is threadedly connected to a threaded shaft (17); the top end of the threaded shaft (17) is fixedly connected to a rotating plate (18); the bottom end of the threaded shaft (17) is fixedly connected to a clamping shaft (19); the clamping shaft (19) is fixed in the mounting hole (15) of the upper rectangular plate through the self-rotation clamping of the threaded shaft, and the upper rectangular plate is provided with at least four mounting holes.

2. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: The adjustable anchor cable (7) is a flexible steel strand.

3. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: The upper rectangular plate is provided with eight mounting holes, wherein the central angle of the arcs of adjacent mounting holes with the rotating shaft (20) as the center is 45°.

4. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: The anchor cable (6) is vertically driven into the ground between the rear row support piles (5) or in the rear row support piles.

5. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: The anchor head of the vertical anchor cable (6) is anchored on the crown beam (1).

6. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: The vertical anchor cable (6) is tensioned by prestressing, and secondary grouting and tensioning are completed.

7. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: The adjustable anchor cable (7) is provided with a stress sensor, and the stress sensor is connected to the mobile terminal via communication.

8. The vertical anchor-type reinforced double-row pile support according to claim 1 is characterized by: When the soil pressure changes, the stress sensor receives the stress change. When the stress value exceeds 5% and not more than 10% of the limit load of the adjustable anchor cable, the anchor plate (72) can be removed and the rotating handle can be rotated forward by one hole position by external power to tighten it. After tightening, the anchor plate can be installed to re-anchor it. When the stress value exceeds 10% and not more than 20% of the limit load of the adjustable anchor cable, the anchor plate (72) can be removed and the rotating handle can be rotated backward by one hole position by external power to loosen it. After loosening, the anchor plate can be installed to re-anchor it. When the stress value exceeds 20% of the limit load of the adjustable anchor cable, the foundation pit soil layer enters a damage warning mode, and the construction personnel are reminded to repair and inspect the foundation pit and leave in time to ensure the safety of the personnel.

9. A construction method for vertical anchor-type reinforced double-row pile support according to any one of claims 1 to 8, characterized in that: The steps include: Step (1): Determine the depth of the foundation pit, the surrounding environment level and the safety level of the foundation pit based on the project's architectural, structural and hydrogeological data; establish a two-dimensional cantilever double-row pile model based on the Lizheng software, and preliminarily determine the diameter, spacing and embedding depth of the support piles; Step (2): Establish a finite element model of double-row piles, vertical anchor cables and adjustable anchor cables using the three-dimensional Midas finite element software. Finally, determine the diameter, spacing, reinforcement and embedding depth of the support piles, and determine the length and spacing parameters of the vertical anchor cables and adjustable anchor cables based on the displacement and bending moment of the support structure. Step (3): To construct double-row piles, first position the pile driver, lay out and position the holes according to the hole position calculated in the previous stage, install the pile driver, and move it to the designed pile position for construction. First, start the mixer to reach the designed depth and then complete the drilling. Then, install the steel cage and pour concrete. After completing the construction of one pile, proceed to the construction of the next pile body. Finally, complete the pouring of the front row support piles and the rear row support piles. According to the design requirements, construct the cap beam and the connecting beam on the front row support piles and the rear row support piles to complete the construction of the double-row piles. Step (4): constructing vertical anchor cables. According to the requirements of the vertical anchor cable position, the vertical anchor cables are driven vertically to the ground between the rear support piles or in the rear support piles. The vertical anchor cable anchor heads are anchored on the crown beam and form an integral body with the crown beam. Step (5): construct the adjustable anchor cable, first construct the adjustment well, and install the vertical plate and two rectangular plates, then drill and install the adjustable anchor cable, one end of the adjustable anchor cable is fixed to the locking piece of the front support pile, and the other end is fixed to the vertical plate through the anchor plate and the anchor sheet, the adjustable anchor cable (7) is provided with a stress sensor, and the stress sensor is connected to the mobile terminal through communication; when the soil pressure changes, the stress sensor receives the stress change, and when its stress value exceeds 5% and not more than 10% of the limit load of the adjustable anchor cable, the adjustable anchor cable can be removed by removing the anchor sheet and passing The handle is rotated forward one hole position by external power and tightened, and then the anchor plate is installed to re-anchor after tightening; when the stress value exceeds 10% and not more than 20% of the adjustable anchor cable's ultimate load, the anchor plate can be removed and the handle is rotated reversely one hole position by external power to loosen it, and then the anchor plate can be installed to re-anchor after loosening; when the stress value exceeds 20% of the adjustable anchor cable's ultimate load, the foundation pit soil layer enters the damage warning mode, and the construction personnel are reminded to repair and inspect the foundation pit and leave in time to ensure personnel safety.

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