Large-area deep foundation pit supporting structure and construction technology

Abstract

The invention discloses a large-area deep foundation pit supporting structure and a construction technology, and belongs to the technical field of foundation pit engineering. The large-area deep foundation pit supporting structure comprises a supporting stress system, and the supporting stress system comprises row piles, high-pressure jet grouting anchor cables, a top beam, a retaining wall and a waist beam; the row piles are arranged on the inner side of the anti-seepage system along the periphery of the foundation pit; the top beam is poured at the top of the row pile and is anchored and connected with the row pile reinforcing steel bar; the bottom of the retaining wall extends into the top beam and is fixed with the top beam steel bar; the high-pressure jet grouting anchor cables are obliquely arranged on one side of the top beam, and the waist beam is connected with the row piles in an attached mode. The anti-seepage system comprises a waterproof curtain and a shotcrete anchor protection slope; the drainage system comprises a foundation pit top drainage ditch, a foundation pit bottom drainage ditch and a water collecting pit; top beam reinforcing steel bars and retaining wall construction reinforcing steel bars are constructed at the tops of the row piles, the top beam reinforcing steel bars and the retaining wall construction reinforcing steel bars are bound or welded and fixed, and a top beam and a retaining wall are poured, so that the top beam and the retaining wall form an integral structure, construction is facilitated, and stability is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of foundation pit engineering technology, specifically to a large-area deep foundation pit support structure and construction process. Background Technology

[0002] With the acceleration of urbanization, spatial development in urban core areas is extending underground, leading to an increasing number of large-scale projects such as urban complexes, underground transportation hubs, and basements of super high-rise buildings. These projects generally involve large-area deep foundation pit construction (pit area exceeding 1000㎡, excavation depth exceeding 8m). These foundation pits face a dual challenge: on the one hand, the pits are often adjacent to existing buildings, underground pipelines, subway tunnels, and other sensitive facilities, requiring stringent deformation control (lateral wall horizontal displacement ≤30mm, surface settlement ≤20mm); on the other hand, the sites often have complex geological conditions such as soft soil, water-rich sand layers, and confined aquifers, which can easily lead to safety hazards such as collapse, piping, and leakage, posing a great challenge to support design and construction.

[0003] In existing technologies, deep foundation pit support often employs a simple combination of single pile rows, ordinary anchor cables, and a cutoff wall, which has significant shortcomings: First, the structural coordination is poor, with insufficient connection strength between components such as pile rows, anchor cables, and capping beams, resulting in an imperfect overall stress system and limited deformation control capabilities. Second, the seepage prevention system has weak links, with insufficient reinforcement between the cutoff wall and the soil between the piles, leading to a high risk of leakage. Third, the drainage system design is simplistic, only providing drainage at the bottom of the foundation pit, which cannot quickly remove surface and internal water, exacerbating soil softening. Fourth, the construction process lacks standardization, and key parameter control is unclear, resulting in unstable construction quality. For example, the "pile row + anchor cable + cutoff wall" scheme used in some projects (such as the Xiamen Tongxiang High-tech City project) can meet basic support requirements, but it fails to address the issues of structural integration, seepage prevention and drainage coordination, and insufficient anchoring force in complex strata, making it difficult to meet the stringent requirements of highly sensitive environments. Therefore, developing a structurally integrated and standardized large-area deep foundation pit support structure and construction process has become an urgent need in the industry. Summary of the Invention

[0004] The purpose of this invention is to provide a support structure and construction process for large-area deep foundation pits to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a support structure and construction process for a large-area deep foundation pit, comprising a support force system, wherein the support force system includes piles, high-pressure jet grouting anchor cables, a capping beam, a retaining wall, and a waist beam; the piles are arranged along the perimeter of the foundation pit inside the seepage prevention system; the capping beam is cast on top of the piles and anchored to the pile reinforcement; the bottom of the retaining wall extends into the capping beam and is fixed to the capping beam reinforcement, forming a closed top structure; the high-pressure jet grouting anchor cables are inclinedly arranged on one side of the capping beam, one end is anchored to the stable soil around the foundation pit, and the other end is fixed to the waist beam through an anchor; the waist beam is closely connected to the piles. The seepage prevention system includes a water-stop curtain and shotcrete slope protection; The drainage system includes drainage ditches at the top of the pit, drainage ditches at the bottom of the pit, and sump pits.

[0006] Preferably, the high-pressure jet grouting anchor cable includes an anchor, an anchor cable, and an anchoring end. The anchoring end includes an anchor hole and an anchor plate. The anchor includes a main body, a transmission assembly, and an anchor ring for locking the anchor cable. The transmission assembly is used to control the rotation of the anchor ring relative to the main body, so that the anchor ring can actively adapt to anchor holes of different angles.

[0007] Preferably, the main body includes a pad, the pad having a through hole, and two support seats fixedly connected to the pad symmetrically arranged above and below the through hole. The ends of the support seats are fixedly connected to a mounting plate, the transmission assembly is mounted on the mounting plate, and the anchor ring is mounted on the transmission assembly.

[0008] Preferably, the transmission assembly includes a base, which is mounted on a mounting plate. The base has a frame, and the anchor ring is fixedly connected to the frame. One end of the frame is rotatably connected to the base, and the other end is provided with a drive unit for driving the frame to rotate relative to the base.

[0009] Preferably, the drive unit includes a wedge, and the frame has an inclined groove on the side away from the rotating connection end and close to the base end face. The wedge is inserted into the inclined groove and is slidably connected to the base. A bolt is threadedly connected to one end of the base near the wedge, and the end of the bolt abuts against the wedge. The bolt can push the wedge towards the rotating connection end of the frame through threaded transmission.

[0010] Preferably, the base is slidably connected to the mounting plate, and the pad is provided with a calibration component. The calibration component is used to drive the base to slide relative to the mounting plate as the frame rotates, so as to ensure that the anchor cable passes through the anchor ring, the through hole and the anchor hole in a straight line.

[0011] Preferably, the calibration assembly includes two hinged frames symmetrically arranged on the front and rear sides of the through hole. The hinged frames are fixedly connected to the pad, and each hinged frame is rotatably connected to a telescopic rod. The telescopic rod is fixedly connected to the anchor ring and is parallel to the axis of the anchor ring.

[0012] A construction technique for a large-area deep foundation pit support structure is as follows: S1. Construction preparation: Complete site leveling, equipment debugging and material acceptance; S2. Measurement, Positioning and Verification: GPS is used to accurately locate the position of each structural component. Four symmetrical protective piles and cross control piles are set up. Construction is carried out after the supervisor has verified the measurement. S3. Construction of the seepage prevention system: First, construct the water-stop curtain using the three-axis mixing pile technology, with the piles interlocking by half the pile diameter; after the pile construction is completed, clean the slope and construct the shotcrete slope protection, and then complete the soil nailing hole installation, steel mesh laying and concrete spraying in sequence. S4. Construction of the support system: Piling construction: adopts mud slurry wall protection positive circulation drilling and one-step-one-step construction method. After the steel casing is buried, the hole is drilled, and after secondary hole cleaning, concrete is poured; capping beam and retaining wall construction: tie and fix the reinforcing steel of capping beam and retaining wall, and pour concrete as a whole; High-pressure jet grouting anchor cable construction: the anchor hole positioning, cable-driven drilling and jet grouting, waist beam installation and graded tensioning and locking are completed in sequence; S5. Drainage system construction: Simultaneously pour drainage ditches at the top and bottom of the foundation pit, reserve a sump pit, and install drainage pumps and hoses; S6. Earthwork excavation.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. By constructing the capping beam reinforcement and retaining wall structural reinforcement at the top of the pile, the capping beam reinforcement and retaining wall structural reinforcement are tied or welded to be fixed, and the capping beam and retaining wall are poured to form an integral structure, which facilitates construction and ensures stability.

[0014] 2. The anchor ring is driven to rotate relative to the main body through the transmission component, so that the anchor ring actively adapts to the actual angle of the anchor hole, ensuring that the anchor cable is straight and without additional bending stress during the installation and tensioning process, and realizing reliable tensioning and locking of the high-pressure jet grouting anchor cable under different angle working conditions.

[0015] 3. By using the sliding compensation angle deviation of the base, it works in coordination with the rotation of the frame to ensure that the anchor cable always passes through the anchor ring, the cable threading hole and the anchor hole in a straight line, avoiding deflection or misalignment. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the high-pressure jet grouting anchor cable. Figure 3 This is a schematic diagram of the anchorage structure; Figure 4A schematic diagram and a front view of the structure at the anchor expansion joint; Figure 5 This is a schematic diagram of the exploded structure of the anchor. Figure 6 This is a schematic diagram of the process flow of the present invention.

[0017] The attached diagram lists the components represented by each number as follows: Original topography 1. Drainage ditch 2. Retaining wall 3. Crown beam 4. Proposed building 5. Anchor 6. Anchor ring 61. Pad 62. Through hole 63. Support seat 64. Mounting plate 65. Base 66. Frame 67. Wedge 68. Bolt 69. Hinged frame 610. Telescopic rod 611. Anchor cable 8. Anchor end 9. Anchor hole 91. Anchor plate 92. Water-stop curtain 10. Detailed Implementation

[0018] Please see Figure 1-6 This invention provides a technical solution: a support structure and construction process for a large-area deep foundation pit, comprising a support force system, wherein the support force system includes piles, high-pressure jet grouting anchors, a capping beam 4, a retaining wall 3, and a waist beam; the piles are arranged along the perimeter of the foundation pit inside the seepage prevention system; the capping beam 4 is cast on top of the piles and anchored to the pile reinforcement; the bottom of the retaining wall 3 extends into the capping beam 4 and is fixed to the capping beam 4 reinforcement, forming a closed top structure; the high-pressure jet grouting anchors are inclinedly arranged on one side of the capping beam 4, one end is anchored to the stable soil around the foundation pit, and the other end is fixed to the waist beam through an anchor; the waist beam is closely connected to the piles. The seepage prevention system includes a water-stop curtain 10 and shotcrete slope protection; The drainage system includes drainage ditch 2 at the top of the foundation pit, drainage ditch 2 at the bottom of the foundation pit, and a sump.

[0019] like Figure 1Under the original topography 1 and the proposed building 5, the site leveling, equipment debugging, and material acceptance were completed first. Then, GPS was used to accurately locate the positions of each structural component, and four symmetrical protective piles and cross control piles were set up. Construction was carried out after the supervisor's re-measurement was qualified. The anti-seepage system was constructed first. During this process, the water-stop curtain 10 was constructed using the three-axis mixing pile technology, with the piles interlocking by half the pile diameter to form a wall (after the subsequent pile construction was completed, the slope was cleaned and shotcrete slope protection was constructed, and the soil nailing hole placement, steel mesh laying, and concrete spraying were completed in sequence). Then, the support was carried out. For the construction of the load-bearing system, a mud-wall-protected positive circulation drilling and one-step-one-step construction method was adopted for pile construction. During construction, after the steel casing was buried, the holes were drilled, and after secondary cleaning, concrete was poured. Next, the capping beam 4 and retaining wall 3 were constructed: the reinforcing bars of capping beam 4 and retaining wall 3 were tied and fixed, and the concrete was poured as a whole. Then, high-pressure jet grouting anchor cable construction was carried out, and the anchor hole positioning, cable-driven drilling and grouting, waist beam installation, and graded tensioning and locking were completed in sequence. Then, the top and bottom drainage ditches 2 of the foundation pit were poured simultaneously, a water collection pit was reserved, and drainage pumps and hoses were installed to complete the drainage system. Finally, earthwork excavation was carried out.

[0020] By constructing the reinforcing steel bars of the capping beam 4 and the structural reinforcement of the retaining wall 3 at the top of the pile, the reinforcing steel bars of the capping beam 4 and the structural reinforcement of the retaining wall 3 are tied or welded and fixed, and the capping beam 4 and the retaining wall 3 are poured, so that the capping beam 4 and the retaining wall 3 form an integral structure, which facilitates construction and ensures stability.

[0021] The traditional anchor 6 has a fixed angle for the anchor ring 61. This means that the angle of the anchor hole 91 needs to be adapted to the angle of the anchor ring 61 during construction, which makes construction more difficult and has a lower tolerance for error.

[0022] Preferably, the high-pressure jet grouting anchor cable includes an anchor 6, an anchor cable 8, and an anchoring end 9. The anchoring end 9 includes an anchor hole 91 and an anchor plate 92. The anchor 6 includes a main body, a transmission assembly, and an anchor ring 61 for locking the anchor cable 8. The transmission assembly is used to control the rotation of the anchor ring 61 relative to the main body, so that the anchor ring 61 can actively adapt to the anchor hole 91 at different angles.

[0023] Anchor cable 8 passes through anchor hole 91 and is connected to anchor plate 92 at anchor end 9. Anchor end 9 is buried in the soil to form effective anchorage. Anchor 6 is installed on the outside of the support structure. The exposed end of anchor cable 8 passes through anchor 6 and is locked by anchor ring 61. When there is an angular deviation between anchor hole 91 and the installation surface of anchor 6, the anchor ring 61 is driven to rotate relative to the main body through the transmission component, so that anchor ring 61 actively adapts to the actual angle of anchor hole 91, ensuring that anchor cable 8 is straight and without additional bending stress during installation and tensioning, and realizing reliable tensioning and locking of high-pressure jet grouting anchor cable under different angle conditions.

[0024] Preferably, the main body includes a pad 62, the pad 62 has a through hole 63, and two support seats 64 are symmetrically arranged above and below the through hole 63 and fixedly connected to the pad 62. The ends of the support seats 64 are fixedly connected to a mounting plate 65. The transmission assembly is arranged on the mounting plate 65, and the anchor ring 61 is arranged on the transmission assembly.

[0025] Anchor cable 8 passes through threading hole 63 on pad plate 62. Threading hole 63 provides a passage for anchor cable 8 and defines its approximate position. Pad plate 62 supports mounting plate 65 through symmetrically arranged support seats 64, forming a stable installation space between mounting plate 65 and pad plate 62. Transmission component drives anchor ring 61 to move on mounting plate 65. Under the drive of transmission component, anchor ring 61 adjusts its angle relative to pad plate 62 and threading hole 63, actively matching the actual direction of anchor cable 8, ensuring that anchor cable 8 passes smoothly through threading hole 63 and is reliably locked by anchor ring 61, avoiding bending or deviation of anchor cable 8 during threading and tensioning.

[0026] Preferably, the transmission assembly includes a base 66, which is mounted on a mounting plate 65. The base 66 is provided with a frame 67, and the anchor ring 61 is fixedly connected to the frame 67. One end of the frame 67 is rotatably connected to the base 66, and the other end is provided with a drive unit. The drive unit is used to drive the frame 67 to rotate relative to the base 66.

[0027] When there is a deviation between the angle of the anchor hole 91 and the mounting surface of the anchor 6, the drive unit outputs power to drive the frame 67 to rotate around the rotational connection point between it and the base 66. Since the anchor ring 61 is fixedly connected to the frame 67, the frame 67 rotates synchronously, causing the anchor ring 61 to adjust its angle until the axis of the center hole of the anchor ring 61 is completely aligned with the actual direction of the anchor cable 8. At this time, the anchor cable 8 passes straight into the anchor ring 61 without additional bending stress, and the anchor ring 61 can reliably lock the anchor cable 8, ensuring the tensioning accuracy and stress stability of the high-pressure jet grouting anchor cable under different angle conditions.

[0028] Preferably, the drive unit includes a wedge 68. The frame 67 has an inclined groove on the side away from the rotating connection end and close to the end face of the base 66. The wedge 68 is inserted into the inclined groove and is slidably connected to the base 66. A bolt 69 is threadedly connected to one end of the base 66 near the wedge 68. The end of the bolt 69 abuts against the wedge 68. The bolt 69 can push the wedge 68 toward the rotating connection end of the frame 67 through threaded transmission.

[0029] When the axis of the center hole of the anchor ring 61 is not concentric with the direction of the anchor cable 8, the bolt 69 is rotated. Through the threaded engagement between the bolt 69 and the base 66, the bolt 69 is pushed axially toward the rotating connection end of the frame 67. The end of the bolt 69 presses against the wedge block 68, pushing the wedge block 68 to slide along the base 66. The wedge block 68 and the inclined groove of the frame 67 form an inclined plane transmission, converting the axial thrust into the rotational torque of the frame 67. The frame 67 rotates around the rotating connection point with the base 66, causing the fixedly connected anchor ring 61 to adjust its angle until the center hole of the anchor ring 61 is aligned with the direction of the anchor cable 8, thus achieving the straight locking of the anchor cable 8.

[0030] Preferably, the base 66 is slidably connected to the mounting plate 65, and the pad 62 is provided with a calibration component. The calibration component is used to drive the base 66 to slide relative to the mounting plate 65 as the frame 67 rotates, so as to ensure that the anchor cable 8 passes through the anchor ring 61, the cable threading hole 63 and the anchor hole 91 in a straight line.

[0031] Bolt 69 pushes wedge 68 to drive frame 67 to rotate. At this time, two situations may occur. 1. The axes of anchor ring 61 and anchor hole 91 are parallel but do not coincide; 2. The axis of the anchor ring 61 coincides with that of the anchor hole 91, but its axis is too close to the inner wall of the through hole 63, causing the anchor cable 8 to interfere with the inner wall of the through hole 63. Ultimately, due to the angular displacement of the anchor ring 61 after the frame rotates, the anchor cable 8 becomes misaligned with the threading hole 63 and the anchor hole 91. At this time, the calibration component generates a linkage force with the rotation trend of the frame 67, driving the base 66 to slide and adjust along the mounting plate 65. Through the sliding compensation of the base for the angular deviation, it works in coordination with the rotation of the frame to ensure that the anchor cable 8 always passes through the anchor ring 61, the threading hole 63 and the anchor hole 91 in a straight line, avoiding deflection or misalignment.

[0032] Preferably, the calibration assembly includes two hinge frames 610 symmetrically arranged on the front and rear sides of the through hole 63. The hinge frames 610 are fixedly connected to the pad 62. Each hinge frame 610 is rotatably connected to a telescopic rod 611. The telescopic rod 611 is fixedly connected to the anchor ring 61 and is parallel to the axis of the anchor ring 61.

[0033] Bolt 69 pushes wedge block 68 to drive frame body 67 to rotate, and anchor ring 61 deflects synchronously with frame body; telescopic rod 611, which is fixed to anchor ring 61 and parallel to its axis, rotates around hinge frame 610 as anchor ring deflects, and at the same time, through telescopic linkage of telescopic rod, drives base 66 to slide along mounting plate 65; rotation and sliding cooperate to compensate for deviation, ensuring that anchor cable 8 passes straight through anchor ring 61, cable threading hole 63 and anchor hole 91.

[0034] A construction technique for a large-area deep foundation pit support structure is as follows: S1. Construction preparation: Complete site leveling, equipment debugging and material acceptance; S2. Measurement, Positioning and Verification: GPS is used to accurately locate the position of each structural component. Four symmetrical protective piles and cross control piles are set up. Construction is carried out after the supervisor has verified the measurement. S3. Construction of the seepage prevention system: First, construct the water-stop curtain 10, using the three-axis mixing pile technology, with the piles interlocking by half the pile diameter; after the pile construction is completed, clean the slope surface and construct the shotcrete slope protection, and then complete the soil nail hole drilling and placement, steel mesh laying and concrete spraying in sequence. S4. Construction of the support system: Piling construction: adopts mud slurry wall protection positive circulation drilling and one-step-one-step construction method. After the steel casing is buried, the hole is drilled, and after secondary hole cleaning, concrete is poured; construction of cap beam 4 and retaining wall 3: tie the reinforcing steel of cap beam 4 and retaining wall 3 and fix them, and pour concrete as a whole; High-pressure jet grouting anchor cable construction: the anchor hole positioning, cable-driven drilling and jet grouting, waist beam installation and graded tensioning and locking are completed in sequence; S5. Drainage system construction: Simultaneously pour drainage ditches 2 at the top and bottom of the foundation pit, reserve a water collection pit, and install drainage pumps and hoses; S6. Earthwork excavation.

Claims

1. A support structure for large-area deep foundation pits, characterized in that: The support system includes a pile foundation, a high-pressure jet grouting anchor cable, a capping beam (4), a retaining wall (3), and a waist beam. The pile foundation is arranged along the perimeter of the foundation pit inside the seepage prevention system. The capping beam (4) is cast on top of the pile foundation and anchored to the pile reinforcement. The bottom of the retaining wall (3) extends into the capping beam (4) and is fixed to the capping beam (4) reinforcement to form a closed top structure. The high-pressure jet grouting anchor cable is inclined on one side of the capping beam (4), with one end anchored to the stable soil around the foundation pit and the other end fixed to the waist beam through an anchor. The waist beam is closely connected to the pile foundation. The seepage prevention system includes a water-stop curtain (10) and shotcrete slope protection; The drainage system includes a drainage ditch at the top of the pit (2), a drainage ditch at the bottom of the pit (2), and a sump.

2. The large-area deep foundation pit support structure according to claim 1, characterized in that: The high-pressure jet grouting anchor cable includes an anchor (6), an anchor cable (8), and an anchoring end (9). The anchoring end (9) includes an anchor hole (91) and an anchor plate (92). The anchor (6) includes a main body, a transmission assembly, and an anchor ring (61) for locking the anchor cable (8). The transmission assembly is used to control the anchor ring (61) to rotate relative to the main body, so that the anchor ring (61) can actively adapt to the anchor hole (91) at different angles.

3. The large-area deep foundation pit support structure according to claim 2, characterized in that: The main body includes a pad (62), the pad (62) has a through hole (63), and the through hole (63) has two support seats (64) fixedly connected to the pad (62) symmetrically arranged on the upper and lower sides. The ends of the support seats (64) are fixedly connected to an mounting plate (65). The transmission assembly is set on the mounting plate (65), and the anchor ring (61) is set on the transmission assembly.

4. The large-area deep foundation pit support structure according to claim 3, characterized in that: The transmission assembly includes a base (66), which is mounted on a mounting plate (65). The base (66) is provided with a frame (67). The anchor ring (61) is fixedly connected to the frame (67). One end of the frame (67) is rotatably connected to the base (66), and the other end is provided with a drive unit. The drive unit is used to drive the frame (67) to rotate relative to the base (66).

5. A large-area deep foundation pit support structure according to claim 4, characterized in that: The drive unit includes a wedge (68). The frame (67) has an inclined groove on the side away from the rotating connection end and close to the end face of the base (66). The wedge (68) is inserted into the inclined groove. The wedge (68) is slidably connected to the base (66). The base (66) has a bolt (69) threadedly connected to one end near the wedge (68). The end of the bolt (69) abuts against the wedge (68). The bolt (69) can push the wedge (68) toward the rotating connection end of the frame (67) by means of thread transmission.

6. A large-area deep foundation pit support structure according to claim 5, characterized in that: The base (66) is slidably connected to the mounting plate (65), and the pad (62) is provided with a calibration component. The calibration component is used to drive the base (66) to slide relative to the mounting plate (65) as the frame (67) rotates, so as to ensure that the anchor cable (8) passes through the anchor ring (61), the through hole (63) and the anchor hole (91) in a straight line.

7. A large-area deep foundation pit support structure according to claim 6, characterized in that: The calibration assembly includes two hinge frames (610) symmetrically arranged on the front and rear sides of the through hole (63). The hinge frames (610) are fixedly connected to the pad (62). Each hinge frame (610) is rotatably connected to a telescopic rod (611). The telescopic rod (611) is fixedly connected to the anchor ring (61) and is parallel to the axis of the anchor ring (61).

8. A construction process for a large-area deep foundation pit support structure, applicable to any one of the large-area deep foundation pit support structures according to claims 1-7, characterized in that: The process is as follows: S1. Construction preparation: Complete site leveling, equipment debugging and material acceptance; S2. Measurement, Positioning and Verification: GPS is used to accurately locate the position of each structural component. Four symmetrical protective piles and cross control piles are set up. Construction is carried out after the supervisor has verified the measurement. S3, seepage prevention system construction: first construct the water-stop curtain (10), adopt the three-axis mixing pile process, and the pile body is interlocked by half the pile diameter; after the pile construction is completed, clean the slope surface and construct the sprayed anchor slope protection, and then complete the soil nail hole placement, steel mesh laying and concrete spraying in sequence. S4. Construction of the support system: Piling construction: adopt the mud wall protection positive circulation drilling and one-step-one-step construction method. After the steel casing is buried, the hole is drilled, and after the hole is cleaned twice, concrete is poured. Construction of cap beam (4) and retaining wall (3): tie the reinforcing bars of cap beam (4) and retaining wall (3) and fix them, and pour concrete as a whole. High-pressure jet grouting anchor cable construction: the anchor hole positioning, cable-driven drilling and jet grouting, waist beam installation and graded tensioning and locking are completed in sequence; S5. Drainage system construction: Simultaneously pour drainage ditches (2) at the top and bottom of the foundation pit, reserve a water collection pit, and install drainage pumps and hoses; S6. Earthwork excavation.

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