Suction and irrigation integrated dewatering excavation ultra-deep foundation pit in narrow sensitive confined space and construction method thereof

Abstract

The invention relates to a narrow sensitive confined space pumping and irrigation integrated dewatering excavation ultra-deep foundation pit and a construction method thereof, and provides a modular supporting system in order to solve the problems of joint leakage, water level regulation and control delay, low construction efficiency and the like existing in a traditional foundation pit supporting technology. The H-shaped connector box is connected with the isolation plate piles, stud locking and grouting sealing are used as assistance, and a space anchoring network is formed in combination with the inclined anchor rods. Dynamic balance of underground water is achieved through the integrated pumping and irrigation double-control precipitation system, and the earthwork transfer efficiency is improved through a built-in working platform of the enclosure ring beam; the turnover rate is improved by adopting a finalization template rapid assembly technology, and construction parameters are corrected in real time in cooperation with a twin-well monitoring system. The technology effectively solves the problems of difficult leakage control, poor deformation coordination, large resource waste and the like of the deep foundation pit in a narrow space, and is suitable for urban underground engineering under complex geological conditions.

Description

Technical Field

[0001] This invention is applicable to the excavation and construction of foundation pits in confined spaces, and is especially applicable to the construction method of ultra-deep foundation pits in narrow and sensitive confined spaces with integrated pumping and irrigation for dewatering, i.e., the distance between the foundation pit and the existing building is ≤3m, or the working face width is ≤5m. Background Technology

[0002] Traditional foundation pit support technology faces multi-dimensional technical bottlenecks: At the structural design level, cast-in-place pile-slab isolation piles suffer from complex formwork assembly processes and insufficient joint waterproofing, making seepage channels easily form at precast component connection points; redundant design of ring support systems leads to low material utilization, and the lack of systematic stress analysis in trestle reinforcement results in an imbalance between structural stability and construction economy. In terms of construction technology, conventional excavation methods for irregularly shaped foundation pits are difficult to adapt to asymmetric load distribution characteristics, resulting in poor coordination between excavation efficiency and stress release, easily inducing tilting or cracking of the retaining structure; traditional dewatering technologies rely on static control modes, with sluggish water level regulation response, making it difficult to match dynamic hydrogeological conditions. Regarding material management, low reuse rate of cast-in-place formwork and rough demolding processes lead to structural damage, and insufficient steel support turnover efficiency exacerbates resource waste.

[0003] Therefore, there is an urgent need for a construction method for ultra-deep foundation pits that integrate pumping and irrigation in confined and sensitive spaces to solve the problems existing in the current technology. Summary of the Invention

[0004] The purpose of this invention is to address the construction problems of existing deep foundation pits and pit-within-a-pit in water-rich soft soil strata, and to propose a method for local dewatering of deep foundation pits in water-rich soft soil pits and its construction. To achieve this purpose, the invention adopts the following technical solution: The present invention relates to an integrated pumping and irrigation dewatering excavation method for ultra-deep foundation pits in confined and sensitive spaces, including isolation sheet piles, standardized joint boxes, anchor bolts, horizontal ring beams, retaining ring beams, observation wells, and dewatering wells; The isolation sheet piles are installed along the outer side of the excavation edge of the foundation pit, located between the foundation pit and the existing building, and adjacent isolation sheet piles are connected by a standardized joint box. The horizontal ring beam is set close to the outside of the isolation sheet pile, and the anchor rod passes through the horizontal ring beam and the standardized joint box, and is anchored in the soil outside the isolation sheet pile. The retaining ring beam is set along the inner side of the isolation sheet piles to form a closed ring structure; Dewatering wells are installed inside the foundation pit, while observation wells are installed outside the isolation sheet piles to monitor the groundwater level.

[0005] Preferably, the standardized joint box is H-shaped, with mating grooves on both sides and an anchoring box in the middle; The isolation sheet piles are inserted into the docking groove, which is equipped with studs and lateral grouting holes; The studs are arranged in a quincunx pattern with a spacing of 200mm, in 3 rows on one side, with 5 M20 high-strength studs in each row; The lateral grouting hole connects the anchor box and the docking groove, and is used to inject cement grout to seal the joint.

[0006] Preferably, the anchor box is provided with a guide tube, and the two ends of the guide tube pass through the anchor box to form anchor bolt holes. The guide tube is set at an inclination angle of 15° to 25° to guide the anchor bolt to be anchored at an inclination.

[0007] Preferably, the anchorage length is ≥8m, the prestress is applied to 1.1 times the design value and locked, and the locking load is 220kN.

[0008] Preferably, the dewatering well is equipped with a water pump, a water level sensor, a pumping pipe, and a reinjection pipe; The pumping pipe is connected to the pumping pump, and the reinjection pipe is inserted into the dewatering well and connected to the municipal water supply pipe. The water level sensor's pumping linkage threshold is: when the water level is 1.0m below the design elevation, pumping is initiated; when the water level is 0.5m above the design elevation, pumping is initiated; dynamic balance accuracy is ±0.2m. The pumping pipe has a diameter of DN150, and the recharge pipe has a diameter of DN100.

[0009] Preferably, a water level sensor is installed in the observation well, and the water level data is uploaded to the monitoring platform in real time via a 4G module to realize remote dynamic monitoring of the groundwater level.

[0010] Preferably, the retaining ring beam is provided with a working platform extending into the center of the foundation pit, and the surface of the working platform is flush with the ground. One end of the working platform is rigidly connected to the retaining ring beam, and the other end is supported by the lattice column, which is fixed to the stable stratum below the foundation pit.

[0011] Preferably, the retaining ring beam is cast using a standardized ring beam template, with mating grooves at both ends of the template, and is fixed by standardized clips; The fixed buckle consists of a strip tie rod and a limiting plate. Two pairs of limiting plates are provided at both ends of the strip tie rod to form a limiting groove, into which the ring beam template is inserted. PVC formwork is laid at the bottom of the ring beam formwork to avoid direct contact with the ground.

[0012] The construction method for excavating ultra-deep foundation pits using integrated pumping and irrigation dewatering in confined, sensitive spaces includes the following construction steps: Step 1: Excavate a trench along the outer edge of the foundation pit excavation line, place prefabricated joint boxes at intervals, and pour underwater concrete to form isolation sheet piles; Step 2: Grout the anchor box into the docking groove through the lateral grouting hole. The grouting pressure is 0.3~0.5MPa, the water-cement ratio is 1:1, and the grouting volume is 0.1m. 3 / m, grouting is carried out in sections from bottom to top, and each section is left to stand for 30 minutes; Step 3: Drill anchor holes through the guide tube, insert anchor rods, pour horizontal ring beams, and after the ring beams reach the required strength, tension the anchor rods to 220kN and lock them; Step 4: Lay out the retaining ring beam and working platform inside the foundation pit, construct the lattice columns, erect the standardized ring beam formwork, lay PVC formwork at the bottom, and pour concrete. Step 5: Drill dewatering wells inside the foundation pit at intervals of ≤10m, with the wells extending 2m beyond the bottom of the foundation pit, and install water pumps, water level sensors, and recharge pipes; drill observation wells within 1m outside the foundation pit and install water level sensors. Step 6: Excavate the foundation pit in layers, with each layer having a depth of ≤2m. After each layer is excavated, install anchor bolts and horizontal ring beams. Step 7: Real-time monitoring using water level sensors. Recharge when the water level is 1.0m below the design elevation and pump out when it is 0.5m above the design elevation to dynamically balance the groundwater level.

[0013] Compared with the prior art, the technical solution provided by this invention has the following advantages: 1. Through the precise matching design of modular H-type joint boxes and isolation sheet piles, combined with the dual processes of stud mechanical locking and grouting sealing, the potential for joint leakage is effectively eliminated, and the shear bearing capacity of the nodes is enhanced; the inclined anchoring system guided by the guide pipe forms a spatial force network, which significantly improves the adaptability of the retaining structure to asymmetric loads.

[0014] 2. The integrated pumping and irrigation system establishes a dynamic balance mechanism for groundwater levels through real-time water level monitoring and automatic recharge compensation, avoiding sudden changes in water pressure caused by the lag in regulation in traditional precipitation processes and reducing the risk of subsidence of surrounding strata.

[0015] 3. The design of the ring retaining beam integrated working platform enables seamless connection between earthwork excavation and transportation processes, reducing blind spots in mechanical operations; the three-dimensional support system formed by the lattice columns and ring beams enhances the bearing reliability of deep strata.

[0016] 4. The standardized formwork system adopts a rapid assembly structure and ground isolation technology, which greatly shortens the formwork cycle and improves the quality of concrete molding, realizes high turnover of formwork, and significantly reduces material waste. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the installation of dewatering wells and isolation piles in the foundation pit; Figure 2 This is a schematic diagram of the retaining ring beam structure for foundation pit excavation; Figure 3 This is a plan view of the foundation pit retaining structure; Figure 4 This is a schematic diagram of the foundation pit excavation process; Figure 5 This is a schematic diagram of the foundation pit excavation process; Figure 6 This is a schematic diagram of the lateral support structure for foundation pit excavation; Figure 7 This is a plan view of the lateral support structure for the foundation pit excavation; Figure 8 This is a three-dimensional structural diagram of a standardized joint box; Figure 9 This is a three-dimensional structural diagram of a standardized joint box; Figure 10 This is a cross-sectional view of a standardized joint box; Figure 11 This is a detailed drawing of a precipitation well; Figure 12 This is a schematic diagram of the formwork structure for the casting of the retaining ring beam; Figure 13 This is a three-dimensional structural diagram of the retaining ring beam formwork. Figure 14 Schematic diagram of the three-dimensional structure of the fixed buckle.

[0018] The diagram is labeled as follows: 11. Existing building; 12. Ground surface; 13. Excavation face; 14. Foundation pit; 21. Sheet pile; 22. Standardized joint box; 23. Butt groove; 24. Anchor box; 25. Guide pipe; 26. Anchor hole; 27. Stud; 28. Lateral grouting hole; 31. Anchor bolt; 32. Horizontal ring beam; 33. Anchor; 41. Retaining ring beam; 42. Lattice column; 43. Working platform; 51. Observation well; 52. Dewatering well; 53. Water level sensor; 54. Water pump; 55. Pumping pipe; 56. Recharge pipe; 61. Ring beam formwork; 62. Butt groove; 63. Standardized buckle; 64. Strip tie rod; 65. Limiting plate; 66. Limiting groove; 67. PVC formwork. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0020] Those skilled in the art should understand that, in the disclosure of this application, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limitations on this application.

[0021] To enhance understanding of the present invention, reference will be made below to the appendix. Figure 1 To be continued Figure 14 The embodiments of the present invention will be described in detail below. The following embodiments are implemented based on the technical solution of the present invention and provide detailed implementation methods. However, the protection scope of the present invention is not limited to the following embodiments.

[0022] Example 1 like Figure 1-14 As shown, the present invention relates to an ultra-deep foundation pit for integrated pumping and irrigation dewatering excavation in a confined and sensitive space, including isolation sheet piles 21, standardized joint boxes 22, anchor bolts 31, horizontal ring beams 32, retaining ring beams 41, observation wells 51, dewatering wells 52, etc. Among them, the isolation sheet piles 21 are set between the excavation edge of the foundation pit and the existing building 11, and adjacent isolation sheet piles 21 are connected by a standardized joint box 22; the horizontal ring beam 32 is set close to the isolation sheet piles 21, and the anchor rod 31 passes through the horizontal ring beam 32 and the standardized joint box 22 and is anchored in the soil outside the isolation sheet piles 21; the retaining ring beam 41 is set along the inner side of the isolation sheet piles 21, forming a closed ring structure; the dewatering well 52 is set inside the foundation pit, and the groundwater level observation well 51 is set outside the isolation sheet piles 21.

[0023] Preferably, the standardized joint box 22 is H-shaped, with mating grooves 23 on both sides and an anchoring box 24 in the middle. The isolation sheet pile 21 is inserted into the mating groove 23, which is equipped with studs 27 and lateral grouting holes 28. The studs 27 enhance the connection strength between the isolation sheet pile 21 and the standardized joint box 22, while the grouting holes 28 allow cement grout to be injected into the mating groove 23 from the anchoring box 24, improving the sealing between the isolation sheet pile 21 and the mating groove 23. The studs are arranged in a staggered pattern with a spacing of 200mm, in three rows on each side, with five M20 high-strength studs in each row.

[0024] Preferably, the anchor box 24 is further provided with a guide tube 25, the two ends of which protrude from the surface of the anchor box 24 to form an anchor hole 26 that penetrates the anchor box 24. The guide tube is inclined at an angle of 15° to 25° to guide the anchor rod to be anchored obliquely.

[0025] Preferably, the anchor rod 31 passes through the anchor rod hole 26 on the standardized joint box 22 and is anchored in the soil outside the foundation pit. The guide pipe 25 is inclined to facilitate the oblique insertion of the anchor rod 31 into the soil for anchoring. The anchor rod anchorage length is ≥8m, the prestress is loaded to 1.1 times the design value and locked, and the locking load is 220kN.

[0026] Preferably, the dewatering well 52 is equipped with a water pump 54, a water level sensor 53, a pumping pipe 55, and a reinjection pipe 56. The pumping pipe 55 is connected to the pumping pipe 54, and the reinjection pipe 56 is inserted into the dewatering well 52. When the water level in the dewatering well 52 is lower than the design value, water is replenished into the dewatering well 52 through the reinjection pipe 56 to balance the groundwater level in the foundation pit area. The pumping pipe has a diameter of DN150, and the reinjection pipe has a diameter of DN100.

[0027] Preferably, the observation well 51 is equipped with a water level sensor 53, which monitors the groundwater level in the foundation pit area in real time with a dynamic balance accuracy of ±0.2m, thereby enabling dynamic control of the groundwater.

[0028] Preferably, a working platform 43 extending into the center of the foundation pit is provided in a part of the retaining ring beam 41. The surface of the working platform 43 is basically flush with the ground 12, which facilitates the transfer of earth and stone from the excavation surface 13 of the foundation pit through the platform 43, thereby improving the efficiency of earth removal. One end of the working platform 43 is rigidly connected to the retaining ring beam 41, and the other end is supported on the lattice column 42, which is supported in the stable stratum below the foundation pit.

[0029] Preferably, the ring beam template 61 used for pouring the retaining ring beam 41 adopts a standardized support and splicing structure. The ring beam template 61 has butt grooves 62 at both ends to facilitate the extension of the ring beam template 61. The ring beam template 61 is supported and fixed by standardized buckles 63. A set of ring beam templates 61 is provided with four standardized buckles 63 at the top, bottom and ends to fix the ring beam template 61. The bottom of the ring beam template 61 is provided with a PVC template 67 to prevent the lower surface of the retaining ring beam 41 from directly contacting the ground 12 during pouring, thereby improving the pouring quality of the retaining ring beam 41.

[0030] Preferably, the shaping buckle 63 is composed of a strip tie rod 64 and a limiting plate 65. Two pairs of limiting plates 65 are respectively provided at the ends of the strip tie rod 64, and a limiting groove 66 is formed between each pair of limiting plates 65. The ring beam template 61 is inserted into the limiting groove 66 to fix the ring beam template 61.

[0031] Example 2 Based on the same concept, this embodiment is based on the construction method of ultra-deep foundation pit excavation for integrated pumping and irrigation in confined and sensitive spaces according to Embodiment 1, and includes the following construction steps: Step 1: Construction of Isolation Sheet Piles 21 Along the outer edge of the excavation line of the foundation pit 14, excavate the trench for the isolation sheet pile 21, and then place the prefabricated joint box 22 at intervals into the trench for the isolation sheet pile 21. The isolation sheet pile 21 is then poured by injecting underwater concrete into the adjacent joint box 22. The isolation sheet pile 21 is then poured. Step 2: Grouting and sealing of joint box 22 Cement grout is injected into the mating groove 23 through the grouting hole 28 from the anchor box 24 to improve the sealing between the isolation sheet pile 21 and the mating groove 23; the grouting pressure is 0.3~0.5MPa, the water-cement ratio of the grout is 1:1, and the grouting volume is 0.1m. 3 / m control; the grouting sequence is segmented grouting from bottom to top, and after each segment is completed, it is left to stand for 30 minutes before the next segment is grouted; Step 3: Construction of the first-floor anchor bolts 31 and horizontal ring beams 32 Anchoring holes are drilled into the soil outside the foundation pit 14 through the anchor holes 26 on the guide pipe 25, and anchor rods 31 are inserted into the anchoring holes. Then, the horizontal ring beam 32 is poured close to the isolation sheet pile 21. The horizontal ring beam 32 is poured with C30 concrete. The anchor rods 31 pass through the horizontal ring beam 32. After the horizontal ring beam 32 reaches the design strength, the anchor 33 is installed on the anchor rod 31, and the anchor rod 31 is prestressed. The prestress of the anchor rod 31 is loaded to 220kN and the anchor 33 is locked. Step 4: Construction of retaining ring beam 41 The positions of the retaining ring beam 41 and the extended working platform 43 are marked out inside the excavation line of the foundation pit 14. According to the position of the extended working platform 43, the bored piles and lattice columns 42 are constructed. The ring beam formwork 61 is erected according to the position of the retaining ring beam 41 and the extended working platform 43. The ring beam formwork 61 is fixed with the fixed buckle 63. A layer of PVC formwork 67 is laid at the bottom of the ring beam formwork 61. Then, concrete is poured into the ring beam formwork 61 to complete the construction of the retaining ring beam 41 and the working platform 43. Step 5: Layout and installation of dewatering wells 52 Dewatering wells 52 are drilled along the inner side of the excavation line of foundation pit 14, with a spacing of no more than 10m between adjacent dewatering wells 52. The bottom of the dewatering well 52 extends 2m into the bottom of foundation pit 14. A water pump 54 and a water level sensor 53 are installed in the dewatering well 52. The water pump 54 is connected to a water pumping pipe 55. A recharge pipe 56 is inserted into the dewatering well 52 and connected to the municipal water supply pipe. Observation wells 51 are drilled within 1m of the outer side of the excavation line of foundation pit 14. The bottom of the observation well 51 extends 2m into the bottom of foundation pit 14. A water level sensor 53 is installed in the observation well 51. Step 6: Excavation of the foundation pit in 14 layers The foundation pit 14 is excavated in layers, with each layer excavated to a depth of no more than 2m. After each layer is excavated, anchor bolts 31 and horizontal ring beams 32 are installed in accordance with step 3 until the design depth is reached. Step 7: Dynamic water level monitoring and pumping control During the excavation of foundation pit 14, the groundwater level is monitored in real time by water level sensor 53. When the water level is 1.0m lower than the design elevation, water is injected into the ground through recharge pipe 56. When the water level is higher than 0.5m, water pump 54 is started to pump out the groundwater.

[0032] The parts not described in detail in this application are prior art, and therefore are not described in detail in this application.

[0033] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0034] Although this document uses a significant amount of technical terminology, the possibility of using other terms is not excluded. These terms are used merely to facilitate the description and explanation of the nature of this application; interpreting them as any additional limitation would be contrary to the spirit of this application.

[0035] This application is not limited to the above-described preferred embodiments. Anyone can derive other products in various forms under the guidance of this application. However, regardless of any changes made to their shape or structure, any technical solution that is the same as or similar to that of this application falls within the protection scope of this application.

Claims

1. An ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces, characterized in that: Including sheet piles (21), standardized joint boxes (22), anchor bolts (31), horizontal ring beams (32), retaining ring beams (41), observation wells (51) and dewatering wells (52); The isolation sheet piles (21) are set along the outer side of the excavation edge of the foundation pit (14) and are located between the foundation pit (14) and the existing building (11). Adjacent isolation sheet piles (21) are connected by a standardized joint box (22). The horizontal ring beam (32) is set close to the outside of the isolation sheet pile (21), and the anchor rod (31) passes through the horizontal ring beam (32) and the standardized joint box (22) and is anchored in the soil outside the isolation sheet pile (21); The retaining ring beam (41) is set along the inner side of the isolation sheet pile (21) to form a closed ring structure; The dewatering wells (52) are located inside the foundation pit (14), and the observation wells (51) are located outside the isolation sheet piles (21) to monitor the groundwater level.

2. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces as described in claim 1, characterized in that: The standardized joint box (22) is H-shaped, with docking grooves (23) on both sides and an anchoring box (24) in the middle. The isolation sheet pile (21) is inserted into the docking groove (23), and the docking groove (23) is provided with a stud (27) and a lateral grouting hole (28). The studs (27) are arranged in a quincunx pattern with a spacing of 200mm, in 3 rows on one side, with 5 M20 high-strength studs in each row. The lateral grouting hole (28) connects the anchor box (24) and the docking groove (23) and is used to inject cement grout to seal the joint.

3. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces as described in claim 2, is characterized in that... The anchor box (24) is provided with a guide tube (25), and the two ends of the guide tube (25) pass through the anchor box (24) to form anchor holes (26). The guide tube (25) is set at an angle of 15°~25° to guide the anchor rod (31) to be anchored at an angle.

4. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces as described in claim 3, is characterized in that... The anchor rod (31) has an anchorage length of ≥8m, is prestressed to 1.1 times the design value and locked, and the locking load is 220kN.

5. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces according to claim 1, characterized in that, The dewatering well (52) is equipped with a water pump (54), a water level sensor (53), a water pumping pipe (55), and a reinjection pipe (56). The pumping pipe (55) is connected to the pumping pump (54), and the reinjection pipe (56) is inserted into the dewatering well (52) and connected to the municipal water supply pipe; The pumping linkage threshold of the water level sensor (53) is: when the water level is 1.0m below the design elevation, the pumping is started; when the water level is 0.5m above the design elevation, the pumping is started; and the dynamic balance accuracy is ±0.2m. The pumping pipe (55) has a diameter of DN150, and the recharge pipe (56) has a diameter of DN100.

6. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces according to claim 1, characterized in that, The observation well (51) is equipped with a water level sensor (53), and the water level data is uploaded to the monitoring platform in real time through a 4G module to realize remote dynamic monitoring of groundwater level.

7. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces according to claim 1, characterized in that, The retaining ring beam (41) is provided with a working platform (43) extending into the center of the foundation pit (14), and the surface of the working platform (43) is flush with the ground (12); One end of the working platform (43) is rigidly connected to the retaining ring beam (41), and the other end is supported by the lattice column (42), which is fixed to the stable stratum below the foundation pit (14).

8. The ultra-deep foundation pit excavation method for integrated pumping and irrigation in confined, sensitive spaces according to claim 1, characterized in that, The retaining ring beam (41) is cast using a standardized ring beam template (61), with mating grooves (62) at both ends of the template, and fixed by standardized buckles (63); The fixed buckle (63) consists of a strip tie rod (64) and a limiting plate (65). Two pairs of limiting plates (65) are provided at both ends of the strip tie rod (64) to form a limiting groove (66). The ring beam template (61) is inserted into the limiting groove (66). The bottom of the ring beam template (61) is covered with PVC template (67) to avoid direct contact with the ground (12).

9. A construction method for excavating ultra-deep foundation pits in confined, sensitive spaces using integrated pumping and irrigation dewatering as described in any one of claims 1-8, characterized in that, The construction steps include the following: Step 1: Excavate a trench along the outer edge of the foundation pit (14), place prefabricated joint boxes (22) at intervals, and pour underwater concrete to form isolation sheet piles (21). Step 2: Grout from the anchor box (24) into the docking groove (23) through the lateral grouting hole (28), with a grouting pressure of 0.3~0.5MPa, a water-cement ratio of 1:1, and a grouting volume of 0.1m. 3 / m, grouting is carried out in sections from bottom to top, and each section is left to stand for 30 minutes; Step 3: Drill anchor holes through guide tube (25), insert anchor rods (31), pour horizontal ring beam (32), and after the ring beam reaches the strength standard, tension the anchor rods (31) to 220kN and lock them; Step 4: Lay out the retaining ring beam (41) and working platform (43) inside the foundation pit (14), construct the lattice column (42), erect the standardized ring beam formwork (61), lay PVC formwork (67) at the bottom, and pour concrete; Step 5: Drill dewatering wells (52) inside the foundation pit (14) with a spacing of ≤10m and a depth 2m beyond the bottom of the foundation pit. Install water pumps (54), water level sensors (53), and recharge pipes (56). Drill observation wells (51) within 1m outside the foundation pit and install water level sensors (53). Step 6: Excavate the foundation pit in layers (14), with each layer having a depth of ≤2m. After each layer is excavated, install anchor bolts (31) and horizontal ring beams (32). Step 7: Real-time monitoring is conducted using a water level sensor (53). When the water level is 1.0m below the design elevation, recharge is performed; when it is 0.5m above the design elevation, water is pumped out to dynamically balance the groundwater level.

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