Construction method and pressure relief well system for controlled gravity-flow drainage in foundation pits

Abstract

This invention discloses a construction method and system for a self-flowing controllable drainage and pressure relief well for foundation pits, belonging to the field of foundation pit anti-surge. The method includes the following steps: S1, determining the number and arrangement of pressure relief wells; S2, construction of the pressure relief well system: S21, arranging pressure relief wells within the foundation pit support structure according to the determined number and arrangement; S22, excavating a ring-shaped drainage ditch along the inner edge of the foundation pit and connecting the ring-shaped drainage ditch to the pressure relief wells using a drainage hose; S23, setting at least one water collection well within the foundation pit support structure, ensuring the water collection well is connected to the ring-shaped drainage ditch; S3, excavating the foundation pit in layers, and dynamically adjusting the wellhead elevation of the pressure relief wells based on the current foundation pit excavation surface elevation during the excavation process. Using the above-mentioned construction method and system for a self-flowing controllable drainage and pressure relief well for foundation pits, the difference in formation water head can be used to achieve gravity-flow drainage without electricity, realizing precise pressure relief.

Description

Technical Field

[0001] This invention relates to the field of foundation pit anti-surge technology, and in particular to the construction method and system of self-flow controllable drainage and pressure relief wells for foundation pit anti-surge. Background Technology

[0002] With the continued acceleration of urbanization and the sharp increase in demand for underground space development, deep foundation pit engineering has become an indispensable core component of urban construction. The dense emergence of super high-rise buildings and the rapid expansion of underground transportation, integrated pipe corridors and other underground projects are driving the evolution of underground space towards a two-way trend of "deep vertical extension" and "planar scale expansion".

[0003] At the same time, the widespread application of the step-by-step excavation technology for ultra-deep foundation pits has placed more stringent requirements on the dynamic adaptability of the pressure relief well system and the accuracy of groundwater control.

[0004] In special areas such as those near rivers or the sea, foundation pits often face a typical geological system of "a weakly permeable layer overlying a confined, highly permeable layer." In this type of stratum, the confined, highly permeable layer often forms a direct hydraulic connection with the surrounding water body, resulting in the interface between the strongly and weakly permeable layers bearing significant buoyancy forces from the confined water. If the thickness of the overlying weakly permeable layer is insufficient, and the soil's own weight cannot resist the buoyancy forces generated by the confined water head, the bottom of the foundation pit is highly susceptible to destructive accidents such as sudden inrush and piping, seriously threatening construction safety and project stability. Therefore, groundwater control has become a core aspect of ensuring the safety of such foundation pit projects.

[0005] However, existing technologies still have many shortcomings that are difficult to overcome:

[0006] Firstly, conventional pressure relief well groups generally employ a fixed wellhead elevation design, lacking dynamic adaptability. During the dynamic construction process of phased and zoned excavation of the foundation pit, pressure relief wells with fixed elevations cannot flexibly adjust the pressure relief intensity according to the excavation depth of different areas. This easily leads to problems such as insufficient pressure relief in localized areas (increased risk of sudden surges in deep excavation areas) or excessive pressure relief (design redundancy in shallow excavation areas). For example, if a uniform standard is set based on the pressure relief requirements of the deepest area of ​​the foundation pit, the pressure relief effect in shallow excavation areas will far exceed the actual needs, not only wasting resources and increasing project costs but also potentially causing uneven settlement of the surrounding strata, threatening the safety of nearby buildings and structures.

[0007] Secondly, traditional drainage and pressure relief well systems are heavily reliant on electrically driven pumps. Conventional solutions fail to fully utilize natural groundwater head differences, instead relying on electric pumps to extract groundwater to reduce the head pressure of confined, highly permeable layers, thereby decreasing the buoyancy force on the foundation pit floor and preventing sudden inrush. However, this approach presents significant safety risks: in deep foundation pits, remote construction sites, or other environments with unstable or interrupted power supplies, the pumps cannot operate continuously, directly causing the pressure relief system to fail, resulting in a sharp drop in drainage efficiency and a significant increase in the risk of foundation pit inrush.

[0008] Third, existing technologies are prone to causing damage to the surrounding environment. When the pressure-bearing permeable layer at the bottom of the foundation pit has a direct hydraulic connection with the adjacent water area, and there are settlement-sensitive buildings and structures distributed around it, traditional decompression and dewatering methods are prone to causing abnormal drops in the groundwater level outside the foundation pit, which in turn can lead to secondary disasters such as ground subsidence and cracking of buildings and structures, making it difficult to control the environmental impact.

[0009] In summary, the existing decompression well technology has shortcomings in dynamic adaptability, power dependence avoidance, decompression accuracy control, and environmental impact prevention, making it difficult to meet the safety and environmental protection requirements of deep and large foundation pit projects. Summary of the Invention

[0010] The purpose of this invention is to provide a construction method and system for a self-flowing, pressure-reducing drainage well for foundation pits to prevent sudden inrush, thereby solving the aforementioned technical problems.

[0011] To achieve the above objectives, this invention provides a construction method for a self-flowing, pressure-reducing drainage well for foundation pits, comprising the following steps:

[0012] S1. Collect the thickness of the weak permeable layer, the self-weight of the weak permeable layer soil, the thickness of the confined strong permeable layer, the permeability coefficient of the confined strong permeable layer, and the confined water head within the scope of the foundation pit support structure, and determine the number and arrangement of pressure relief wells based on the collected data.

[0013] S2. Construction of the pressure relief well system:

[0014] S21. Within the scope of the foundation pit support structure, determine the drilling position according to the number and arrangement of the pressure relief wells determined in step S1, and drill holes at the corresponding drilling positions. Then insert the pressure relief wells into the boreholes until the filter pipes of the pressure relief wells are completely inserted into the pressure-bearing permeable layer. Backfill with sand and gravel filter material, and make the length of the well pipe of the pressure relief well greater than the burial depth of the support structure.

[0015] S22. Excavate a ring-shaped drainage ditch along the inner edge of the foundation pit, then seal and connect the ring-shaped drainage ditch with one end of the drainage hose, and extend the other end of the drainage hose into the pressure relief well, leaving a drainage gap between the end of the drainage hose and the inner wall of the bottom of the pressure relief well.

[0016] S23. At least one water collection well shall be provided within the scope of the foundation pit support structure, and the water collection well shall be connected to the annular drainage ditch.

[0017] S3. The foundation pit is excavated in layers. During the excavation process, the wellhead elevation of the pressure relief well is dynamically and synchronously adjusted based on the current foundation pit excavation surface elevation to ensure that the wellhead of the pressure relief well is always 0.5m-1.0m higher than the foundation pit excavation surface. The wellhead height of the pressure relief well is reduced synchronously as the excavation depth increases. At this time, the groundwater flows into the pressure relief well under the hydraulic head difference between the pressure-bearing strong permeable layer and the weak permeable layer, and is then discharged through the drainage hose, drainage ditch and collection well in sequence.

[0018] Meanwhile, during the adjustment process, based on the changes in the confined water head, the vertical confined water buoyancy force and the self-weight of the weakly permeable soil layer after excavation were calculated, and the vertical confined water buoyancy force and the self-weight of the weakly permeable soil layer were compared to verify the pit's resistance to sudden heave.

[0019] Preferably, in step S1, the number of pressure relief wells The calculation formula is as follows:

[0020] ;

[0021] in,

[0022] ;

[0023] ;

[0024] In the formula, Indicates the total required drainage capacity; Indicates the design drainage capacity of a single drainage well; Indicates the safety factor against sudden surges; Indicates the water yield of a pressurized, highly permeable aquifer; This represents the volume of the confined, highly permeable layer within the support structure of the foundation pit, and , Indicates the area of ​​the foundation pit; Indicates the initial confined head; Indicates the safe pressure head; Indicates the thickness of the pressure-bearing, highly permeable layer; This represents the permeability coefficient of a pressure-bearing, highly permeable layer. Indicates hydraulic gradient; This indicates the area of ​​water flowing around the well, and ,in, Indicates the outer diameter of the water filter pipe. This indicates the length of the filter pipe in the pressure relief well.

[0025] Preferably, the arrangement of the equilateral triangular grid and square grid in step S1 is adapted to the shape of the foundation pit, the distance between two adjacent pressure relief wells is 10m-20m, and the distance between any pressure relief well and the inner side of the support structure is not less than 2m.

[0026] Preferably, in step S21, the borehole diameter is 50mm-100mm larger than the outer diameter of the decompression well;

[0027] The well casing of the relief well adopts a segmented and detachable structure. Adjacent sections are sealed and connected by quick-connect joints. The well casing length is 5m-6m, the well casing diameter is 100mm-200mm, and the well casing length is 1.2 times the depth of the pit.

[0028] The length of the filter pipe is 50%-70% of the length of the well pipe. The depth of the filter pipe into the pressure-bearing, highly permeable layer is not less than 3m. The filter pipe has multiple filter holes with an opening rate of 15%-20%, a hole spacing of 50mm, and a hole diameter of 10mm.

[0029] The bottom end of the filter pipe is connected to a sedimentation pipe, which is 0.5m-1.0m long and is used to collect sediment.

[0030] The burial depth of the relief well is greater than the burial depth of the support structure.

[0031] Preferably, the distance between the outer edge of the annular drainage ditch and the inner edge of the foundation pit described in step S22 is 0.3m, the ditch depth is 0.5m, the bottom width is 0.4m, the longitudinal slope is 0.3%-0.5%, the drainage ditch is located below the excavation surface of the foundation pit, and the elevation of the drainage ditch is... The following dynamic adjustments will be made as the foundation pit excavation face is prepared:

[0032] ;

[0033] In the formula, Indicates the elevation of the excavation surface of the foundation pit; This indicates the safe elevation difference between the drainage ditch and the excavation surface of the foundation pit. ;

[0034] The drainage hose uses a flexible pipe with a diameter of 50mm. The installation elevation in the pressure relief well is adjusted synchronously according to the elevation of the wellhead, and the drainage gap is 0.3m-0.5m.

[0035] Preferably, in step S23, if multiple water collection wells are set up, the distance between two adjacent water collection wells is 20m-30m, and the two adjacent water collection wells are interconnected.

[0036] Preferably, in step S3, the wellhead elevation of the pressure relief well is... The dynamic adjustment formula is as follows:

[0037] ;

[0038] In the formula, This indicates the safety elevation difference between the wellhead of the pressure relief well and the excavation face of the foundation pit. .

[0039] Preferably, in step S3, the wellhead elevation of the relief well is adjusted by disassembling the well casing sections from high to low.

[0040] Preferably, the vertical pressure buoyancy force after excavation described in step S3 is... The calculation formula is as follows:

[0041] ;

[0042] In the formula, Indicates the specific gravity of water; This indicates the pressure head of the water after pressure reduction in the relief well;

[0043] Self-weight of weakly permeable soil The calculation formula is as follows:

[0044] ;

[0045] In the formula, This indicates the effective unit weight of the weakly permeable soil layer.

[0046] like If the test is passed, the foundation pit anti-surge verification is deemed successful.

[0047] A pressure relief well system constructed according to the construction method of a self-flowing controllable drainage and pressure relief well for pit anti-surge.

[0048] Therefore, the present invention employs the above-mentioned construction method and system for a self-flowing, controllable drainage and pressure-reducing well for foundation pit anti-surge, and has the following beneficial effects:

[0049] 1. Controllable and safe against sudden surges, with significantly reduced environmental impact: This invention uses a controllable pressurized water decompression design to precisely reduce the pressurized water head of the highly permeable layer at the bottom of the foundation pit, so that the self-weight of the soil in the weakly permeable layer at the bottom of the foundation pit and the buoyancy force of the pressurized water after decompression form a stable balance, eliminating safety hazards such as sudden surges and piping from the root. At the same time, by accurately calculating the decompression intensity, it avoids the uneven settlement of the surrounding strata caused by excessive decompression in traditional technologies, minimizing the adverse impact on surrounding buildings and the ecological environment, and taking into account both construction safety and environmental friendliness.

[0050] 2. Strong geological adaptability and efficient gravity-flow decompression mechanism: This invention is specifically adapted to typical geological environments where a weakly permeable layer lies beneath a confined, highly permeable layer. It fully utilizes the natural head difference between the confined water level and the surrounding water level as a driving force to promote spontaneous seepage of groundwater into the decompression well. The confined water head can be reduced without additional power, effectively reducing the buoyancy force at the interface between the weakly permeable layer and the confined, highly permeable layer, ensuring the safety against sudden surges within the scope of the foundation pit support structure. It is especially suitable for complex geological scenarios with high confined water heads and close hydraulic connections, such as those near rivers and seas.

[0051] 3. Eliminating dependence on electricity and significantly improving system reliability: The gravity-flow pressure relief well adopts a non-mechanical drainage design, without the installation of water pumps and power lines, completely eliminating the dependence on the power system of traditional technologies. This effectively solves the problem of pressure relief system failure caused by unstable or interrupted power supply in scenarios such as deep foundation pits and remote construction sites. At the same time, groundwater that is not discharged in time will form downward back pressure at the foundation pit excavation face, forming an additional safety reserve against sudden surges. This not only avoids the economic waste caused by excessive pressure relief, but also further improves the safety redundancy of the project.

[0052] 4. Dynamically adaptable to excavation, with precise and controllable decompression accuracy: Through the segmented and detachable well pipe structure and standard quick connector design, the wellhead elevation of the decompression well can be dynamically and synchronously adjusted with the elevation of the excavation surface of the foundation pit. The wellhead elevation is adjusted every 2m of excavation to ensure that the decompression intensity is precisely matched with the excavation progress. Combined with the needs of zoning and step-by-step excavation of the foundation pit, the wellhead elevation of different areas can be designed to achieve precise control of the confined water head in different zones. This completely solves the pain points of "insufficient decompression" or "excessive decompression" of traditional fixed elevation decompression wells and ensures the overall safety of surrounding buildings.

[0053] 5. Highly efficient and convenient construction, easy quality control, and excellent economy: This invention adopts a standardized joint design, eliminating the need for on-site welding or precision machining for well pipe installation and disassembly. The construction process is simple and convenient, significantly reducing construction difficulty and technical barriers. At the same time, the well group can be divided into zones and steps for control design, flexibly adapting to the construction needs of different excavation depths and different areas, effectively improving construction efficiency. The detachable well pipe and standard connection joints can be recycled and reused, reducing building material waste. Combined with gravity-flow pressure reduction, it reduces power consumption, significantly reducing project costs and achieving a triple optimization of construction efficiency, project quality, and economy.

[0054] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0055] Figure 1 This is a flowchart of the construction method for the self-flowing controllable drainage and pressure relief well for preventing sudden inrush in the foundation pit according to the present invention.

[0056] Figure 2This is a schematic diagram of the working state of the pressure relief well system in the construction method of the self-flow controllable drainage pressure relief well for anti-surge in the foundation pit according to the present invention, as the foundation pit excavation progresses. Among them, (a) is a schematic diagram of the working state of the pressure relief well system in the initial stage of the foundation pit distributed excavation, and (b) is a schematic diagram of the working state of the pressure relief well system in the subsequent stage of the foundation pit distributed excavation.

[0057] Figure 3 This is a schematic diagram of the planar distribution of the decompression well system of the present invention.

[0058] Figure Labels

[0059] 10. Pressure relief well; 20. Support structure; 30. Circular drainage ditch; 40. Drainage hose; 50. Water collection well. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0061] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, such as a process, method, system, product, or server that includes a series of steps or units, not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or device.

[0062] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0063] like Figures 1-3 As shown, the construction method of the self-flowing controllable drainage and pressure relief well for foundation pit anti-surge includes the following steps:

[0064] S1. Collect the thickness of the weak permeable layer, the self-weight of the weak permeable layer soil, the thickness of the confined strong permeable layer, the permeability coefficient of the confined strong permeable layer, and the confined water head within the 20 range of the foundation pit support structure, and determine the number and arrangement of the pressure relief wells 10 based on the collected data.

[0065] In step S1, the number of pressure relief wells is 10. The calculation formula is as follows:

[0066] ;

[0067] in,

[0068] ;

[0069] ;

[0070] In the formula, Indicates the total required drainage capacity; Indicates the design drainage capacity of a single drainage well; Indicates the safety factor against sudden surges; Indicates the water yield of a pressurized, highly permeable aquifer; This represents the volume of the pressure-bearing, highly permeable layer within a 20mm radius of the foundation pit support structure, and , Indicates the area of ​​the foundation pit; Indicates the initial confined head; Indicates the safe pressure head; Indicates the thickness of the pressure-bearing, highly permeable layer; This represents the permeability coefficient of a pressure-bearing, highly permeable layer. Indicates hydraulic gradient; This indicates the area of ​​water flowing around the well, and ,in, Indicates the outer diameter of the water filter pipe. This indicates the length of the filter pipe in pressure relief well 10.

[0071] The arrangement method described in step S1 is an equilateral triangular grid and a square grid adapted to the shape of the foundation pit. The distance between two adjacent pressure relief wells 10 is 10m-20m, and the distance between any pressure relief well 10 and the inner side of the support structure 20 is not less than 2m.

[0072] Construction of S2 and relief well 10 system:

[0073] S21. Within the area of ​​the foundation pit support structure 20, determine the drilling positions according to the number and arrangement of the pressure relief wells 10 determined in step S1, and drill holes at the corresponding drilling positions. Then, insert the pressure relief wells 10 into the boreholes until the filter pipes of the pressure relief wells 10 are completely inserted into the pressure-bearing permeable layer. Backfill with sand and gravel filter material, and ensure that the length of the well pipe of the pressure relief wells 10 is greater than the burial depth of the support structure 20.

[0074] In step S21, the borehole diameter is 50mm-100mm larger than the outer diameter of the decompression well 10;

[0075] The well casing of relief well 10 adopts a segmented and detachable structure. Adjacent sections are sealed and connected by quick-connect joints. The well casing length is 5m-6m, the well casing diameter is 100mm-200mm, and the well casing length is 1.2 times the depth of the pit.

[0076] In this embodiment, the quick-connect connector is a sealed pipe section structure with an external thread section, an internal thread section, and a built-in sealing ring. The thread specifications are M100×2~M200×3, and the sealing ring is made of water-resistant rubber material.

[0077] The length of the filter pipe is 50%-70% of the length of the well pipe. The depth of the filter pipe into the pressure-bearing, highly permeable layer is not less than 3m. The filter pipe has multiple filter holes with an opening rate of 15%-20%, a hole spacing of 50mm, and a hole diameter of 10mm.

[0078] The bottom end of the filter pipe is connected to a sedimentation pipe, which is 0.5m-1.0m long and is used to collect sediment.

[0079] The burial depth of relief well 10 is greater than the burial depth of support structure 20.

[0080] S22. Excavate a ring-shaped drainage ditch 30 along the inner edge of the foundation pit, then seal and connect one end of the ring-shaped drainage ditch 30 with one end of the drainage hose 40, and extend the other end of the drainage hose 40 into the pressure relief well 10, so that there is a drainage gap between the end of the drainage hose 40 and the inner wall of the bottom of the pressure relief well 10.

[0081] The distance between the outer edge of the annular drainage ditch 30 and the inner edge of the foundation pit described in step S22 is 0.3m, the ditch depth is 0.5m, the bottom width is 0.4m, and the longitudinal slope is 0.3%-0.5%. The drainage ditch is located below the excavation surface of the foundation pit, and the elevation of the drainage ditch is... The following dynamic adjustments will be made as the foundation pit excavation face is prepared:

[0082] ;

[0083] In the formula, Indicates the elevation of the excavation surface of the foundation pit; This indicates the safe elevation difference between the drainage ditch and the excavation surface of the foundation pit. ;

[0084] The drainage hose 40 uses a flexible pipe with a diameter of 50mm. Its installation elevation in the pressure relief well 10 is adjusted synchronously according to the wellhead elevation, and the drainage gap is 0.3m-0.5m.

[0085] S23. At least one water collection well 50 shall be provided within the area of ​​the foundation pit support structure 20, and the water collection well 50 shall be connected to the annular drainage ditch 30.

[0086] In step S23, if multiple water collection wells 50 are set, the distance between two adjacent water collection wells 50 is 20m-30m, and the two adjacent water collection wells 50 are interconnected.

[0087] Preferably, in step S3, the wellhead elevation of the pressure relief well 10 is... The dynamic adjustment formula is as follows:

[0088] ;

[0089] In the formula, This indicates the safe elevation difference between the wellhead of relief well 10 and the excavation face of the foundation pit. .

[0090] S3. The foundation pit is excavated in layers. During the excavation process, the wellhead elevation of the pressure relief well 10 is dynamically and synchronously adjusted based on the current foundation pit excavation surface elevation to ensure that the wellhead of the pressure relief well 10 is always 0.5m-1.0m higher than the foundation pit excavation surface. The wellhead height of the pressure relief well 10 is reduced synchronously as the excavation depth increases. At this time, the groundwater flows into the pressure relief well 10 under the head difference between the pressure-bearing strong permeable layer and the weak permeable layer, and is then discharged through the drainage hose 40, drainage ditch and collection well 50 in sequence.

[0091] Meanwhile, during the adjustment process, based on the changes in the confined water head, the vertical confined water buoyancy force and the self-weight of the weakly permeable soil layer after excavation were calculated, and the vertical confined water buoyancy force and the self-weight of the weakly permeable soil layer were compared to verify the pit's resistance to sudden heave.

[0092] In step S3, the wellhead elevation of the decompression well 10 is adjusted by disassembling the well casing sections from high to low.

[0093] The vertical buoyancy force after excavation described in step S3 The calculation formula is as follows:

[0094] ;

[0095] In the formula, Indicates the specific gravity of water; The pressure head after pressure reduction in pressure well 10 is indicated. In this embodiment, the monitoring accuracy of the pressure head is ±5cm, and the monitoring frequency is twice a day.

[0096] Self-weight of weakly permeable soil The calculation formula is as follows:

[0097] ;

[0098] In the formula, This indicates the effective unit weight of the weakly permeable soil layer.

[0099] like If the test is passed, the foundation pit anti-surge verification is deemed successful.

[0100] In this embodiment, the elevation of the wellhead of relief well 10 can also be controlled according to segmented and zoned excavation, and the wellhead elevation... The elevation of the excavation face of the foundation pit is dynamically adjusted as the excavation depth decreases. When the excavation depth of the foundation pit decreases by 2m, the elevation of the pressure relief well 10 wellhead is reduced accordingly.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A construction method for a gravity-flow controllable drainage and pressure-reducing well for foundation pits, characterized in that: The method comprises the following steps: S1, collecting the thickness of the weak water-permeable layer, the self-weight of the weak water-permeable layer soil, the thickness of the pressure-bearing strong water-permeable layer, the permeability coefficient of the pressure-bearing strong water-permeable layer and the pressure-bearing water head in the range of the foundation pit supporting structure, and determining the number and arrangement of the pressure-relief wells based on the collected data; S2, pressure-relief well system construction: S21, determining the drilling position according to the number and arrangement of the pressure-relief wells determined in step S1 in the range of the foundation pit supporting structure, drilling a hole at the corresponding drilling position, then inserting the pressure-relief well into the hole until the filter pipe of the pressure-relief well completely enters the pressure-bearing strong water-permeable layer, backfilling sandstone filter material, and making the length of the well pipe of the pressure-relief well greater than the burial depth of the supporting structure; S22, excavating a ring-shaped drainage ditch along the inner edge of the foundation pit, then sealingly connecting the ring-shaped drainage ditch with one end of the drainage hose, and extending the other end of the drainage hose into the pressure-relief well, and leaving a drainage gap between the end of the drainage hose and the inner wall of the bottom end of the pressure-relief well; S23, arranging at least one water collecting well in the range of the foundation pit supporting structure, and making the water collecting well communicate with the ring-shaped drainage ditch; S3, excavating the foundation pit in layers, and dynamically and synchronously adjusting the well mouth elevation of the pressure-relief well based on the current foundation pit excavation surface elevation during the excavation process, to ensure that the well mouth of the pressure-relief well is always 0.5m-1.0m higher than the foundation pit excavation surface, and the well mouth height of the pressure-relief well is synchronously reduced with the increase of the excavation depth, at this time, the groundwater flows into the pressure-relief well under the driving of the water head difference between the pressure-bearing strong water-permeable layer and the weak water-permeable layer, and then is discharged through the drainage hose, the drainage ditch and the water collecting well in turn; Meanwhile, during the adjustment process, the vertical pressure-bearing water floatation force and the self-weight of the weak water-permeable layer soil after excavation are calculated according to the change of the pressure-bearing water head, and the foundation pit anti-bursting is verified by comparing the vertical pressure-bearing water floatation force with the self-weight of the weak water-permeable layer soil. In step S1, the number of relief wells The calculation formula is as follows: ； Wherein, ; ； wherein, represents the total required drainage capacity; represents the design drainage capacity of a single drainage well; represents the anti-inrush safety factor; represents the specific yield of the strong and permeable confined layer; represents the volume of the strong and permeable confined layer within the foundation pit support structure, and , represents the area of the foundation pit; represents the initial confined water head; represents the safe confined water head; represents the thickness of the strong and permeable confined layer; represents the permeability coefficient of the strong and permeable confined layer; represents the hydraulic slope; represents the water passing area around the well, and wherein, represents the outer diameter of the filter pipe, represents the filter pipe length of the pressure relief well; The vertical water buoyancy force after excavation in step S3 The calculation formula is as follows: ； In the formula, Gw represents the specific weight of water; Gw represents the specific weight of water; Weakly permeable layer soil self weight The calculation formula is as follows: ； wherein effective unit weight of the weak pervious layer soil; thickness of the weak pervious layer If then the foundation pit anti-inrushing verification is determined to pass.

2. The construction method of the anti-burst self-flow controllable drainage relief well for foundation pit according to claim 1, characterized in that: The arrangement mode of step S1 is an equilateral triangle grid and a square grid which are adapted to the shape of the foundation pit, the distance between two adjacent pressure-relief wells is 10m-20m, and the distance between any one pressure-relief well and the inner side of the supporting structure is not less than 2m.

3. The construction method of the anti-burst self-flow controllable drainage relief well for foundation pit according to claim 1, characterized in that: In step S21, the hole diameter of the drilling is 50mm-100mm larger than the outer diameter of the pressure-relief well; The well pipe of the pressure-relief well adopts a segmented detachable structure, the adjacent two pipe segments are sealingly connected through a quick connection joint, the length of the well pipe is 5m-6m, the diameter of the well pipe is 100mm-200mm, and the length of the well pipe is 1.2 times the depth of the foundation pit; The length of the filter pipe is 50%-70% of the length of the well pipe, the depth of the filter pipe entering the pressure-bearing strong water-permeable layer is not less than 3m, a plurality of filter holes are arranged on the filter pipe, the opening rate is 15%-20%, the hole spacing is 50mm, and the hole diameter is 10mm; The bottom end of the filter pipe is connected with a sedimentation pipe, and the length of the sedimentation pipe is 0.5m-1.0m for collecting silt; The burial depth of the pressure-relief well is greater than the burial depth of the supporting structure.

4. The construction method of the anti-burst self-flow controllable drainage relief well for foundation pit according to claim 1, characterized in that: The distance between the outer edge of the ring-shaped drainage ditch and the inner edge of the foundation pit is 0.3 m, the ditch depth is 0.5 m, the bottom width is 0.4 m, the longitudinal slope is 0.3%-0.5%, the drainage ditch is arranged below the excavation surface of the foundation pit, and the elevation of the drainage ditch is 0.3-0.5 m lower than the elevation of the excavation surface of the foundation pit The following dynamic adjustment is made along with the excavation surface of the foundation pit: ； In the formula, represents the elevation of the foundation pit excavation surface; represents the safety elevation difference between the drainage ditch and the foundation pit excavation surface, ; The drainage hose adopts a flexible pipe material with a diameter of 50mm, the installation elevation in the pressure-relief well is synchronously adjusted according to the well mouth elevation, and the drainage gap is 0.3m-0.5m.

5. The construction method of the anti-burst self-flow controllable drainage relief well for foundation pit according to claim 1, characterized in that: In step S23, if multiple water collecting wells are arranged, the distance between two adjacent water collecting wells is 20m-30m, and the two adjacent water collecting wells are connected with each other.

6. The construction method of the anti-burst self-flow controllable drainage relief well for foundation pit according to claim 3, characterized in that: In step S3, the wellhead elevation of the relief well is determined The dynamic adjustment formula is as follows: ； In the formula, represents the safety elevation difference between the wellhead of the relief well and the excavation surface of the foundation pit, .

7. The construction method of the anti-burst self-flow controllable drainage relief well for foundation pit according to claim 6, characterized in that: In step S3, the wellhead elevation of the relief well is adjusted by disassembling the pipe sections of the well pipe from high to low.

8. The construction method of a foundation pit anti-burst self-flow controllable drainage relief well system according to any one of claims 1-7.

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