Foundation pit dewatering system and foundation pit dewatering arrangement method

Abstract

The invention relates to the technical field of foundation pit construction, in particular to a foundation pit dewatering system and a foundation pit dewatering arrangement method.The foundation pit dewatering system comprises a first-stage platform, a second-stage platform and a third-stage platform which are arranged around a foundation pit, and the elevations of the first-stage platform, the second-stage platform and the third-stage platform are sequentially decreased; a plurality of first dewatering deep wells are arranged on the first-stage platform, a plurality of second dewatering deep wells are arranged on the second-stage platform, and a plurality of third dewatering deep wells are arranged on the third-stage platform; drainage ditches and / or water collecting wells are dug in the base of the foundation pit; digging a drainage channel at the top of the foundation pit; sewage in the first precipitation deep well, the second precipitation deep well, the third precipitation deep well, the drainage ditch and / or the water collecting well is discharged into the drainage channel and discharged into the sea through the drainage channel. According to the foundation pit dewatering system, through scientific arrangement of the graded dewatering deep wells and efficient cooperation of drainage facilities, the limitation of a traditional dewatering technology under the tidal influence and complex geological conditions is overcome, the construction safety, reliability and efficiency are improved, and the stability of a foundation pit is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit construction, and particularly relates to a foundation pit dewatering system and a foundation pit dewatering layout method. Background Technique

[0002] Foundation pit dewatering is a crucial technology in construction engineering, mainly to solve the adverse effects of groundwater on foundation pit construction. When the groundwater level is higher than the excavation bottom surface, groundwater will continuously seep into the pit, posing a serious threat to the construction environment and engineering quality. Through scientific and effective dewatering techniques, a dry and stable construction environment can be ensured within the foundation pit, and the safety of the engineering structure can be guaranteed.

[0003] Traditional foundation pit dewatering techniques are mainly applied to infrastructure construction far from water sources, such as subways, high-rise buildings, and underground parking lots. However, when constructing in coastal areas (the straight-line distance from the coastline does not exceed 250m), the engineering construction faces more complex hydrogeological challenges. The soil layers in coastal areas are mainly composed of silt, silty clay, and clay; the rock layers are mainly composed of sandstone and mudstone, with the rock strength ranging from very weak to moderately weak, and the degree of rock weathering ranging from very severe to moderate. These unique geological conditions, combined with the dynamic influence of ocean tides, make the foundation pit dewatering work in coastal areas extremely difficult. The periodic change of the sea tide level directly affects the groundwater level at the site, causing the water level to continuously rise and fall with the tide. When constructing projects such as coastal water intake pump stations, serious groundwater problems such as piping and heaving are often encountered, which not only threatens the safety and reliability of the project but also greatly increases the implementation difficulty of dewatering techniques. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem that it is difficult to dewater the foundation pit due to the special hydrogeology in coastal areas when excavating the foundation pit, and to provide a foundation pit dewatering system and a foundation pit dewatering layout method.

[0005] In the first aspect, the present invention provides a foundation pit dewatering system, including a first-level platform, a second-level platform, and a third-level platform arranged around the foundation pit, and the elevations of the first-level platform, the second-level platform, and the third-level platform decrease in sequence; a number of first dewatering deep wells are arranged on the first-level platform, a number of second dewatering deep wells are arranged on the second-level platform, and a number of third dewatering deep wells are arranged on the third-level platform; a drainage ditch and / or a sump are dug at the base of the foundation pit; a drainage channel is dug at the top of the foundation pit; the sewage in the first dewatering deep well, the second dewatering deep well, the third dewatering deep well, the drainage ditch and / or the sump is discharged into the drainage channel and then discharged into the sea through the drainage channel.

[0006] The foundation pit dewatering system provided by the present invention, by designing three - level elevation - decreasing platforms (the first - level platform, the second - level platform, and the third - level platform), distributes dewatering deep wells at different elevations, and can perform hierarchical dewatering for the special geological conditions in coastal areas (such as soil layers like silty sand, silt, clay, etc. and weakly weathered rock layers), effectively reducing the influence of groundwater at different depths, and is particularly suitable for the dynamic fluctuations of the groundwater level caused by tides in coastal areas. By setting dewatering deep wells (the first dewatering deep well, the second dewatering deep well, and the third dewatering deep well) at different elevations, it is possible to layer - drain groundwater at different depths, reduce the burden of single - well pumping of the dewatering wells, evenly lower the groundwater level, and avoid the risk of local soil settlement and deformation caused by single - point drainage. This hierarchical dewatering strategy can more precisely control the groundwater level and reduce the possibility of soil instability in areas with complex geological conditions. The coordinated action of the drainage ditch, the sump well, and the drainage channel realizes the rapid drainage of water inside and outside the foundation pit, preventing the influence of water seepage or gushing on the foundation pit caused by the rising water level during the flood tide of the tide. The drainage ditch and the sump well further optimize the drainage capacity of the foundation bottom. Even in the case of frequent changes in the sea - water tide level, the inside of the foundation pit can still remain dry, ensuring the safety of the foundation pit construction.

[0007] The foundation pit dewatering system provided by the present invention, through the scientific layout of hierarchical dewatering deep wells and the efficient coordination of drainage facilities, overcomes the limitations of traditional dewatering techniques under the influence of tides and complex geological conditions, effectively improves the safety, reliability, and efficiency of construction, while reducing the project cost and construction difficulty, reducing the groundwater pressure inside the foundation pit, avoiding phenomena such as piping and gushing, and enhancing the stability of the foundation pit.

[0008] Preferably, a first standby deep well is further provided on the sea - facing side of the first - level platform, a second standby deep well is further provided on the sea - facing side of the second - level platform, and a third standby deep well is further provided on the sea - facing side of the third - level platform.

[0009] The standby deep wells provided on the sea - facing side can provide additional dewatering capacity for the drastic fluctuations of the groundwater level caused by tides. When the tide level rises and the pressure of groundwater intrusion increases, the standby deep wells can cooperate with other dewatering deep wells to quickly drain the excess groundwater, effectively relieving the seepage pressure inside the foundation pit and ensuring the dryness of the foundation pit. And the setting of the standby deep wells provides a redundant design for the foundation pit dewatering system. Even when the main dewatering deep wells fail or their drainage capacity is insufficient, the standby deep wells can be immediately started to ensure the continuous and effective operation of the entire dewatering system, avoiding construction interruptions caused by single - point failures. Through the auxiliary pumping of the standby deep wells, it is possible to more evenly lower the groundwater level around the foundation pit, avoiding the instability or settlement problems of the foundation pit slope caused by uneven local water - level reduction. Especially in the case of greater water pressure on the sea - facing side, the standby deep wells help to balance the groundwater level around the foundation pit and reduce the influence of the hydraulic gradient on the soil stability.

[0010] Preferably, the first precipitation deep well and the first standby deep well are evenly distributed on the first-level platform; the second precipitation deep well and the second standby deep well are evenly distributed on the second-level platform; the third precipitation deep well and the third standby deep well are evenly distributed on the third-level platform.

[0011] The main deep well and the standby deep well are evenly arranged on each platform, which can more comprehensively cover the precipitation area around the foundation pit, reduce the phenomenon of sudden drop in water level caused by overly concentrated local pumping, thereby more evenly control the groundwater level around the foundation pit, and reduce the risk of uneven settlement or slope instability during the excavation of the foundation pit.

[0012] Preferably, at least five fourth standby deep wells are also arranged at the base of the foundation pit.

[0013] The base position is usually the area with the highest groundwater seepage pressure. Arranging the fourth standby deep well can significantly enhance the precipitation capacity of the base. As a supplementary precipitation measure, the fourth standby deep well can more efficiently lower the groundwater level at the bottom of the foundation pit, ensure that the base always remains dry, and facilitate construction operations.

[0014] Preferably, the elevation difference between the first-level platform and the second-level platform does not exceed 5.5 m, and the elevation difference between the second-level platform and the third-level platform does not exceed 5.5 m.

[0015] By reasonably distributing the elevation difference, the hydraulic gradient distribution around the foundation pit can be optimized, avoiding the problem of concentrated groundwater seepage pressure caused by excessive vertical height difference, thereby reducing the occurrence of seepage failure phenomena such as piping and heaving, and ensuring the stability of the soil mass.

[0016] Preferably, the first precipitation deep well, the first standby deep well, the second precipitation deep well, the second standby deep well, the third precipitation deep well, and the third standby deep well all include a filter pipe and a sedimentation pipe. The sedimentation pipe is fixed at the bottom of the filter pipe, and the filter pipe is a PVC pipe with a porosity ≥ 15%.

[0017] The filter pipe is designed with a PVC pipe with a porosity ≥ 15%, which can efficiently filter fine particle impurities in the groundwater, such as sand grains and sediment, to prevent these impurities from entering the deep well interior and reducing the risk of pipeline blockage. The groundwater seeps into the well evenly through the filter pipe, which helps to maintain the stability of the water level around the foundation pit and avoid the adverse impact of too high local water level on the soil mass stability. The sedimentation pipe is connected to the bottom of the filter pipe, so that the sediment and other particles settling in the well can be concentrated in the sedimentation pipe and are not easily accumulated on the surface of the filter pipe, thereby reducing the wear and blockage of the filter pipe. The filter pipe made of PVC material has excellent corrosion resistance and chemical erosion resistance, and is especially suitable for the saline environment in coastal areas, effectively preventing the filter pipe from being corroded and damaged due to long-term contact with saline groundwater.

[0018] In a second aspect, the present invention provides a method for arranging foundation pit dewatering, which is used to arrange the above-mentioned foundation pit dewatering system, and includes the following steps:

[0019] S1. Conduct a pumping test: Set up several test pumping wells and several test observation wells. The test pumping wells are arranged in a rectangle along the direction perpendicular to the coastline and parallel to the coastline. The test observation wells are equally spaced along the direction perpendicular to the coastline and parallel to the coastline from the center point of the shape enclosed by the test pumping wells; the well depths of the test pumping wells and the test observation wells are 18 - 40m, and the depths of the test pumping wells are all different. Conduct the pumping test in the order of single-well pumping test first and then group-well pumping test to obtain hydrogeological parameters.

[0020] S2. According to the hydrogeological parameters obtained in S1, combined with the engineering geological and water level geological conditions, construct a three-dimensional unsteady flow numerical calculation model of groundwater, conduct an inverse analysis by the three-dimensional finite difference method for the group-well pumping test, and invert reasonable hydraulic parameters of the three-dimensional unsteady flow numerical calculation model of groundwater according to the water level fitting of the test observation wells in the group-well pumping test, and conduct three-dimensional numerical simulation and settlement calculation for the foundation pit dewatering construction.

[0021] S3. Foundation pit dewatering design: Arrange dewatering wells according to the three-dimensional unsteady flow numerical calculation model of groundwater constructed in S1. Arrange the first dewatering deep well and the first standby deep well on the first platform; arrange the second dewatering deep well and the second standby deep well on the second platform; arrange the third dewatering deep well and the third standby deep well on the third platform.

[0022] S4. Check the dewatering wells designed in S3: Conduct a simulation calculation after the dewatering wells are arranged. Assume that the foundation pit dewatering operates for at least 90 days. If the water level drawdown meets the excavation requirements of the foundation pit after 90 days of foundation pit dewatering, the arrangement of the dewatering wells is completed; otherwise, repeat S3 until the water level drawdown meets the excavation requirements of the foundation pit after 90 days of foundation pit dewatering.

[0023] S5. Conduct foundation pit excavation design: The foundation pit is excavated in the form of multi-level slope cutting. Design four-level slopes from the top to the bottom of the foundation pit. The slope ratios of the first two levels from top to bottom are 1:2.5, and the slope ratios of the last two levels are 1:2; the elevation of the first platform is 1.90 - 2.00m, the elevation of the second platform is -3.50 - -3.6m, and the elevation of the third platform is -9.00 - -9.10m.

[0024] The foundation pit dewatering layout method provided by the present invention arranges the test pumping wells in a rectangular pattern in the directions perpendicular and parallel to the coastline. The test observation wells are evenly distributed at equal distances from the center in two directions, covering both the vertical and horizontal directions, and can accurately obtain the distribution characteristics of groundwater and hydrogeological parameters at different positions. The operation sequence of first conducting single-well pumping tests and then group-well pumping tests is adopted. The design of wells at different depths makes the hydrogeological data more comprehensive, can better reflect the site's infiltration characteristics and the dewatering effect of the foundation pit, and can fully reflect the three-dimensional dynamic changes of groundwater. According to the hydrogeological parameters and combined with the engineering geological conditions, a three-dimensional unsteady flow numerical calculation model of groundwater is constructed, which can accurately simulate the dynamic behavior of groundwater flow during the foundation pit dewatering process. Using three-dimensional finite difference method for inverse analysis to optimize the hydraulic parameters to ensure that the model can truly reflect the variation law of groundwater and provide a scientific basis for the layout of dewatering wells. By fitting the water level data of the test observation wells through the model, the model accuracy is verified, and the reliability of the dewatering design is enhanced. Dewatering deep wells and standby deep wells are respectively arranged on different platforms, fully considering the distribution characteristics of the groundwater level within the foundation pit area and the elevation differences of the platforms to ensure the uniformity of dewatering. A standby deep well is set on each platform, enhancing the redundancy of the dewatering system. Even if the main dewatering deep well fails, the standby deep well can be immediately activated, thereby improving the stability and reliability of the dewatering system. By simulating the water level changes after the layout of the dewatering wells for 90 days, the layout effect of the dewatering wells is verified to ensure that the water level drawdown meets the requirements of foundation pit excavation. If the verification fails, the layout plan can be adjusted by optimizing it, gradually improving the dewatering well design, reducing the uncertainty in the actual operation of the dewatering system, and effectively reducing the construction risk. The simulation process comprehensively considers the settlement calculation and the impact of foundation pit excavation on the water level, avoiding potential safety hazards caused by non-dropping water level or ineffective settlement control during excavation. In the foundation pit excavation design, four-level slopes are designed according to the depth of the foundation pit, and the slope ratios of the first two levels are reasonably set to 1:2.5 and the last two levels are 1:2. The design effectively reduces the sliding risk of the soil body during the slope excavation process. The stepped slope form reduces the risk of slope instability and at the same time facilitates the coordinated operation of dewatering wells at different stages.

[0025] The foundation pit dewatering layout method provided by the present invention can efficiently lower the water level in the foundation pit by optimizing the layout of dewatering wells and the distribution of multi-level platforms, avoid quicksand or heaving phenomena caused by too high groundwater level, enable the dewatering system to adapt to the complex hydrogeological conditions around the foundation pit, and ensure the stability of the soil body in the excavation area.

[0026] Preferably, the single-well pumping test in S1 includes the following steps:

[0027] S111. Conduct data collection and collation: Put a water pump into one test pumping well for pumping water, conduct dynamic observations of the groundwater levels of other test pumping wells and test observation wells, and draw the relationship curve between the single-well water level drawdown and time;

[0028] S112. Use the AquiferTest software to fit the measured water level drawdown - time relationship curve of the test observation wells at the same horizon obtained in S111 with the standard curve, and calculate the horizontal hydraulic conductivity K, h transmissivity T, storage coefficient S, and influence radius R of the test observation wells at the same horizon;

[0029] S113. Conduct a water level recovery test on the test pumping well, and continuously monitor the water levels of the test observation wells during the water level recovery period until the water levels become stable;

[0030] S114. Repeat S111 - S113 until single - well pumping tests are completed for all test pumping wells.

[0031] In the initial stage of the single - well pumping test, by pumping water through a water pump placed in the test pumping well and comprehensively monitoring the dynamic changes of the groundwater levels in other test pumping wells and test observation wells, it can fully reflect the response of the groundwater system during the pumping process, draw the water level drawdown - time relationship curve, which not only intuitively shows the dynamic characteristics of the water level change during the pumping process but also provides direct data support for subsequent analysis and fitting; using the AquiferTest software to fit and analyze the measured data of the test observation wells with the standard curve ensures that the calculated horizontal hydraulic conductivity, transmissivity, storage coefficient, and influence radius have high precision and reliability. By analyzing the data of the test observation wells at the same horizon, accurately characterize the hydraulic properties of the groundwater layer to ensure that these key hydro - logical parameters can reflect the infiltration and diversion capabilities of groundwater in the horizontal plane, providing a solid basis for the design of the dewatering system; after the single - well pumping test, conduct a water level recovery test on the test pumping well, dynamically observe the whole process of the water level recovering from the low point after pumping to the stable state, providing more dynamic data support for the hydro - logical model. Synchronously observe the water level changes of the test observation wells during the water level recovery process to further verify the connectivity and dynamic response ability of the groundwater system, ensuring the comprehensiveness and reliability of the test data; conduct pumping and recovery tests on all test pumping wells one by one to ensure that the collected data cover various hydro - logical conditions within the test site, avoiding analysis deviations caused by insufficient data from a single pumping well. The systematic data collection method can ensure that the test results have wide applicability, providing more real and reliable input conditions for the subsequent constructed groundwater model.

[0032] Preferably, the multi - well pumping test in S1 includes the following steps:

[0033] S121. Place water pumps in multiple test pumping wells and pump water simultaneously, use the test observation wells to conduct dynamic groundwater level observations, and draw the multi - well water level drawdown - time relationship curve;

[0034] S122. Conduct a water level recovery test on the test pumping well, and track and observe the water levels of all test observation wells during the water level recovery until the water level stabilizes.

[0035] Compared with the single-well pumping test, the multi-well pumping test can better reflect the site seepage characteristics and the effect of foundation pit dewatering. Conducting pumping operations on multiple test pumping wells simultaneously can more realistically simulate the scenario of the combined action of multiple wells in actual foundation pit dewatering, and comprehensively reflect the dynamic response characteristics of the groundwater system under regional pumping conditions. Record the change process of the groundwater level in real time and dynamically to ensure that the collected data cover the hydrogeological characteristics within the entire test range, and form an integral curve of the relationship between the drawdown and time. The drawing of the drawdown curve clearly shows the overall impact of multi-well pumping on the groundwater level, reflects the groundwater flow trend and the drawdown distribution law, and provides a basis for the reasonable layout of dewatering wells and the prediction of dewatering effects.

[0036] Preferably, S2 includes the following steps:

[0037] S21. Use the groundwater flow continuity equation and its definite solution conditions to describe the three-dimensional unsteady seepage law of groundwater, establish a three-dimensional unsteady seepage mathematical model of groundwater, discretize the entire seepage area, and use the backward difference method to discretize the three-dimensional unsteady seepage mathematical model of groundwater to obtain a three-dimensional unsteady flow numerical calculation model of groundwater;

[0038] The groundwater flow continuity equation is:

[0039]

[0040] Where:

[0041]

[0042]

[0043] In the formula: S: storage coefficient; S y : specific yield; M: thickness of the confined aquifer; B: saturated thickness of groundwater in the unconfined aquifer; k xx 、k yy 、k zz : main direction permeability coefficients of anisotropy; H: head value at point (x, y, z) at time t; W: source-sink term (1 / d);

[0044] The definite solution conditions are:

[0045] Initial condition: H(x, y, z, t)| t＝0 = H0(x, y, z, t0)

[0046] Boundary condition: H(x, y, z, t)| Γ1= H1(x, y, x, t)

[0047] Where: H0(x, y, z, t): the initial water level at point (x, y, z); Γ1: a type of boundary condition; H1(x, y, z, t): the known water level at the boundary at point (x, y, z) at time t;

[0048] S22. According to the hydrogeological parameters obtained from S1, combined with the engineering geological and water level geological conditions, determine the aquifer structure characteristics, the parameters characteristics of the three-dimensional unsteady flow numerical calculation model of groundwater, the hydraulic characteristics of the three-dimensional unsteady flow numerical calculation model of groundwater, the simulation period and stress period of the three-dimensional unsteady flow numerical calculation model of groundwater, and the treatment method of the source-sink term of the three-dimensional unsteady flow numerical calculation model of groundwater;

[0049] S23. According to the results of the group well pumping test, organize the measured data of the test pumping wells. Set up pumping wells in the three-dimensional unsteady flow numerical calculation model of groundwater, substitute the measured water output of the test pumping wells into the three-dimensional unsteady flow numerical calculation model of groundwater, conduct numerical simulation calculations of the group well pumping test, compare the calculation results with the water level changes of the measured test observation wells, continuously adjust and optimize the hydrogeological parameters until the theoretical water level burial depth in the test area is consistent with the actual water level drawdown change of the group well pumping test, and obtain reasonable confined water analysis parameters.

[0050] The three-dimensional unsteady flow description and high-precision discretization processing of the three-dimensional unsteady seepage mathematical model of groundwater can more comprehensively reflect the complex dynamic characteristics of the groundwater system. The comparison and optimization of the simulation results with the actual data of the group well pumping test ensure the accuracy and reliability of the model. Using the group well pumping test data to dynamically adjust the model parameters can quickly and efficiently invert hydrogeological parameters such as permeability coefficient and storage coefficient, making it more in line with the actual situation. The optimized model can be used to predict the groundwater level drawdown and its dynamic change trend, support the design of the foundation pit dewatering scheme, accurately evaluate the recharge capacity and flow characteristics of the confined water, and reduce the risks in the implementation of the dewatering project.

[0051] Compared with the prior art, the beneficial effects of the present invention are:

[0052] 1. The foundation pit dewatering system provided by the present invention, through the scientific layout of the stepped dewatering deep wells and the efficient coordination of the drainage facilities, overcomes the limitations of the traditional dewatering technology under the influence of tides and complex geological conditions, effectively improves the safety, reliability and efficiency of construction, reduces the engineering cost and construction difficulty at the same time, reduces the groundwater pressure in the foundation pit, avoids phenomena such as piping and heaving, and enhances the stability of the foundation pit.

[0053] 2. The foundation pit dewatering layout method provided by the present invention can efficiently lower the water level in the foundation pit by optimizing the dewatering well layout and multi-level platform distribution, avoid quicksand or gushing phenomena caused by too high groundwater level, enable the dewatering system to adapt to the complex hydrogeological conditions around the foundation pit, and ensure the stability of the soil mass in the excavation area. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is the plan view of the foundation pit dewatering design;

[0055] Figure 2 is the sectional view of the foundation pit dewatering design;

[0056] Figure 3 is Figure 1 the enlarged view of part A in

[0057] Figure 4 is the cross-sectional view of the foundation pit;

[0058] Figure 5 is the curve of the relationship between the single-well water level drawdown and time during the pumping test of Well K1;

[0059] Figure 6 is the plan view of the water level change of each well during the pumping test of Well K1;

[0060] Figure 7 is the fitting result diagram of the measured curve and the standard curve of the test observation well at the same layer during the pumping test of Well K1;

[0061] Figure 8 is the diagram of the relationship between the water level drawdown and the well spacing during the pumping test of Well K1;

[0062] Figure 9 is the water level recovery curve of the test observation well at the same layer during the test of Well K1;

[0063] Figure 10 is the curve of the relationship between the group well water level drawdown and time during the pumping test of Well K1, K2, and K4;

[0064] Figure 11 is the plan view of the water level change of each well during the pumping test of Well K1, K2, and K4;

[0065] Figure 12 is the three-dimensional diagram of the discrete model network constructed in Example 3;

[0066] Figure 13 is the three-dimensional sectional view of the model stratum in Example 3;

[0067] Figure 14 is the schematic diagram of the model settings of Well K1 and Well G1 in Example 3;

[0068] Figure 15It is a comparison diagram of the measured drawdown curve and the simulated drawdown curve of the observation well in Example 3;

[0069] Figure 16 It is a standard residual histogram distribution relationship diagram of the water level results of the observation wells simulated by the group well pumping test in Example 3;

[0070] Figure 17 It is an isogram of the water level after 7 days of the group well pumping test in Example 3 (unit: m);

[0071] Figure 18 It is an isogram of the predicted foundation pit water level in the foundation pit after precipitation operation in Example 3.

[0072] Markings in the figure:

[0073] 11 - The first precipitation deep well, 12 - The first standby deep well, 21 - The second precipitation deep well, 22 - The second standby deep well, 31 - The third precipitation deep well, 32 - The third standby deep well, 4 - The fourth standby deep well, 51 - The filter pipe, 52 - The sedimentation pipe, 53 - The water-stop sealing layer, 61 - The test pumping well, 62 - The test observation well, 100 - The foundation pit, 101 - The first-level platform, 102 - The second-level platform, 103 - The third-level platform, 104 - The drainage ditch, 105 - The sump, 106 - The drainage channel, 107 - The inter-slope filter layer, 108 - The sedimentation tank. Specific implementation mode

[0074] The present invention will be further described in detail below in conjunction with specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0075] In the description of the specific embodiments of the present invention, without special explanation, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the invention product / device / equipment is usually used and placed. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present invention or simplifying the description in the specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present invention.

[0076] In addition, when terms such as "horizontal", "vertical", "hanging", "parallel" appear, it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but it can be slightly inclined or deviated. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and it does not mean that the structure must be completely horizontal, but it can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in directions such as "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably an error / deviation within ±8%, more preferably an error / deviation within ±6%, more preferably an error / deviation within ±5%, more preferably an error / deviation within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still achieve its function in the solution of the present invention.

[0077] In addition, when expressions such as "first", "second", "third", etc. appear in the terms, they are only used to distinguish the descriptions of the same or similar components, and should not be understood as emphasizing or implying the relative importance of specific components.

[0078] In addition, in the description of the embodiments of the present invention, "several", "multiple", "a number of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., and even can be a situation exceeding 9.

[0079] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / limited, when terms such as "set", "installed", "connected", "connected", "provided with", "laid", "arranged" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be connection means commonly used in the art such as welding, riveting, bolting, threaded connection, etc. This kind of connection can be a mechanical connection, an electrical connection or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components.

[0080] Embodiment 1

[0081] As Figure 1 、 Figure 2 shown, this embodiment provides a foundation pit dewatering system for dewatering the foundation pit 100 in the offshore area (the straight-line distance from the coastline does not exceed 250m).

[0082] The foundation pit dewatering system provided in this embodiment includes a first-level platform 101, a second-level platform 102, and a third-level platform 103 arranged around the foundation pit 100. Specifically, as Figure 1 、 Figure 2As shown, the elevation of the first-level platform 101 can be +1.95 m, the elevation of the second-level platform 102 can be -3.55 m, the elevation of the third-level platform 103 can be -9.05 m, and the bottom elevation of the foundation pit 100 can be -14.55 m. The elevations of the first-level platform 101, the second-level platform 102, and the third-level platform 103 decrease in sequence. Further, the elevation difference between the first-level platform 101 and the second-level platform 102 does not exceed 5.5 m. Preferably, the elevation difference between the first-level platform 101 and the second-level platform 102 is 5.5 m. The elevation difference between the second-level platform 102 and the third-level platform 103 does not exceed 5.5 m. Preferably, the elevation difference between the second-level platform 102 and the third-level platform 103 is 5.5 m.

[0083] As Figure 1 , Figure 2 shown, a drainage ditch 104 and / or a sump 105 are dug at the bottom of the foundation pit 100. The sump 105 can be set to four as Figure 1 shown. The four sump wells 105 can be distributed around the bottom of the foundation pit 100 to ensure that there is no accumulated water at the bottom of the foundation pit 100. A drainage channel 106 is dug at the top of the foundation pit 100.

[0084] As Figure 1 shown, a number of first dewatering deep wells 11 are arranged on the first-level platform 101, a number of second dewatering deep wells 21 are arranged on the second-level platform 102, and a number of third dewatering deep wells 31 are arranged on the third-level platform 103. The sewage in the first dewatering deep wells 11, the second dewatering deep wells 21, the third dewatering deep wells 31, the drainage ditch 104 and / or the sump 105 is pumped out by a water pump and discharged into the drainage channel 106. As Figure 1 shown, the accumulated water in the drainage channel 106 can flow into the sedimentation tank 108. In this embodiment, the sedimentation tank 108 is a three-stage sedimentation tank, and the sewage is discharged into the sea after being sedimented in the sedimentation tank 108.

[0085] Further, as Figure 1 shown, a first standby deep well 12 is also arranged on the sea side of the first-level platform 101 to Figure 1 take Figure 1 as an example. There are forty-five first dewatering deep wells 11 arranged on the first-level platform 101 in

[0086] which are numbered Q1 to Q45. A first standby deep well 12 numbered BQ1 is arranged between the first dewatering deep wells 11 numbered Q5 and Q6, a first standby deep well 12 numbered BQ2 is arranged between the first dewatering deep wells 11 numbered Q7 and Q8, and a first standby deep well 12 numbered BQ3 is arranged between the first dewatering deep wells 11 numbered Q9 and Q10;

[0086] A second standby deep well 22 is also arranged on the sea side of the second-level platform 102. Take Figure 1 as an example. Figure 1On the middle - level platform 102, twenty second precipitation deep wells 21 are set, numbered S1 - S20, and a second standby deep well 22 numbered BS1 is set between the second precipitation deep wells 21 numbered S3 and S4;

[0087] On the side of the third - level platform 103 close to the sea, a third standby deep well 32 is also set to Figure 1 take... as an example. Figure 1 On the third - level platform 103, thirteen third precipitation deep wells 31 are set, numbered Z1 - Z13, and a third standby deep well 32 numbered BZ1 is set between the third precipitation deep wells 31 numbered Z2 and Z3.

[0088] The standby deep wells set on the side close to the sea can provide additional precipitation capacity for the drastic fluctuation of the groundwater level caused by tides. When the tide level rises and the pressure of groundwater intrusion increases, the standby deep wells can cooperate with other precipitation deep wells to quickly drain the excess groundwater, effectively relieve the seepage pressure in the foundation pit 100, and ensure the dryness of the foundation pit 100; moreover, the setting of the standby deep wells provides a redundant design for the precipitation system of the foundation pit 100. Even when the main precipitation deep wells fail or the drainage capacity is insufficient, the standby deep wells can be immediately started (it can be understood that the standby deep wells can also work together with the precipitation deep wells), ensuring the continuous and effective operation of the entire precipitation system and avoiding construction interruption caused by single - point failure; through the auxiliary pumping of the standby deep wells, the groundwater level around the foundation pit 100 can be reduced more evenly, avoiding the instability or settlement problems of the foundation pit 100 slope caused by uneven local water level reduction. Especially in the case of greater water pressure on the side close to the sea, the standby deep wells help to balance the groundwater level around the foundation pit 100 and reduce the influence of the hydraulic gradient on the soil stability.

[0089] Furthermore, in this embodiment, the first precipitation deep well 11 and the first standby deep well 12 can be evenly distributed on the first - level platform 101; the second precipitation deep well 21 and the second standby deep well 22 can be evenly distributed on the second - level platform 102; the third precipitation deep well 31 and the third standby deep well 32 can be evenly distributed on the third - level platform 103.

[0090] Furthermore, as Figure 1 、 Figure 2 shown, at least five fourth standby deep wells 4 can also be arranged at the bottom of the foundation pit 100. In this embodiment, the number of the fourth standby deep wells 4 is five. The fourth standby deep wells 4 can be arranged at structural positions and can also serve as water - level observation wells (for example, Figure 1 the five fourth standby deep wells 4 numbered BG1 - BG5 in...).

[0091] The foundation pit dewatering system provided in this embodiment can perform hierarchical dewatering for the special geological conditions in the coastal area (such as soil layers like silty sand, silt, clay, etc. and weakly weathered rock layers) by designing three-level elevation decreasing platforms (the first platform 101, the second platform 102, and the third platform 103), distributing the dewatering deep wells at different elevations, effectively reducing the influence of groundwater at different depths, and is particularly suitable for the dynamic fluctuations of the groundwater level caused by tides in the coastal area.

[0092] By setting dewatering deep wells (the first dewatering deep well 11, the second dewatering deep well 21, and the third dewatering deep well 31) at different elevations, the groundwater at different depths can be pumped and drained in layers, reducing the burden of single pumping of the dewatering wells, evenly lowering the groundwater level, avoiding the risk of local soil settlement and deformation caused by single-point pumping, and this hierarchical dewatering strategy can more precisely control the groundwater level and reduce the possibility of soil instability in areas with complex geological conditions.

[0093] The coordinated action of the drainage ditch 104, the sump 105, and the drainage channel 106 realizes the rapid diversion of water inside and outside the foundation pit 100, preventing the water level from rising during high tide from causing seepage or gushing impact on the foundation pit 100. The drainage ditch 104 and the sump 105 further optimize the drainage capacity of the foundation bottom. Even in the case of frequent changes in the sea tide level, the inside of the foundation pit 100 can still remain dry, ensuring the safety of the construction of the foundation pit 100.

[0094] The foundation pit dewatering system provided in this embodiment, through the scientific layout of hierarchical dewatering deep wells and the efficient coordination of drainage facilities, overcomes the limitations of traditional dewatering technologies under the influence of tides and complex geological conditions, effectively improving the safety, reliability, and efficiency of construction, while reducing the project cost and construction difficulty, reducing the groundwater pressure inside the foundation pit 100, avoiding phenomena such as piping and gushing, and enhancing the stability of the foundation pit 100.

[0095] Embodiment 2

[0096] On the basis of Embodiment 1, this embodiment describes the specific structures and construction methods of the first dewatering deep well 11, the first standby deep well 12, the second dewatering deep well 21, the second standby deep well 22, the third dewatering deep well 31, and the third standby deep well 32.

[0097] As Figure 2 shown, the well depths of the first dewatering deep well 11 and the first standby deep well 12 ( Figure 2 not shown in Figure 2 ) can both be 30m, the well depths of the second dewatering deep well 21 and the second standby deep well 22 ( Figure 2 not shown in

[0098] The first dewatering deep well 11, the first standby deep well 12, the second dewatering deep well 21, the second standby deep well 22, the third dewatering deep well 31, the third standby deep well 32, and the fourth standby deep well 4 all include a filter pipe 51 and a sedimentation pipe 52. The sedimentation pipe 52 is fixed to the bottom of the filter pipe 51. The filter pipe 51 is a PVC pipe with a porosity of ≥15%.

[0099] The filter pipe 51 is designed with a PVC pipe having a porosity of ≥15%, which can efficiently filter fine particle impurities in groundwater, such as sand grains, sediment, etc., and prevent these impurities from entering the interior of the deep well, reducing the risk of pipeline blockage. The groundwater seeps into the well evenly through the filter pipe 51, which helps to maintain the stability of the water level around the foundation pit 100 and avoid the adverse impact of excessive local water level on the soil stability. The bottom of the filter pipe 51 is connected to the sedimentation pipe 52, so that the sediment and other particles settling in the well can be concentrated in the sedimentation pipe 52 and are not easily accumulated on the surface of the filter pipe 51, thereby reducing the wear and blockage of the filter pipe 51. The filter pipe 51 made of PVC material has excellent corrosion resistance and chemical erosion resistance, and is especially suitable for the saline water environment in the coastal area, effectively preventing the filter pipe 51 from being corroded and damaged due to long-term contact with saline groundwater.

[0100] Any of the construction of the first dewatering deep well 11, the first standby deep well 12, the second dewatering deep well 21, the second standby deep well 22, the third dewatering deep well 31, the third standby deep well 32, and the fourth standby deep well 4 includes the following steps: (1) Measuring and setting out the lines to determine the position and elevation. According to the well point layout plan, measure and set out the well positions. When the arranged well points are affected by ground obstacles or construction conditions, appropriate adjustments can be made on site, and the drilling rig is positioned according to the well point positions. (2) Site preparation (leveling and compaction if necessary). Bury the hole protection pipe, which is perpendicular to the ground. The hole protection pipe is driven into the original soil for 10 - 20 cm, and the periphery of the hole protection pipe is filled and tamped with clay. The hole inclination of the drilling does not exceed 1%. (3) Drilling and hole cleaning. During the drilling process, use the large hook to hang tightly and then feed slowly (i.e., always under reduced pressure drilling) to avoid the drill string from being bent once. After drilling each drill pipe, repeat the hole cleaning once and then connect a new drill pipe. After the final hole is drilled, thoroughly clean the hole until the sand content in the returned water is < 12% and then lift the drill. The well completion technology and the drill string used should be appropriately adjusted according to the actual situation compared with the conventional well completion. (4) Install the PVC filter pipe 51 and the sedimentation pipe 52. According to the designed well depth, arrange and combine the filter pipe 51 and the sedimentation pipe 52 in advance. When sinking the well pipe, the bottoms of all deep wells are strictly controlled according to the elevation, and the wellhead elevations are kept consistent. In order to ensure that the well pipe does not lean against the well wall and ensure the gravel filling thickness, add a set of centralizers at the upper and lower parts of the filter pipe 51 to ensure that the thickness of the annular gravel filling gap is greater than 150 mm. A 50 - 60 mesh nylon net can be wrapped outside the PVC filter pipe 51 to further improve the durability of the filter pipe 51. (5) Filling the sand and gravel mixture. When filling the material, seal the mouth of the filter pipe 51, and then use an excavator to fill the crushed stones into the hole, and continuously shake the pipe body during the process to make the crushed stones evenly distributed around the filter pipe 51 as much as possible. A water stop sealing layer 53 is set at the top of the well, and the water stop sealing layer 53 can be backfilled with cohesive soil to the wellhead. (6) Well washing. Fix the air compressor air pipe at the bottom of a galvanized steel pipe, and weld an elbow at the bottom position of the galvanized steel pipe; turn on the air compressor and use the air pressure of the air compressor to bring out the water and sediment deposits together; continuously turn on the air compressor until no obvious sediment is brought out. (7) Lowering the pump and trial pumping. Before installing the deep well pump, measure the well depth and the thickness of the sediment at the bottom of the well. After meeting the requirements, use a rope to lift the deep well pump to the bottom of the well pipe. After installation, a single well test pumping should be carried out to ensure the drawdown of the single well water output and check whether the dewatering equipment is normal. After meeting the requirements, transfer to normal operation.

[0101] Embodiment 3

[0102] This embodiment provides a method for arranging foundation pit dewatering. This method for arranging foundation pit dewatering is used to arrange the foundation pit dewatering system provided in Embodiment 1 or Embodiment 2, and includes the following steps:

[0103] S1. Conduct a pumping test: Set up several test pumping wells 61 and several test observation wells 62. The test pumping wells 61 are arranged in a rectangle along the directions perpendicular and parallel to the coastline. The test observation wells 62 are equidistantly distributed along the directions perpendicular and parallel to the coastline from the center point of the shape enclosed by the test pumping wells 61. The well depths of the test pumping wells 61 and the test observation wells 62 are 18 - 40 m, and the depths of the four test pumping wells 61 are all different. Conduct the pumping test in the order of single-well pumping test first and then group-well pumping test to obtain hydrogeological parameters. The test pumping wells 61 are arranged in a rectangle along the directions perpendicular and parallel to the coastline, and the test observation wells 62 are equidistantly distributed in two directions from the center, covering both the vertical and horizontal directions, which can accurately obtain the distribution characteristics of groundwater at different positions and hydrogeological parameters. By operating in the order of single-well pumping test first and then group-well pumping test, the design of the test pumping wells 61 with different depths makes the hydrogeological data more comprehensive, can better reflect the site infiltration characteristics and the dewatering effect of the foundation pit 100, and fully reflects the three-dimensional dynamic changes of groundwater.

[0104] Specifically, as Figure 1 、 Figure 3 shown, Figure 1 in the northwest corner of the foundation pit 100 is the pumping test area ( Figure 1 the dotted rectangle area A in Figure 3 ), as

[0105] shown, four test pumping wells 61 numbered K1 - K4 and seven test observation wells 62 numbered G1 - G7 can be set. The connection line of the test pumping wells 61 numbered K1 and K4 and the connection line of the test pumping wells 61 numbered K2 and K3 are in the direction parallel to the coastline. The distance between K1 and K4 can be specifically 15 m, and the distance between K2 and K3 can be specifically 15 m. The connection line of the test pumping wells 61 numbered K1 and K2 and the connection line of the test pumping wells 61 numbered K3 and K4 are in the direction perpendicular to the coastline. The distance between K1 and K2 can be specifically 19 m, and the distance between K3 and K4 can be specifically 19 m. The four test pumping wells 61 are arranged in a rectangle, that is, the test pumping wells 61 are arranged in a rectangle along the directions perpendicular and parallel to the coastline.

[0105] The test observation well 62 numbered G1 is located at the center of the shape enclosed by the four test pumping wells 61 arranged in a rectangle. Taking the test observation well 62 numbered G1 as the origin, the test observation wells 62 numbered G2 - G4 are equidistantly distributed along the direction parallel to the coastline, and the test observation wells 62 numbered G5 - G7 are equidistantly distributed along the direction perpendicular to the coastline. Specifically, in this embodiment, the distance between adjacent test observation wells 62 is 10 m.

[0106] In this embodiment, the structural parameters of the test wells are shown in Table 1.

[0107] Furthermore, the single-well pumping test includes the following steps:

[0108] S111. Conduct data collection and collation: Put a water pump into a test pumping well 61 for pumping water, conduct dynamic observations on the groundwater levels of other test pumping wells 61 and test observation wells 62, and draw a curve of the relationship between the single-well water level drawdown and time;

[0109] S112. Use AquiferTest software to fit the measured water level drawdown-time relationship curve of the test observation well 62 at the same horizon obtained in S111 with the standard curve, and calculate the horizontal permeability coefficient K h , transmissivity T, storage coefficient S, and influence radius R of the test observation well 62 at the same horizon;

[0110] S113. Conduct a water level recovery test on the test pumping well 61, and track and observe the water levels of the test observation wells 62 during the water level recovery period until the water levels are stable;

[0111] S114. Repeat S111 - S113 until the single-well pumping test is completed for all test pumping wells 61.

[0112] Table 1 Summary of test well structure parameters

[0113]

[0114] Now, take Well K1 as an example to illustrate the single-well pumping test.

[0115] Before conducting the pumping test, the engineering geological and hydrogeological conditions can be obtained first. For example, the physical and mechanical parameters of the test site area can be obtained, including formation characteristics, rock formation characteristics, depth, formation thickness, cone tip resistance, earth pressure, unconfined compressive strength, hole diameter, cohesion, unit weight, Young's modulus, etc.; information such as the groundwater elevation of the test site and the permeability coefficients of siltstone and sandstone can be obtained.

[0116] The depth of Well K1 is 27m, and the length of the filter pipe 51 is 21m. Put a water pump with a rated flow rate of 60m 3 / h into Well K1 for pumping water. The actual average flow rate of the whole test is 60m 3 / h. During the test, the dynamic groundwater levels can be observed using other test pumping wells 61 and / or test observation wells 62. The duration is about 20 hours, and the water levels have basically stabilized. The water level drawdown statistics of each well are shown in Table 2. The curve of the relationship between the single-well water level drawdown and time during the pumping test of Well K1 is as Figure 5 shown, and the plan view of the water level changes of each well during the pumping test of Well K1 is as Figure 6 shown.

[0117] As shown in Table 2, during the pumping process of Well K1, the water levels of each well dropped by 1.4 - 2.5 m, and the drawdown was not significant. As Figure 6 shown, for the wells close to Well K1, whether arranged perpendicular or parallel to the coastline, the drawdowns are basically the same.

[0118] Table 2 Statistical Table of Water Level Drawdown of Each Well and Distance from Well K1

[0119] Number Well depth / m Distance to Well K1 / m Drawdown / m K1 27 / 8.37 (dynamic drawdown) K2 33 19 2.01 K3 36 24.21 1.48 K4 40 15 1.22 G1 33 12.1 2.4 G2 33 19.91 1.82 G3 27 25.78 1.68 G4 18 35.27 1.4 G5 27 20.89 1.92 G6 27 30.44 1.66 G7 27 40.21 1.4

[0120] In this embodiment, the hydrogeological parameters are calculated based on the data of the unsteady flow pumping test. According to the specific hydrogeological conditions of the test site, the corresponding methods are selected to calculate the hydrogeological parameters.

[0121] AquiferTest is a specially designed software for graphical analysis and report editing of pumping tests, with the function of calculating various aquifer characteristics, including: confined aquifer, unconfined aquifer, leaky aquifer, fractured aquifer, etc. Now, the software calculation theory of AquiferTest is described as follows:

[0122] (1) Basic assumptions

[0123] 1) The confined aquifer extends infinitely laterally; 2) The aquifer and semi-pervious layer in the pumping influence area are of equal thickness, homogeneous, and horizontally isotropic, and the well diameter is infinitely small; 3) The piezometric surface of the confined water is horizontal before pumping, and the water head of the un-pumped aquifer is constant; 4) Constant flow pumping.

[0124] (2) Calculation data

[0125] 1) Drawdown - time data of the observation well; 2) Distance from the pumping well to the observation well; 3) Pumping volume.

[0126] (3) Hydrogeological parameter calculation method

[0127] Well flow formula for a confined incomplete well:

[0128]

[0129] In the formula: s: drawdown (m); T: transmissivity (m 2 / d); U r = r 2 ·S / (4T·t); S: storage coefficient; B: leakage factor (m); r: distance from the pumping well to any point (m); t: pumping time (d); M: aquifer thickness (m); Q: well discharge (m 3 / d); K z : vertical permeability coefficient (m / d); K r: Horizontal permeability coefficient (m / d); L: Distance from the lower end of the pumping well filter to the aquifer roof (m); L1: Distance from the lower end of the observation well filter to the aquifer roof (m); d: Distance from the upper end of the pumping well filter to the aquifer roof (m); d1: Distance from the upper end of the observation well filter to the aquifer roof (m).

[0130] The application conditions of the above formula are for pumping from a non-complete well in an unbounded semi-confined aquifer.

[0131] Hantush-Jacob well flow formula for unsteady flow constant-discharge pumping from a confined complete well:

[0132]

[0133] In the formula: s: Drawdown of the observation well water level (m); Q: Discharge of the pumping well (m 3 / d); T: Transmissivity (m 2 / d); r: Radial distance (m); B: Leakage factor (m).

[0134] Type curve method:

[0135]

[0136] (4) Numerical model of groundwater seepage

[0137] According to the hydrogeological conditions of the test site, including the static water level of the test site, the burial conditions and distribution characteristics of groundwater, the soil properties and permeability characteristics of the aquifer medium, etc., a numerical model of groundwater seepage for this plot is established using Visual Modflow software. After parameter identification and verification of the model, the spatio-temporal distribution law of the groundwater seepage field during the pumping test is determined using this numerical model.

[0138] Data analysis can be completed by matching the drawdown curve drawn from the measured data of the same well structure with the standard curve. Using AquiferTest software, the measured curves and standard curves of the observation wells at the same layer as the K1 well pumping test in this case are fitted, and the fitting results are as Figure 7 shown. According to the fitting curve, relevant hydrogeological parameters can be calculated. In this embodiment, wells G3, G5, G6, and G7 and the K1 well are all 27m deep wells with the same well structure. Calculated according to the Hantush-Jacob method, the hydrogeological parameters of the aquifer obtained are shown in Table 3.

[0139] Table 3 Statistical table of hydrogeological parameters

[0140] Well number <![CDATA[Horizontal permeability coefficient K h (m / d)]]> <![CDATA[Hydraulic conductivity T (m 2 / d)]]> Storage coefficient S G3 8.38 335 4.56E-04 G5 7.9 316 5.48E-04 G6 8.13 325 4.15E-04 G7 7.9 316 5.48E-04 Average 8.08 323 4.92E-04

[0141] For a confined aquifer, there is a formula It can be obtained that Among them That is, the drawdown of the water level in the test observation well 62 has a natural logarithm relationship with the distance to the test pumping well 61. Let s = 0, and the influence radius R = exp(B / A) can be obtained.

[0142] In the formula: R: influence radius (m); s: drawdown of the water level in the observation well (m); r: distance from the observation well to the pumping well (m); k: permeability coefficient of the aquifer (m / d); M: thickness of the aquifer (m); T: transmissivity of the aquifer (m 2 / d); Q: discharge of the pumping well (m 3 / d).

[0143] As Figure 8 shows the relationship between the drawdown and the well spacing. It can be analyzed from Figure 8 that: 1) The drawdown decreases with the increase of the distance, but it is a non-linear relationship, showing a natural logarithm relationship form, presenting the characteristics of confined water. 2) The influence radius of this group of single-well tests is about 271 m, and the transmissivity T = 313.6 m 2 / d can be obtained.

[0144] A water level recovery test was carried out on Well K1. During the water level recovery period, the water levels of the test observation well 62 were tracked and observed until the water level was stable. As Figure 9 shows the water level recovery curve of the test observation well at the same layer during the test of Well K1. As Figure 9 shown, after Well K1 stopped pumping, the water level recovered extremely quickly. The water level could recover 10% about 3 minutes after stopping pumping. The water level could recover 90% about 60 minutes (about 1 hour) after stopping pumping.

[0145] In the initial stage of the single-well pumping test, by pumping water by putting a water pump into the test pumping well 61 and monitoring the dynamic changes of the groundwater levels of other test pumping wells and test observation wells throughout the process, the response of the groundwater system during the pumping process can be comprehensively reflected, and the curve of the drawdown versus time can be drawn, which not only intuitively shows the dynamic characteristics of the water level change during the pumping process, but also provides direct data support for subsequent analysis and fitting;

[0146] Use AquiferTest software to fit and analyze the measured data of the test observation wells and the standard curve to ensure that the calculated horizontal permeability coefficient, transmissivity, storage coefficient and influence radius have high precision and reliability. By analyzing the data of the test observation wells at the same layer, accurately characterize the hydraulic characteristics of the groundwater layer to ensure that these key hydrogeological parameters can reflect the infiltration and diversion ability of groundwater on the horizontal plane, providing a solid basis for the design of the precipitation system;

[0147] After the single-well pumping test, a water level recovery test is carried out on the test pumping well, and the whole process of the dynamic observation of the water level recovering from the low point after pumping to the stable state is carried out, providing more dynamic data support for the hydrological model. During the water level recovery process, the water level changes of the test observation wells are synchronously observed to further verify the connectivity and dynamic response ability of the groundwater system, ensuring the comprehensiveness and reliability of the test data;

[0148] The pumping and recovery tests are carried out one by one on all the test pumping wells to ensure that the collected data cover various hydrological conditions within the test site, avoiding analysis deviations caused by insufficient data of a single pumping well. The systematic data collection method can ensure that the test results have wide applicability and provide more real and reliable input conditions for the subsequent constructed groundwater model.

[0149] Furthermore, the multi-well pumping test includes the following steps:

[0150] S121. Pumps are put into multiple test pumping wells 61 and pumped simultaneously, and the dynamic observation of the groundwater level is carried out by using the test observation wells 62, and the relationship curve between the drawdown of the multi-well water level and time is drawn;

[0151] S122. A water level recovery test is carried out on the test pumping wells 61, and the water levels of all the test observation wells 62 are tracked and observed during the water level recovery period until the water level is stable.

[0152] Specifically, taking wells K1, K2, and K4 as examples to carry out the multi-well test. During the test process, the water level is observed by using other test observation wells 62. Pumps with a rated flow rate of 60.00 m 3 / h are put into K1, K2, and K4 and pumped simultaneously. The actual average flow rate of each well in the whole test is 60 m 3 / h. At the same time, the dynamic observation of the groundwater level of other observation wells is carried out. The duration is about 20 hours, and the water level has basically tended to be stable. The statistical table of the drawdown of each well water level is shown in Table 4, and the relationship curve between the drawdown of the multi-well water level and time is as Figure 10 shown, and the plan view of the water level change of each well during the pumping test of the K1, K2, and K4 multi-well is as Figure 11 shown.

[0153] Table 4 Statistical table of the drawdown of the water level of each observation well and the distance from the pumping well during the pumping test of the K1, K2, and K4 multi-well

[0154] Number Well depth (m) Distance to pumping well (m) Drawdown (m) K1 27 / 10.36 (dynamic drawdown) K2 33 / 9.26 (dynamic drawdown) K3 36 10.64 5.76 K4 40 / 8.01 (dynamic drawdown) G1 33 5.97 6.8 G2 33 13.52 6.06 G3 27 19.61 5.45 G4 18 29.35 4.67 G5 27 15.67 6.49 G6 27 25.6 5.74 G7 27 35.57 5.09

[0155] It can be seen from the analysis that during the pumping process of the K1, K2, and K4 multi-well, when the flow rate of the pumping well remains unchanged, the water level is basically stable one day after the start of pumping. The drawdown of the dynamic water level of the pumping well is small, resulting in a small drawdown of the water level of the observation well. One more test observation well 62 can be added to carry out the multi-well test, or the flow rate of the pump can be increased.

[0156] Compared with the single-well pumping test, the group-well pumping test can better reflect the site seepage characteristics and the dewatering effect of the foundation pit. Conducting pumping operations on multiple test pumping wells simultaneously can more realistically simulate the scenario of the combined action of multiple wells in actual foundation pit dewatering, and comprehensively reflect the dynamic response characteristics of the groundwater system under regional pumping conditions. Record the change process of the groundwater level in real time and dynamically to ensure that the collected data cover the hydrogeological characteristics within the entire test range, and form an integral curve of the water level drawdown versus time. The drawing of the water level drawdown curve clearly shows the overall impact of group-well pumping on the groundwater level, reflects the groundwater flow trend and the drawdown distribution law, and provides a basis for the reasonable layout of dewatering wells and the prediction of dewatering effects.

[0157] S2. Based on the hydrogeological parameters obtained in S1 and the results of the group-well pumping test, combined with the engineering geological and water level geological conditions, construct a three-dimensional unsteady flow numerical calculation model of groundwater. The initial hydrogeological parameters are determined according to the exploration report and the results of the group-well pumping test. Conduct an inversion analysis of the three-dimensional finite difference method for the group-well pumping test, and invert reasonable hydraulic parameters of the three-dimensional unsteady flow numerical calculation model of groundwater according to the water level fitting of the test observation wells in the group-well pumping test, and conduct three-dimensional numerical simulation and settlement calculation of the foundation pit dewatering construction.

[0158] Based on the hydrogeological parameters, combined with the engineering geological conditions, construct a three-dimensional unsteady flow numerical calculation model of groundwater, which can accurately simulate the dynamic behavior of groundwater flow during the foundation pit dewatering process. Use the three-dimensional finite difference method for inversion analysis to optimize the hydraulic parameters to ensure that the model can truly reflect the variation law of groundwater and provide a scientific basis for the layout of dewatering wells. Verify the model accuracy by fitting the water level data of the test observation wells through the model, and enhance the reliability of the dewatering design.

[0159] Furthermore, S2 includes the following steps:

[0160] Solving groundwater problems can be simplified to solving the problem of groundwater flow in porous media. The three-dimensional unsteady seepage law of groundwater can be described by using the groundwater flow continuity equation and its definite solution conditions. According to the hydrogeological conditions suitable for the site, the following three-dimensional unsteady seepage mathematical model of groundwater suitable for it can be established. Discretize the entire seepage area, and use the backward difference method to discretize the three-dimensional unsteady seepage mathematical model of groundwater to obtain a three-dimensional unsteady flow numerical calculation model of groundwater. Relevant hydrogeological parameters can be inversely obtained by using the three-dimensional unsteady flow finite difference method of groundwater according to the data of the test pumping wells and the test observation wells.

[0161] The partial differential control equation for solving the unsteady Darcy seepage field when the porous medium and the fluid are incompressible, that is, the groundwater flow continuity equation is:

[0162]

[0163] Wherein:

[0164]

[0165]

[0166] In the formula: S: storage coefficient; S y : specific yield; M: thickness of confined aquifer (m); B: saturated thickness of groundwater in unconfined aquifer (m); k xx 、k yy 、k zz : main direction permeability coefficients of anisotropy (m / d); H: head value (m) of point (x, y, z) at time t; W: source-sink term (1 / d);

[0167] The definite solution conditions are:

[0168] Initial condition: H(x, y, z, t)| t＝0 = H0(x, y, z, t0)

[0169] Boundary conditions:

[0170] In the formula: H0(x, y, z, t): initial water level (m) at point (x, y, z); Γ1: type I boundary condition; H1(x, y, z, t): known boundary water level (m) of point (x, y, z) at time t.

[0171] S22. According to the hydrogeological parameters obtained from S1, combined with the engineering geology and water level geology conditions, determine the aquifer structure characteristics, the parameters characteristics of the three-dimensional unsteady flow numerical calculation model of groundwater, the hydraulic characteristics of the three-dimensional unsteady flow numerical calculation model of groundwater, the simulation period and stress period of the three-dimensional unsteady flow numerical calculation model of groundwater, and the treatment method of the source-sink term of the three-dimensional unsteady flow numerical calculation model of groundwater.

[0172] Specifically, according to the existing geotechnical engineering investigation reports, hydrogeological conditions, and borehole data, the plane scope of the simulation area is determined according to the following principle: with the foundation pit as the center, the boundary is arranged outside the influence radius of the dewatering well.

[0173] In this embodiment, according to the information such as the engineering geology and hydrogeological characteristics of the study area, the hydrogeological conceptual model is divided into 304 rows and 356 columns in the horizontal direction. The grid three-dimensional division diagram is as Figure 12 shown, and the three-dimensional section diagram of the model stratum is as Figure 13 shown.

[0174] In this embodiment, the model parameter features are used to initially assign values to the model based on the parameters obtained from the previous single-well pumping test, and the actual model parameters are continuously adjusted and optimized according to numerical inversion.

[0175] Model hydraulic characteristics: The groundwater seepage system conforms to the law of conservation of mass and the law of conservation of energy; the aquifer is widely distributed and thick, and the groundwater movement conforms to Darcy's law under normal temperature and pressure; considering the flow exchange and seepage characteristics between the shallow and deep layers, the groundwater movement can be generalized into a three-dimensional flow in space; the vertical movement of the groundwater system is mainly the leakage between layers, and the three-dimensional solid structure model can well solve the leakage problem; the input and output of the groundwater system change with time and space, and the parameters change with space, reflecting the heterogeneity of the system, but there is no obvious directionality, so the parameters are generalized as horizontally isotropic.

[0176] In summary, the simulation area can be generalized into a three-dimensional unsteady groundwater seepage system with heterogeneous horizontal isotropy. The hydrogeological seepage system in the simulation area can form a three-dimensional unsteady groundwater seepage model through generalization and unit meshing.

[0177] Determination of the simulation period and stress period: The simulation period of the numerical simulation in this embodiment is 7 days, and the entire simulation period is divided into 10 calculation cycles. In each calculation cycle, the intensity of all external source-sink terms remains unchanged.

[0178] Treatment method of source-sink terms:

[0179] 1) Treatment of relief wells: In Visual Modflow, parameters such as the filter length and water discharge of relief wells can be set, which have a strong comparability with actual data. According to the existing observation results of pumping tests, the water discharge of the pumping well remains unchanged, and the test wells are set as shown in Figure 14 the figure. 2) Treatment of boundary conditions: In the simulation of foundation pit dewatering this time, the model boundary is outside the influence boundary of the dewatering well, so the model boundary can be defined as a constant head boundary with a constant water level, and the constant head boundary is determined according to the influence radius of the single-well test.

[0180] S23. According to the results of the group well pumping test, the measured data of the test pumping well 61 are sorted out. A pumping well is set in the three-dimensional unsteady groundwater flow numerical calculation model, and the water discharge of the actual test pumping well 61 is substituted into the three-dimensional unsteady groundwater flow numerical calculation model for numerical simulation calculation of the group well pumping test. By comparing the calculation results with the water level changes of the actual test observation well 62, the hydrogeological parameters are continuously adjusted and optimized until the theoretical water level depth in the test area is consistent with the water level drawdown change of the actual group well pumping test, and reasonable confined water analysis parameters are obtained.

[0181] By comparing and analyzing the measured drawdown curves of the observation wells at different horizons in the group well pumping test with the calculated drawdown curves obtained from numerical simulation, the water levels of each observation well are compared as Figure 15 shown.

[0182] It can be seen from the simulation analysis results of the group well pumping test that Figure 15 the laws of the numerically simulated head drawdown and the measured head drawdown of each observation well in

[0183] are basically the same. The numerical simulation results reflect the changes in the water levels of the observation wells during the precipitation process of the group well pumping test. It can be seen that the deviation between the two is very small, meeting the engineering accuracy requirements. Figure 16 As

[0184] known, the median of the error is about 0.122, and at the same time, the distribution of the standard residuals satisfies the standard normal distribution.

[0185] Table 5 Inversion parameter table for pumping test

[0186]

[0187] By recalculating the three-dimensional unsteady flow numerical calculation model of groundwater with the continuously adjusted and optimized parameters, the simulated results of the confined water head drawdown in the test site and its surrounding environment 7 days after the group well pumping stage are obtained. As Figure 17 shown, the theoretical water level burial depth in the test area after group well pumping is basically consistent with the change in the actual water level drawdown of the pumping test, indicating that the inverted parameters and the three-dimensional unsteady flow numerical calculation model of groundwater can represent the hydrogeological characteristics of this field area.

[0188] The three-dimensional unsteady flow description and high-precision discretization processing of the three-dimensional unsteady seepage mathematical model of groundwater can more comprehensively reflect the complex dynamic characteristics of the groundwater system. The comparison and optimization of the simulation results with the actual data of the group well pumping test ensure the accuracy and reliability of the model. Using the group well pumping test data to dynamically adjust the model parameters can quickly and efficiently invert hydrogeological parameters such as the permeability coefficient and storage coefficient, making it more in line with the actual situation. The optimized model can be used to predict the groundwater level drawdown and its dynamic change trend, support the design of the dewatering plan for Foundation Pit 100, accurately evaluate the recharge capacity and flow characteristics of the confined water, and reduce the risks in the implementation of the dewatering project.

[0189] S3. Dewatering design for Foundation Pit 100: According to the three-dimensional unsteady flow numerical calculation model of groundwater constructed in S1, dewatering wells are arranged. The first dewatering deep well 11 and the first standby deep well 12 are arranged on the first-level platform 101; the second dewatering deep well 21 and the second standby deep well 22 are arranged on the second-level platform 102; the third dewatering deep well 31 and the third standby deep well 32 are arranged on the third-level platform 103.

[0190] Precipitation deep wells and standby deep wells are arranged on different platforms respectively, fully considering the distribution characteristics of the groundwater level within the foundation pit area 100 and the elevation differences between platforms, ensuring the uniformity of precipitation. A standby deep well is set on each platform, enhancing the redundancy of the precipitation system. Even if the main precipitation deep well fails, the standby deep well can be immediately activated, thereby improving the stability and reliability of the precipitation system.

[0191] Specifically, as Figure 1 shown, 48 deep wells with a depth of 30m (including the first precipitation deep wells 11 numbered Q1 - Q45 and the first standby deep wells 12 numbered BQ1 - BQ3) are arranged on the first - level platform 101 with an elevation of +1.95m, and the designed water output is 100m 3 / h; 21 deep wells with a depth of 35m (including the second precipitation deep wells 21 numbered S1 - S20 and the second standby deep well 22 numbered BS1) are arranged on the second - level platform 102 with an elevation of - 3.55m, and the designed water output is 150m 3 / h; 14 deep wells with a depth of 30m (including the third precipitation deep wells 31 numbered Z1 - Z13 and the third standby deep well 32 numbered BZ1) are arranged on the third - level platform 103 with an elevation of - 9.05m, and the designed water output is 150m 3 / h.

[0192] Furthermore, 5 standby and water - level observation wells with a depth of 40m (the fourth standby deep wells 4 numbered BG1 - BG5 as shown Figure 1 in the figure) can also be arranged at the structural position. Furthermore, in addition to the above - mentioned newly added precipitation wells, the pumping test wells should be properly maintained and can also be used as precipitation wells for dewatering during the excavation of the foundation pit.

[0193] S4. Checking the designed precipitation wells: After the precipitation wells are arranged, a simulation calculation is carried out. Assume that the dewatering of the foundation pit 100 runs for at least 90 days. If the water - level drawdown meets the excavation requirements of the foundation pit 100 after 90 days of dewatering of the foundation pit 100, the arrangement of the precipitation wells is completed; otherwise, repeat S3 until the water - level drawdown meets the excavation requirements of the foundation pit 100 after 90 days of dewatering of the foundation pit 100.

[0194] By simulating the water - level changes during 90 - day operation after the precipitation wells are arranged, the arrangement effect of the precipitation wells is verified to ensure that the water - level drawdown meets the excavation requirements of the foundation pit 100. If the check fails, it can be readjusted by optimizing the arrangement plan, gradually improving the design of the precipitation wells, reducing the uncertainty in the actual operation of the precipitation system, and effectively reducing the construction risk. The simulation process fully considers the settlement calculation and the influence of the excavation of the foundation pit 100 on the water level, avoiding potential safety hazards caused by non - dropping water level or ineffective settlement control during excavation.

[0195] Specifically, the visual modflow software can be used to simulate precipitation. Assume that the foundation pit dewatering operation lasts for 90 days, and the water level drawdown after 90 days of foundation pit dewatering is as Figure 18 shown. It can be seen that under the operation of the existing number of dewatering wells, the requirements for foundation pit excavation can be met.

[0196] S5. Carry out the excavation design of foundation pit 100: The foundation pit 100 adopts the form of multi-level slope cutting for foundation pit excavation. As Figure 4 shown, four levels of slopes are designed from the top to the bottom of the foundation pit 100. The slope ratios of the first two levels from top to bottom are 1:2.5, and the slope ratios of the last two levels are 1:2. The elevation of the first-level platform 101 is 1.90 - 2.00m, and the elevation of the first-level platform 101 in this embodiment is 1.95m. The elevation of the second-level platform 102 is -3.50 - -3.6m, and the elevation of the second-level platform 102 in this embodiment is -3.55m. The elevation of the third-level platform 103 is -9.00 - -9.10m, and the elevation of the third-level platform 103 in this embodiment is -9.05m. The intermediate platform can be set to 6m.

[0197] In the excavation design of the foundation pit 100, four levels of slopes are designed according to the depth of the foundation pit 100, and a design scheme with the slope ratios of the first two levels being 1:2.5 and the last two levels being 1:2 is reasonably set, effectively reducing the sliding risk of the soil body during the slope excavation process. The form of multi-level slope cutting reduces the risk of slope instability and facilitates the coordinated operation of dewatering wells at different stages. Further, due to the easy occurrence of extreme rainstorm weather in the coastal area, for the slope protection during rainfall, a waterproof geotextile is used for protection, and sandbags are used to compact at the joint points of the geotextile to ensure that rainwater does not flow onto the slope to wash the slope. Further, as Figure 4 shown, to prevent the seepage of water at the slope toe of the foundation pit from causing the loss of sandy soil at the slope toe, an intermediate filter layer 107 can be set at the slope toe between the intermediate platform and the upper-level slope. The intermediate filter layer 107 can be set to a depth of 0.5m, a top width of 1.5m, and a bottom width of 0.5m, and is filled with poorly graded pebbles.

[0198] The foundation pit 100 dewatering layout method provided in this embodiment can efficiently reduce the water level in the foundation pit 100 by optimizing the dewatering well layout and multi-level platform distribution, avoid quicksand or gushing phenomena caused by too high groundwater level, enable the dewatering system to adapt to the complex hydrogeological conditions around the coastal foundation pit 100, and ensure the stability of the soil body in the excavation area.

[0199] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A foundation pit dewatering system, characterized in that: It comprises a primary platform (101), a secondary platform (102) and a tertiary platform (103) arranged around a foundation pit (100), wherein the elevations of the primary platform (101), the secondary platform (102) and the tertiary platform (103) decrease in sequence; A plurality of first deep dewatering wells (11) are arranged on the first-level platform (101), a plurality of second deep dewatering wells (21) are arranged on the second-level platform (102), and a plurality of third deep dewatering wells (31) are arranged on the third-level platform (103); A drainage ditch (104) and / or a water collection well (105) is dug at the bottom of the foundation pit (100); a drainage channel (106) is dug at the top of the foundation pit (100); The sewage in the first precipitation deep well (11), the second precipitation deep well (21), the third precipitation deep well (31), the drainage ditch (104) and / or the collection well (105) is discharged into the drainage channel (106) and discharged into the sea through the drainage channel (106).

2. A foundation pit dewatering system according to claim 1, characterized in that: A first backup deep well (12) is also provided on the seaward side of the first-level platform (101), a second backup deep well (22) is also provided on the seaward side of the second-level platform (102), and a third backup deep well (32) is also provided on the seaward side of the third-level platform (103).

3. A foundation pit dewatering system according to claim 2, characterized in that: The first dewatering deep well (11) and the first backup deep well (12) are both distributed on the first-level platform (101); the second dewatering deep well (21) and the second backup deep well (22) are both distributed on the second-level platform (102); and the third dewatering deep well (31) and the third backup deep well (32) are both distributed on the third-level platform (103).

4. A foundation pit dewatering system according to claim 1, characterized in that: At least five fourth backup deep wells (4) are also arranged at the bottom of the foundation pit (100).

5. The foundation pit dewatering system according to claim 1, characterized in that: The elevation difference between the first-level platform (101) and the second-level platform (102) does not exceed 5.5 m, and the elevation difference between the second-level platform (102) and the third-level platform (103) does not exceed 5.5 m.

6. A foundation pit dewatering system according to claim 2, characterized in that: The first precipitation deep well (11), the first standby deep well (12), the second precipitation deep well (21), the second standby deep well (22), the third precipitation deep well (31), and the third standby deep well (32) all comprise a filter tube (51) and a sedimentation tube (52); the sedimentation tube (52) is fixed to the bottom of the filter tube (51); and the filter tube (51) is a PVC tube with a porosity of ≥15%.

7. A method for arranging foundation pit dewatering, characterized in that: The method for arranging the foundation pit dewatering system according to any one of claims 1 to 6 comprises the following steps: S1. Conducting a pumping test: setting up a number of test pumping wells (61) and a number of test observation wells (62), wherein the test pumping wells (61) are arranged in a rectangular shape in a direction perpendicular to the coastline and in a direction horizontal to the coastline, and the test observation wells (62) are distributed equidistantly from the center point of the shape formed by the test pumping wells (61) in a direction perpendicular to the coastline and in a direction horizontal to the coastline; The depths of the test pumping well (61) and the test observation well (62) are 18 to 40 meters. The depths of the test pumping wells (61) are different. Pumping tests are carried out in the order of first a single well pumping test and then a group well pumping test to obtain hydrogeological parameters. S2. Based on the hydrogeological parameters obtained in S1, combined with engineering geological and water level geological conditions, a three-dimensional unsteady flow numerical calculation model of groundwater is constructed, and a three-dimensional finite difference method inversion analysis of the group well pumping test is performed. According to the water level fitting of the test observation well (62) in the group well pumping test, reasonable hydraulic parameters of the three-dimensional unsteady flow numerical calculation model of groundwater are inverted, and three-dimensional numerical simulation and settlement calculation of foundation pit dewatering construction are performed; S3. Dewatering design of foundation pit (100): Dewatering wells are arranged according to the three-dimensional unsteady flow numerical calculation model of groundwater constructed in S1. A first dewatering deep well (11) and a first backup deep well (12) are arranged on the first-level platform (101); a second dewatering deep well (21) and a second backup deep well (22) are arranged on the second-level platform (102); and a third dewatering deep well (31) and a third backup deep well (32) are arranged on the third-level platform (103); S4. Verify the dewatering wells designed in S3: After the dewatering wells are arranged, a simulation calculation is performed, assuming that the dewatering of the foundation pit (100) is operated for at least 90 days. If the water level drop after 90 days of dewatering of the foundation pit (100) meets the excavation requirements of the foundation pit (100), the dewatering well arrangement is completed. Otherwise, S3 is repeated until the water level drop after 90 days of dewatering of the foundation pit (100) meets the excavation requirements of the foundation pit (100); S5. Design the excavation of the foundation pit (100): The foundation pit (100) is excavated in the form of multi-level slope reduction. Four levels of side slopes are designed from the top of the foundation pit (100) to the bottom of the foundation pit (100). From top to bottom, the slope ratio of the first two levels is 1:2.5, and the slope ratio of the last two levels is 1:

2. The elevation of the first platform (101) is 1.90 to 2.00 m, the elevation of the second platform (102) is -3.50 to -3.6 m, and the elevation of the third platform (103) is -9.00 to -9.10 m.

8. A foundation pit dewatering arrangement method according to claim 7, characterized in that: The single well pumping test in S1 includes the following steps: S111. Data collection and processing: A water pump is put into a test pumping well (61) to pump water, and other test pumping wells (61) and test observation wells (62) are used for dynamic observation of groundwater levels, and a single well water level drop and time relationship curve is drawn; S112. Using AquiferTest software, the measured water level drop and time relationship curve of the same-layer test observation well (62) obtained in S111 is fitted with the standard curve to calculate the horizontal permeability coefficient K of the same-layer test observation well (62). h , hydraulic conductivity T, water storage coefficient S, influence radius R; S113. Perform a water level recovery test on the test pumping well (61), and track and observe the water level of the test observation well (62) during the water level recovery period until the water level stabilizes; S114. Repeat S111 to S113 until all test pumping wells (61) have completed the single well pumping test.

9. A foundation pit dewatering arrangement method according to claim 8, characterized in that: The group well pumping test in S1 includes the following steps: S121. Put water pumps into multiple test wells (61) and pump water simultaneously, use the test observation well (62) to observe the dynamic underground water level, and draw a curve of the relationship between the water level drop and time in the group of wells; S122. Perform a water level recovery test on the test pumping well (61), and during the water level recovery period, track and observe the water levels of all test observation wells (62) until the water levels stabilize.

10. A foundation pit dewatering arrangement method according to claim 9, characterized in that: S2 includes the following steps: S21. Use the groundwater flow continuity equation and its boundary conditions to describe the three-dimensional unsteady seepage law of groundwater, establish a mathematical model of three-dimensional unsteady seepage of groundwater, discretize the entire seepage zone, use the backward difference method to discretize the mathematical model of three-dimensional unsteady seepage of groundwater, and obtain a numerical calculation model of three-dimensional unsteady flow of groundwater; The continuity equation for groundwater flow is: Where: S: water storage coefficient; S y : water supply degree; M: thickness of confined aquifer; B: groundwater saturated thickness of the phreatic aquifer; k xx , k yy , k zz : Anisotropic permeability coefficient in the main direction; H: water head value at point (x, y, z) at time t; W: source and sink term (1 / d); The solution conditions are: Initial conditions: H(x, y, z, t)| t＝0 =H0(x, y, z, t0) Boundary conditions: H(x, y, z, t)| Γ1 =H1(x, y, z, t) Where: H0(x, y, z, t): initial water level at point (x, y, z); Γ1: a type of boundary condition; H1(x, y, z, t): the known water level at the boundary of point (x, y, z) at time t; S22. According to the hydrogeological parameters obtained in S1, combined with engineering geological and water level geological conditions, determine the aquifer structure characteristics of the groundwater three-dimensional unsteady flow numerical calculation model, the parameter characteristics of the groundwater three-dimensional unsteady flow numerical calculation model, the hydraulic characteristics of the groundwater three-dimensional unsteady flow numerical calculation model, the simulation period and stress period of the groundwater three-dimensional unsteady flow numerical calculation model, and the source and sink item processing method of the groundwater three-dimensional unsteady flow numerical calculation model; S23. According to the results of the group well pumping test, the measured data of the test pumping well (61) are sorted out, and the pumping well is set in the groundwater three-dimensional unsteady flow numerical calculation model. The water output of the actual test pumping well (61) is substituted into the groundwater three-dimensional unsteady flow numerical calculation model, and the numerical simulation calculation of the group well pumping test is carried out. The calculation results are compared with the measured water level changes of the test observation well (62), and the hydrogeological parameters are continuously adjusted and optimized until the theoretical water level burial depth of the test area is consistent with the actual water level drop change of the group well pumping test, so as to obtain reasonable pressurized water analysis parameters.

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