Deep foundation pit safe dewatering method suitable for water-rich sand layer

Abstract

The invention discloses the technical field of deep foundation pit dewatering construction methods, and particularly relates to a deep foundation pit safe dewatering method suitable for a water-rich sand layer. The method comprises the following specific steps that a foundation pit deformation monitoring instrument, an underground water flow monitoring instrument and an underground water level monitoring instrument are used for monitoring foundation pit pile top horizontal displacement, vertical displacement, ground surface settlement, underground water flow speed, underground water flow, gap water pressure foundation pit deformation and underground water flow in the deep foundation pit dewatering process; the underground water level data is wirelessly transmitted to the cloud deep foundation pit underground water comprehensive simulation and water discharge and return calculation system, and the cloud deep foundation pit underground water comprehensive simulation and water discharge and return calculation system processes the data, gives a calculation result and transmits the calculation result to the water discharge reduction terminal or the water return compensation terminal. The safe dewatering method for the deep foundation pit is good and accurate, the underground water condition can be monitored in real time, and water can be supplemented and drained in time.

Description

Technical Field

[0001] The present invention relates to the technical field of deep foundation pit dewatering construction methods, and specifically relates to a safe dewatering method for deep foundation pits applicable to water-rich sand layers. Background Technique

[0002] Foundation pit construction is an important engineering project in projects such as water conservancy projects, municipal engineering, and civil engineering. Especially for water conservancy projects and municipal engineering, their foundation pits are often deep foundation pits, with large volumes, deep excavations, and complex construction operations. Due to the engineering nature of water conservancy projects and municipal engineering, deep foundation pits are often located on water-rich sand layers with high groundwater levels and rich water content in the soil sand layer. This makes it easy for deep foundation pits in water-rich sand layers to experience large fluctuations in groundwater levels, uncertain groundwater flow directions and flow rates during the dewatering construction process, which in turn causes engineering safety risks and even accidents such as quicksand, piping, and bursting in deep foundation pits to occur frequently.

[0003] The existing general dewatering construction for deep foundation pits in water-rich sand layers is carried out by means of dewatering wells, groundwater monitoring, and compensation wells. This method is to arrange dewatering wells around the deep foundation pit for pumping operations according to the engineering design requirements. After the groundwater level drops below the design requirements, the foundation pit excavation operation is carried out. If the groundwater level drops too low or the water content in the soil sand layer is too small, compensation recharge is carried out through the compensation well. Groundwater monitoring is to monitor the groundwater level and the water content of the soil sand layer in the deep foundation pit using a groundwater monitoring device. However, this monitoring method can only monitor the groundwater level and the water content of the soil sand layer around the deep foundation pit, and it is an alarm type, which makes it have hysteresis in data and operation, resulting in too much or too little dewatering of the dewatering wells and even the operation of backwater compensation, making the groundwater level fluctuate too much and the groundwater flow direction and flow rate uncertain and uncontrollable, thus triggering engineering safety risks.

[0004] A Chinese patent with the patent number 202210785079.8 discloses an intelligent control method for the foundation pit dewatering system at a construction site. It involves inputting a sample comprehensive vector set into a fully connected neural network and training the network using the first loss function, the second loss function, the third loss function, the weights corresponding to the first loss function, and the weights corresponding to the second loss function to obtain a target network for the target foundation pit after training. Then, the reference comprehensive vector is input into the target network, and based on the output result of the target network, the parameters of each dewatering well pump and each recharge well pump during the construction of the target foundation pit are adjusted. By controlling the pumping rate of the dewatering well pumps and the irrigation rate of the recharge well pumps, this control method makes the pumped water volume and the irrigated water volume approach the same when the entire dewatering system operates stably, which can better ensure the stability of the groundwater level and thus reduce the risk of settlement of the surrounding buildings of the foundation pit. Although this patent involves an intelligent control method for foundation pit dewatering, in engineering practice, foundation pit dewatering will cause the flow of the groundwater layer and change the direction and magnitude of the seepage force, which may lead to foundation pit deformation or even collapse, posing a difficulty in the safety control of foundation pit dewatering, and this patent does not solve this technical problem.

[0005] Therefore, it is crucial to develop a safe dewatering method for deep foundation pits in water-rich sand layers that is good, accurate, can monitor the groundwater conditions in real time, and can supply and drain water in a timely manner to ensure the smooth progress of construction and engineering safety. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a safe dewatering method for deep foundation pits in water-rich sand layers that is good, accurate, can monitor the groundwater conditions in real time, and can supply and drain water in a timely manner.

[0007] To solve the above technical problem, the present invention is realized through the following technical solutions:

[0008] A safe dewatering method for deep foundation pits in water-rich sand layers, the specific steps are as follows: The foundation pit deformation monitoring instrument, the groundwater flow monitoring instrument, and the groundwater level monitoring instrument wirelessly transmit the horizontal displacement, vertical displacement, surface settlement, groundwater flow velocity, groundwater flow rate, pore water pressure, foundation pit deformation, groundwater flow, and groundwater level data during the dewatering process of the deep foundation pit to the cloud deep foundation pit groundwater comprehensive simulation and drainage / return water calculation system. The cloud deep foundation pit groundwater comprehensive simulation and drainage / return water calculation system processes the data and gives the calculation results, which are transmitted to the drainage reduction terminal or the return water compensation terminal. The simulation and calculation results of the cloud deep foundation pit groundwater comprehensive simulation and drainage / return water calculation system are transmitted to the human-computer interaction terminal through a wireless transmission method.

[0009] The above-mentioned cloud-based comprehensive simulation and drainage and return water calculation system for deep foundation pit groundwater includes a groundwater flow simulation module, a foundation pit deformation simulation module, an analysis and judgment module, and a drainage and return water replenishment terminal working module.

[0010] The input end of the above-mentioned groundwater flow simulation module is connected to the groundwater level monitoring instrument, the output end of the groundwater flow simulation module is connected to the input end of the foundation pit deformation simulation module, the foundation pit deformation monitoring instrument, the groundwater level monitoring instrument, and the output end of the foundation pit deformation simulation module are connected to the analysis and judgment module, the output end of the analysis and judgment module is connected to the drainage and return water replenishment terminal working module, and the output end of the drainage and return water replenishment terminal working module is connected to the drainage terminal or the return water compensation terminal.

[0011] The calculation logic process of the above-mentioned groundwater flow simulation module is as follows:

[0012] Divide the foundation pit dewatering operation range into 0.1x0.1m 3 as the calculation grid, and calculate the groundwater flow rate, water flow velocity, and pore water pressure of each grid based on the water flow data measured by the existing monitoring points, and then establish the topological grid data of the groundwater flow simulation.

[0013] The calculation formula is as follows:

[0014] (Groundwater flow velocity in the X-axis direction of each calculation grid)

[0015] (Groundwater flow velocity in the Y-axis direction of each calculation grid)

[0016] (Groundwater flow velocity in the Z-axis direction of each calculation grid)

[0017] (Pore water pressure of each calculation grid)

[0018] (Calculation formula for water flow rate of each calculation grid)

[0019] In the formula, V nx is the groundwater flow velocity in the X-axis direction of each calculation grid (m / d), V ny is the groundwater flow velocity in the Y-axis direction of each calculation grid (m / d), V nz is the groundwater flow velocity in the Z-axis direction of each calculation grid (m / d), L x is the x-axis distance of each calculation grid from the monitoring point (m), L y is the y-axis distance of each calculation grid from the monitoring point (m), L z is the z-axis distance of each calculation grid from the monitoring point (m), L n is the distance of each calculation grid from the monitoring point (m), Q nFor the water flow rate (m 3 / d) of each computational grid, μ i is the pore water pressure (kPa) at the monitoring point, V ix is the groundwater flow velocity (m / d) in the X-axis direction at the monitoring point, V iy is the groundwater flow velocity (m / d) in the Y-axis direction at the monitoring point, V iz is the groundwater flow velocity (m / d) in the Z-axis direction at the monitoring point, Q i is the water flow rate (m3 / d) at the monitoring point, μ n is the pore water pressure (kPa) of each computational grid, △c is the influence factor of adjacent computational grids, ρ is the water density (10 3 kg / m 3 ), d: soil density (1.97*10 3 kg / m 3 ), and k is the permeability coefficient of soil moisture in each grid layer.

[0020] The calculation logic flow of the above foundation pit deformation simulation module is as follows:

[0021] Transfer the water flow simulation topological grid data to the foundation pit deformation simulation module, calculate the foundation pit deformation situation, and obtain the calculation results of the foundation pit deformation simulation;

[0022] The calculation formula of the foundation pit deformation simulation module is as follows:

[0023]

[0024] In the formula, w xy is the simulated value of the horizontal displacement of the pile top (mm), w Z is the simulated value of the vertical displacement of the pile top (mm), w zz is the simulated value of the ground surface settlement (mm), V nx is the groundwater flow velocity (m / d) in the X-axis direction of each computational grid, V ny is the groundwater flow velocity (m / d) in the Y-axis direction of each computational grid, V nz is the groundwater flow velocity (m / d) in the Z-axis direction of each computational grid, μ n is the pore water pressure (kPa) of each computational grid, Q n is the groundwater flow rate (m 3 / d) of each computational grid, H n is the height (m) of this calculation point, H zz is the height (m) from this calculation point to the ground surface, L n is the distance (m) from this calculation point to the pile top of the foundation pit, γ is the soil unit weight, measured according to the geological exploration (kN / m 3 ), and g is the unit weight of water (9.8 kN / m 3 ).

[0025] The calculation logic process of the above analysis and determination module is as follows:

[0026] Compare the simulation results obtained by the foundation pit deformation simulation module with the actual monitored foundation pit deformation data results, and compare the monitored water level with the designed water level value. Determine the foundation pit pumping to reduce drainage or return water compensation according to the formula;

[0027]

[0028] And Hs_monitored - Hs_design ≥ 0

[0029] When this formula is satisfied, reduce the pumping of the drainage terminal pump to lower the water level;

[0030]

[0031] And Hs_monitored - Hs_design ≤ 0

[0032] When this formula is satisfied, the return water compensation terminal pump conducts return water compensation;

[0033]

[0034] When this formula is satisfied, stop the foundation pit lowering and return water operation, and conduct a foundation pit inspection;

[0035] In the above formula, w xy is the simulated value of the horizontal displacement of the pile top (mm), w Z is the simulated value of the vertical displacement of the pile top (mm), w zz is the simulated value of the ground surface settlement (mm), w xy设 is the designed value of the horizontal displacement of the pile top (mm), w Z设 is the designed value of the vertical displacement of the pile top (mm), w zz设 is the designed value of the ground surface settlement (mm), w xy监 is the monitored value of the horizontal displacement of the pile top (mm), w Z监 is the monitored value of the vertical displacement of the pile top (mm), w zz监 is the monitored value of the ground surface settlement (mm), Hs 监 is the monitored value of the underground water level (mm), Hs 设 is the designed value of the underground water level (mm).

[0036] The calculation logic process of the above drainage and return water supplement terminal working module is as follows:

[0037] When receiving the data processing result of the analysis and determination module, conduct the work operation, output a control signal to the drainage terminal or the return water compensation terminal, and the drainage terminal or the return water compensation terminal is a pump;

[0038] The workload of the pump pumping / returning water operation is calculated according to the following formula:

[0039] S = P * η * T / 2.73H

[0040] In the above formula, S is the water pumping / return volume of the water pump (m3 / h), P is the shaft power of the water pump (KW), η is the efficiency of the water pump (0.5 - 0.9), T is the working time of the water pump (h), and H is the pumping / return water head (m).

[0041] The above human-computer interaction terminal is a computer, a tablet computer, or a mobile phone.

[0042] The above drainage reduction terminal or return water compensation terminal is a water pump equipped with a GIS locator, a pumping rate sensor, an embedded data processing module, a wireless communication module, and a solar power generation component.

[0043] The above foundation pit deformation monitoring instruments include a theodolite, a total station, and a level; the underground water flow monitoring instruments include a flow velocity sensor, a flow rate sensor, and a pressure sensor; the underground water level monitoring instruments include a PVC pipe and an electric water level gauge.

[0044] Due to the adoption of the above technical solution, the present invention has the following effects:

[0045] The present invention solves the technical problem that the dewatering of the foundation pit will cause the flow of the groundwater layer and the change of the direction and magnitude of the seepage force, which is likely to cause the deformation and even collapse of the foundation pit. It is a good, accurate, and real-time groundwater monitoring method that can timely replenish and drain water, and is applicable to the safe dewatering of deep foundation pits in water-rich sand layers. Brief Description of the Drawings

[0046] Figure 1 It is a flowchart block diagram of the present invention.

[0047] Figure 2 It is a structural block diagram of the drainage reduction terminal and the return water compensation terminal of the present invention.

[0048] Figure 3 It is a schematic diagram of the three-dimensional structure of the foundation pit of the present invention. Detailed Embodiments

[0049] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The protection scope of the present invention is not limited by the embodiments.

[0050] Such as Figure 1As shown in the figure, a safe dewatering method for deep foundation pits applicable to water-rich sand layers according to the present invention comprises the following specific steps: Instruments for monitoring foundation pit deformation, underground water flow, and underground water level transmit data such as the horizontal displacement, vertical displacement, ground settlement, underground water flow velocity, underground water flow rate, and pore water pressure of the foundation pit during the dewatering process of the deep foundation pit to the cloud-based comprehensive simulation and drainage and return water calculation system for deep foundation pit groundwater through wireless transmission. The cloud-based comprehensive simulation and drainage and return water calculation system for deep foundation pit groundwater processes the data and gives calculation results, which are transmitted to the drainage reduction terminal or the return water compensation terminal. The simulation and calculation results of the cloud-based comprehensive simulation and drainage and return water calculation system for deep foundation pit groundwater are transmitted to the human-computer interaction terminal through a wireless transmission method. The cloud-based comprehensive simulation and drainage and return water calculation system for deep foundation pit groundwater includes an underground water flow simulation module, a foundation pit deformation simulation module, an analysis and judgment module, and a working module for the drainage and return water compensation terminal. The input end of the underground water flow simulation module is connected to the underground water level monitoring instrument, the output end of the underground water flow simulation module is connected to the input end of the foundation pit deformation simulation module, the output ends of the foundation pit deformation monitoring instrument, the underground water level monitoring instrument, and the foundation pit deformation simulation module are connected to the analysis and judgment module, the output end of the analysis and judgment module is connected to the working module for the drainage and return water compensation terminal, and the output end of the working module for the drainage and return water compensation terminal is connected to the drainage reduction terminal or the return water compensation terminal. The human-computer interaction terminal is a computer, a tablet computer, or a mobile phone. As Figure 2 shown, the drainage reduction terminal or the return water compensation terminal is a water pump provided with a GIS locator, a pumping rate sensor, an embedded data processing module, a wireless communication module, and a solar power generation component. The foundation pit deformation monitoring instruments include a theodolite, a total station, and a level; the underground water flow monitoring instruments include a flow velocity sensor, a flow rate sensor, and a pressure sensor; the underground water level monitoring instruments include a PVC pipe and an electric water level gauge.

[0051] For the specific types, layouts, and detection data of the above-mentioned foundation pit deformation monitoring instruments, underground water flow monitoring instruments, and underground water level monitoring instruments, see Figure 3 and Table 1.

[0052] Table 1: Data Sheet for Types of Foundation Pit Monitoring Data, Instruments, and Layout of Control Points

[0053]

[0054] The calculation logic flow of the underground water flow simulation module is as follows:

[0055] Divide the dewatering operation range of the foundation pit into 0.1x0.1m 3 as the calculation grid. Based on the water flow data measured by the existing monitoring points, calculate the groundwater flow rate, water flow velocity, and pore water pressure of each grid, and then establish the topological grid data for underground water flow simulation.

[0056] The calculation formula is as follows:

[0057] (Groundwater flow velocity in the X-axis direction of each computational grid)

[0058] (Groundwater flow velocity in the Y-axis direction of each computational grid)

[0059] (Groundwater flow velocity in the Z-axis direction of each computational grid)

[0060] (Pore water pressure of each computational grid)

[0061] (Calculation formula for water flow of each computational grid)

[0062] In the formula, V nx is the groundwater flow velocity in the X-axis direction of each computational grid (m / d), V ny is the groundwater flow velocity in the Y-axis direction of each computational grid (m / d), V nz is the groundwater flow velocity in the Z-axis direction of each computational grid (m / d), L x is the x-axis distance of each computational grid from the monitoring point (m), L y is the y-axis distance of each computational grid from the monitoring point (m), L z is the z-axis distance of each computational grid from the monitoring point (m), L n is the distance of each computational grid from the monitoring point (m), Q n is the water flow of each computational grid (m 3 / d), μ i is the pore water pressure of the monitoring point (kPa), V ix is the groundwater flow velocity in the X-axis direction of the monitoring point (m / d), V iy is the groundwater flow velocity in the Y-axis direction of the monitoring point (m / d), V iz is the groundwater flow velocity in the Z-axis direction of the monitoring point (m / d), Q i is the water flow of the monitoring point (m3 / d), μ n is the pore water pressure of each computational grid (kPa), △c is the influence factor between adjacent computational grids, ρ is the water density (10 3 kg / m 3 ), d: soil density (1.97*10 3 kg / m 3 ), k is the permeability coefficient of soil moisture in each grid layer.

[0063] The calculation logic process of the foundation pit deformation simulation module is as follows:

[0064] Transfer the water flow simulation topological grid data to the foundation pit deformation simulation module, calculate the foundation pit deformation situation, and obtain the calculation result of the foundation pit deformation simulation;

[0065] The calculation formula of the foundation pit deformation simulation module is as follows:

[0066]

[0067] In the formula, w xy is the simulated value of the horizontal displacement of the pile top (mm), w Z is the simulated value of the vertical displacement of the pile top (mm), w zz is the simulated value of the ground surface settlement (mm), V nx is the groundwater flow velocity in the X-axis direction of each calculation grid (m / d), V ny is the groundwater flow velocity in the Y-axis direction of each calculation grid (m / d), V nz is the groundwater flow velocity in the Z-axis direction of each calculation grid (m / d), μ n is the pore water pressure of each calculation grid (kPa), Q n is the groundwater flow rate of each calculation grid (m 3 / d), H n is the height of this calculation point (m), H zz is the height from this calculation point to the ground surface (m), L n is the distance from this calculation point to the pile top of the foundation pit, γ is the soil unit weight, measured according to the geological exploration (kN / m 3 ), g is the unit weight of water (9.8 kN / m 3 ).

[0068] The calculation logic flow of the analysis and judgment module is as follows:

[0069] Compare the simulation results obtained by the foundation pit deformation simulation module with the actual monitoring results of the foundation pit deformation, and compare the monitored water level with the designed water level value, and determine the pumping drainage or backwater compensation of the foundation pit according to the formula;

[0070]

[0071] And when Hs_monitored - Hs_design ≥ 0

[0072] When this formula is satisfied, the water pump at the drainage terminal pumps water for dewatering;

[0073]

[0074] And when Hs_monitored - Hs_design ≤ 0

[0075] When this formula is satisfied, the water pump at the backwater compensation terminal conducts backwater compensation;

[0076]

[0077] When this formula is satisfied, the foundation pit dewatering and backwater operation stops, and the foundation pit is inspected;

[0078] In the above formula, w xy is the simulated value of the horizontal displacement of the pile top (mm), w Z is the simulated value of the vertical displacement of the pile top (mm), w zz is the simulated value of the ground settlement (mm), w xy设 is the designed value of the horizontal displacement of the pile top (mm), w Z设 is the designed value of the vertical displacement of the pile top (mm), w zz设 is the designed value of the ground settlement (mm), w xy监 is the monitored value of the horizontal displacement of the pile top (mm), w Z监 is the monitored value of the vertical displacement of the pile top (mm), w zz监 is the monitored value of the ground settlement (mm), Hs 监 is the monitored value of the groundwater level (mm), Hs 设 is the designed value of the groundwater level (mm).

[0079] The calculation logic flow of the drainage and return water replenishment terminal working module is as follows:

[0080] After receiving the data processing result of the analysis and judgment module, it starts to operate, outputs a control signal to the drainage terminal or the return water compensation terminal, and the drainage terminal or the return water compensation terminal is a water pump;

[0081] The workload of the water pump for pumping / returning water is calculated according to the following formula:

[0082] S = P * η * T / 2.73H

[0083] In the above formula, S is the water pumping / returning volume of the water pump (m3 / h), P is the shaft power of the water pump (KW), η is the water pump efficiency (0.5 - 0.9), T is the working time of the water pump (h), and H is the pumping / returning head (m).

Claims

1. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers, characterized in that The specific steps are as follows: the foundation pit deformation monitoring instrument, the groundwater flow monitoring instrument, and the groundwater level monitoring instrument transmit the foundation pit pile top horizontal displacement, vertical displacement, surface settlement, groundwater flow velocity, groundwater flow rate, pore water pressure foundation pit deformation, groundwater flow, and groundwater level data during the deep foundation pit dewatering process wirelessly to the cloud-based deep foundation pit groundwater comprehensive simulation and drainage and backwater calculation system, which processes the data and gives the calculation results, which are transmitted to the drainage lowering terminal or the backwater compensation terminal. The simulation and calculation results of the cloud-based deep foundation pit groundwater comprehensive simulation and drainage and backwater calculation system are transmitted to the human-computer interaction terminal via wireless transmission.

2. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 1, characterized in that The cloud-based deep foundation pit groundwater comprehensive simulation and drainage and backwater calculation system includes a groundwater flow simulation module, a foundation pit deformation simulation module, an analysis and judgment module, and a drainage and backwater replenishment terminal working module.

3. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 2, characterized in that The input end of the groundwater flow simulation module is connected to the groundwater level monitoring instrument, the output end of the groundwater flow simulation module is connected to the input end of the foundation pit deformation simulation module, the output ends of the foundation pit deformation monitoring instrument, the groundwater level monitoring instrument and the foundation pit deformation simulation module are connected to the analysis and judgment module, the output end of the analysis and judgment module is connected to the drainage and backwater replenishment terminal working module, and the output end of the drainage and backwater replenishment terminal working module is connected to the drainage lowering terminal or the backwater compensation terminal.

4. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 3, characterized in that The calculation logic flow of the groundwater flow simulation module is as follows: Divide the scope of foundation pit dewatering operation into 0.1x0.1m 3 To calculate the grid, the water flow data measured at the existing monitoring points are used to calculate the groundwater flow, water flow velocity, and pore water pressure of each grid, and then the topological grid data for groundwater flow simulation is established; The calculation formula is as follows: (Groundwater flow velocity in the X-axis direction of each calculation grid) (Groundwater flow velocity in the Y-axis direction of each calculation grid) (Groundwater flow velocity in the Z-axis direction of each calculation grid) (Pore water pressure of each calculation grid) (Calculation formula for water flow in each calculation grid) In the formula, V nx is the groundwater velocity in the X-axis direction of each calculation grid (m / d), V ny is the groundwater velocity in the Y-axis direction of each calculation grid (m / d), V nz is the groundwater velocity in the Z-axis direction of each calculation grid (m / d), L x is the x-axis distance (m) of each calculation grid from the monitoring point, L y is the y-axis distance (m) of each calculation grid from the monitoring point, L z is the z-axis distance (m) of each calculation grid from the monitoring point, L n is the distance (m) between each computing grid and the monitoring point, Q n The water flow rate of each calculation grid (m 3 / d)、μ i is the pore water pressure at the monitoring point (kPa), V ix is the groundwater velocity in the X-axis direction of the monitoring point (m / d), V iy is the groundwater velocity in the Y-axis direction of the monitoring point (m / d), V iz is the groundwater velocity in the Z-axis direction of the monitoring point (m / d), Q i is the water flow rate at the monitoring point (m3 / d), μ n is the pore water pressure of each computational grid (kPa), c is the influence factor of the adjacent computational grid, ρ is the water density (10 3 kg / m 3 ), d: soil density (1.97*10 3 kg / m 3 ) and k is the water permeability coefficient of each grid soil layer.

5. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 3, characterized in that The calculation logic flow of the foundation pit deformation simulation module is as follows: The water flow simulation topological grid data is transferred to the foundation pit deformation simulation module to calculate the foundation pit deformation and obtain the foundation pit deformation simulation calculation results; The calculation formula of the foundation pit deformation simulation module is as follows: ； ； ； w in the formula xy is the simulated value of pile top horizontal displacement (mm), w Z is the simulated value of the vertical displacement of the pile top (mm), w zz is the simulated value of surface settlement (mm), V nx is the groundwater velocity in the X-axis direction of each calculation grid (m / d), V ny is the groundwater velocity in the Y-axis direction of each calculation grid (m / d), V nz is the groundwater velocity in the Z-axis direction of each calculation grid (m / d), μ n is the pore water pressure (kPa), Q n is the groundwater flow rate of each calculation grid (m 3 / d)、H n is the height of the calculation point (m), H zz is the height from the calculation point to the ground surface (m), L n is the distance from the calculation point to the top of the foundation pit pile (m), γ is the soil density, obtained by ground survey (kN / m 3 ), g is the specific gravity of water (9.8kN / m 3 ).

6. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 3, characterized in that The calculation logic flow of the analysis and determination module is as follows: Compare the simulation results obtained by the foundation pit deformation simulation module with the actual monitoring foundation pit deformation data, and compare the monitored water level with the design water level value, and determine the foundation pit pumping to reduce drainage or backwater compensation according to the formula; And Hs 监 -Hs 设 ≥0, when this formula is satisfied, reduce the water pumping precipitation of the drainage terminal water pump; And Hs 监 -Hs 设 ≤0, when this formula is satisfied, the return water compensation terminal water pump return water compensation; When this formula is satisfied, the foundation pit backwater operation is stopped and the foundation pit inspection is carried out; In the above formula w xy is the simulated value of pile top horizontal displacement (mm), w Z is the simulated value of the vertical displacement of the pile top (mm), w zz is the simulated value of surface settlement (mm), w xy设 is the design value of pile top horizontal displacement (mm), w Z设 is the design value of the vertical displacement of the pile top (mm), w zz设 is the design value of ground settlement (mm), w xy监 is the monitoring value of pile top horizontal displacement (mm), w Z监 is the monitoring value of the vertical displacement of the pile top (mm), w zz监 is the surface settlement monitoring value (mm), Hs 监 is the groundwater level monitoring value (mm), Hs 设 is the design value of groundwater level (mm).

7. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 3, characterized in that The calculation logic flow of the drainage lowering and water return compensation terminal working module is as follows: after receiving the data processing result of the analysis and judgment module, it performs working operation and outputs a control signal to the drainage lowering terminal or the water return compensation terminal, and the drainage lowering terminal or the water return compensation terminal is a water pump; The workload of water pumping / returning operation is calculated according to the following formula: S=P*η*T / 2.73H In the above formula, S is the pumping / returning volume of the pump (m3 / h), P is the pump shaft power (KW), η is the pump efficiency (0.5-0.9), T is the pump working time (h), and H is the pumping / returning head (m).

8. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 1, characterized in that The human-computer interaction terminal is a computer, a tablet computer, or a mobile phone.

9. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 1, 2, 3 or 6, characterized in that The drainage lowering terminal or the backwater compensation terminal is a water pump equipped with a GIS locator, a pumping rate sensor, an embedded data processing module, a wireless communication module, and a solar power generation component.

10. A method for safe dewatering of deep foundation pits suitable for water-rich sand layers according to claim 1, characterized in that The foundation pit deformation monitoring instrument includes a theodolite, a total station, and a level; the groundwater flow monitoring instrument includes a flow velocity sensor, a flow sensor, and a pressure sensor; Groundwater level monitoring instruments include PVC pipes and electric water level gauges.

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