Ground settlement monitoring system under the condition of extremely large water level drawdown

Abstract

The invention discloses a ground settlement monitoring system under conditions of extremely large water level drop, and relates to the technical field of foundation pit dewatering. A seepage field change analysis module equipped with the system can analyze the movement process of groundwater in the foundation pit wall soil according to the real-time monitored water state data, combined with the saturation state and permeability of the soil. Through this module, the system can automatically divide the soil in the foundation pit wall into layers, obtain the spatiotemporal distribution of the water head of each soil layer during the dewatering process, and make subsequent stress analysis and settlement evaluation more accurate. Based on the spatiotemporal distribution of the water head of each soil layer, the effective stress change of the soil during the dewatering process can be accurately calculated, and the influence of the settlement of the upper soil layer on the additional stress of the lower soil layer can be analyzed, so as to obtain the settlement of each layer of soil. This stress and settlement monitoring based on layered analysis enables the system to conduct detailed evaluation of uneven settlement and interlayer stress changes, and effectively prevent the risk of structural instability caused by settlement differences.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit dewatering, and particularly to a ground settlement monitoring system under the condition of ultra-large water level drawdown. Background Art

[0002] In the fields of civil engineering and geological engineering, foundation pit engineering and ground treatment are important topics for controlling the groundwater level, managing soil stability, and preventing settlement instability. In this field, foundation pit construction under the condition of ultra-large water level drawdown faces special technical challenges. Under such conditions, a significant reduction in the groundwater level may lead to changes in soil moisture content and redistribution of hydraulic conditions, thereby affecting the settlement characteristics around the foundation pit. Especially for ground settlement monitoring under the environment of ultra-large water level drawdown, it is necessary to accurately analyze the seepage field and stress field to understand how the dynamic changes of water in the soil affect the soil stability. At the same time, the settlement between soil layers will produce an interlayer transfer effect of additional stress, making the settlement deformation of the foundation pit structure more complex. In this case, the monitoring system not only needs to track the movement of groundwater flow, but also analyze the influence of the seepage field on the internal stress field of the soil, so as to comprehensively evaluate the settlement and instability risks that may be caused during the dewatering process.

[0003] When conducting ground settlement monitoring under the condition of ultra-large water level drawdown, the current monitoring methods have many deficiencies. First, the existing monitoring systems usually only focus on the changes in water level or settlement amount and other parameters for separate monitoring, and insufficiently analyze the differences in seepage characteristics and saturation states between different soil layers, failing to fully reveal the influence of the seepage field on the soil stress distribution. Second, due to the large differences in the settlement characteristics of each soil layer, it is easy to ignore the stress transfer and additional stress effects between different soil layers, which is likely to exacerbate the settlement differences, making it difficult to accurately predict the settlement behavior of multi-layer soils during dewatering. Once these abnormal phenomena occur, the stability of the foundation pit is difficult to guarantee, which will directly affect the project safety and even lead to serious accidents such as collapses. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a ground settlement monitoring system under the condition of ultra-large water level drawdown, which solves the problems in the above background art.

[0005] To achieve the above objectives, the present invention is realized through the following technical solutions: A ground settlement monitoring system under the condition of ultra-large water level drawdown, including a foundation pit monitoring module, a seepage field change analysis module, a stress change analysis module, a comprehensive evaluation module, and a safety feedback module;

[0006] The foundation pit monitoring module is used to monitor the spatial distribution characteristics of the flow of groundwater in the soil during the foundation pit dewatering construction process to obtain relevant water body state data information;

[0007] The seepage field change analysis module is used to preliminarily judge the saturation state of the soil mass, and analyze the permeability performance of the soil mass and the movement process of water in the soil mass according to the saturation state and relevant water state data information. According to the permeability performance of the soil mass around the foundation pit, the soil mass inside the foundation pit wall is hierarchically divided to obtain the temporal and spatial distribution of the water head at the corresponding soil layer during the dewatering process. ;

[0008] The stress change analysis module will be based on the temporal and spatial distribution of the water head at the corresponding soil layer during the dewatering process , obtain the effective stress Yxy at the corresponding time period, and analyze the influence degree of the settlement of the upper soil layer on the additional stress of the lower soil layer according to the changes of each soil layer before and after dewatering, so as to obtain the settlement amount Cjz of the corresponding layer;

[0009] The comprehensive evaluation module is used to construct a foundation pit structure prediction model by using convolutional neural network technology, and input relevant water state data information into the foundation pit structure prediction model. After training and linear normalization processing, the foundation pit structure instability index Jszs is fitted and output;

[0010] The safety feedback module is used to preset an evaluation threshold, and compare and analyze it with the foundation pit structure instability index Jszs to estimate the stability status in the current foundation pit, and present it in a visual form to the operation background to adjust the dewatering process.

[0011] Preferably, the foundation pit monitoring module includes a pre-dewatering monitoring unit and a post-dewatering monitoring unit;

[0012] The pre-dewatering monitoring unit is used to preliminarily monitor the spatial distribution characteristics of the groundwater flow in the soil mass before the foundation pit dewatering construction, so as to obtain a pre-data group, and the pre-data group includes the initial water head at different positions in the foundation pit and water flux ;

[0013] The post-dewatering monitoring unit is used to monitor the spatial distribution characteristics of the groundwater flow in the soil mass again after the foundation pit dewatering construction, so as to obtain a post-data group, and the post-data group includes the water content at the corresponding position in the foundation pit , the saturated water content at the corresponding position , the residual water content at the corresponding position , the specific weight of water , porosity , the viscosity of water , the diameter of 10% of the particles in the soil mass , water density , the density of the soil layer , the depth of the soil layer , the externally applied load , compression modulus and lateral displacement ;

[0014] The relevant water body state data information includes the previous data group and the subsequent data group.

[0015] Preferably, the seepage field change analysis module includes a state judgment unit, a permeability performance analysis unit, a soil body monitoring unit, and a seepage distribution unit;

[0016] The state judgment unit is used to calculate the saturation degree of water in the soil at different positions around the foundation pit according to the subsequent data group, so as to obtain the effective saturation degree Ubd at the corresponding position. The effective saturation degree Ubd is obtained in the following way:

[0017] ;

[0018] In the formula, represents the water content at the corresponding position; represents the residual water content at the corresponding position, reflecting the water content when the water in the soil can no longer flow; represents the saturated water content at the corresponding position;

[0019] When the effective saturation degree Ubd = 1, it means that the soil at the current position reaches the fully saturated state;

[0020] When 0 ≤ effective saturation degree Ubd < 1, it means that the soil at the current position does not reach the fully saturated state.

[0021] Preferably, the permeability performance analysis unit is used to analyze the permeability performance of the soil at different positions around the foundation pit according to the judgment in the state judgment unit and in combination with the relevant water body state data information, so as to obtain the permeability coefficient Stxs. Specifically, it is obtained in the following way:

[0022] ;

[0023] In the formula, when the soil at the corresponding position reaches the fully saturated state, this formula holds; among them, represents the saturated permeability coefficient, Ubd represents the effective saturation degree, and are both constants;

[0024] Among them, the saturated permeability coefficient is obtained in the following way:

[0025] ;

[0026] In the formula, represents the unit weight of water, represents the porosity, Expressed as the viscosity of water, Expressed as the diameter of 10% of the particles in the soil mass, used to characterize the influence of particle size;

[0027] The soil monitoring unit is used to draw a seepage distribution map based on the Stxs values of the permeability coefficients at different positions around the foundation pit when the soil at the corresponding position reaches the fully saturated state, presenting the seepage changes at each depth in the foundation pit, so as to divide the soil in the foundation pit into different layers of soil; when the soil at the corresponding position does not reach the fully saturated state, according to the saturated permeability coefficient at different positions around the foundation pit values, draw a seepage distribution map, presenting the seepage changes at each depth in the foundation pit, so as to divide the soil in the foundation pit into different layers of soil.

[0028] Preferably, the seepage distribution unit is used to analyze the movement process of water in the soil according to the permeability coefficient Stxs and the saturated permeability coefficient obtained by the permeability performance analysis unit and combine relevant water body state data information to obtain the spatio-temporal distribution of the water head at the corresponding soil layer during the precipitation process The spatio-temporal distribution of the water head is obtained through the following formula:

[0029] ;

[0030] In the formula, is expressed as the water capacity function; is the initial water head; is expressed as the monitoring time period, is the partial derivative of the initial water head with respect to time t; is the gradient operator; is expressed as the permeability coefficient under the corresponding saturated state; is the source-sink term; is expressed as the divergence of the seepage flow; is expressed as the water flux.

[0031] Preferably, the stress change analysis module includes a pressure analysis unit, an interlayer stress transfer unit, and a settlement analysis unit;

[0032] The pressure analysis unit is used to analyze and obtain the effective stress Yxy during the corresponding time period in the foundation pit during the precipitation process according to the spatio-temporal distribution of the water head at the corresponding soil layer during the precipitation process Specifically, it is obtained in the following way:

[0033] ;

[0034] In the formula, represents the total stress, represents the pore water pressure;

[0035] Among them, the pore water pressure Ksy is obtained through the following formula:

[0036] ;

[0037] In the formula, represents the water density, represents the acceleration due to gravity;

[0038] Among them, the total stress is obtained through the following formula:

[0039] ;

[0040] In the formula, represents the density of the corresponding soil layer, represents the depth of the corresponding soil layer, represents the externally applied load.

[0041] Preferably, the interlayer stress transfer unit is used to analyze the influence degree of the settlement of the upper soil layer on the additional stress of the lower soil layer according to the changes of each soil layer before and after dehydration, so as to obtain the settlement amount Cjz of the corresponding layer, and specifically obtain it in the following way:

[0042] ;

[0043] In the formula, represents the increase in effective stress of the j-th layer, is the interlayer stress transfer coefficient between adjacent layers; represents the increase in effective stress of the i-th layer, represents the depth of the j-th layer, represents the compression modulus of the j-th layer, and both i and j are soil layer numbers.

[0044] Preferably, the settlement analysis unit is used to obtain the settlement difference and the cumulative settlement amount Zcjz between adjacent soil layers according to the settlement amount Cjz of the corresponding layer obtained in the interlayer stress transfer unit and combined with the statistical algorithm.

[0045] Preferably, the comprehensive evaluation module is used to map the corresponding data values to the interval after linear normalization using the trained foundation pit structure prediction model, so as to fit and output the foundation pit structure instability index Jszs when the precipitation drops to the corresponding soil layer:

[0046] ;

[0047] In the formula, represents the lateral displacement, Expressed as the cumulative settlement Expressed as the settlement difference between adjacent soil layers 、 and are all weight values Expressed as a correction constant, where 、 and The specific values are set by the user according to the situation.

[0048] Preferably, the safety feedback module is used to compare and analyze the foundation pit structure instability index Jszs with the evaluation threshold to judge the stability status in the foundation pit during the current dewatering process. The specific judgment content is as follows:

[0049] If the foundation pit structure instability index Jszs exceeds the evaluation threshold, it is judged that the foundation pit is not in a stable state during the current dewatering process. At this time, the pumping frequency of the dewatering well will be adjusted, and while gradually reducing the dewatering speed, it is monitored whether the foundation pit structure instability index Jszs exceeds the evaluation threshold. If the foundation pit structure instability index Jszs does not exceed the evaluation threshold, the adjustment of the dewatering speed will be stopped;

[0050] If the foundation pit structure instability index Jszs does not exceed the evaluation threshold, it is judged that the foundation pit is in a stable state during the current dewatering process. At this time, the dewatering rate of the current dewatering well will be maintained in the foundation pit.

[0051] The present invention provides a ground settlement monitoring system under the condition of ultra-large water level drawdown, which has the following beneficial effects:

[0052] (1) Through the foundation pit monitoring module, the system can monitor the flow characteristics of groundwater in real time during the foundation pit dewatering construction process, accurately obtain water body state data, which provides a detailed data basis for subsequent seepage field and stress analysis, helps to comprehensively understand the water flow distribution of the soil around the foundation pit in multiple dimensions, and improves the monitoring accuracy. The equipped seepage field change analysis module can analyze the movement process of groundwater in the soil of the foundation pit wall according to the real-time monitored water body state data, combined with the saturation state and permeability of the soil. Through this module, the system can automatically divide the soil in the foundation pit wall into layers, obtain the temporal and spatial distribution of the water head in each soil layer during the dewatering process, making the subsequent stress analysis and settlement evaluation more accurate. Based on the temporal and spatial distribution of the water head in each soil layer, the effective stress change of the soil during the dewatering process can be accurately calculated, and the additional stress influence of the settlement of the upper soil layer on the lower soil layer can be analyzed, so as to obtain the settlement amount of each soil layer. This stress and settlement monitoring based on layered analysis enables the system to conduct a detailed evaluation of uneven settlement and interlayer stress changes, effectively preventing the risk of structural instability caused by settlement differences. At the same time, a foundation pit structure prediction model is constructed using convolutional neural network technology. After inputting the real-time monitored data into the model, the foundation pit structure instability index Jszs is finally output. The instability prediction based on machine learning technology makes the system have stronger adaptability and prediction accuracy in the face of complex hydrogeological conditions, providing scientific instability risk quantification indicators for construction personnel.

[0053] (2) Through the permeability analysis unit, the system can analyze the permeability of the soil at different positions of the foundation pit based on the state judgment of the effective saturation. The permeability analysis unit automatically selects a matching permeability coefficient algorithm according to whether the soil reaches the saturated state to ensure the accuracy of the permeability calculation. This automated analysis process reduces human errors, improves data processing efficiency, and at the same time converts complex permeability data into an intuitive permeability distribution map, enabling operators to quickly view the permeability conditions at different depths in the foundation pit, so as to timely and effectively guide on-site operations, improving the efficiency of data processing and on-site decision-making.

[0054] (3) By dynamically monitoring the water head over time and space, the system enables construction personnel to grasp the water level changes of different soil layers around the foundation pit in real time, and timely identify possible water flow concentration areas or abnormal water flow change areas, further ensuring the stability of the dewatering process.

[0055] (4) The pressure analysis unit of the system automatically calculates the effective stress for each time period based on the spatio-temporal distribution of the soil head during the precipitation process. The effective stress is obtained by the difference between the total stress and the pore water pressure, which reflects the actual net stress state borne by the soil layer during the precipitation process. Since the change in the effective stress is directly related to the stability of the soil mass, the pressure analysis unit can dynamically reflect the stress change of the soil layer during precipitation, providing an early warning for the instability risk of the foundation pit side wall. At the same time, by calculating the settlement difference, the risk of uneven settlement can be accurately identified, further avoiding the instability of the foundation pit caused by differential settlement during the period.

[0056] (5) By comprehensively considering the different stress and deformation characteristics of the soil mass during the foundation pit dewatering process, the system can accurately reflect the instability risk of the foundation pit at different depths of the soil layer, helping the operator to timely adjust various parameters of the dewatering construction in the foundation pit to further reduce the instability risk. Description of the Drawings

[0057] Figure 1 It is a block diagram of the ground settlement monitoring system under the condition of ultra-large water level drawdown of the present invention. Detailed Embodiment

[0058] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0059] Embodiment 1

[0060] Please refer to Figure 1 , the present invention provides a ground settlement monitoring system under the condition of ultra-large water level drawdown, including a foundation pit monitoring module, a seepage field change analysis module, a stress change analysis module, a comprehensive evaluation module and a safety feedback module;

[0061] The foundation pit monitoring module is used to monitor the spatial distribution characteristics of the groundwater flow in the soil mass during the foundation pit dewatering construction to obtain relevant water body state data information;

[0062] The seepage field change analysis module is used to initially judge the saturation state of the soil mass, and based on the saturation state and relevant water body state data information, analyze the permeability of the soil mass and the movement process of the water in the soil mass, and divide the soil mass inside the foundation pit wall into layers according to the permeability of the soil mass around the foundation pit to obtain the spatio-temporal distribution of the water head at the corresponding soil layer during the precipitation process ;

[0063] The stress change analysis module will be based on the spatio-temporal distribution of the water head at the corresponding soil layer during the precipitation process , obtain the effective stress Yxy during the corresponding period, and analyze the influence degree of the settlement of the upper soil layer on the additional stress of the lower soil layer according to the changes of each soil layer before and after dehydration, so as to obtain the settlement amount Cjz of the corresponding layer;

[0064] The comprehensive evaluation module is used to construct a foundation pit structure prediction model by using convolutional neural network technology, and input relevant water body state data information into the foundation pit structure prediction model. After training and linear normalization processing, the foundation pit structure instability index Jszs is fitted and output;

[0065] The safety feedback module is used to preset an evaluation threshold, compare and analyze it with the foundation pit structure instability index Jszs, so as to estimate the stability status in the current foundation pit, present it in a visual form to the operation background, and adjust the dewatering process.

[0066] During the operation of this system, the foundation pit monitoring module monitors the flow of groundwater in the soil in real time during the dewatering construction process, so as to accurately obtain key water body state data such as the spatio-temporal distribution of water heads, groundwater levels, and pore water pressures. The data monitored in real time flows to each analysis module, enabling the system to dynamically adjust the dewatering speed and support design, improving the real-time performance and accuracy of monitoring, and ensuring the safety of the foundation pit project. The seepage field change analysis module automatically discriminates the saturation state of the soil through real-time water body state data, selects a suitable permeability calculation model according to different saturation degrees, dynamically calculates the permeability coefficient of the soil, divides the soil within the foundation pit wall into layers, and identifies the spatial distribution of different permeability soil layers. By accurately obtaining the water head distribution data of each soil layer, the system can identify areas with higher seepage in advance, thus laying a foundation for effectively reducing the risk of uneven settlement during the dewatering process. The stress change analysis module combines the water head distribution data and analyzes the settlement amount of each soil layer during the dewatering process based on the spatio-temporal changes of the effective stress of the soil, and evaluates the influence degree of the upper layer settlement on the additional stress of the lower soil layer. This module can dynamically evaluate the settlement amount and additional stress of the stratum, enabling the system to take measures in advance in strata with higher soil compressibility to control the differential settlement within the foundation pit and further avoid the inclination or instability of the foundation pit wall caused by settlement differences. The comprehensive evaluation module uses the foundation pit structure prediction model constructed by convolutional neural network to predict and analyze the water body state data using the trained model, and obtains the instability index Jszs of the foundation pit structure. After training and normalization processing, the system can fit the possible structural instability trend of the foundation pit during the dewatering process. The prediction model provides an efficient intelligent means for identifying instability hazards and can quickly alarm when the data is abnormal. The safety feedback module presets an evaluation threshold and compares it with the foundation pit structure instability index Jszs. If it exceeds the threshold, an alarm will be triggered immediately, and key information such as the foundation pit instability trend, instability index, and soil saturation state will be fed back to the operation background in a visual form. The real-time early warning function provided by the system can quickly adjust the dewatering process, and ensure the construction safety of the foundation pit by measures such as slowing down the dewatering speed and strengthening the support of the foundation pit wall. Through visual information display, engineering personnel can monitor the stability status within the foundation pit at any time, achieve precise management and scientific adjustment, and significantly improve the safety and construction efficiency of the foundation pit project.

[0067] Embodiment 2

[0068] Please refer to Figure 1 , specifically: the foundation pit monitoring module includes a pre-dewatering monitoring unit and a post-dewatering monitoring unit;

[0069] The pre-dewatering monitoring unit is used to preliminarily monitor the spatial distribution characteristics of the flow of groundwater in the soil before the foundation pit dewatering construction to obtain a pre-data set, and the pre-data set includes the initial water heads and water fluxes ;

[0070] The post-precipitation monitoring unit is used to monitor the spatial distribution characteristics of groundwater flow in the soil again after the foundation pit dewatering construction, so as to obtain a post-data set, and the post-data set includes the water content at corresponding positions in the foundation pit , the saturated water content at corresponding positions , the residual water content at corresponding positions , the specific weight of water , the porosity , the viscosity of water , the diameter of 10% particles in the soil , the water density , the density of the soil layer , the depth of the soil layer , the externally applied load , the compression modulus and the lateral displacement ;

[0071] The relevant water body state data information includes the pre-data set and the post-data set.

[0072] The seepage field change analysis module includes a state judgment unit, a permeability performance analysis unit, a soil body monitoring unit and a seepage distribution unit;

[0073] The state judgment unit is used to calculate the saturation degree of water in the soil at different positions around the foundation pit according to the post-data set, so as to obtain the effective saturation Ubd at the corresponding positions. The effective saturation Ubd is obtained in the following way:

[0074] ;

[0075] In the formula, represents the water content at the corresponding position; represents the residual water content at the corresponding position, reflecting the water content when the water in the soil can no longer flow; represents the saturated water content at the corresponding position; among them, the range of the effective saturation Ubd is between 0 and 1;

[0076] The above-mentioned water content at the corresponding position refers to the instantaneous content of water in the soil, which can be measured quickly and continuously on site by a time domain reflectometer (TDR), a frequency domain reflectometer (FDR) or a soil moisture sensor;

[0077] The saturated water content at the corresponding position refers to the water content of the soil in a fully saturated state, which can be obtained by completely immersing the soil sample in water so that its pores are completely filled with water, and then measuring the water content;

[0078] Residual water content at the corresponding position It refers to the water content when the water in the soil can no longer flow freely and can be measured by a pressure plate apparatus. The soil sample is placed under a lower negative pressure condition to measure the equilibrium water content of the soil sample.

[0079] When the effective saturation Ubd = 1, it indicates that the soil at the current position reaches the fully saturated state;

[0080] When 0 ≤ effective saturation Ubd < 1, it indicates that the soil at the current position does not reach the fully saturated state.

[0081] In this embodiment, before precipitation, the system acquires the initial water head and water flux at different positions in the foundation pit. After precipitation, it acquires multiple data such as water content, saturated water content, residual water content, and soil layer density. This precise comparison and monitoring before and after precipitation provide a detailed data basis for the analysis of the moisture characteristics and water flow dynamics of the foundation pit soil, helping to comprehensively understand the hydraulic influence of foundation pit dewatering on the soil and improving the accuracy of foundation pit monitoring. The pre - data group and post - data group monitored by the system include multiple parameters such as initial water head, water content, soil layer density, viscosity of water, and lateral displacement, covering the hydraulic and physical characteristics of the soil around the foundation pit. These rich data can provide accurate input for subsequent seepage analysis and settlement assessment, thereby improving the calculation accuracy and adaptability of the entire system and enabling it to cope with complex geological and hydrological conditions. In the seepage field change analysis module, the system can accurately distinguish the saturated state of the soil at different positions by calculating the effective saturation of the soil in real - time through the state judgment unit. The calculation result of the effective saturation is between 0 and 1, reflecting the degree of soil saturation and helping to judge whether the soil reaches the fully saturated state. This judgment accuracy lays the foundation for the seepage performance analysis, especially significantly improving the accuracy of the system in the permeability analysis of unsaturated soils. The permeability performance analysis unit analyzes the permeability performance of each soil layer according to the saturated state of the soil and the physical characteristics of the water body to effectively identify the differences in the permeability characteristics of the soil on the foundation pit wall. This refined analysis enables the system to understand the resistance of different soil layers to water flow during the foundation pit dewatering process in real - time, especially making a hierarchical judgment between high - permeability and low - permeability soil layers, improving the accuracy of seepage analysis. At the same time, through hierarchical monitoring, it helps the construction personnel to timely understand the water flow changes on the high - precision seepage field map and effectively prevent the problem of soil instability caused by seepage.

[0082] Embodiment 3

[0083] Please refer to Figure 1 Specifically: The permeability performance analysis unit is used to analyze the permeability performance of the soil at different positions around the foundation pit according to the judgment in the state judgment unit and in combination with the relevant water body state data information to obtain the permeability coefficient Stxs, and the specific way to obtain it is as follows:

[0084] ;

[0085] In the formula, when the soil at the corresponding position reaches the fully saturated state, this formula holds; where, is expressed as the saturated permeability coefficient, Ubd is expressed as the effective saturation degree, and are both constants, and reflect the seepage characteristics of the soil, and the parameter values are different for different soil types. Many studies have given the empirical parameter values of common soil types, which can be directly obtained by referring to the soil parameter table.

[0086] Among them, the saturated permeability coefficient is obtained in the following way:

[0087] ;

[0088] In the formula, is expressed as the unit weight of water, is expressed as the porosity, is expressed as the viscosity of water, is expressed as the diameter of 10% of the particles in the soil, which is used to characterize the influence of particle size;

[0089] The diameter of 10% of the particles in the soil is an important characteristic value of the particle size distribution and can be obtained by laser particle size analysis;

[0090] The unit weight of water is a known physical constant. Under normal circumstances, the value is 9.81 kN / m³ (or 9800 N / m³);

[0091] The porosity is calculated by the volume and dry weight of the soil sample, combined with the soil particle density;

[0092] The viscosity of water is obtained by monitoring with a rotational viscometer;

[0093] The soil monitoring unit is used to draw a seepage distribution map according to the seepage coefficient Stxs values at different positions around the foundation pit when the soil at the corresponding position reaches the fully saturated state, presenting the seepage changes at each depth in the foundation pit, so as to divide the soil in the foundation pit into different layers of soil; when the soil at the corresponding position does not reach the fully saturated state, draw a seepage distribution map according to the saturated permeability coefficient values at different positions around the foundation pit, presenting the seepage changes at each depth in the foundation pit, so as to divide the soil in the foundation pit into different layers of soil. The higher the seepage coefficient, the smaller the resistance of the soil to water flow;

[0094] Among them, dividing the soil in the foundation pit into different layers of soil specifically involves highly permeable soil layers (such as sand layers, pebble layers), moderately permeable layers (such as silt layers), and low-permeable layers (such as clay layers): The permeability coefficient of highly permeable soil layers is generally between and m / s, with strong water flow-through ability and prone to seepage; the permeability coefficient of moderately permeable layers is generally around m / s, which has a certain obstructive effect on water flow; the permeability coefficient of low-permeable layers is generally less than m / s, and water flow is difficult to pass through, having good water isolation properties.

[0095] In this embodiment, the permeability performance analysis unit in the system combines the saturation state judgment result of the state judgment unit, and based on the relevant water body state data information of the soil, dynamically analyzes the permeability performance at different positions around the foundation pit, obtains the permeability coefficient of each point. When the soil reaches the fully saturated state, the saturated permeability coefficient calculation formula is adopted, combined with the calculation of effective saturation and particle parameters, which improves the accuracy of permeability performance evaluation and provides a scientific basis for the foundation pit dewatering scheme. Especially in heterogeneous soil, considering the particle characteristics of the soil effectively improves the reliability of permeability coefficient evaluation. The judgment result of effective saturation helps the system distinguish between saturated and unsaturated states of the soil. Through the seepage distribution map, the system can accurately divide different soil layers in the foundation pit, identify highly permeable and low-permeable soil layers, and provide fine soil layer data support for the formulation of the dewatering scheme. In short, through the refined monitoring of the permeability coefficient and water flow resistance of different soil layers, the construction safety and efficiency of the foundation pit project can be effectively improved.

[0096] Embodiment 4

[0097] Please refer to Figure 1 Specifically: The seepage distribution unit is used to analyze the movement process of water in the soil according to the permeability coefficient Stxs and the saturated permeability coefficient obtained by the permeability performance analysis unit and, in combination with relevant water body state data information, to obtain the spatio-temporal distribution of the water head at the corresponding soil layer during the dewatering process The spatio-temporal distribution of the water head is obtained through the following formula:

[0098] ;

[0099] In the formula, represents the water capacity function, which is a function of the water content and is used to describe the water storage characteristics of the soil at different water contents. The water capacity function reflects the dynamic change ability of water in the soil, and the unit is usually ; is the initial water head, indicating the height of the water level, with the unit of meter. The initial water head is a key variable in the seepage field, usually expressed as the sum of the position head and the pressure head; is expressed as the monitoring period, is the partial derivative of the initial head with respect to time t, representing the rate of change of the head with time, with the unit of m / s. This describes the change of the head with time at a specific location; is the gradient operator, representing the change in the spatial direction. For the head, reflects the spatial gradient of the head, that is, the change of the head in space; is expressed as the permeability coefficient under the corresponding saturated state. Among them, when the soil at the corresponding location reaches the fully saturated state, is the permeability coefficient Stxs. When the soil at the corresponding location does not reach the fully saturated state, is the saturated permeability coefficient ; is the source-sink term, with the unit of m / s, representing the increase or decrease of water in the soil. For example, in the cases of precipitation, groundwater extraction, etc., can be used to represent the increase or decrease of water volume; is expressed as the divergence of the seepage flow, with the unit of m / s. This term describes the change of the water flow rate per unit volume, reflecting the distribution and change of the seepage flow in the soil; is expressed as the water flux, which refers to the amount of water passing through a unit area per unit time. It is usually used to describe the flow rate of water in porous media (such as soil, rock formation). Generally speaking, the water flux reflects the "intensity" of water flow in a certain direction, that is, how much water passes through a specific area per unit time.

[0100] The above-mentioned head is monitored and obtained through a pore water pressure sensor;

[0101] In this embodiment, the system selects the permeability coefficient or the saturated permeability coefficient according to whether the soil has reached the saturated state, and realizes the dynamic tracking of the water head distribution of different soil layers in the foundation pit, which provides a solid data foundation for the subsequent soil stress analysis and settlement assessment, and ensures that the monitoring of the hydraulic characteristics of the foundation pit is scientific and accurate. The system uses the gradient operator to perform real-time analysis on the spatial distribution of the water head, thereby obtaining the spatial gradient of the water head, and then inferring the flow direction and intensity of the water flow. Combined with the water flow data, the system can accurately describe the flow rate of water in different directions, especially the change of water flow direction in the boundary area between high permeability soil layer and low permeability soil layer. This refined seepage monitoring makes the permeability and flow characteristics of the water flow in the foundation pit dewatering process clearer, and provides an effective prevention and control measure for the risk of seepage damage caused by water flow. The formula of the seepage distribution unit includes water flow divergence and source and sink terms, which respectively reflect the volume change of water flow and the increase and decrease of water content in the soil. By dynamically monitoring the divergence changes and the increase and decrease of water volume during the foundation pit dewatering process, the system can timely detect the rate of change of water head and evaluate the impact of groundwater extraction or dewatering operations on the seepage field. This dynamic evaluation provides a scientific basis for controlling the hydraulic balance in the foundation pit and adjusting the dewatering rate, reducing the risk of seepage instability in the foundation pit.

[0102] Example 5

[0103] Please refer to Figure 1 , specifically: the stress change analysis module includes a pressure analysis unit, an interlayer stress transfer unit and a settlement analysis unit;

[0104] The pressure analysis unit is used to analyze the temporal and spatial distribution of water head at the corresponding soil layer during precipitation. , analyze and obtain the effective stress Yxy in the foundation pit during the corresponding period of precipitation, which can be obtained in the following way:

[0105] ;

[0106] In the formula, represents the total stress, represents the pore water pressure;

[0107] Among them, the pore water pressure Ksy is obtained by the following formula:

[0108] ;

[0109] In the formula, represents the water density, represents the acceleration due to gravity;

[0110] Among them, the total stress Obtained by the following formula:

[0111] ;

[0112] In the formula, represents the density of the corresponding soil layer, represents the depth of the corresponding soil layer, represents the externally applied load, such as the pressure of mechanical equipment.

[0113] The density of the corresponding soil layer can be monitored and obtained by a nuclear densitometer;

[0114] The depth of the corresponding soil layer can be monitored and obtained by a geological profiler;

[0115] The externally applied load can be monitored and obtained by a load sensor;

[0116] The interlayer stress transfer unit is used to analyze the influence degree of the settlement of the upper soil layer on the additional stress of the lower soil layer according to the changes of each soil layer before and after dehydration, so as to obtain the settlement amount Cjz of the corresponding layer, and the specific method for obtaining it is as follows:

[0117] ;

[0118] In the formula, represents the increase in effective stress of the j-th layer, is the interlayer stress transfer coefficient between adjacent layers, indicating the influence degree of the additional stress of the upper soil layer on the lower soil layer; represents the increase in effective stress of the i-th layer, represents the depth of the j-th layer, represents the compression modulus of the j-th layer, where i and j are soil layer numbers, and the j-th layer is the lower layer of the i-th layer;

[0119] The increase in effective stress of each layer mentioned above refers to the difference in effective stress of the soil layer before and after precipitation or groundwater level change, and this increase reflects the increase in effective stress caused by the reduction of pore water pressure due to precipitation or water level decline.

[0120] The increase in effective stress will cause the compression and settlement of the soil. When the external load increases or the groundwater level drops, the net stress between soil particles increases, thereby causing further compression and settlement of the soil. This situation is a common scenario in settlement calculation.

[0121] The compression modulus of each layer can be monitored and obtained by a triaxial testing machine;

[0122] Among them, the interlayer stress transfer coefficient between adjacent layers is obtained by the following method:

[0123] ;

[0124] In the formula, represents the depth of the i-th layer, represents the depth of the j-th layer, represents the compression modulus of the j-th layer, represents the compression modulus of the i-th layer.

[0125] The settlement analysis unit is used to obtain the settlement difference between adjacent soil layers and the cumulative settlement Zcjz according to the settlement Cjz of the corresponding layer obtained from the interlayer stress transfer unit and combining statistical algorithms.

[0126] In this embodiment, the system calculates the effective stress of each time period based on the spatio-temporal distribution of the water head through the pressure analysis unit. This unit calculates the effective stress using the formulas of total stress and pore water pressure respectively, so as to accurately reflect the stress change of the foundation pit soil during the dewatering process. This real-time effective stress calculation can identify possible stress anomalies or stress concentration areas during the dewatering process, providing important data support for the foundation pit stability assessment. By considering the influence of external loads such as mechanical equipment, the calculation of total stress is more comprehensive and real, which can accurately reflect the stress conditions of different soil layers and avoid the settlement calculation deviation caused by the estimation error of total stress. The interlayer stress transfer unit analyzes the additional stress influence of the upper soil layer on the lower soil layer using the interlayer stress transfer coefficient, which is obtained through the comprehensive calculation of soil layer thickness and compression modulus, and can accurately reflect the stress transfer situation between soil layers. The analysis of interlayer stress transfer can identify possible stress concentration and settlement differences, providing scientific support for preventing the instability of the foundation pit and avoiding misjudgment of the overall settlement assessment caused by the stress change of a single layer. The system obtains the settlement of each layer through the interlayer stress transfer unit and performs high-precision calculation using the compression modulus and the increase in effective stress, so that the settlement of each soil layer during the dewatering process can be dynamically tracked and accurately quantified.

[0127] Embodiment 6

[0128] Please refer to Figure 1 , specifically: The comprehensive evaluation module is used to use the trained foundation pit structure prediction model. After linear normalization processing, map the corresponding data values to the interval to fit and output the foundation pit structure instability index Jszs when the dewatering reaches the corresponding soil layer:

[0129] ;

[0130] In the formula, represents the lateral displacement, represents the cumulative settlement, represents the settlement difference between adjacent soil layers, , and are both weight values, which is expressed as a correction constant. Among them, , and The specific values are set by the user according to the situation.

[0131] Lateral displacement can be monitored and obtained through an inclinometer or a laser displacement sensor;

[0132] The safety feedback module is used to compare and analyze the instability index Jszs of the foundation pit structure with the evaluation threshold to judge the stability status in the foundation pit during the current dewatering process. The specific judgment content is as follows:

[0133] If the instability index Jszs of the foundation pit structure exceeds the evaluation threshold, it is judged that the foundation pit is not in a stable state during the current dewatering process. At this time, the pumping frequency of the dewatering well will be adjusted, and while gradually reducing the dewatering speed, it is monitored whether the instability index Jszs of the foundation pit structure exceeds the evaluation threshold. If the instability index Jszs of the foundation pit structure does not exceed the evaluation threshold, the adjustment of the dewatering speed will be stopped. In necessary cases, the dewatering can also be temporarily stopped to observe the change of the foundation pit stability, and the shear strength and anti-deformation ability of the foundation pit can be improved by strengthening the foundation pit support structure, reducing the lateral displacement, increasing the number of anchor rods or increasing the depth and thickness of the support piles around the foundation pit to improve the bearing capacity and compressive capacity of the soil mass, and reducing the settlement and lateral displacement;

[0134] If the instability index Jszs of the foundation pit structure does not exceed the evaluation threshold, it is judged that the foundation pit is in a stable state during the current dewatering process. At this time, the dewatering rate of the current dewatering well will be maintained in the foundation pit to gradually lower the groundwater level and ensure a dry construction environment.

[0135] In this embodiment, the comprehensive evaluation module outputs the foundation pit structure instability index Jszs. The instability index maps each monitoring data to a unified interval, comprehensively considering various influencing factors, enabling the quantification of the stability state of the foundation pit. This quantification process helps the operator have an intuitive and scientific evaluation basis for the safety state of the foundation pit. The safety feedback module compares the real-time generated instability index with the preset evaluation threshold to judge the current stability state of the foundation pit. When the instability index exceeds the evaluation threshold, the system can quickly identify potential risks, thereby triggering a series of stability control measures. The high sensitivity of this real-time comparison and analysis ensures that the monitoring system can promptly respond to possible unstable situations during the dewatering process, enhancing the safety during the foundation pit dewatering construction. When the instability index exceeds the evaluation threshold, the system will intelligently adjust the pumping frequency and dewatering speed of the dewatering wells, gradually reducing the dewatering rate to decrease the rate of water level drop, thereby reducing the risks of settlement and lateral displacement caused by the sudden drop of pore water pressure. While adjusting the dewatering speed, the system continuously monitors the instability index. If the index does not exceed the evaluation threshold, the regulation will stop. The intelligent control of the dewatering speed ensures the stability of the foundation pit dewatering process and avoids the problem of foundation pit structure instability caused by excessive dewatering. In summary, the system utilizes the instability index Jszs and the intelligent feedback mechanism to achieve real-time stability evaluation and control during the foundation pit dewatering process. Through the quantified instability index Jszs and flexible regulation of the dewatering speed, combined with reinforcement support and visual feedback, the system can accurately and dynamically control the dewatering stability of the foundation pit, further reducing the risks brought by instability and providing a strong guarantee for the safe construction of the foundation pit project.

[0136] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. The ground subsidence monitoring system under extremely large water level drop conditions is characterized by: It includes foundation pit monitoring module, seepage field change analysis module, stress change analysis module, comprehensive evaluation module and safety feedback module; The foundation pit monitoring module is used to monitor the spatial distribution characteristics of groundwater flowing in the soil in real time during the foundation pit dewatering construction process to obtain relevant water state data information; The seepage field change analysis module is used to preliminarily determine the saturation state of the soil, and analyze the permeability of the soil and the movement of water in the soil according to the saturation state and related water state data information, and divide the soil inside the foundation pit wall into layers according to the permeability of the soil around the foundation pit, so as to obtain the temporal and spatial distribution of the water head at the corresponding soil layer during the precipitation process. ; The stress change analysis module will be based on the temporal and spatial distribution of water head at the corresponding soil layer during precipitation. , obtain the effective stress Yxy of the corresponding period, and analyze the influence of the settlement of the upper soil layer on the additional stress of the lower soil layer according to the changes of each soil layer before and after dehydration, so as to obtain the settlement Cjz of the corresponding layer; The comprehensive evaluation module is used to construct a foundation pit structure prediction model using convolutional neural network technology, and input relevant water body status data information into the foundation pit structure prediction model. After training and linear normalization processing, the foundation pit structure instability index Jszs is fitted and output; The safety feedback module is used to pre-set an evaluation threshold and compare and analyze it with the foundation pit structure instability index Jszs to estimate the current stability status in the foundation pit, and present it in a visual form to the operation background to adjust the precipitation process.

2. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 1 is characterized in that: The foundation pit monitoring module includes a pre-precipitation monitoring unit and a post-precipitation monitoring unit; The pre-dewatering monitoring unit is used to preliminarily monitor the spatial distribution characteristics of groundwater flow in the soil before the foundation pit dewatering construction to obtain a pre-data group, which includes the initial water head at different positions in the foundation pit. and water flow ; The post-precipitation monitoring unit is used to monitor the spatial distribution characteristics of groundwater flow in the soil again after the foundation pit precipitation construction to obtain a post-data group, which includes the water content at the corresponding position in the foundation pit. , saturated moisture content at the corresponding position , the residual moisture content at the corresponding position , water weight , porosity , Viscosity of water , the diameter of 10% of the particles in the soil , water density , soil density , depth of soil layer , externally applied loads , compression modulus and lateral displacement ; The relevant water body status data information includes the front data group and the rear data group.

3. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 2 is characterized in that: The seepage field change analysis module includes a state judgment unit, a permeability analysis unit, a soil monitoring unit and a seepage distribution unit; The state judgment unit is used to calculate the saturation degree of water in the soil at different positions around the foundation pit according to the post data group, so as to obtain the effective saturation Ubd at the corresponding position, and the effective saturation Ubd is obtained by the following method: ； In the formula, Expressed as the moisture content at the corresponding position; It is expressed as the residual moisture content at the corresponding position, reflecting the moisture content when the water in the soil can no longer flow; Expressed as the saturated moisture content at the corresponding position; When the effective saturation Ubd=1, it means that the soil at the current position has reached a fully saturated state; When 0≤effective saturation Ubd<1, it means that the soil at the current position has not reached a fully saturated state.

4. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 3 is characterized in that: The permeability analysis unit is used to analyze the permeability of soil at different positions around the foundation pit according to the judgment in the state judgment unit and in combination with the relevant water state data information to obtain the permeability coefficient Stxs, which is specifically obtained in the following manner: ； In the formula, this formula is valid when the soil at the corresponding position reaches a fully saturated state; It is expressed as saturated permeability coefficient, Ubd is expressed as effective saturation, and are all constants; Among them, the saturated permeability coefficient Obtained through: ； In the formula, Expressed as the weight of water, Expressed as porosity, Expressed as the viscosity of water, It is expressed as the diameter of 10% of the particles in the soil, and is used to characterize the effect of particle size; The soil monitoring unit is used to draw a permeability distribution diagram according to the permeability coefficient Stxs values ​​at different positions around the foundation pit when the soil at the corresponding position reaches a fully saturated state, presenting the permeability changes at various depths in the foundation pit, so as to divide the soil in the foundation pit into different layers of soil; when the soil at the corresponding position has not reached a fully saturated state, according to the saturated permeability coefficient Stxs values ​​at different positions around the foundation pit, The permeability distribution diagram is drawn based on the numerical value, which shows the permeability changes at various depths in the foundation pit, so as to divide the soil in the foundation pit into different layers.

5. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 4 is characterized in that: The seepage distribution unit is used to obtain the permeability coefficient Stxs and the saturated permeability coefficient according to the permeability performance analysis unit. , and combined with relevant water state data information, analyze the movement of water in the soil to obtain the temporal and spatial distribution of water head at the corresponding soil layer during precipitation , the temporal and spatial distribution of water head Obtained by the following formula: ； In the formula, Expressed as a water capacity function; is the initial water head; It is represented as the monitoring period, is the partial derivative of the initial water head with respect to time t; is the gradient operator; Expressed as the permeability coefficient at the corresponding saturated state; is the source-sink term; It is expressed as the divergence of the permeate flow; Expressed as water flux.

6. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 2 is characterized in that: The stress change analysis module includes a pressure analysis unit, an interlayer stress transfer unit and a settlement analysis unit; The pressure analysis unit is used to analyze the temporal and spatial distribution of water head at the corresponding soil layer during precipitation. , analyze and obtain the effective stress Yxy in the foundation pit during the corresponding period of precipitation, which can be obtained in the following way: ； In the formula, represents the total stress, represents the pore water pressure; Among them, the pore water pressure Ksy is obtained by the following formula: ； In the formula, represents the water density, represents the acceleration due to gravity; Among them, the total stress Obtained by the following formula: ； In the formula, represents the density of the corresponding soil layer, represents the depth of the corresponding soil layer, Represents externally applied loads.

7. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 6 is characterized in that: The interlayer stress transfer unit is used to analyze the influence of the settlement of the upper soil layer on the additional stress of the lower soil layer according to the changes of each soil layer before and after dehydration, so as to obtain the settlement amount Cjz of the corresponding layer, which is obtained specifically in the following way: ； In the formula, Expressed as the effective stress increase of the jth layer, is the stress transfer coefficient between adjacent layers; Expressed as the effective stress increase of the i-th layer, Denotes the depth of the jth layer, It is expressed as the compression modulus of the jth layer, where i and j are the soil layer numbers.

8. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 7 is characterized in that: The settlement analysis unit is used to obtain the settlement difference between adjacent soil layers based on the settlement Cjz of the corresponding layer obtained in the interlayer stress transfer unit in combination with a statistical algorithm. And the cumulative settlement Zcjz.

9. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 8, characterized in that: The comprehensive evaluation module is used to use the trained foundation pit structure prediction model and map the corresponding data values ​​to the interval after linear normalization. The instability index Jszs of the foundation pit structure when the precipitation falls to the corresponding soil layer is fitted and output: ； In the formula, Expressed as lateral displacement, Expressed as cumulative sedimentation, It is expressed as the settlement difference between adjacent soil layers. , and are weight values, Expressed as a correction constant, where , and The specific value is set by the user according to the situation.

10. The land subsidence monitoring system under extremely large water level drawdown conditions according to claim 1, characterized in that: The safety feedback module is used to compare and analyze the foundation pit structure instability index Jszs with the evaluation threshold to determine the stability of the foundation pit during the current precipitation process. The specific determination content is as follows: If the foundation pit structure instability index Jszs exceeds the evaluation threshold, it is judged that the foundation pit is not in a stable state during the current precipitation process. At this time, the pumping frequency of the precipitation well will be adjusted to gradually reduce the precipitation speed while monitoring whether the foundation pit structure instability index Jszs exceeds the evaluation threshold. If the foundation pit structure instability index Jszs does not exceed the evaluation threshold, the adjustment of the precipitation speed will be stopped; If the foundation pit structure instability index Jszs does not exceed the evaluation threshold, it is judged that the foundation pit is in a stable state during the current precipitation process. At this time, the precipitation rate of the current precipitation well will be maintained in the foundation pit.

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