Ground subsidence monitoring system under ultra-large water level drawdown condition

Abstract

The invention discloses a ground subsidence monitoring system under the condition of ultra-large water level drawdown, and relates to the technical field of foundation pit dewatering, a seepage field change analysis module arranged on the system can analyze the movement process of underground water in a soil body of a foundation pit wall according to water body state data monitored in real time and in combination with the saturation state and permeability of the soil body, and the seepage field change analysis module can analyze the movement process of underground water in the soil body of the foundation pit wall through the module. The system can automatically perform hierarchical division on the soil body in the foundation pit wall, obtain the spatial and temporal distribution of the water head of each soil layer in the precipitation process, make the subsequent stress analysis and settlement evaluation more accurate, and accurately calculate the effective stress change of the soil body in the precipitation process based on the spatial and temporal distribution of the water head of each soil layer. And the additional stress influence of the settlement of the upper layer soil layer on the lower layer soil layer is analyzed, so that the settlement volume of each layer of soil body is obtained, and the stress and settlement monitoring based on stratified analysis enables the system to carry out detailed evaluation on differential settlement and interlayer stress change, so that the risk of structural instability caused by settlement difference is effectively prevented.

Description

Technical Field

[0001] The invention relates to the technical field of foundation pit dewatering, and in particular to a ground settlement monitoring system under conditions of extremely large water level drop. Background Art

[0002] In the field of civil engineering and geological engineering, foundation pit engineering and foundation treatment are important topics for controlling groundwater levels, managing soil stability, and preventing settlement instability. In this field, foundation pit construction under conditions of extremely large water level drawdown faces special technical challenges. Under such conditions, a significant decrease in groundwater levels may lead to changes in soil moisture content and redistribution of hydraulic conditions, which in turn affect the settlement characteristics around the foundation pit. In particular, ground settlement monitoring under extremely large water level drawdown environments requires precise analysis of the seepage field and stress field to understand how the dynamic changes of water in the soil affect the stability of the soil. 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 complicated. In this case, the monitoring system must not only track the movement of groundwater flow, but also analyze the impact of the seepage field on the internal stress field of the soil, so as to comprehensively assess the settlement and instability risks that may be caused during the precipitation process.

[0003] When monitoring ground settlement under conditions of extremely large water level drawdown, current monitoring methods face many shortcomings. First, the existing monitoring systems usually only focus on individual monitoring of parameters such as water level changes or settlement, and do not adequately analyze the differences in permeability characteristics and saturation states between different soil layers, failing to fully reveal the impact of the seepage field on soil stress distribution. Secondly, due to the large differences in settlement characteristics of each soil layer, it is easy to ignore the stress transfer and additional stress effects between different soil layers, which can easily lead to aggravated settlement differences and make it difficult to accurately predict the settlement behavior of multi-layer soil during precipitation. Once these abnormal phenomena occur, the stability of the foundation pit is difficult to guarantee, which will directly affect the safety of the project and even cause serious accidents such as collapse. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a ground subsidence monitoring system under conditions of extremely large water level drop, which solves the problems in the above-mentioned background technology.

[0005] To achieve the above objectives, the present invention is implemented through the following technical solutions: a ground settlement monitoring system under conditions of extremely large water level drop, 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 groundwater flowing in the soil in real time during the foundation pit dewatering construction process to obtain relevant water state data information;

[0007] 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. ;

[0008] 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;

[0009] 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;

[0010] 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.

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

[0012] 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 ;

[0013] 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 ;

[0014] The relevant water body status data information includes the front data group and the rear data group.

[0015] Preferably, the seepage field change analysis module includes a state judgment unit, a permeability analysis unit, a soil 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 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: ;

[0017] 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;

[0018] When the effective saturation Ubd=1, it means that the soil at the current position has reached a fully saturated state;

[0019] When 0≤effective saturation Ubd<1, it means that the soil at the current position has not reached a fully saturated state.

[0020] Preferably, 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: ;

[0021] 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;

[0022] Among them, the saturated permeability coefficient Obtained through: ;

[0023] 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;

[0024] 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 levels of soil layers.

[0025] Preferably, the seepage distribution unit is used to obtain the permeability coefficient Stxs and the saturated permeability coefficient Stxs obtained by 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: ;

[0026] 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.

[0027] Preferably, the stress change analysis module includes a pressure analysis unit, an interlayer stress transfer unit and a settlement analysis unit;

[0028] 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: ;

[0029] In the formula, represents the total stress, represents the pore water pressure;

[0030] Among them, the pore water pressure Ksy is obtained by the following formula: ;

[0031] In the formula, represents the water density, represents the acceleration due to gravity;

[0032] Among them, the total stress Obtained by the following formula: ;

[0033] In the formula, represents the density of the corresponding soil layer, represents the depth of the corresponding soil layer, Represents externally applied loads.

[0034] Preferably, 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 specifically obtained in the following way: ;

[0035] 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.

[0036] Preferably, 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.

[0037] Preferably, the comprehensive evaluation module is used to use the trained foundation pit structure prediction model to 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: ;

[0038] 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.

[0039] Preferably, 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:

[0040] 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;

[0041] 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.

[0042] The present invention provides a ground subsidence monitoring system under conditions of extremely large water level drop, which has the following beneficial effects:

[0043] (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 and accurately obtain water status data. This provides a detailed data basis for subsequent seepage field and stress analysis, helps to grasp the water flow distribution of the soil around the foundation pit in multiple dimensions, and improves the monitoring accuracy. The 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 precipitation process, and make the subsequent stress analysis and settlement assessment more accurate. Based on the spatiotemporal distribution of the water head of each soil layer, the effective stress change of the soil during the precipitation 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 hierarchical analysis enables the system to conduct a detailed assessment of uneven settlement and interlayer stress changes, and effectively prevent the risk of structural instability caused by settlement differences. At the same time, the convolutional neural network technology is used to construct a foundation pit structure prediction model. After the real-time monitoring data is input into the model, the foundation pit structure instability index Jszs is finally output. The instability prediction based on machine learning technology enables the system to have stronger adaptability and prediction accuracy when facing complex hydrogeological conditions, and provides construction personnel with scientific quantitative indicators of instability risk.

[0044] (2) Through the permeability analysis unit, the system can analyze the permeability of the soil at different locations in the foundation pit based on the effective saturation state. The permeability analysis unit automatically selects a matching permeability coefficient algorithm based on whether the soil has reached a saturated state to ensure the accuracy of the permeability calculation. This automated analysis process reduces human errors and improves data processing efficiency. At the same time, it converts complex permeability data into an intuitive permeability distribution map, allowing operators to quickly view the permeability conditions at various depths in the foundation pit, so that they can guide on-site operations in a timely and effective manner, thereby improving the efficiency of data processing and on-site decision-making.

[0045] (3) The system dynamically monitors the water head over time and space, enabling construction personnel to grasp the water level changes in different soil layers around the foundation pit in real time, promptly identify possible areas of water concentration or abnormal water flow changes, and further ensure the stability of the precipitation process.

[0046] (4) The system's pressure analysis unit automatically calculates the effective stress at each time period based on the temporal and spatial distribution of the water head of the soil during the precipitation process. The effective stress is obtained through the difference between the total stress and the pore water pressure, reflecting the net stress state actually borne by the soil layer during the precipitation process. Since the change in effective stress is directly related to the stability of the soil, the pressure analysis unit can dynamically reflect the stress change of the soil layer during precipitation, providing an early warning for the risk of instability of the foundation pit side wall. At the same time, the risk of uneven settlement can be accurately identified through the calculation of the settlement difference, further avoiding the instability of the foundation pit caused by differential settlement during the period.

[0047] (5) The system can accurately reflect the instability risk of the foundation pit at different soil depths by comprehensively considering the different stress and deformation characteristics of the soil during the foundation pit dewatering process, which helps operators to timely adjust various parameters of the dewatering construction in the foundation pit to further reduce the instability risk. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a block diagram of the ground subsidence monitoring system under conditions of extremely large water level drawdown of the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] See also Figure 1, the present invention provides a ground settlement monitoring system under conditions of extremely large water level drop, 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;

[0052] 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;

[0053] 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. ;

[0054] 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;

[0055] 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;

[0056] 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.

[0057] 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 status data such as the temporal and spatial distribution of water head, groundwater level and pore water pressure. The real-time monitoring data flows to each analysis module, enabling the system to dynamically adjust the dewatering speed and support design, improving the real-time and accuracy of monitoring and ensuring the safety of the foundation pit project. The seepage field change analysis module automatically determines the saturation state of the soil through real-time water status data, selects the appropriate permeability calculation model according to different saturations, and dynamically calculates the permeability coefficient of the soil to hierarchically divide the soil in the foundation pit wall and identify the spatial distribution of different permeable soil layers. By accurately obtaining the water head distribution data of each soil layer, the system can identify the areas with higher permeability in advance, thus laying the foundation for effectively reducing the risk of uneven settlement during dewatering. The stress change analysis module combines the head distribution data and analyzes the settlement of each layer of soil during precipitation based on the spatiotemporal changes of effective stress of the soil, and evaluates the influence of the upper settlement on the additional stress of the lower soil layer. This module can dynamically evaluate the settlement and additional stress of the stratum, so that the system can take measures in advance in the stratum with high soil compressibility to control the differential settlement in the foundation pit, and further avoid the inclination or instability of the foundation pit wall caused by the settlement difference. The comprehensive evaluation module uses the foundation pit structure prediction model constructed by the convolutional neural network, and uses the trained model to predict and analyze the water state data to obtain the instability index Jszs of the foundation pit structure. After training and normalization, the system can fit the structural instability trend that may occur in the foundation pit during precipitation. The prediction model provides an efficient and intelligent means for identifying instability hazards, and can quickly alarm when the data is abnormal. The safety feedback module presets the evaluation threshold and compares it with the foundation pit structure instability index Jszs. If it exceeds the threshold, the alarm is triggered immediately, and the key information such as the foundation pit instability trend, instability index, and soil saturation state are fed back to the operation background in a visual form. The real-time early warning function provided by the system can quickly adjust the precipitation process, and ensure the safety of foundation pit construction by slowing down the precipitation speed, strengthening the support of the foundation pit wall, etc. Through the visual information display, engineering personnel can monitor the stability of 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.

[0058] Example 2

[0059] Please refer to Figure 1 ,Specifically: the foundation pit monitoring module includes a pre-precipitation monitoring unit and a post-precipitation monitoring unit;

[0060] 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 ;

[0061] 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 ;

[0062] The relevant water body status data information includes the front data group and the rear data group.

[0063] The seepage field change analysis module includes a state judgment unit, a permeability analysis unit, a soil monitoring unit and a seepage distribution unit;

[0064] 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: ;

[0065] 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; It is expressed as the saturated water content at the corresponding position; where the effective saturation Ubd ranges from 0 to 1;

[0066] The moisture content at the corresponding position above It refers to the instantaneous moisture content in the soil, which can be measured quickly and continuously on site by time domain reflectometry (TDR), frequency domain reflectometry (FDR) or soil moisture sensors;

[0067] Saturated moisture content at the corresponding position It refers to the moisture content of the soil in a fully saturated state. The moisture content can be measured by completely immersing the soil sample in water so that its pores are completely filled with water.

[0068] Residual moisture content at the corresponding position It refers to the moisture content in the soil when the water can no longer flow freely. It can be measured by a pressure plate instrument. The soil sample is placed under a relatively low negative pressure condition to measure the equilibrium moisture content of the soil sample.

[0069] When the effective saturation Ubd=1, it means that the soil at the current position has reached a fully saturated state;

[0070] When 0≤effective saturation Ubd<1, it means that the soil at the current position has not reached a fully saturated state.

[0071] In this embodiment, before precipitation, the system obtains the initial water head and water flow at different positions in the foundation pit, and obtains multiple data such as water content, saturated water content, residual water content, soil layer density, etc. after precipitation. This precise comparative monitoring before and after precipitation provides a detailed data basis for the analysis of the moisture characteristics and water flow dynamics of the foundation pit soil, which helps to fully grasp the hydraulic impact of foundation pit precipitation on the soil and improve the accuracy of foundation pit monitoring. The front data group and the rear data group monitored by the system include multiple parameters such as initial water head, water content, soil layer density, water viscosity, lateral displacement, etc., covering the hydraulic and physical properties of the soil around the foundation pit. These rich data can provide accurate input for subsequent permeability analysis and settlement assessment, thereby improving the calculation accuracy and adaptability of the entire system, enabling it to cope with complex geological and hydrological conditions. In the seepage field change analysis module, the effective saturation of the soil is calculated in real time through the state judgment unit, and the system can accurately distinguish the saturation state of the soil at different positions. The calculation result of effective saturation is between 0 and 1, reflecting the saturation degree of the soil and helping to determine whether the soil has reached a fully saturated state. The judgment accuracy lays the foundation for the analysis of seepage performance, especially in the permeability analysis of unsaturated soil, which significantly improves the accuracy of the system. The permeability performance analysis unit analyzes the permeability of each soil layer according to the saturation state of the soil and the physical properties of the water body, so as to effectively identify the differences in the permeability characteristics of the foundation pit wall soil. This refined analysis enables the system to understand in real time the resistance of different soil layers to water flow during the foundation pit dewatering process, especially to make layered judgments between high-permeability and low-permeability soil layers, thereby improving the accuracy of seepage analysis. At the same time, layered monitoring helps construction personnel to timely understand the changes in water flow on the high-precision seepage field map, effectively preventing soil instability caused by seepage.

[0072] Example 3

[0073] Please refer to Figure 1 Specifically: 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 obtained specifically in the following manner: ;

[0074] 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 constants, and It reflects the permeability characteristics of the soil. Different soil types have different parameter values. Many studies have given empirical parameter values ​​for common soil types, which can be obtained directly by referring to the soil parameter table.

[0075] Among them, the saturated permeability coefficient Obtained through: ;

[0076] 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;

[0077] The diameter of 10% of the particles in the soil It is an important characteristic value of particle size distribution and can be obtained by laser particle size analysis;

[0078] Weight of water is a known physical constant. Under normal circumstances, its value is 9.81 kN / m³ (or 9800 N / m³).

[0079] Porosity The porosity is calculated by combining the volume and dry weight of the soil sample with the density of the soil particles;

[0080] Viscosity of water The acquisition is monitored by a rotational viscometer;

[0081] 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 value, showing the permeability changes at various depths in the foundation pit, so as to divide the soil in the foundation pit into different layers. The higher the permeability coefficient, the smaller the resistance of the soil to water flow;

[0082] Among them, the soil in the foundation pit is divided into different layers of soil, which specifically involves high permeability soil layers (such as sand layers and gravel layers), medium permeability layers (such as silt layers) and low permeability layers (such as clay layers). The permeability coefficient of high permeability soil layers is generally arrive m / s, the water flow is strong and seepage is likely to occur; the permeability of the medium permeability layer is generally m / s, which has a certain hindering effect on water flow; the permeability coefficient of the low permeability layer is generally less than m / s, water flow is difficult to pass through and it has good water-blocking properties.

[0083] In this embodiment, the permeability analysis unit in the system combines the saturation state judgment result of the state judgment unit, and based on the relevant water state data information of the soil, dynamically analyzes the permeability at different positions around the foundation pit, obtains the permeability coefficient of each point, and when the soil reaches a fully saturated state, the saturated permeability coefficient calculation formula is used, combined with the calculation of effective saturation and particle parameters, to improve the accuracy of the permeability evaluation and provide a scientific basis for the foundation pit dewatering plan. Especially in heterogeneous soil, the particle characteristics of the soil are taken into account to effectively improve the reliability of the permeability coefficient evaluation. The judgment result of the effective saturation helps the system distinguish between the saturated and unsaturated states of the soil. Through the permeability distribution map, the system can accurately divide the different soil layers in the foundation pit, identify the high permeability and low permeability soil layers, and provide fine soil layer data support for the formulation of the dewatering plan. 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.

[0084] Example 4

[0085] Please refer to Figure 1 Specifically: the seepage distribution unit is used to obtain the permeability coefficient Stxs and 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: ;

[0086] In the formula, Expressed as a water capacity function, it is the water content It is used to describe the water storage characteristics of soil at different water contents. The water capacity function reflects the dynamic change ability of water in the soil. The unit is usually ; is the initial water head, indicating the height of the water level in meters. It is the key variable of the seepage field, usually expressed as the sum of the position head and the pressure head; It is represented as the monitoring period, is the partial derivative of the initial hydraulic head with respect to time t, which indicates the rate of change of hydraulic head with time, in m / s. This item describes the change of hydraulic head with time at a specific location; is the gradient operator, which indicates the change in the spatial direction. For the water head, Reflects the spatial gradient of water head, that is, the change of water head in space; It is expressed as the permeability coefficient under the corresponding saturated state, where when the soil at the corresponding position reaches a fully saturated state, is the permeability coefficient Stxs. When the soil at the corresponding position is not fully saturated, Saturated permeability coefficient ; is the source-sink term, in m / s, which indicates the increase or decrease of water in the soil, for example, in the case of precipitation, groundwater extraction, etc. Can be used to indicate an increase or decrease in the amount of water; It is expressed as the divergence of the seepage flow, with the unit of m / s. This item describes the change of water flow per unit volume and reflects the distribution and change of the seepage flow in the soil. Expressed as water flux, it 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 and rock formations). In layman's terms, 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.

[0087] The above-mentioned water head is monitored and obtained by a pore water pressure sensor;

[0088] 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.

[0089] Example 5

[0090] 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;

[0091] 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: ;

[0092] In the formula, represents the total stress, represents the pore water pressure;

[0093] Among them, the pore water pressure Ksy is obtained by the following formula: ;

[0094] In the formula, represents the water density, represents the acceleration due to gravity;

[0095] Among them, the total stress Obtained by the following formula: ;

[0096] In the formula, represents the density of the corresponding soil layer, represents the depth of the corresponding soil layer, Represents externally applied loads, such as pressure from mechanical equipment.

[0097] Density of the corresponding soil layer It can be monitored and obtained through a nuclear density meter;

[0098] Depth of corresponding soil layer It can be monitored and obtained through geological profiler;

[0099] Externally applied loads It can be monitored and obtained through load sensors;

[0100] 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: ;

[0101] In the formula, Expressed as the effective stress increase of the jth layer, is the stress transfer coefficient between adjacent layers, indicating the influence of the upper soil layer on the additional stress of the lower soil layer; 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, i and j are soil layer numbers, where the jth layer is the lower layer of the ith layer;

[0102] 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. This increase reflects the increase in effective stress caused by the decrease in pore water pressure due to precipitation or water level drop.

[0103] The increase in effective stress will lead to compression and settlement of the soil. When the external load increases or the groundwater level drops, the net stress between soil particles increases, causing further compression and settlement of the soil. This is a common scenario for settlement calculations.

[0104] Compression modulus of each layer It can be monitored and obtained through a triaxial testing machine;

[0105] Among them, the stress transfer coefficient between adjacent layers is Obtained through: ;

[0106] In the formula, Denotes the depth of the i-th layer, Denotes the depth of the jth layer, Expressed as the compression modulus of the jth layer, Denoted as the compression modulus of the i-th layer.

[0107] 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.

[0108] In this embodiment, the system calculates the effective stress of each period based on the temporal and spatial distribution of water head through the pressure analysis unit. The unit uses the formula of total stress and pore water pressure to calculate the effective stress, thereby accurately reflecting the stress changes of the foundation pit soil during the precipitation process. This real-time effective stress calculation can identify the stress anomalies or stress concentration areas that may occur in the soil during the precipitation process, and provide 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 true, and can accurately reflect the stress conditions of different soil layers, avoiding the settlement calculation deviation caused by the total stress estimation error. The interlayer stress transfer unit uses the interlayer stress transfer coefficient to analyze the additional stress influence of the upper soil layer on the lower soil layer. The coefficient is obtained by the comprehensive calculation of the soil layer thickness and the compression modulus, and can accurately reflect the stress transfer between soil layers. The analysis of interlayer stress transfer can identify possible stress concentration and settlement differences, provide scientific support for preventing the instability of the foundation pit, and avoid the misjudgment of the overall settlement assessment by the stress change of a single layer. The system obtains the settlement of each layer through the interlayer stress transfer unit, and uses the compression modulus and effective stress increase to perform high-precision calculations, so that the settlement of each layer of soil during precipitation can be dynamically tracked and accurately quantified.

[0109] Example 6

[0110] Please refer to Figure 1 Specifically: the comprehensive evaluation module is used to use the trained foundation pit structure prediction model, and after linear normalization, map the corresponding data values ​​to the interval The instability index Jszs of the foundation pit structure when the precipitation falls to the corresponding soil layer is fitted and output: ;

[0111] 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.

[0112] Lateral displacement It can be monitored and acquired through an inclinometer or a laser displacement sensor;

[0113] 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:

[0114] 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 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 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 precipitation speed will be stopped. If necessary, precipitation can also be temporarily stopped to observe the changes in the stability of the foundation pit, and the shear strength and deformation resistance of the foundation pit can be improved by strengthening the foundation pit support structure, reducing lateral displacement, increasing the number of anchor rods around the foundation pit or increasing the depth and thickness of the support piles to improve the bearing capacity and compressive resistance of the soil and reduce settlement and lateral displacement;

[0115] If the foundation pit structure instability index Jszs does not exceed the assessment 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 to gradually lower the groundwater level and ensure a dry construction environment.

[0116] In this embodiment, the comprehensive evaluation module outputs the instability index Jszs of the foundation pit structure. The instability index maps each monitoring data to a unified interval, comprehensively considers various influencing factors, and makes the stability state of the foundation pit quantifiable. This quantification process helps operators have an intuitive and scientific basis for evaluating the safety state of the foundation pit. The safety feedback module compares the instability index generated in real time with the preset evaluation threshold to determine 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 analysis ensures that the monitoring system can respond to possible instability during the precipitation process in a timely manner, thereby improving the safety of the foundation pit precipitation construction process. When the instability index exceeds the evaluation threshold, the system will intelligently adjust the pumping frequency and precipitation speed of the precipitation well, gradually reduce the precipitation rate to reduce the rate of water level drop, thereby reducing the risk of settlement and lateral displacement caused by the sudden drop in pore water pressure. While adjusting the precipitation speed, the system continuously monitors the instability index. If the index does not exceed the evaluation threshold, the regulation is stopped. Intelligent precipitation speed control ensures the stability of the foundation pit precipitation process and avoids the instability of the foundation pit structure caused by excessive precipitation. In short, the system uses the instability index Jszs and intelligent feedback mechanism to realize real-time stability evaluation and control during the foundation pit precipitation process. Through the quantitative instability index Jszs and flexible precipitation speed control, coupled with reinforcement support and visual feedback, the system can accurately and dynamically control the precipitation stability of the foundation pit, further reduce the risks caused by instability, and provide strong guarantees for the safe construction of the foundation pit project.

[0117] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that 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 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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