A method and system for evaluating the safety of a goaf tunnel lining structure under heavy rainfall

Abstract

The application provides a kind of gob tunnel lining structure safety evaluation method and system under heavy rainfall, relate to underground and tunnel engineering technical field, the application is by obtaining rainfall intensity, rainfall duration, geological characteristics and soil permeability etc. Data, to generate tunnel evaluation index, analyze the interaction of rainfall water on lining water pressure and surrounding soil deformation, and calculate the stress of surrounding rock, by calculating the water pressure generated after rainfall infiltration, quantifying its dynamic influence on lining water pressure, then comprehensive tunnel evaluation index, stress of surrounding rock and water pressure after infiltration, calculate the safety factor of lining structure, obtain lining displacement, crack development speed and water flow infiltration data, generate risk coefficient, and compare with safety factor, judge whether to issue early warning. The application establishes tunnel safety evaluation and early warning mechanism by comprehensive analysis of the related data of tunnel lining, ensures the safety of gob tunnel lining structure under heavy rainfall.

Description

Technical Field

[0001] This invention relates to the field of underground and tunnel engineering technology, specifically to a method and system for evaluating the safety of tunnel lining structures in mining subsidence areas under heavy rainfall. Background Technology

[0002] With the rapid development of transportation infrastructure in my country, a large number of extra-long highway (railway) tunnels will be constructed, inevitably traversing or already traversing coal mines, metal or non-metal mines, and other areas with mining subsidence. Shanxi Province, in particular, is a major coal-producing province with unique geological conditions. Long-term exploitation and utilization of natural resources have resulted in numerous mining subsidence areas. During tunnel construction and operation, extreme weather events, such as heavy rainfall, frequently occur. Under conditions of heavy rainfall infiltration, the stability of the tunnel's surrounding rock and support structure becomes extremely fragile. The existence of mining subsidence areas further complicates the tunnel's seepage field, posing significant challenges to tunnel construction and subsequent operational safety.

[0003] In the prior art, CN116070322B discloses a method for evaluating the safety of karst tunnel lining structures under heavy rainfall. This method establishes a circumferential action range matrix of tunnel water pressure based on the tunnel structure type and design parameters, establishes a load-structure model of the tunnel lining structure and surrounding rock, determines the circumferential range with the smallest safety factor in the tunnel circumferential range matrix, compares the stress state under different water pressure modes based on the measured water inflow and lining water pressure values, calculates the safety factor under the most unfavorable state, and thus judges the safety of karst tunnel lining structures under heavy rainfall conditions.

[0004] Insufficiency of existing technology:

[0005] First, karst tunnels typically exist in soluble rock formations such as carbonate rocks. These rocks, under the long-term erosion of water flow, form complex underground channels and cavities. The path and properties of groundwater flow are highly influenced by geological structure and hydrological conditions. Furthermore, since the physical properties of karst bodies and water flow paths may change with geological variations, models based on fixed parameters may not accurately reflect actual water pressure and flow conditions. In contrast, the goaf tunnels in this invention are usually related to mining or engineering construction. The stability of the surrounding rock mass and water flow characteristics are more influenced by human factors such as mining activities and subsequent backfilling. The existence of cavities and the redistribution of stress in the surrounding rock mass may lead to abnormal changes in water flow. This necessitates that the water pressure model consider more dynamic and nonlinear factors.

[0006] Existing technologies primarily rely on tunnel structural types and design parameters to establish the circumferential water pressure range matrix, which leads to model limitations. Specifically, parameter selection and model construction are often based on assumptions and simplifications, relying mainly on the selection of model parameters and structural types. These parameters are largely based on historical data and assumptions, failing to fully consider the complexity and dynamic changes of actual geological conditions. The physical properties of karst bodies can vary significantly due to geological changes, making models based on fixed parameters potentially inaccurate in reflecting actual conditions. Furthermore, changes in water flow and pressure caused by heavy rainfall are highly random and time-varying. Existing methods lack dynamic monitoring and real-time analysis mechanisms, making it difficult to update model parameters in a timely manner to cope with sudden hydrological changes.

[0007] Secondly, existing technologies for safety evaluation mainly focus on comparing the stress state under different water pressure modes and calculating the safety factor under the most unfavorable condition. This single evaluation method may not be sufficient to comprehensively reflect the actual safety of the tunnel lining structure. Under complex heavy rainfall conditions, the stress state of the tunnel is not only affected by water pressure, but may also be affected by other factors such as soil stress, structural deformation, and construction quality. Relying solely on water pressure values ​​to evaluate the safety of the lining structure may ignore the influence of multiple load interactions, thus leading to the safety factor calculation results not accurately reflecting the tunnel's safety status.

[0008] Therefore, it is necessary to provide a method and system for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall to solve the aforementioned problem.

[0009] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0010] The purpose of this invention is to provide a method and system for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, so as to solve the problems mentioned in the background art.

[0011] To achieve the above objectives, the present invention provides the following technical solution:

[0012] A method for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, comprising the following steps:

[0013] Step 1: Obtain the rainfall and duration of rainfall in the mining subsidence tunnel over seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors;

[0014] Step 2: Calculate the surrounding rock stress of the tunnel in the goaf;

[0015] Step 3: Calculate the water pressure generated by rainfall infiltration in the goaf area and quantify the water pressure.

[0016] Step 4: Calculate the safety factor of the lining structure by taking into account the tunnel evaluation index, the surrounding rock stress of the tunnel in the goaf, and the water pressure generated after rainfall infiltration.

[0017] Step 5: Establish a monitoring and early warning mechanism, obtain relevant monitoring data, including lining structure displacement, crack development rate and water seepage data, generate a risk coefficient using the monitoring data and compare it with the safety coefficient. If the risk coefficient is greater than the safety coefficient, an early warning will be issued.

[0018] Furthermore, the method for generating the tunnel evaluation index is as follows:

[0019] Based on the principle of permeability analysis, and considering the effects of rainfall, geological conditions, and soil permeability, rainfall intensity and duration directly affect seepage pressure and soil saturation. Specifically, this manifests as changes in rainfall infiltration in tunnels within mining subsidence areas. The formula for calculating rainfall infiltration is as follows:

[0020]

[0021] Among them, Q rain The rainfall infiltration rate of the tunnel in the goaf area is represented by I, which is the rainfall amount, T is the duration of rainfall, A is the area affected by the tunnel in the goaf area, and C8 is the geological characteristic coefficient, with a value range of [0.5, 1.5].

[0022] The formula for calculating the permeability coefficient is:

[0023]

[0024] Where K is the permeability coefficient, L is the flow path length, S is the cross-sectional area of ​​the seepage, and Δh is the head difference;

[0025] The tunnel evaluation index is calculated based on the above formula. This index is used to comprehensively assess the tunnel's hydrogeological conditions and their impact on the stability of the tunnel lining structure and water seepage. The formula used is as follows:

[0026]

[0027] GEC stands for Tunnel Evaluation Index.

[0028] Furthermore, the method used to calculate the surrounding rock stress of the tunnel in the goaf is as follows:

[0029] The surrounding rock stress in a goaf tunnel consists of additional stress and effective stress. Additional stress exists because pore water cannot quickly drain from the pores during tunnel excavation, causing it to accumulate and generate pressure. This pore water pressure exerts an additional force on the surrounding rock, forming additional stress. Effective stress depends on the soil's elastic modulus. When external loads are applied to the soil, it deforms. The elastic modulus controls the soil's deformation stiffness; the larger the elastic modulus, the smaller the deformation; conversely, the smaller the elastic modulus, the larger the deformation. The formulas for calculating additional stress, effective stress, and surrounding rock stress are:

[0030] σ p =ρ w *g*h

[0031] σ eff =∈E

[0032] σ all =σ p +σ eff

[0033] Where, σ p ρ represents the additional pressure caused by pore water pressure. w Let ρ be the density of pore water, g be the acceleration due to gravity, h be the hydraulic head, ∈ represent the strain of the soil, and σ be the density of pore water. eff It is the effective stress, σ all E is the surrounding rock stress of the tunnel in the goaf area, and E is the elastic modulus of the soil.

[0034] Furthermore, the water pressure generated by rainfall infiltration in the goaf was calculated and quantified using the following method:

[0035] Based on the pore water pressure calculation in step 3, considering that the water head changes gradually over time after rainfall infiltrates into the goaf, and that the infiltrated water gradually increases the water pressure on the lining surface, the dynamic impact of rainfall is reflected in the duration of water infiltration and the gradual accumulation of water pressure. The longer the rainfall duration, the greater the infiltrated water pressure. The specific water pressure change is simulated by the change in water head over time, and the relevant linear equations for rainfall infiltration are established. The following dynamic water pressure change formula is used:

[0036]

[0037] F(t)=ρgh(t)

[0038] Where F(t) represents the dynamic water pressure changing over time, ρ is the infiltration water density, h(t) is the hydraulic head changing over time, Δh is the head difference, and T is the duration of rainfall. Let t be the rate of change of water head, and t be a point in time during the rainfall process;

[0039] The dynamic water pressure is quantified, from the initial moment of rainfall infiltration to the end moment, i.e., the cumulative effect of water pressure over time. The integral formula for calculating the quantified water pressure is as follows:

[0040]

[0041] Among them, F N It is the water pressure after quantification.

[0042] Furthermore, the safety factor of the lining structure is calculated, taking into account water pressure, soil pressure, and surrounding rock deformation factors, to assess the bearing capacity and stability of the lining structure. The method used is as follows:

[0043] The formula for calculating the safety factor of the lining structure is:

[0044]

[0045] Where SF is the safety factor, GEC is the tunnel evaluation index, and σ all It is the surrounding rock stress, F N It is the water pressure after quantification.

[0046] Furthermore, relevant monitoring data, including lining structure displacement, crack propagation rate, and water seepage data, were obtained using the following methods:

[0047] Lining deformation is a key indicator for assessing the stability of tunnel linings. It is necessary to monitor the displacement, strain, and bending degree of the lining, and to calculate it using the displacement calculation formula and Hooke's law in elasticity.

[0048]

[0049] Where Δu represents the displacement of the lining structure, P is the load applied to the lining, and L c E is the length of the lining. c I represents the elastic modulus of the lining material. c The moment of inertia of the lining;

[0050] Crack propagation rate is an important parameter reflecting the long-term stability of tunnel lining structures. The crack propagation rate is obtained by acquiring the crack lengths before and after rainfall using the following method:

[0051]

[0052] Among them, V c l represents the crack propagation rate. c The length of the crack before rainfall, l z The length of the crack after rainfall is represented by T, where T is the duration of the rainfall.

[0053] The flow rate of water seepage is determined by the permeability coefficient and the head difference. According to Darcy's law, water seepage is calculated using the following formula:

[0054]

[0055] Where Q represents water permeability, K is the permeability coefficient, A is the cross-sectional area through which the water flows, Δh is the head difference, i.e., the water level difference between the two sections of the flow, and L... q This indicates the path length of the water flow.

[0056] Furthermore, a risk coefficient is generated using monitoring data and compared with a safety coefficient. If the risk coefficient is greater than the safety coefficient, an early warning is issued. The method used is as follows:

[0057]

[0058] Where R represents the risk coefficient, ω1, ω2, and ω3 represent their respective proportional weights, and ω1>ω2>ω3>0, U allow V allow Q allow These represent the maximum allowable displacement, maximum crack propagation rate, and maximum water seepage, respectively. M represents the logical value used to determine whether the relevant design parameters of the tunnel lining need to be adjusted. When M = 0, it means that the risk factor has not exceeded the safety factor and no adjustment of the design parameters is required. When M = 1, it means that the risk factor has exceeded the safety factor and the design parameters need to be adjusted. SF is the safety factor.

[0059] This invention also provides a safety evaluation system for tunnel lining structures in goaf areas under heavy rainfall. The safety evaluation system is used to perform the aforementioned method for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, including:

[0060] The rainfall and geological characteristics assessment module is used to obtain the rainfall and duration of rainfall in the mining subsidence tunnel within seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors.

[0061] A water pressure and soil deformation analysis module is used to calculate the surrounding rock stress of tunnels in goaf areas.

[0062] A dynamic water pressure calculation module is used to calculate the water pressure generated after rainfall infiltration in the goaf area and to quantify the water pressure.

[0063] The safety factor comprehensive calculation module is used to calculate the safety factor of the lining structure by comprehensively considering the tunnel evaluation index, the surrounding rock stress of the tunnel in the goaf area, and the water pressure generated after rainfall infiltration.

[0064] The monitoring and early warning mechanism module is used to establish a monitoring and early warning mechanism, acquire relevant monitoring data, including lining structure displacement, crack development rate and water seepage data, generate a risk coefficient using the monitoring data and compare it with a safety coefficient. If the risk coefficient is greater than the safety coefficient, an early warning is issued.

[0065] Compared with the prior art, the beneficial effects of the present invention are:

[0066] First, this invention establishes a systematic tunnel evaluation index by comprehensively considering rainfall intensity, duration, geological characteristics, and soil permeability. This multi-parameter evaluation system can more comprehensively reflect the hydrogeological conditions of tunnels in mining subsidence areas under heavy rainfall conditions, thereby improving the accuracy of the assessment of lining structure stability. Furthermore, through dynamic water pressure calculation and surrounding rock stress analysis, it can promptly identify water pressure changes caused by rainfall and their impact on the lining structure, thus providing a scientific basis for decision-making and ensuring tunnel safety.

[0067] Secondly, this invention significantly improves the real-time performance and responsiveness of safety assessments by introducing a dynamic monitoring and early warning mechanism. Previous technologies often relied on static analysis based on theoretical models, making it difficult to quickly reflect sudden hydrological changes. In contrast, this invention, in its monitoring and early warning mechanism module, acquires real-time data on lining displacement, crack development rate, and water seepage. By generating a risk coefficient and comparing it with a safety coefficient, it ensures timely warnings when the risk level exceeds the safe range. This dynamic assessment not only enhances the tunnel's adaptability to complex geological conditions but also effectively reduces potential safety hazards, providing strong protection for the safe operation of the tunnel.

[0068] This invention comprehensively considers rainfall intensity, duration, geological characteristics, and soil permeability, and introduces a dynamic monitoring and early warning mechanism to achieve real-time assessment and effective early warning of the safety of tunnel lining structures in mining areas under heavy rainfall, thereby improving the safety and stability of tunnels. Attached Figure Description

[0069] Figure 1 This is a schematic diagram of the overall method flow of the present invention.

[0070] Figure 2 This is a schematic diagram of the system module flow of the present invention. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0072] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0073] Example:

[0074] Please see Figure 1 A method for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, comprising the following steps:

[0075] Step 1: Obtain the rainfall and duration of rainfall in the mining subsidence tunnel over seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors;

[0076] Step 2: Calculate the surrounding rock stress of the tunnel in the goaf;

[0077] Step 3: Calculate the water pressure generated by rainfall infiltration in the goaf area and quantify the water pressure.

[0078] Step 4: Calculate the safety factor of the lining structure by taking into account the tunnel evaluation index, the surrounding rock stress of the tunnel in the goaf, and the water pressure generated after rainfall infiltration.

[0079] Step 5: Establish a monitoring and early warning mechanism, obtain relevant monitoring data, including lining structure displacement, crack development rate and water seepage data, generate a risk coefficient using the monitoring data and compare it with the safety coefficient. If the risk coefficient is greater than the safety coefficient, an early warning will be issued.

[0080] It should be noted that by acquiring rainfall intensity, duration, geological characteristics, and soil permeability factors for tunnels in goaf areas, a tunnel evaluation index can be scientifically generated, thereby comprehensively assessing the hydrogeological conditions of the tunnel under heavy rainfall conditions. This evaluation index not only reflects the direct impact of rainfall on the stability of the tunnel lining structure but also considers changes in seepage pressure and soil saturation, ensuring accurate identification of potential safety risks under complex geological conditions. This setting provides fundamental data for subsequent water pressure calculations, surrounding rock stress analysis, and safety assessments, thus providing a scientific basis for engineering decisions and risk management.

[0081] Therefore, the method for generating the tunnel evaluation index is as follows:

[0082] Based on the principle of permeability analysis, and considering the effects of rainfall, geological conditions, and soil permeability, rainfall intensity and duration directly affect seepage pressure and soil saturation. Specifically, this manifests as changes in rainfall infiltration in tunnels within mining subsidence areas. The formula for calculating rainfall infiltration is as follows:

[0083]

[0084] Among them, Q rain The formula represents the rainfall infiltration rate in tunnels located in goaf areas. I represents the rainfall amount, T represents the duration of rainfall, A represents the area affected by the tunnel (the area through which rainwater flows when it infiltrates), and C8 is a geological characteristic coefficient with a value range of [0.5, 1.5]. In this formula, the greater the rainfall amount, the longer the duration of rainfall, and the larger the affected area, the greater the rainfall infiltration rate. The value of C8 depends on the geological characteristics. A larger C8 value indicates that the geology is relatively hard and difficult for rainwater to infiltrate, resulting in a smaller rainfall infiltration rate; conversely, a smaller C8 value indicates that the geology is relatively soft and easily infiltrated by rainwater, resulting in a larger rainfall amount.

[0085] The formula for calculating the permeability coefficient is:

[0086]

[0087] Where K is the permeability coefficient, L is the flow path length, S is the cross-sectional area of ​​the seepage, and Δh is the head difference, which refers to the difference between the initial position of the seepage flow and the position of the flow when the seepage process is completed. In the above formula, as the rainfall infiltration amount increases, the path of the infiltrated rainwater increases, which leads to a larger permeability coefficient. Increasing the cross-sectional area helps to disperse the water flow, thereby reducing the water flow per unit area, which leads to a smaller permeability coefficient. As the head difference increases, the driving force of the flow increases. The seepage needs to overcome the driving force generated, so the seepage becomes slower and the permeability coefficient becomes smaller.

[0088] The tunnel evaluation index is calculated based on the above formula. This index is used to comprehensively assess the tunnel's hydrogeological conditions and their impact on the stability of the tunnel lining structure and water seepage. The formula used is as follows:

[0089]

[0090] GEC stands for Tunnel Evaluation Index. In the formula above, increasing rainfall infiltration directly increases the tunnel evaluation index, indicating that under conditions of heavy rainfall, the water infiltration rate in the tunnel increases, potentially affecting structural stability. An increase in the permeability coefficient also leads to an increase in the tunnel evaluation index, indicating enhanced soil permeability and faster water flow, which may put greater pressure on the stability of the lining structure. A higher GEC indicates that under specific rainfall conditions, the rainwater infiltrates the soil more rapidly, demonstrating strong soil permeability. This may indicate a threat to the stability of the tunnel lining, especially under conditions of heavy rainfall and high permeability. If the GEC value is significantly higher than normal, it may suggest the need for further monitoring and maintenance to prevent water damage to the structure. Conversely, a lower GEC value indicates lower rainfall infiltration and infiltration rate, or poorer soil permeability. This suggests that the tunnel has favorable hydrogeological conditions, with less impact from water flow on the lining structure, generally indicating better tunnel quality and lower risk.

[0091] It is important to note that calculating the surrounding rock stress in tunnels located in goaf areas allows for a deeper understanding of the impact of rainfall on tunnel stability, particularly the stress state of the surrounding rock under varying hydrological conditions. The calculation of surrounding rock stress not only considers the additional stress caused by pore water pressure but also incorporates the soil's elastic modulus to assess the impact of effective stress on the surrounding soil. This process is crucial for identifying potential safety hazards, as the stress state of the surrounding rock directly relates to the tunnel's structural safety and long-term stability.

[0092] Therefore, it is necessary to calculate the surrounding rock stress of tunnels in goaf areas, and the method used is as follows:

[0093] The surrounding rock stress in a goaf tunnel consists of additional stress and effective stress. Additional stress exists because pore water cannot quickly drain from the pores during tunnel excavation, causing it to accumulate and generate pressure. This pore water pressure exerts an additional force on the surrounding rock, forming additional stress. Effective stress depends on the soil's elastic modulus. When external loads are applied to the soil, it deforms. The elastic modulus controls the soil's deformation stiffness; the larger the elastic modulus, the smaller the deformation; conversely, the smaller the elastic modulus, the larger the deformation. The formulas for calculating additional stress, effective stress, and surrounding rock stress are:

[0094] σ p =ρ w *g*h

[0095] σ eff =∈E

[0096] σ all =σ p +σ eff

[0097] Where, σ p ρ represents the additional pressure caused by pore water pressure. w Let ρ be the density of pore water, g be the acceleration due to gravity, h be the hydraulic head, ∈ represent the strain of the soil, and σ be the density of pore water. eff It is the effective stress, σ all E is the surrounding rock stress of the tunnel in the goaf area, and E is the elastic modulus of the soil.

[0098] It should be noted that calculating the water pressure generated after rainfall infiltration allows for a deeper understanding of the dynamic impact of rainfall on tunnel lining, especially the gradual accumulation effect of water pressure due to changes in water head over time. Quantifying water pressure using dynamic water pressure change formulas and the mean-integral method enables accurate assessment of water pressure intensity under different rainfall conditions, providing a scientific basis for engineering design, construction, and maintenance. This, in turn, improves the tunnel's impermeability, prevents potential safety hazards, and ensures its long-term safe operation.

[0099] Therefore, it is necessary to calculate and quantify the water pressure generated by rainfall infiltration in the goaf area. The method used is as follows:

[0100] Based on the pore water pressure calculation in step 3, considering that the water head changes gradually over time after rainfall infiltrates into the goaf, and that the infiltrated water gradually increases the water pressure on the lining surface, the dynamic impact of rainfall is reflected in the duration of water infiltration and the gradual accumulation of water pressure. The longer the rainfall duration, the greater the infiltrated water pressure. The specific water pressure change is simulated by the change in water head over time, and the relevant linear equations for rainfall infiltration are established. The following dynamic water pressure change formula is used:

[0101]

[0102] F(t)=ρgh(t)

[0103] Where F(t) represents the dynamic water pressure changing over time, ρ is the infiltration water density, h(t) is the hydraulic head changing over time, Δh is the head difference, and T is the duration of rainfall. Let t be the rate of change of water head, and t be a point in time during the rainfall process;

[0104] The dynamic water pressure is quantified, from the initial moment of rainfall infiltration to the end moment, i.e., the cumulative effect of water pressure over time. The integral formula for calculating the quantified water pressure is as follows:

[0105]

[0106] Among them, F N This is the quantified water pressure; the integral formula above represents the accumulation of water pressure at each moment during rainfall, calculating the total water pressure applied to the lining throughout the entire rainfall period. This accumulation takes into account the change of water pressure over time, reflecting the dynamic impact of rainfall on water pressure. This represents the rate of change of water head, which is the average rate of change of water head over the duration of rainfall. This term emphasizes the impact of rainfall duration on water head change; the longer the duration, the greater the average water head change.

[0107] It should be noted that by comprehensively considering factors such as water pressure, soil pressure, and surrounding rock deformation, the bearing capacity and stability of the tunnel can be fully assessed. Furthermore, by quantifying the water pressure, surrounding rock stress, and tunnel evaluation index caused by rainfall, and by calculating the safety factor using the geological evaluation equation, an objective safety margin indicator can be provided.

[0108] Therefore, it is necessary to calculate the safety factor of the lining structure, comprehensively consider water pressure, soil pressure, and surrounding rock deformation factors, and evaluate the bearing capacity and stability of the lining structure. The method used is as follows:

[0109] The formula for calculating the safety factor of the lining structure is:

[0110]

[0111] Where SF is the safety factor, GEC is the tunnel evaluation index, and σ all It is the surrounding rock stress, F N This is the quantified water pressure. In the above formula, the numerator of the geological evaluation equation represents the bearing capacity of the geological engineering, indicating the maximum load that the lining structure can withstand in a specific environment, such as a goaf or heavy rainfall. The denominator is the product of the surrounding rock stress and the quantified water pressure, representing the product of stress loads, that is, the stress intensity borne by the lining structure under normal load, specifically σ. all This describes the magnitude of the stress inside the lining structure, F. NThe SF value represents the normal load applied to the structure. Greater surrounding rock stress and water pressure indicate greater pressure exerted by the soil or rock on the lining. Higher water pressure means stronger effects of water infiltration and buoyancy on the structure. These two factors put pressure on the load-bearing capacity of the lining structure, increasing its burden. A high SF value indicates that the maximum load the lining structure can withstand is greater than or equal to the actual stress load, meaning the structure is relatively safe and has good stability under current conditions. Conversely, a low SF value indicates that the lining structure's load-bearing capacity is insufficient to cope with the actual stress load, potentially leading to structural instability or damage, especially under heavy rainfall or other extreme conditions.

[0112] It should be noted that monitoring lining deformation uses Hooke's Law to calculate displacement, which can identify potential structural problems; while crack development rate reflects the performance changes of the lining under long-term load, which can detect and respond to the risk of crack expansion in a timely manner; monitoring water infiltration assesses water flow through Darcy's Law, which helps to understand the impact of water pressure on the lining and prevent soil liquefaction or structural instability caused by water intrusion.

[0113] Therefore, it is necessary to obtain relevant monitoring data, including lining structure displacement, crack propagation rate, and water seepage data. The method used is as follows:

[0114] Lining deformation is a key indicator for assessing the stability of tunnel linings. It is necessary to monitor the displacement, strain, and bending degree of the lining, and to calculate it using the displacement calculation formula and Hooke's law in elasticity.

[0115]

[0116] Where Δu represents the displacement of the lining structure, P is the load applied to the lining, and L c E is the length of the lining. c I represents the elastic modulus of the lining material. c The moment of inertia of the lining;

[0117] Crack propagation rate is an important parameter reflecting the long-term stability of tunnel lining structures. The crack propagation rate is obtained by acquiring the crack lengths before and after rainfall using the following method:

[0118]

[0119] Among them, V c l represents the crack propagation rate. c The length of the crack before rainfall, l z The length of the crack after rainfall is represented by T, where T is the duration of the rainfall.

[0120] The flow rate of water seepage is determined by the permeability coefficient and the head difference. According to Darcy's law, water seepage is calculated using the following formula:

[0121]

[0122] Where Q represents water permeability, K is the permeability coefficient, A is the cross-sectional area through which the water flows, Δh is the head difference, i.e., the water level difference between the two sections of the flow, and L... q This indicates the path length of the water flow.

[0123] It should be noted that the risk coefficient comprehensively considers key parameters such as lining displacement, crack propagation rate, and water seepage. By assigning different weights, it can more accurately reflect the impact of each factor on the safety of the lining. When the risk coefficient is greater than the safety coefficient, it means that there may be potential risks in the current structural state. At this time, it is necessary to issue an early warning so that appropriate measures can be taken in a timely manner to intervene or adjust the design parameters, thereby preventing accidents from occurring. Through this systematic assessment and response mechanism, the safety and stability of the tunnel can be effectively improved, ensuring its reliable operation under various working conditions, thereby protecting the safety of personnel and property.

[0124] Therefore, it is necessary to generate a risk coefficient using monitoring data and compare it with a safety coefficient. If the risk coefficient is greater than the safety coefficient, an early warning is issued. The method used is as follows:

[0125]

[0126] Where R represents the risk coefficient, ω1, ω2, and ω3 represent their respective proportional weights, and ω1>ω2>ω3>0, U allow V allow Q allow, representing the maximum allowable displacement, maximum crack propagation rate, and maximum water seepage, respectively. M represents the logical value used to determine whether the relevant design parameters of the tunnel lining need adjustment. When M = 0, it indicates that the risk factor has not exceeded the safety factor, and no adjustment to the design parameters is required; when M = 1, it indicates that the risk factor exceeds the safety factor, and the design parameters need adjustment. SF is the safety factor. In the above formula, the proportional weights are set to ω1 > ω2 > ω3 > 0 because lining displacement is a direct indicator for assessing the stability of the tunnel lining. Excessive displacement is usually a precursor to structural instability and may lead to serious safety hazards. Therefore, the contribution weight ω1 of displacement to the risk factor should be the largest. Crack propagation rate is another key indicator, which is directly related to material fatigue and the long-term stability of the structure. Although crack development may not lead to immediate consequences... Factors leading to catastrophic consequences, but an increased rate of expansion usually implies a decline in material properties, therefore, it is assigned the second highest weight ω2; water infiltration, while equally important, usually has an indirect impact relative to displacement and crack propagation rates. Increased water pressure may accelerate soil liquefaction or have other adverse effects on the lining, but this requires time to accumulate and its effects are not direct or obvious, therefore, its weight is set to the lowest ω3; and by comparing these actual monitoring data with the corresponding allowable values, the contribution of different indicators to the overall risk can be quantified. The calculation results of each ratio reflect the relative relationship between the current monitoring status and the safety standard, and thus, in the calculation of the risk coefficient, ω1, ω2, and ω3 are comprehensively considered to form a comprehensive safety assessment; and the smaller the risk coefficient, the safer the tunnel lining structure.

[0127] Please see Figure 2 The present invention also provides a safety evaluation system for tunnel lining structures in goaf areas under heavy rainfall. This safety evaluation system is used to perform the aforementioned method for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, comprising:

[0128] The rainfall and geological characteristics assessment module is used to obtain the rainfall and duration of rainfall in the mining subsidence tunnel within seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors.

[0129] A water pressure and soil deformation analysis module is used to calculate the surrounding rock stress of tunnels in goaf areas.

[0130] A dynamic water pressure calculation module is used to calculate the water pressure generated after rainfall infiltration in the goaf area and to quantify the water pressure.

[0131] The safety factor comprehensive calculation module is used to calculate the safety factor of the lining structure by comprehensively considering the tunnel evaluation index, the surrounding rock stress of the tunnel in the goaf area, and the water pressure generated after rainfall infiltration.

[0132] The monitoring and early warning mechanism module is used to establish a monitoring and early warning mechanism, acquire relevant monitoring data, including lining structure displacement, crack development rate and water seepage data, generate a risk coefficient using the monitoring data and compare it with a safety coefficient. If the risk coefficient is greater than the safety coefficient, an early warning is issued.

[0133] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0134] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

[0135] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0136] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for evaluating the safety of a gob tunnel lining structure under heavy rainfall, characterized in that, The specific steps include: Step 1: Obtain the rainfall and rainfall duration of the goaf tunnel in the past seven days from the meteorological bureau database, and combine the geological characteristics and soil permeability factors to generate a tunnel evaluation index; Step 2: Calculate the stress of the surrounding rock of the goaf tunnel; Step 3: Calculate the water pressure generated after the rainfall permeation in the goaf, and quantitatively process the water pressure; Step 4: Calculate the safety factor of the lining structure by comprehensively considering the tunnel evaluation index, the stress of the surrounding rock of the goaf tunnel, and the water pressure generated after the rainfall permeation; Step 5: Establish a monitoring and early warning mechanism to obtain relevant monitoring data, including the displacement of the lining structure, the crack development speed, and the water flow permeation data, use the monitoring data to generate a risk coefficient, and compare it with the safety factor. If the risk coefficient is greater than the safety factor, an early warning will be issued; The method for generating the tunnel evaluation index is: Based on the principle of permeation analysis, the influence of rainfall, geological conditions, and soil permeability is considered. The rainfall intensity and the duration of rainfall directly affect the permeation pressure and the soil saturation. Specifically, the rainfall permeation quantity of the goaf tunnel changes. The formula for calculating the rainfall permeation quantity is: wherein Q rain represents the rainfall infiltration of the goaf tunnel, I is the rainfall, T is the rainfall duration, A is the goaf tunnel influence area, C8 is the geological characteristic coefficient, and the value range is [0.5, 1.5]; The formula for calculating the permeation coefficient is: Where K is the permeation coefficient, L is the flow path length, S is the cross-sectional area of the seepage, and Δh is the water head difference; The tunnel evaluation index is calculated according to the above formula, which is used to comprehensively evaluate the hydrogeological conditions of the tunnel and the influence on the stability of the tunnel lining structure and water flow permeation. The formula is: Where GEC is the tunnel evaluation index; The method for calculating the stress of the surrounding rock of the goaf tunnel is: The stress of the surrounding rock of the goaf tunnel is composed of additional stress and effective stress. The existence of additional stress is due to the fact that pore water cannot be quickly discharged from the pore during tunnel excavation. The pore water accumulates in the area, generating pressure. This pore water pressure will generate additional force on the surrounding rock, forming additional stress. The effective stress depends on the elastic modulus of the soil. When external load acts on the soil, the soil will deform. The elastic modulus controls the deformation stiffness of the soil. The larger the elastic modulus of the soil, the smaller the deformation of the soil. Conversely, the smaller the elastic modulus, the greater the deformation of the soil. The formulas for calculating additional stress, effective stress, and surrounding rock stress are: σ p = p w *g*h σ eff = ∈E σ all = σ p + σ eff where σ p represents the additional pressure caused by pore water pressure, ρ w is the density of pore water, g is the acceleration of gravity, h is the water head, ∈ represents the strain of the soil body, σ eff is the effective stress, σ all is the stress of the surrounding rock of the goaf tunnel, and E is the elastic modulus of the soil body. The method for calculating the water pressure generated after the rainfall permeation in the goaf and quantifying the water pressure is: Based on the calculation of pore water pressure in step 3, considering that the water head changes gradually over time after the rainfall permeates into the goaf, and the water pressure on the lining surface gradually increases, the dynamic influence of rainfall is reflected in the duration of water flow permeation and the gradual accumulation of water pressure. The longer the duration of rainfall, the greater the permeation water pressure. The specific water pressure change is simulated through the change of water head over time. A linear equation related to rainfall permeation is established, and the following dynamic water pressure change formula is used: F(t) = ρgh(t) where F(t) represents a dynamic water pressure that varies with time, p is a permeable water density, h(t) is a water head that varies with time, Ah is a water head difference, T is a duration of rainfall, is a water head change rate, and t is a time point during a rainfall duration; Quantitative processing of dynamic water pressure is performed from the initial time to the end time of rainfall permeation, i.e. the cumulative effect of water pressure over time. The integral formula for calculating the quantitatively processed water pressure is: wherein F N is the water pressure after quantization processing; The safety factor of the lining structure is calculated, the water pressure, the soil pressure and the surrounding rock deformation factors are comprehensively considered, the bearing capacity and the stability of the lining structure are evaluated, and the method is as follows: The formula for calculating the safety factor of the lining structure is as follows: Wherein, SF is the safety factor, GEC is the tunnel evaluation index, σ all is the stress of surrounding rock, F N is the water pressure after quantization processing; Relevant monitoring data are acquired, including the lining structure displacement, the crack development speed and the water flow permeation data, and the method is as follows: The lining deformation is a key index for evaluating whether the tunnel lining is stable, the displacement, the strain and the bending degree of the lining need to be monitored, the displacement calculation formula is used, and the Hook's law in the elastic mechanics is used for calculation: wherein Δu represents the displacement of the lining structure, P is the load applied on the lining, L c is the length of the lining, E c is the elastic modulus of the lining material, I c is the moment of inertia of the lining; The crack development speed is an important parameter for reflecting the long-term stability of the tunnel lining structure, the length of the crack before the rainfall and the length of the crack after the rainfall are acquired, and the crack development speed is obtained in the following manner: where V c is the propagation speed of the crack, l c denotes the length of the crack before the rainfall, l z denotes the length of the crack after the rainfall, and T is the duration of the rainfall; The flow of the water flow permeation is determined by the permeation coefficient and the water head difference, according to the Darcy's law, the water flow permeation is calculated by using the following formula: where Q represents the water flow permeation, K is the permeation coefficient, A is the cross-sectional area through which the water flows, Δh is the water head difference, i.e. the water level difference of two sections of the water flow, L q represents the path length of the water flow; The monitoring data are used to generate the risk coefficient, and the risk coefficient is compared with the safety factor, if the risk coefficient is greater than the safety factor, an early warning is given, and the method is as follows: Wherein, R represents a risk coefficient, ω1, ω2, ω3 respectively represent respective corresponding proportional weights, and ω1>ω2>ω3>0, U allow , V allow , Q allow respectively represent the maximum allowable displacement, the maximum crack propagation speed, the maximum water flow penetration, M represents a logical value for judging whether the design parameters of the tunnel lining need to be adjusted, when M=0, it means that the risk coefficient does not exceed the safety factor, and the design parameters do not need to be adjusted; when M=1, it means that the risk coefficient exceeds the safety factor, and the design parameters need to be adjusted, SF is the safety factor.

2. A system for evaluating the safety of a tunnel lining structure in a goaf under heavy rainfall, characterized by, The safety evaluation system is used for executing the strong rainfall tunnel lining structure safety evaluation method, and comprises the following modules: The rainfall and geological property evaluation module is used for acquiring the rainfall and the rainfall duration of the tunnel in the goaf in seven days from the meteorological bureau database, and combining the geological property and the soil permeability factor to generate a tunnel evaluation index; The water pressure and soil deformation analysis module is used for calculating the surrounding rock stress of the tunnel in the goaf; The dynamic water pressure calculation module is used for calculating the water pressure generated after the rainfall permeation in the goaf, and quantitatively processing the water pressure; The safety factor comprehensive calculation module is used for comprehensively calculating the safety factor of the lining structure by combining the tunnel evaluation index, the surrounding rock stress of the tunnel in the goaf and the water pressure generated after the rainfall permeation; The monitoring and early warning mechanism module is used for establishing a monitoring and early warning mechanism, acquiring relevant monitoring data, including the lining structure displacement, the crack development speed and the water flow permeation data, generating the risk coefficient by using the monitoring data, comparing the risk coefficient with the safety factor, and giving an early warning if the risk coefficient is greater than the safety factor.

Images