Method and system for evaluating safety of goaf tunnel lining structure under heavy rainfall

Abstract

The invention provides a goaf tunnel lining structure safety evaluation method and system under heavy rainfall, and relates to the technical field of underground and tunnel engineering.The method comprises the steps that a tunnel evaluation index is generated by obtaining rainfall intensity, rainfall duration, geological characteristics, soil permeability and other data; the method comprises the following steps: analyzing interaction of rainfall moisture on lining water pressure and surrounding soil deformation, calculating surrounding rock stress, calculating water pressure generated after rainfall permeation, quantifying dynamic influence of the water pressure on the lining water pressure, and calculating a safety coefficient of a lining structure by integrating a tunnel evaluation index, the surrounding rock stress and the water pressure after permeation. And obtaining lining displacement, crack development speed and water flow permeation data, generating a risk coefficient, comparing the risk coefficient with a safety coefficient, and judging whether to give out early warning or not. According to the method, related data of the tunnel lining are comprehensively analyzed, a tunnel safety evaluation and early warning mechanism is established, and the safety of the goaf tunnel lining structure under the heavy rainfall condition is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of underground and tunnel engineering, and in particular to a method and system for evaluating the safety of a tunnel lining structure in a goaf area under heavy rainfall. Background Art

[0002] With the rapid development of transportation construction in my country, a large number of extra-long highway (railway) tunnels will be built, which will inevitably pass through or have already passed through coal mines, metal or non-metallic mines and other goafs. Shanxi is a province with rich coal mineral resources, and its geological conditions are special. During the long-term exploitation and utilization of natural resources, a large number of goafs have been formed. During the construction and operation of tunnels, due to the occurrence of extreme weather, heavy rainfall is often encountered. Under the conditions of heavy rainfall infiltration, the stability of the tunnel surrounding rock and support structure becomes extremely fragile. The existence of goafs also makes the tunnel seepage field more complicated, and the safety of tunnel construction and later operation is facing huge challenges.

[0003] In the prior art, publication number CN116070322B discloses a method for evaluating the safety of a karst tunnel lining structure under heavy rainfall. The method establishes a tunnel water pressure circumferential action range matrix through tunnel structural 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 states under different water pressure modes based on the measured water inflow and lining water pressure value, calculates the safety factor under the most unfavorable state, and thereby determines the safety of the karst tunnel lining structure under heavy rainfall conditions.

[0004] Insufficient existing technology:

[0005] First of all, karst tunnels usually exist in soluble rock layers such as carbonate rocks. These rocks have formed complex underground passages and cavities under the long-term erosion of water flow. The path and properties of groundwater flow are highly affected by geological structure and hydrological conditions. In addition, since the physical properties of karst bodies and water flow paths may change with geological changes, models established based on fixed parameters may not accurately reflect actual water pressure and flow conditions. The goaf tunnels in the present invention are usually related to mine mining or engineering construction. The stability of the surrounding rock mass and water flow characteristics are more affected by human factors such as mining activities and subsequent backfilling. The existence of cavities and the stress redistribution of the surrounding rock mass may lead to abnormal changes in water flow, which requires the water pressure model to consider more dynamic and nonlinear factors.

[0006] Existing technologies mainly rely on tunnel structural types and design parameters to establish the water pressure circumferential range matrix, which leads to model limitations. Specifically, the selection of parameters and the construction of models are often based on assumptions and simplifications, that is, they mainly rely on the selection of model parameters and structural types. These parameters are mostly based on historical data and assumptions, and fail to fully consider the complexity and dynamic changes of actual geological conditions. The complex geological conditions and dynamic changes of karst tunnels have not been fully considered. The physical properties of karst bodies may vary greatly due to geological changes, which makes it possible for models based on fixed parameters to not accurately reflect the actual situation. In addition, the changes in water flow and water 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, the existing technology mainly focuses on comparing the stress state under different water pressure modes and calculating the safety factor under the most unfavorable state in the process of safety evaluation. This single evaluation method may not be sufficient to fully 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 the water pressure, but also by other factors such as soil stress, structural deformation, and construction quality. Relying only on the water pressure value to evaluate the safety of the lining structure may ignore the influence of the interaction of multiple loads, resulting in the calculation result of the safety factor cannot truly reflect the safety status of the tunnel.

[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 above problems.

[0009] The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not constitute the prior art that is already known to one of ordinary skill in the art. Summary of the invention

[0010] The purpose of the present invention is to provide a method and system for evaluating the safety of a tunnel lining structure in a goaf area under heavy rainfall, so as to solve the problems raised in the above-mentioned background technology.

[0011] To achieve the above object, the present invention provides the following technical solutions:

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

[0013] Step 1: Obtain the rainfall and rainfall duration of the goaf tunnel within seven days from the meteorological bureau database, and generate the tunnel evaluation index by combining the 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 and quantify the water pressure;

[0016] Step 4: 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 by rainfall penetration;

[0017] Step 5: Establish a monitoring and early warning mechanism to obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data. Use the monitoring data to generate a risk factor and compare it with the safety factor. If the risk factor is greater than the safety factor, issue an early warning.

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

[0019] Based on the principle of permeability analysis, the influence of rainfall, geological conditions and soil permeability is comprehensively considered. The rainfall intensity and duration directly affect the permeability pressure and soil saturation. Specifically, the rainfall permeability of the tunnel in the goaf changes. The formula for calculating the rainfall permeability is:

[0020]

[0021] Among them, Q rain represents the rainfall infiltration of the goaf tunnel, I is the rainfall, T is the rainfall duration, A is the affected area of ​​the goaf tunnel, C 8 is the geological characteristic coefficient, and its value range is [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 ​​seepage, and Δh is the hydraulic head difference;

[0025] The tunnel evaluation index is calculated according to the above formula to comprehensively evaluate the hydrogeological conditions of the tunnel and its impact on the stability of the tunnel lining structure and water flow penetration. The formula is:

[0026]

[0027] Among them, GEC is the tunnel evaluation index.

[0028] Furthermore, the surrounding rock stress of the tunnel in the goaf is calculated based on the following method:

[0029] The surrounding rock stress of the goaf tunnel is composed of additional stress and effective stress. The existence of additional stress is due to the fact that the pore water cannot be quickly discharged from the pores during tunnel excavation. The pore water accumulates in this area and generates 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 the 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 formula for calculating additional stress, effective stress and surrounding rock stress is:

[0030]

[0031] Among them, σ p represents the additional pressure caused by pore water pressure, ρ w is the density of pore water, g is the gravitational acceleration, h is the water head, ∈ represents the strain of the soil, σ eff is the effective stress, σ all is the surrounding rock stress of the tunnel in the goaf, and E is the elastic modulus of the soil.

[0032] Furthermore, the water pressure generated by rainfall infiltration in the goaf is calculated and quantified based on the following method:

[0033] Based on the calculation of pore water pressure in step 3, considering that after rainfall infiltrates into the goaf, the change of water head changes gradually over time, and the infiltrated water will gradually increase 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 duration of rainfall, the greater the infiltration water pressure. The specific water pressure change is simulated by the change of water head over time, and the relevant linear equation of rainfall infiltration is established, using the following dynamic water pressure change formula:

[0034]

[0035] F(t)=ρgh(t)

[0036] Where F(t) represents the dynamic water pressure that changes with time, ρ is the infiltration water density, h(t) is the water head that changes with time, Δh is the water head difference, T is the duration of rainfall, is the rate of change of water head, t is the time point during the rainfall process;

[0037] The dynamic water pressure is quantified from the initial moment to the end moment of rainfall infiltration, that is, the cumulative effect of water pressure over time. The integral formula for calculating the water pressure after quantification is:

[0038]

[0039] Among them, F N It is the water pressure after quantification.

[0040] Furthermore, the safety factor of the lining structure is calculated, and the water pressure, soil pressure and surrounding rock deformation factors are comprehensively considered to evaluate the bearing capacity and stability of the lining structure. The method is based on:

[0041] The formula for calculating the safety factor of the lining structure is:

[0042]

[0043] Among them, SF is the safety factor, GEC is the tunnel evaluation index, σ all is the surrounding rock stress, F N It is the water pressure after quantification.

[0044] Furthermore, relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data, are obtained based on the following method:

[0045] Lining deformation is a key indicator for evaluating whether the tunnel lining is stable. It is necessary to monitor the displacement, strain and bending of the lining and calculate it using the displacement calculation formula and Hooke's law in elastic mechanics:

[0046]

[0047] Where, Δu represents the displacement of the lining structure, P is the load applied to the lining, and 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;

[0048] The crack growth rate is an important parameter reflecting the long-term stability of the tunnel lining structure. The length of the crack before and after rainfall is obtained, and the crack growth rate is obtained by the following method:

[0049]

[0050] Among them, V c is the crack expansion speed, l c represents the length of the crack before rainfall, l z represents the length of the crack after rainfall, and T is the duration of rainfall;

[0051] The flow rate of water infiltration is determined by the permeability coefficient and the head difference. According to Darcy's law, water infiltration is calculated using the following formula:

[0052]

[0053] Among them, Q represents water flow penetration, K is the permeability coefficient, A is the cross-sectional area through which the water flows, Δh is the head difference, that is, the water level difference between the two sections of the water flow, and L q Represents the path length of the water flow.

[0054] Furthermore, the monitoring data is used to generate a risk factor and compared with the safety factor. If the risk factor is greater than the safety factor, an early warning is issued. The method is based on:

[0055]

[0056] Among them, R represents the risk factor, ω 1 ,ω 2 ,ω 3 Respectively represent their corresponding proportional weights, and ω 1 >ω 2 >ω 3 >0,U allow 、V allow , Q allow They represent the maximum allowable displacement, maximum crack expansion speed, and maximum water penetration respectively. M represents the logical value for judging whether the relevant design parameters of the tunnel lining need to be adjusted. When M=0, it means that the risk factor does not exceed the safety factor and the design parameters do not need to be adjusted. When M=1, it means that the risk factor exceeds the safety factor and the design parameters need to be adjusted. SF is the safety factor.

[0057] The present invention also provides a system for evaluating the safety of a tunnel lining structure in a goaf area under heavy rainfall, wherein the system is used to execute the above-mentioned method for evaluating the safety of a tunnel lining structure in a goaf area under heavy rainfall, and comprises:

[0058] A rainfall and geological characteristics evaluation module, which is used to obtain the rainfall amount and rainfall duration of the goaf tunnel within seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors;

[0059] A water pressure and soil deformation analysis module, which is used to calculate the surrounding rock stress of the tunnel in the goaf;

[0060] A dynamic water pressure calculation module, which is used to calculate the water pressure generated by rainfall infiltration in the goaf and quantify the water pressure;

[0061] A safety factor comprehensive calculation module, which is used to comprehensively calculate the tunnel evaluation index, the surrounding rock stress of the goaf tunnel and the water pressure generated after rainfall penetration, and calculate the safety factor of the lining structure;

[0062] The monitoring and early warning mechanism module is used to establish a monitoring and early warning mechanism, obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data, use the monitoring data to generate a risk factor, and compare it with the safety factor. If the risk factor is greater than the safety factor, an early warning is issued.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] First, the present invention forms a systematic tunnel evaluation index by comprehensively considering rainfall intensity, duration, geological characteristics and soil permeability factors. This multi-parameter evaluation system can more comprehensively reflect the hydrogeological conditions of goaf tunnels under heavy rainfall conditions, thereby improving the accuracy of the assessment of lining structure stability. In addition, through dynamic water pressure calculation and surrounding rock stress analysis, it is possible to timely identify water pressure changes caused by rainfall and their impact on the lining structure, thereby providing a scientific basis for decision-making and ensuring the safety of the tunnel;

[0065] Secondly, the present invention significantly improves the real-time and responsiveness of safety evaluation by introducing a dynamic monitoring and early warning mechanism. Previous technologies often performed static analysis based on theoretical models, which made it difficult to quickly reflect sudden hydrological changes. In the monitoring and early warning mechanism module, the present invention obtains lining displacement, crack development speed, and water flow penetration data in real time, and generates a comparison between the risk factor and the safety factor to ensure that an early warning is issued in a timely manner when the risk level exceeds the safety range. This dynamic assessment not only enhances the adaptability of tunnels under complex geological conditions, but also effectively reduces potential safety hazards, providing a strong guarantee for the safe operation of tunnels.

[0066] The present invention comprehensively considers rainfall intensity, duration, geological characteristics and soil permeability factors, and introduces a dynamic monitoring and early warning mechanism to achieve real-time evaluation and effective early warning of the safety of tunnel lining structures in goaf areas under heavy rainfall, thereby improving the safety and stability of the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 It is a schematic diagram of the overall method flow of the present invention.

[0068] Figure 2 It is a schematic diagram of the system module flow of the present invention. DETAILED DESCRIPTION

[0069] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0070] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0071] Example:

[0072] See also Figure 1 A method for evaluating the safety of tunnel lining structure in goaf areas under heavy rainfall, comprising the following specific steps:

[0073] Step 1: Obtain the rainfall and rainfall duration of the goaf tunnel within seven days from the meteorological bureau database, and generate the tunnel evaluation index by combining the geological characteristics and soil permeability factors;

[0074] Step 2: Calculate the surrounding rock stress of the tunnel in the goaf;

[0075] Step 3: Calculate the water pressure generated by rainfall infiltration in the goaf and quantify the water pressure;

[0076] Step 4: 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 by rainfall penetration;

[0077] Step 5: Establish a monitoring and early warning mechanism to obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data. Use the monitoring data to generate a risk factor and compare it with the safety factor. If the risk factor is greater than the safety factor, issue an early warning.

[0078] It should be noted that by obtaining the rainfall intensity, rainfall duration, geological characteristics and soil permeability factors of the tunnel in the goaf area, a tunnel evaluation index can be scientifically generated to comprehensively evaluate 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 takes into account the changes in seepage pressure and soil saturation, ensuring that potential safety risks can be accurately identified under complex geological conditions. This setting provides basic data for subsequent water pressure calculations, surrounding rock stress analysis and safety evaluation, and thus provides a scientific basis for engineering decision-making and risk management.

[0079] Therefore, the tunnel evaluation index is generated based on the following method:

[0080] Based on the principle of permeability analysis, the influence of rainfall, geological conditions and soil permeability is comprehensively considered. The rainfall intensity and duration directly affect the permeability pressure and soil saturation. Specifically, the rainfall permeability of the tunnel in the goaf changes. The formula for calculating the rainfall permeability is:

[0081]

[0082] Among them, Q rain It represents the rainfall infiltration of the goaf tunnel, I is the rainfall, T is the rainfall duration, A is the tunnel influence area of ​​the goaf, that is, the area flowing through the goaf when rainwater infiltrates is called the tunnel influence area, C 8 is the geological characteristic coefficient, and its value range is [0.5,1.5]. In the above formula, the greater the rainfall, the longer the rainfall duration, and the larger the affected area, the greater the rainfall infiltration, and C 8 The size depends on the geological characteristics, C 8 The larger the value, the harder the geology is and the harder it is for rainwater to penetrate, which will result in a smaller rainfall infiltration volume. 8 The smaller the value, the softer the geology is, the easier it is for rainwater to penetrate, which will lead to heavier rainfall;

[0083] The formula for calculating the permeability coefficient is:

[0084]

[0085] Among them, K is the permeability coefficient, L is the length of the flow path, S is the cross-sectional area of ​​the seepage, and Δh is the head difference. The head difference refers to the difference between the initial position of the infiltration water flow and the water flow position when the infiltration process is completed. In the above formula, as the amount of rainfall infiltration increases, the growth of the path through which the infiltration rainwater flows will cause the permeability coefficient to increase, and increasing the cross-sectional area will help disperse the water flow, thereby reducing the water flow per unit area, which will cause the permeability coefficient to decrease. As the head difference increases, the driving force of the flow will increase, and the infiltration needs to overcome the driving force generated, so it will cause the infiltration to become slow and the permeability coefficient to decrease.

[0086] The tunnel evaluation index is calculated according to the above formula to comprehensively evaluate the hydrogeological conditions of the tunnel and its impact on the stability of the tunnel lining structure and water flow penetration. The formula is:

[0087]

[0088] Among them, GEC is the tunnel evaluation index; in the above formula, increasing rainfall infiltration will directly lead to an increase in the tunnel evaluation index, indicating that under heavy rainfall, the water flow infiltration rate of the tunnel increases, which may affect the stability of the structure; and the increase in permeability coefficient will also lead to an increase in the tunnel evaluation index, indicating that the soil's ability to permeate water is enhanced, the water flow rate is accelerated, and it may cause greater pressure on the stability of the lining structure; the higher the GEC, the faster the penetration rate of rainfall water through the soil under specific rainfall conditions, and the stronger the soil's permeability. This may indicate that the stability of the tunnel lining is threatened, especially when the rainfall is heavy and the permeability coefficient is high. If the GEC value is significantly higher than the normal level, it may indicate that further monitoring and maintenance are needed to prevent water flow from causing damage to the structure. On the contrary, a smaller GEC value indicates that the rainfall infiltration and infiltration rate are low, or the soil permeability is poor. This indicates that the hydrogeological conditions of the tunnel are good, and the impact of water flow on the lining structure is small, which usually means that the tunnel is of good quality and has low risk.

[0089] It should be noted that by calculating the surrounding rock stress of the goaf tunnel, we can gain a deeper understanding of the impact of rainfall on tunnel stability, especially the stress state of the surrounding rock under changing hydrological conditions. The calculation of surrounding rock stress not only considers the additional stress caused by pore water pressure, but also combines the elastic modulus of the soil to evaluate the impact of effective stress on the surrounding soil. This process is crucial to identifying potential safety hazards, because the stress state of the surrounding rock is directly related to the structural safety and long-term stability of the tunnel.

[0090] Therefore, it is necessary to calculate the surrounding rock stress of the tunnel in the goaf area, based on the following method:

[0091] The surrounding rock stress of the goaf tunnel is composed of additional stress and effective stress. The existence of additional stress is due to the fact that the pore water cannot be quickly discharged from the pores during tunnel excavation. The pore water accumulates in this area and generates 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 the 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 formula for calculating additional stress, effective stress and surrounding rock stress is:

[0092] σ p =ρ w *g*h

[0093] σ eff =∈E

[0094] σ all =σ p +σ eff

[0095] Among them, σ p represents the additional pressure caused by pore water pressure, ρ w is the density of pore water, g is the gravitational acceleration, h is the water head, ∈ represents the strain of the soil, σ eff is the effective stress, σ all is the surrounding rock stress of the tunnel in the goaf, and E is the elastic modulus of the soil.

[0096] It should be noted that by calculating the water pressure generated after rainfall infiltration, we can deeply understand the dynamic impact of rainfall on tunnel lining, especially the gradual accumulation effect of water pressure caused by the change of water head over time. Quantifying water pressure using the dynamic water pressure change formula and the mean integral method can accurately evaluate the water pressure intensity under different rainfall conditions, providing a scientific basis for engineering design, construction and maintenance, thereby improving the tunnel's anti-penetration ability, preventing potential safety hazards, and ensuring its long-term safe operation.

[0097] Therefore, it is necessary to calculate the water pressure generated by rainfall infiltration in the goaf and quantify the water pressure based on the following method:

[0098] Based on the calculation of pore water pressure in step 3, considering that after rainfall infiltrates into the goaf, the change of water head changes gradually over time, and the infiltrated water will gradually increase 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 duration of rainfall, the greater the infiltration water pressure. The specific water pressure change is simulated by the change of water head over time, and the relevant linear equation of rainfall infiltration is established, using the following dynamic water pressure change formula:

[0099]

[0100] F(t)=ρgh(t)

[0101] Where F(t) represents the dynamic water pressure that changes with time, ρ is the infiltration water density, h(t) is the water head that changes with time, Δh is the water head difference, T is the duration of rainfall, is the rate of change of water head, t is the time point during the rainfall process;

[0102] The dynamic water pressure is quantified from the initial moment to the end moment of rainfall infiltration, that is, the cumulative effect of water pressure over time. The integral formula for calculating the water pressure after quantification is:

[0103]

[0104] Among them, F Nis the water pressure after quantification; in the above integral formula, it means that the water pressure at each moment during the rainfall is accumulated to calculate the total water pressure applied to the lining during the entire rainfall period. This accumulation takes into account the change of water pressure over time and reflects the dynamic effect of rainfall on water pressure. It represents the head change rate, that is, the average rate of change of the head during the rainfall duration. This term emphasizes the impact of rainfall duration on the change of the head. The longer the duration, the greater the average head change.

[0105] 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 comprehensively evaluated, and the water pressure, surrounding rock stress and tunnel evaluation index caused by rainfall can be quantified. The safety factor can be calculated using the geological evaluation equation, which can provide an objective safety margin indicator.

[0106] Therefore, it is necessary to calculate the safety factor of the lining structure, comprehensively consider the water pressure, soil pressure and surrounding rock deformation factors, and evaluate the bearing capacity and stability of the lining structure. The method is based on:

[0107] The formula for calculating the safety factor of the lining structure is:

[0108]

[0109] Among them, SF is the safety factor, GEC is the tunnel evaluation index, σ all is the surrounding rock stress, F N is the water pressure after quantification; in the above formula, the numerator of the geological evaluation equation means the bearing capacity of geological engineering, which represents the maximum load that the lining structure can withstand in a specific environment, such as goaf and heavy rainfall, while the denominator is the product of the surrounding rock stress and the water pressure after quantification, which represents the product of stress load, that is, the stress intensity of the lining structure under the normal load. Specifically, σ all Describes the stress inside the lining structure, F N It indicates the normal load applied to the structure; the greater the surrounding rock stress and the greater the water pressure, the greater the pressure exerted by the soil or rock on the lining; the greater the water pressure, the greater the impact of water penetration and buoyancy on the structure. These two factors put pressure on the bearing capacity of the lining structure and increase the burden on the structure; a high SF value indicates that the maximum load that the lining structure can withstand is greater than or equal to the actual stress load, which means that the structure is relatively safe in the current environment and has good stability, while a low SF value indicates that the bearing capacity of the lining structure is insufficient to cope with the actual stress load, which may cause the structure to become unstable or damaged, especially under heavy rainfall or other extreme conditions.

[0110] It should be noted that the monitoring of lining deformation uses Hooke's law to calculate displacement and can identify potential structural problems; the crack development rate reflects the performance changes of the lining under long-term loads and can promptly detect and respond to the risk of crack expansion; the monitoring of water flow penetration evaluates the water flow rate 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.

[0111] Therefore, it is necessary to obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data, based on the following method:

[0112] Lining deformation is a key indicator for evaluating whether the tunnel lining is stable. It is necessary to monitor the displacement, strain and bending of the lining and calculate it using the displacement calculation formula and Hooke's law in elastic mechanics:

[0113]

[0114] Where, Δu represents the displacement of the lining structure, P is the load applied to the lining, and 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;

[0115] The crack growth rate is an important parameter reflecting the long-term stability of the tunnel lining structure. The length of the crack before and after rainfall is obtained, and the crack growth rate is obtained by the following method:

[0116]

[0117] Among them, V c is the crack expansion speed, l c represents the length of the crack before rainfall, l z represents the length of the crack after rainfall, and T is the duration of rainfall;

[0118] The flow rate of water infiltration is determined by the permeability coefficient and the head difference. According to Darcy's law, water infiltration is calculated using the following formula:

[0119]

[0120] Among them, Q represents water flow penetration, K is the permeability coefficient, A is the cross-sectional area through which the water flows, Δh is the head difference, that is, the water level difference between the two sections of the water flow, and L q Represents the path length of the water flow.

[0121] It should be noted that the risk factor comprehensively considers key parameters such as lining displacement, crack propagation rate and water penetration. By assigning different weights, it can more accurately reflect the impact of various factors on lining safety. When the risk factor is greater than the safety factor, it means that the current structural state may have potential risks. At this time, it is very necessary to issue an early warning so that appropriate measures can be taken in time to intervene or adjust the design parameters to prevent accidents. Through this systematic evaluation 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.

[0122] Therefore, it is necessary to use monitoring data to generate a risk factor and compare it with the safety factor. If the risk factor is greater than the safety factor, an early warning is issued. The method is based on:

[0123]

[0124] Among them, R represents the risk factor, ω 1 ,ω 2 ,ω 3 Respectively represent their corresponding proportional weights, and ω 1 >ω 2 >ω 3 >0,U allow 、V allow , Q allow They represent the maximum allowable displacement, maximum crack expansion speed, and maximum water penetration, respectively. M represents the logical value for judging whether the relevant design parameters of the tunnel lining need to be adjusted. When M = 0, it means that the risk factor does not exceed the safety factor and the design parameters do not need to be adjusted. When M = 1, it means that the risk factor exceeds the safety factor and the design parameters need to be adjusted. SF is the safety factor. In the above formula, the proportional weight is set to ω. 1 >ω 2 >ω 3 >0, because lining displacement is a direct indicator for evaluating tunnel lining stability. Excessive displacement is usually a precursor to structural instability and may lead to serious safety hazards. Therefore, the contribution weight of displacement to the risk factor is ω 1 The crack propagation rate is another key indicator, which is directly related to the fatigue of the material and the long-term stability of the structure. Although the development of the crack may not be a factor that immediately leads to catastrophic consequences, the increase in its propagation rate usually means a decrease in material performance, so the second highest weight ω is set for it. 2 ; Although water penetration is equally important, its influence is usually indirect relative to displacement and crack propagation speed. The increase in water pressure may accelerate the liquefaction of the soil or have other adverse effects on the lining, but it takes time to accumulate and the effect is not directly obvious. Therefore, its weight is set to the lowest ω 3; 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 result of each ratio reflects the relative relationship between the current monitoring status and the safety standard. Then, in the calculation of the risk coefficient, the ω 1 ,ω 2 ,ω 3 Comprehensive consideration is taken to form a comprehensive safety assessment; and the smaller the risk factor, the safer the tunnel lining structure.

[0125] See also Figure 2 The present invention also provides a system for evaluating the safety of a tunnel lining structure in a goaf area under heavy rainfall, wherein the system is used to execute the above-mentioned method for evaluating the safety of a tunnel lining structure in a goaf area under heavy rainfall, and comprises:

[0126] A rainfall and geological characteristics evaluation module, which is used to obtain the rainfall amount and rainfall duration of the goaf tunnel within seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors;

[0127] A water pressure and soil deformation analysis module, which is used to calculate the surrounding rock stress of the tunnel in the goaf;

[0128] A dynamic water pressure calculation module, which is used to calculate the water pressure generated by rainfall infiltration in the goaf and quantify the water pressure;

[0129] A safety factor comprehensive calculation module, which is used to comprehensively calculate the tunnel evaluation index, the surrounding rock stress of the goaf tunnel and the water pressure generated after rainfall penetration, and calculate the safety factor of the lining structure;

[0130] The monitoring and early warning mechanism module is used to establish a monitoring and early warning mechanism, obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data, use the monitoring data to generate a risk factor, and compare it with the safety factor. If the risk factor is greater than the safety factor, an early warning is issued.

[0131] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0132] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product. Those skilled in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0133] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0134] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. A method for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, characterized in that: The specific steps include: Step 1: Obtain the rainfall and rainfall duration of the goaf tunnel within seven days from the meteorological bureau database, and generate the tunnel evaluation index by combining the geological characteristics and soil permeability factors; Step 2: Calculate the surrounding rock stress of the tunnel in the goaf; Step 3: Calculate the water pressure generated by rainfall infiltration in the goaf and quantify the water pressure; Step 4: 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 by rainfall penetration; Step 5: Establish a monitoring and early warning mechanism to obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data. Use the monitoring data to generate a risk factor and compare it with the safety factor. If the risk factor is greater than the safety factor, issue an early warning.

2. The method for evaluating the safety of tunnel lining structure in goaf under heavy rainfall according to claim 1 is characterized in that: The method for generating the tunnel evaluation index is as follows: Based on the principle of permeability analysis, the influence of rainfall, geological conditions and soil permeability is comprehensively considered. The rainfall intensity and duration directly affect the permeability pressure and soil saturation. Specifically, the rainfall permeability of the tunnel in the goaf changes. The formula for calculating the rainfall permeability is: Among them, Q rain represents the rainfall infiltration of the goaf tunnel, I is the rainfall, T is the rainfall duration, A is the affected area of ​​the goaf tunnel, C8 is the geological characteristic coefficient, and the value range is [0.5, 1.5]; The formula for calculating the permeability coefficient is: Among them, K is the permeability coefficient, L is the flow path length, S is the cross-sectional area of ​​seepage, and △h is the head difference; The tunnel evaluation index is calculated according to the above formula to comprehensively evaluate the hydrogeological conditions of the tunnel and its impact on the stability of the tunnel lining structure and water flow penetration. The formula is: Among them, GEC is the tunnel evaluation index.

3. The method for evaluating the safety of tunnel lining structure in goaf under heavy rainfall according to claim 2 is characterized in that: The method for calculating the surrounding rock stress of the tunnel in the goaf is based on: The surrounding rock stress of the goaf tunnel is composed of additional stress and effective stress. The existence of additional stress is due to the fact that the pore water cannot be quickly discharged from the pores during tunnel excavation. The pore water accumulates in this area and generates 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 the 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 formula for calculating additional stress, effective stress and surrounding rock stress is: s p =ρ w *g*h s eff =∈E s all =s p +s eff Among them, σ p represents the additional pressure caused by pore water pressure, ρ w is the density of pore water, g is the gravitational acceleration, h is the water head, ∈ represents the strain of the soil, σ eff is the effective stress, σ all is the surrounding rock stress of the tunnel in the goaf, and E is the elastic modulus of the soil.

4. The method for evaluating the safety of tunnel lining structure in goaf under heavy rainfall according to claim 3 is characterized in that: The water pressure generated by rainfall infiltration in the goaf is calculated and quantified based on the following method: Based on the calculation of pore water pressure in step 3, considering that after rainfall infiltrates into the goaf, the change of water head changes gradually over time, and the infiltrated water will gradually increase 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 duration of rainfall, the greater the infiltration water pressure. The specific water pressure change is simulated by the change of water head over time, and the relevant linear equation of rainfall infiltration is established, using the following dynamic water pressure change formula: F(t)=ρgh(t) Where F(t) represents the dynamic water pressure that changes with time, ρ is the infiltration water density, h(t) is the water head that changes with time, △h is the water head difference, T is the duration of rainfall, is the rate of change of water head, t is the time point during the rainfall process; The dynamic water pressure is quantified from the initial moment to the end moment of rainfall infiltration, that is, the cumulative effect of water pressure over time. The integral formula for calculating the water pressure after quantification is: Among them, F N It is the water pressure after quantification.

5. The method for evaluating the safety of tunnel lining structure in goaf under heavy rainfall according to claim 1 is characterized in that: The safety factor of the lining structure is calculated by comprehensively considering the water pressure, soil pressure and surrounding rock deformation factors to evaluate the bearing capacity and stability of the lining structure. The method is based on: The formula for calculating the safety factor of the lining structure is: Among them, SF is the safety factor, GEC is the tunnel evaluation index, σ all is the surrounding rock stress, F N It is the water pressure after quantification.

6. The method for evaluating the safety of tunnel lining structure in goaf under heavy rainfall according to claim 1 is characterized in that: The relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data, are obtained based on the following methods: Lining deformation is a key indicator for evaluating whether the tunnel lining is stable. It is necessary to monitor the displacement, strain and bending of the lining and calculate it using the displacement calculation formula and Hooke's law in elastic mechanics: Among them, △u represents the displacement of the lining structure, P is the load applied to the lining, and 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 growth rate is an important parameter reflecting the long-term stability of the tunnel lining structure. The length of the crack before and after rainfall is obtained, and the crack growth rate is obtained by the following method: Among them, V c is the crack expansion speed, l c represents the length of the crack before rainfall, l z represents the length of the crack after rainfall, and T is the duration of rainfall; The flow rate of water infiltration is determined by the permeability coefficient and the head difference. According to Darcy's law, water infiltration is calculated using the following formula: Among them, Q represents water flow penetration, K is the permeability coefficient, A is the cross-sectional area through which the water flows, △h is the head difference, that is, the water level difference between the two sections of the water flow, and L q Represents the path length of the water flow.

7. The method for evaluating the safety of tunnel lining structure in goaf under heavy rainfall according to claim 6 is characterized in that: The monitoring data is used to generate a risk factor and compared with the safety factor. If the risk factor is greater than the safety factor, an early warning is issued. The method is based on: Where R represents the risk coefficient, ω1, ω2, and ω3 represent their corresponding proportional weights, and ω1>ω2>ω3>0, U allow 、V allow , Q allow They represent the maximum allowable displacement, maximum crack expansion speed, and maximum water penetration respectively. M represents the logical value for judging whether the relevant design parameters of the tunnel lining need to be adjusted. When M=0, it means that the risk factor does not exceed the safety factor and the design parameters do not need to be adjusted. When M=1, it means that the risk factor exceeds the safety factor and the design parameters need to be adjusted. SF is the safety factor.

8. A system for evaluating the safety of tunnel lining structures in goaf areas under heavy rainfall, characterized in that: The safety evaluation system is used to implement the safety evaluation method for a tunnel lining structure in a goaf under heavy rainfall as described in any one of claims 1 to 7, comprising: A rainfall and geological characteristics evaluation module, which is used to obtain the rainfall amount and rainfall duration of the goaf tunnel within seven days from the meteorological bureau database, and generate a tunnel evaluation index by combining geological characteristics and soil permeability factors; A water pressure and soil deformation analysis module, which is used to calculate the surrounding rock stress of the tunnel in the goaf; A dynamic water pressure calculation module, which is used to calculate the water pressure generated by rainfall infiltration in the goaf and quantify the water pressure; A safety factor comprehensive calculation module, which is used to comprehensively calculate the tunnel evaluation index, the surrounding rock stress of the goaf tunnel and the water pressure generated after rainfall penetration, and calculate the safety factor of the lining structure; The monitoring and early warning mechanism module is used to establish a monitoring and early warning mechanism, obtain relevant monitoring data, including lining structure displacement, crack development speed and water flow penetration data, use the monitoring data to generate a risk factor, and compare it with the safety factor. If the risk factor is greater than the safety factor, an early warning is issued.

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