A method for evaluating slope stability under influence of coal mining

Abstract

The present application relates to the technical field of slope stability analysis, and discloses a kind of coal mining influence under the slope stability evaluation method of mining, comprising the following steps: step 1, obtains topographic parameters and rock-soil parameters;Step 2, obtains coal mining related calculation parameters;Step 3, surface movement deformation is determined by double line calculation;The double line calculation includes: I line theoretical calculation and II line numerical calculation;Step 4, compares the surface movement deformation under the influence of mining obtained in double line calculation, and selects surface movement deformation according to preset conditions;Step 5, the slope stability under the influence of mining is calculated by limit equilibrium method;Step 6, comprehensive analysis and evaluation mining slope stability.The present application combines numerical simulation and limit equilibrium method for calculation and analysis, analysis dimension is comprehensive, can reach higher calculation accuracy;It can provide effective and reliable basis for the stability evaluation of mined-out area in mountainous and hilly areas, construction and utilization, reclamation and repair.

Description

Technical Field

[0001] The present invention relates to the technical field of slope stability analysis, and in particular to a slope stability evaluation method under the influence of coal mining. Background Art

[0002] As we all know, my country's energy structure is characterized by a lack of oil, limited natural gas, and a relative abundance of coal. Coal, the cornerstone of my country's energy, accounts for 70% of primary energy production and 56% of primary energy consumption. Southwest China, as one of my country's key energy bases, boasts not only abundant coal resources but also considerable potential for hydropower development. However, the region's complex geological structure, characterized by mountainous and hilly terrain and rugged terrain, presents unique challenges for underground coal mining.

[0003] During underground coal mining, collapse zones, fracture zones, and bends form in the rock mass above the ore layer. These phenomena can damage the integrity and continuity of the slope rock and soil to varying degrees, causing changes in the physical and mechanical properties of the rock and soil, thereby reducing the overall strength of the slope rock and soil. Furthermore, mining activities disrupt the original stress distribution, exposing the slope to a new stress state that is often detrimental to slope stability and increases the risk of geological hazards such as landslides.

[0004] Currently, research on the impact of coal mining activities on the ground environment is primarily focused on plains, and most studies are conducted based on the premise that the surface is relatively flat. However, in mountainous and hilly areas, due to the complex terrain, diverse stratigraphic structures, and the influence of factors such as precipitation, the geological environment in which the slope is located is complex and changeable, the stress distribution state is uneven and unstable, and it is greatly affected by temporal and spatial effects and environmental factors. Its stability correlation factors are complex, making traditional methods inadequate for assessing slope stability under the influence of mining. For example, the existing patent with publication number CN118171494B discloses a mining slope stability analysis method. This patented technology uses a mining slope critical sliding surface model to search for the mining slope critical sliding surface. The theory is not perfect, there are many human factors, and it does not combine theoretical calculations with numerical simulations. Alternatively, it relies entirely on numerical simulations to calculate the slope stability coefficient, which lacks analytical reliability and accuracy. Another example is the paper "Slope Stability Analysis Combining Numerical Simulation and Limit Equilibrium Method," published in the journal Modern Mining. While this paper proposes a slope stability analysis method combining numerical simulation and limit equilibrium, it does not fully consider the adverse effects of mining on slopes. Therefore, it does not constitute a mining-induced slope and does not address the stability assessment challenges inherent in mining-induced slopes. Therefore, there is an urgent need to develop and improve evaluation systems and technical means for the impact of coal mining on slope stability under complex terrain conditions. In particular, it is necessary to combine advanced methods such as numerical simulation and geostatistics to improve prediction accuracy and develop more scientific and reasonable mining plans and safety measures to ensure environmental safety and social stability during mining operations. Summary of the Invention

[0005] The present invention aims to provide a slope stability evaluation method under the influence of coal mining. It combines numerical simulation and limit equilibrium method for calculation and analysis. The analysis dimensions are comprehensive and can achieve high calculation accuracy. It can provide effective and reliable data reference for stability assessment, construction utilization, reclamation and restoration of goaf areas in mountainous and hilly areas.

[0006] The basic solution provided by the present invention is: a method for evaluating slope stability under the influence of coal mining, comprising the following steps:

[0007] Step 1: Obtain terrain parameters and rock and soil parameters;

[0008] Step 2: Obtain calculation parameters related to underground coal mining;

[0009] Step 3: Determine the surface movement and deformation using a dual-line calculation; the dual-line calculation includes: a theoretical calculation using line I and a numerical calculation using line II.

[0010] In the I-line theoretical calculation, the surface movement and deformation calculation parameters are obtained, and combined with the relevant parameters of underground coal mining, the theoretical calculation of the surface movement and deformation under the influence of mining is carried out based on the probability integral method; the surface movement and deformation under the influence of mining are the surface settlement value W, the inclination value i, the curvature value K, the horizontal displacement value U, and the horizontal deformation value ε;

[0011] In the II-line numerical calculation, the potential sliding surface of the mining slope is obtained through the numerical analysis strength reduction method, and the stability coefficient of the mining slope and the numerical calculation of the surface movement deformation under the influence of mining are performed; combining the topography, rock and soil parameters and underground coal mining related parameters, the surface settlement value W and horizontal displacement value U in the surface movement deformation under the influence of mining are calculated based on the numerical analysis method, and the inclination value i, curvature value K, and horizontal deformation value ε in the surface movement deformation under the influence of mining are obtained by deduction;

[0012] Step 4: Compare the ground movement and deformation under the influence of mining obtained from the theoretical calculation of line I and the numerical calculation of line II, and select the ground movement and deformation according to the preset conditions;

[0013] Step 5: Based on the potential sliding surface of the mining slope and the selected surface movement deformation, the limit equilibrium method is used to calculate the slope stability under the influence of mining;

[0014] Step 6: Comprehensively analyze and evaluate the stability of the mining slope.

[0015] The working principle and advantages of the present invention are:

[0016] This scheme is simple to calculate and easy to implement. The required calculation parameters can be determined by indoor and outdoor tests combined with engineering experience or by design specifications. The calculation method is reasonable, and the sliding surface does not need to be determined manually but is automatically searched and determined by the computer. The results are highly accurate and can provide effective and reliable data reference for stability assessment, construction and utilization, reclamation and restoration of mined-out areas in mountainous and hilly areas.

[0017] In particular, this solution combines numerical simulation and limit equilibrium method for computational analysis. Among them, the numerical analysis method can take into account the constitutive relationship of rock and soil (i.e. stress-strain relationship) in the slope stability analysis, and thus can more accurately determine the deformation characteristics of the slope under different load conditions, accurately determine the potential sliding surface of the slope, and achieve a high degree of numerical simulation accuracy. Then, by using double-line calculation to obtain the surface movement deformation under the influence of mining and taking values ​​from it, it is possible to analyze more realistic deformation conditions under the influence of mining, and provide reliable basic data for stability assessment. It is then coupled with the limit equilibrium method to calculate the stability of the slope. The limit equilibrium method has a small amount of calculation and a simple calculation process. It requires fewer parameters and can reduce errors caused by parameter uncertainty. It is suitable for complex analysis scenarios of slopes under the influence of coal mining in mountainous and hilly areas, which can make the calculation more efficient and the calculation results more reasonable and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a method flow of an embodiment of a method for evaluating slope stability under the influence of coal mining in the present invention;

[0019] Figure 2 A schematic diagram of a slope shape according to an embodiment of a method for evaluating slope stability under the influence of coal mining in the present invention;

[0020] Figure 3 This is a schematic diagram of the strip and block division of an embodiment of a slope stability evaluation method under the influence of coal mining in the present invention. DETAILED DESCRIPTION

[0021] The following is a further detailed description through specific implementation methods:

[0022] The embodiment is basically as shown in the attached Figure 1 As shown: A method for evaluating slope stability under the influence of coal mining, comprising the following steps:

[0023] Step 1: Obtain terrain parameters and rock and soil parameters.

[0024] In this step, the terrain parameters include slope morphological parameters - slope angle β s , slope width B, slope height H s ,like Figure 2 The rock and soil parameters include cohesion c, internal friction angle Severity γ, elastic modulus E, Poisson's ratio μ, structural surface cohesion c1, structural surface internal friction angle Structural surface normal stiffness K n , structural surface tangential stiffness K s .

[0025] Step 2: Obtain calculation parameters related to underground coal mining.

[0026] In this step, the calculation parameters related to underground coal mining include the properties of the coal seam overburden (in this embodiment, specifically the saturated uniaxial compressive strength of the overburden), the coal seam inclination α, the coal seam mining thickness M, the coal seam mining depth H, and the working face mining width D.

[0027] Step 3: Use dual-line calculation to determine the surface movement deformation; the dual-line calculation includes: I-line theoretical calculation and II-line numerical calculation.

[0028] In the I-line theoretical calculation, the surface movement and deformation calculation parameters are obtained, and combined with the relevant parameters of underground coal mining, based on the probability integral method, the theoretical calculation of the surface movement and deformation under the influence of mining is carried out; the surface movement and deformation under the influence of mining are the surface settlement value W, the inclination value i, the curvature value K, the horizontal displacement value U, and the horizontal deformation value ε.

[0029] Specifically, in this embodiment, when obtaining the surface movement and deformation calculation parameters, an analogy method is used to determine them (they can also be obtained based on field measurement data), including the following steps:

[0030] The surface movement deformation calculation parameters are comprehensively determined based on the properties of the coal seam overburden, regional experience and test results. The surface movement deformation calculation parameters include subsidence coefficient q, horizontal movement coefficient b, strike movement angle δ, uphill movement angle γ, downhill movement angle β, strike boundary angle δ0, uphill boundary angle γ0, downhill boundary angle β0, main influencing angle tangent tanβ, mining influence propagation angle θ0, and inflection point offset distance s.

[0031] in:

[0032] (1) The size of the subsidence coefficient q is mainly determined by the coal mining method, roof treatment method, overburden lithology and structure.

[0033] From the perspective of coal mining methods, the sinking coefficient is from large to small: longwall mining > shortwall mining > strip mining;

[0034] From the perspective of roof treatment methods, the subsidence coefficient is from large to small: full collapse method > filling method ≥ coal pillar support method;

[0035] From the perspective of overburden lithology, the weaker the overburden, the greater the subsidence coefficient;

[0036] From the perspective of overburden structure, the more fragmented the overburden is (developed faults, joints, and bedding), the greater the subsidence coefficient.

[0037] (2) The magnitude of the horizontal movement coefficient b is mainly determined by the inclination of the stratum, the thickness and properties of the topsoil layer, the slope shape, and the rock and soil properties of the slope.

[0038] From the perspective of formation dip, the greater the formation dip, the greater the horizontal movement coefficient;

[0039] From the perspective of topsoil thickness and properties, the thicker the topsoil layer and the worse its properties, the greater the horizontal movement coefficient;

[0040] From the perspective of slope morphology, the greater the terrain slope angle, the greater the horizontal movement coefficient;

[0041] From the perspective of slope rock and soil properties, the worse the properties, the greater the horizontal movement coefficient;

[0042] In addition, the horizontal shift coefficient b is corrected using the following formula:

[0043]

[0044] Where b s is the correction coefficient for horizontal movement; x is the horizontal distance from the surface calculation point to the slope foot; B is the horizontal distance from the slope top to the slope foot; β s is the slope angle; k is the slope rock (soil) coefficient.

[0045] When the slope lithology is hard limestone and quartz sandstone, the k value is 1.00-1.05; when the slope lithology is hard sandstone and relatively hard limestone, the k value is 1.05-1.10; when the slope lithology is relatively hard sandstone and limestone, the k value is 1.1-1.2; when the slope lithology is sandy shale (calcareous cementation), the k value is 1.2-1.3; when the slope lithology is muddy shale and sandy mudstone, the k value is 1.3-1.4; when the slope lithology is mudstone and siltstone, the k value is 1.4-1.5; when the slope soil is silty clay to clay, the k value is 1.5-1.8; when the slope soil is slope deposits and sand, the k value is 1.8-2.0.

[0046] The correction ratio of the horizontal movement coefficient is different for different slope shapes.

[0047] (3) The magnitudes of the strike movement angle δ, uphill movement angle γ, downhill movement angle β, strike boundary angle δ0, uphill movement angle γ0, downhill movement angle β0, and the main influencing angle tangent tanβ are mainly determined by the structure and properties of the overburden.

[0048] The weaker and more broken the overburden is (e.g., if there are faults, joints, bedding, and other structures), the smaller the strike movement angle δ, uphill movement angle γ, downhill movement angle β, strike boundary angle δ0, uphill boundary angle γ0, and downhill boundary angle β0, and the larger the main influencing angle tangent tanβ.

[0049] (4) The size of the mining-affected propagation angle θ0 is mainly determined by the properties of the overburden and the inclination of the coal seam.

[0050] The softer the overburden, the larger the mining impact propagation angle θ0; the larger the coal seam inclination, the smaller the mining impact propagation angle θ0.

[0051] (5) The size of the inflection point offset s is mainly determined by the properties of the overburden and the mining depth.

[0052] The weaker the overburden, the smaller the inflection point offset distance s; the smaller the mining depth, the smaller the inflection point offset distance s.

[0053] In addition, during the calculation, an EXCEL table is compiled based on the associated integral function of the surface movement and deformation under the influence of mining, and the integral calculation is completed by the EXCEL table.

[0054] The formula for calculating surface movement deformation (i.e., the associated integral function) is as follows:

[0055] Surface subsidence value W (i.e. subsidence value W):

[0056] Tilt value i:

[0057]

[0058] Curvature value K:

[0059]

[0060] Horizontal displacement value U:

[0061]

[0062] Horizontal deformation value ε:

[0063]

[0064] W cm =M·q·cosα;

[0065] U cm =b s W cm ;

[0066]

[0067] Where D is the mining area of ​​the coal seam, η and ζ are the mining widths of the area in the x and y directions respectively; x and y are the relative coordinates of the calculation points (considering the inflection point offset); W cm U is the maximum surface subsidence value under full mining conditions; cm is the maximum horizontal movement of the ground surface under full mining conditions; r is the main impact radius.

[0068] In the II-line numerical calculation, the potential sliding surface of the mining slope is obtained through the numerical analysis strength reduction method, and the stability coefficient of the mining slope and the numerical calculation of the surface movement deformation under the influence of mining are performed.

[0069] Combining the topography, rock and soil parameters and underground coal mining related parameters, the surface settlement value W and horizontal displacement value U in the surface movement deformation under the influence of mining are calculated based on numerical analysis methods (such as finite element, discrete element and other numerical analysis methods), and the inclination value i, curvature value K and horizontal deformation value ε in the surface movement deformation under the influence of mining are derived.

[0070] Here, the potential sliding surface of the slope includes the potential arc-shaped sliding surface of the soil slope, the extremely soft rock slope, the broken or extremely broken rock slope, and the plane or broken line sliding surface of the rock slope sliding along the structural surface.

[0071] Step 4: Compare the surface movement and deformation under the influence of mining obtained from the theoretical calculation of line I and the numerical calculation of line II, and select the surface movement and deformation according to the preset conditions.

[0072] In this embodiment, the preset conditions for analysis refer to the most unfavorable conditions, that is, the situation where the ground movement and deformation are large. In this step, by performing envelope calculation and analysis of the two lines, possible defects in the calculation and analysis of Line I and Line II can be effectively avoided.

[0073] Step 5: Based on the potential sliding surface of the slope obtained by numerical analysis, a slope stability calculation cross-section diagram is drawn; in the slope stability calculation cross-section diagram, the slope is divided into several strips along the corresponding potential sliding surface of the slope, such as Figure 3 As shown in Figure 2, the sliding force and anti-sliding force of each strip are calculated for slope stability. Here, the width of each strip is set between 2 and 4 meters to achieve better calculation accuracy and convenience.

[0074] Based on the selected surface movement deformation, the limit equilibrium method is used to calculate the slope stability under the influence of mining.

[0075] The slope stability is calculated using an implicit solution method. An EXCEL table is compiled based on the implicit solution association formula, and the single variable solution is performed by the simulation analysis module of the EXCEL table. The implicit solution association formula here includes the following sliding force, anti-sliding force and slope stability calculation formulas. In particular, when using the EXCEL table for solution, the simulation analysis module is also pre-set to simulate the optimal value of the stability coefficient cell by setting the residual sliding force cell of the nth block to 0. In this way, the slope stability coefficient can be obtained quickly and accurately. In this embodiment, the optimal value of the slope stability coefficient is simulated by setting the residual sliding force of the last block to zero.

[0076] Specifically, the sliding force is composed of the gravity of the bar, the component of the seepage pressure along the tangent direction of the sliding surface and the additional stress of the mining slope; the anti-sliding force is mainly provided by the friction between the bottom surface of the bar and the sliding surface.

[0077] The sliding force is calculated using the following formula:

[0078] T i =W i ((1+η i )sinα i +(A+P m (λ(ε i +ε i ′)+ξ(i i +i i ′)))cosα i )+T Di +η i c i L i sinα i ;

[0079] Furthermore, when calculating the anti-sliding force of each strip, the weakening effect of mining and groundwater on the anti-sliding force is taken into account; the anti-sliding force is calculated using the following formula:

[0080] R i =(W i ((1-η i )cosα i -(A+P m (λ(ε i +ε i ′)+ξ(i i +i i ′)))sinα i )-N wi -R Di )tanφ i

[0081] -(ηcosα i tanφ i -(1-η i ))c i L i ;

[0082] In the above formula, the subscript i is used to distinguish the bars; Ti is the sliding force caused by gravity and other external forces per unit width of the i-th bar, and the unit is kN / m. i is the anti-slip force caused by gravity and other external forces per unit width of the i-th block, in kN / m.

[0083] is the parallel sliding surface component force generated by the seepage pressure of the i-th block; TDi =γ w h wi L i cosα i sinβ i cos(α i -β i );

[0084] is the pore water pressure of the i-th block; Among them, γ w is the bulk density of water; is the height of soil below the infiltration line; L i is the sliding surface length of the i-th block; β i is the groundwater flow direction of the i-th block.

[0085] is the vertical sliding surface force generated by the seepage pressure of the i-th block; R Di =γ w h wi L i cosα i sinβ i sin(α i -β i ).

[0086] W i is the weight of the i-th block; φ i is the internal friction angle of the i-th block.

[0087] η is the first calculation coefficient (η i That is, the first calculation coefficient of the i-th block), when H i ≤H s hour, When H i >H s hour, w is the sinking value of the slope top edge; ξ is the second calculation coefficient (ξ i That is the second calculation coefficient of the i-th block), when H i <H s When ξ=1.0, when H i ≥H s hour, H i H is the vertical height from the top of the slope to the bottom of the mined coal seam; s It is the vertical distance from the top of the slope to the toe.

[0088] i, α i is the inclination angle of the sliding surface of the i-th block; A is the comprehensive horizontal seismic coefficient of the slope; c i is the cohesion of the i-th block; λ is the lateral pressure coefficient, μ is Poisson's ratio. i and i' are the final inclination value and dynamic inclination value of the slope top edge, and the inclination is positive when it is the same as the slope body (negative when it is opposite). ε and ε' are the final horizontal deformation value and dynamic horizontal deformation value of the slope top edge, respectively, and the horizontal movement direction is positive when it is the same as the slope free direction, and negative when it is opposite.

[0089] P m is the mining degree coefficient of the slope body; wherein M d is the normal mining thickness of the coal seam below the slope body; H0 is the average mining depth below the slope body; D W is the working face width within the mining influence range of the slope body, and the mining influence range is divided according to the surface movement angle, such as D W ≥1.5H0, D W =1.5H0; β s is the slope angle of the slope; F is the lithology coefficient, and the value is shown in Table 1:

[0090] Table 1: Lithology coefficient value table

[0091] Rock (soil) name F Rock (soil) name F Slope deposits and sub-sand soil 1.0～1.2 Sandy shale (calcareous cementation) 1.8～2.0 Sub-clay to clay 1..2～1.4 Medium hard sandstone and limestone 2.0～2.2 mudstone and siltstone 1.4～1.6 Hard sandstone and limestone 2.2～2.5 Muddy shale and sandy mudstone 1.6～1.8 Very hard limestone and quartz sandstone 2.8～3.0

[0092] The slope stability is calculated by the following formula:

[0093] P n =0;

[0094] P i =P i-1 ψ i-1 +T i -R i / F s ;

[0095]

[0096] In the formula, F s is the slope stability coefficient, which is used to represent the slope stability; α i is the inclination of the ith block sliding surface; φ i is the internal friction angle of the ith block; P n is the residual sliding force per unit width of the nth block, with the unit of kN / m; when P i <0(i<n), P i =0; ψ i-1 is the transmission coefficient of the i-1th block to the ith block.

[0097] Step 6: According to the numerical calculation and theoretical calculation (i.e., based on the analysis content of steps 1-5), the stability of the mining slope is comprehensively analyzed and evaluated. The slope stability coefficient F sAccording to the Technical Code for Building Slope Engineering (GB50330-2013), the stability state of the slope is determined, that is:

[0098] ① The slope stability coefficient F under the influence of mining s <1.00, the slope stability state is unstable;

[0099] ② The slope stability coefficient 1.00≤F under the influence of mining s <1.05, the slope stability state is sub-stable;

[0100] ③ The slope stability coefficient 1.05≤F under the influence of mining s <F st , the slope stability state is basically stable;

[0101] ④ The slope stability coefficient F under the influence of mining s ≥F st , the slope stability state is stable.

[0102] Wherein, F st is the slope stability safety factor, considering the permanent slope general working condition, when the slope engineering safety level is first class, the slope stability safety factor F st is 1.35; when the slope engineering safety level is second class, the slope stability safety factor F st is 1.30; when the slope engineering safety level is third class, the slope stability safety factor F st is 1.25.

[0103] The slope stability evaluation method under the influence of coal mining provided in the embodiment combines numerical simulation and limit equilibrium method for calculation and analysis, can fully consider the constitutive relation of the slope and the complex structure of the slope under the influence of coal mining, and achieve high calculation accuracy; can provide effective and reliable basis for the stability evaluation, construction and utilization, reclamation and repair of the goaf in mountain and hilly areas, and help to effectively reduce the subsequent treatment cost, effectively utilize the abandoned subsidence land, and ensure the sustainable development of local economic construction.

[0104] The key points are that, first, the scheme obtains the potential sliding surface of the slope through numerical analysis method, the numerical analysis method can consider the constitutive relation (i.e. stress-strain relation) of the rock-soil body in the slope stability analysis, and then can more accurately determine the deformation characteristics of the slope under different load conditions, accurately determine the potential sliding surface of the slope, and achieve high numerical simulation accuracy.

[0105] Secondly, the double-line calculation is adopted to obtain the surface movement deformation under the influence of mining, and the more realistic slope surface deformation under the influence of mining and special hill and hilly environment can be analyzed, which can provide reliable basic data for stability evaluation. In the I-line calculation, the slope correction horizontal movement coefficient is proposed by comprehensively considering the rock and soil properties of the slope, the slope angle and the horizontal position of the calculation point, which solves the calculation difficulty of the surface movement deformation of the mining slope in the mountain area.

[0106] Thirdly, the numerical simulation and limit equilibrium method are combined for calculation and analysis. Based on the determination of the sliding surface and the double-line calculation (which also includes numerical simulation) to obtain the required calculation parameters of the slope, combined with the limit equilibrium method, the stability calculation is carried out with fewer accurate parameters, which can reduce the error caused by parameter uncertainty, adapt to the complex analysis scene of the slope under the influence of coal mining in the mountain and hilly area, and make the calculation more efficient and the calculation result more reasonable and accurate.

[0107] Fourthly, the implicit solution is used to solve the slope stability coefficient, which overcomes the problem of complicated calculation steps in the implicit solution. At present, the transfer coefficient method is often used to calculate the stability coefficient of the mining slope, which has the problem of large safety factor. In view of this, the implicit solution of the transfer coefficient method is proposed. The solution of the implicit solution is based on the strict force balance condition, which is more accurate than the explicit solution. At the same time, in order to solve the problem of complicated steps caused by iterative calculation in the implicit solution, the EXCEL table is programmed, and the single variable solution is carried out by the simulation analysis module of the EXCEL table, which simulates the optimal value of the slope stability coefficient by setting the residual sliding force of the last block to zero. The calculation steps and difficulty are simplified, and the calculation efficiency is improved.

[0108] Fifthly, the analysis dimension of the present scheme is more comprehensive. In the calculation of the stability of the mining slope, the influence of the groundwater level is particularly considered (mining may change the flow path and pressure distribution of groundwater, further affecting the mechanical properties of rock and soil), which is suitable for slope stability calculation under various working conditions and has strong universality.

[0109] Sixthly, finally, the stability of the mining slope is evaluated by comprehensive analysis according to the numerical calculation and theoretical calculation (i.e. based on the analysis contents of steps 1-5), and the conclusion is more reliable by mutual verification of the two methods.

[0110] The above is only an embodiment of the present invention. Common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. Ordinary technicians in the relevant field are aware of all common technical knowledge in the technical field of the invention before the application date or priority date, can obtain all existing technologies in the field, and have the ability to apply conventional experimental means before that date. Ordinary technicians in the relevant field can improve and implement this scheme in combination with their own abilities under the guidance of this application. Some typical known structures or known methods should not become obstacles for ordinary technicians in the relevant field to implement this application. It should be pointed out that for those skilled in the art, without departing from the structure of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A method for evaluating slope stability under the influence of coal mining, characterized in that: The following steps are involved: Step 1: Obtain terrain parameters and rock and soil parameters; Step 2: Obtain calculation parameters related to underground coal mining; Step 3, using double-line calculation to determine the surface movement deformation; The dual-line calculation includes: I-line theoretical calculation and II-line numerical calculation; In the I-line theoretical calculation, the surface movement and deformation calculation parameters are obtained, and combined with the relevant parameters of underground coal mining, the theoretical calculation of the surface movement and deformation under the influence of mining is carried out based on the probability integral method; the surface movement and deformation under the influence of mining are the surface settlement value W, the inclination value i, the curvature value K, the horizontal displacement value U, the horizontal deformation value ; In the II line numerical calculation, the potential sliding surface of the mining slope is obtained by the numerical analysis strength reduction method, and the mining slope stability coefficient and the surface movement deformation under the influence of mining are calculated numerically; combined with the topography, rock and soil parameters and underground mining related parameters of the coal mine, the surface settlement value W and horizontal displacement value U in the surface movement deformation under the influence of mining are calculated based on the numerical analysis method, and the inclination value i, curvature value K and horizontal deformation value of the surface movement deformation under the influence of mining are derived by deduction. ; Step 4: Compare the ground movement and deformation under the influence of mining obtained from the theoretical calculation of line I and the numerical calculation of line II, and select the ground movement and deformation according to the preset conditions; Step 5: Based on the potential sliding surface of the mining slope and the selected surface movement deformation, the limit equilibrium method is used to calculate the slope stability under the influence of mining; Step 6: Comprehensively analyze and evaluate the stability of the mining slope; In step 6, the method further includes: drawing a slope stability calculation cross-section diagram based on the potential sliding surface of the slope; dividing the slope into a plurality of strips along the corresponding potential sliding surface of the slope in the slope stability calculation cross-section diagram; and calculating the sliding force and anti-sliding force of each strip to calculate the slope stability. When calculating the anti-sliding force of each strip, the weakening effect of mining and groundwater on the anti-sliding force is taken into account; the anti-sliding force is calculated using the following formula: ； The sliding force is calculated using the following formula: In the formula, the subscript i is used to distinguish the bars. is the anti-sliding force caused by gravity and other external forces per unit width of the i-th block, in kN / m; is the weight of the i-th block; η is the first calculation coefficient, That is the first calculation coefficient of the i-th block, when hour, ,when hour, , w is the sinking value of the slope top edge; It is the vertical height from the top of the slope to the bottom of the mined coal seam; is the vertical distance from the top of the slope to the toe; is the inclination angle of the sliding surface of the i-th block; A is the comprehensive horizontal seismic coefficient of the slope; is the cohesion of the i-th block; is the slope mining degree coefficient; is the lateral pressure coefficient; and are the final horizontal deformation value and dynamic horizontal deformation value of the slope top edge respectively; is the second calculation coefficient, That is the first calculation coefficient of the i-th block, when hour, ,when hour, ; i and are the final inclination value and dynamic inclination value of the slope top edge; is the pore water pressure of the i-th block; ; is the bulk density of water; is the height of soil below the infiltration line; is the sliding surface length of the i-th block; is the vertical sliding surface force generated by the seepage pressure of the i-th block; is the internal friction angle of the i-th block.

2. The method for evaluating slope stability under the influence of coal mining according to claim 1, characterized in that: In step 1, the terrain parameters include slope angle , slope width B, slope height The rock and soil parameters include cohesion c, internal friction angle , severe , elastic modulus E, Poisson's ratio , structural surface cohesion , structural surface internal friction angle , structural surface normal stiffness , structural surface tangential stiffness .

3. The method for evaluating slope stability under the influence of coal mining according to claim 1, characterized in that: In step 2, the calculation parameters related to underground coal mining include coal seam overburden properties, coal seam inclination , coal seam mining thickness M, coal seam mining depth H, working face mining width D.

4. The method for evaluating slope stability under the influence of coal mining according to claim 1, characterized in that: In the I-line theoretical calculation in step 3, the analogy method is used to determine the calculation parameters of surface movement and deformation, including the following steps: The surface movement deformation calculation parameters are determined comprehensively based on the coal seam overburden properties, regional experience and test results. The surface movement deformation calculation parameters include the subsidence coefficient q, the horizontal movement coefficient b, the strike movement angle , uphill movement angle , downhill moving angle , towards the boundary corner , uphill boundary corner , downhill boundary corner , the main influence angle tangent , mining impact propagation angle , inflection point offset s.

5. The method for evaluating slope stability under the influence of coal mining according to claim 4, characterized in that: For the horizontal shift coefficient b, the following formula is also used for correction: ； Where, is the correction factor for horizontal shift; is the horizontal distance from the surface calculation point to the slope foot; B is the horizontal distance from the slope top to the slope foot; is the slope angle; is the slope rock (soil) property coefficient.

6. The method for evaluating slope stability under the influence of coal mining according to claim 1, characterized in that: In step 3, the potential sliding surfaces of the mining slope include potential arc-shaped sliding surfaces of soil slopes, extremely soft rock slopes, broken or extremely broken rock slopes, and plane or broken-line sliding surfaces of rock slopes sliding along structural surfaces.

7. The method for evaluating slope stability under the influence of coal mining according to claim 1, characterized in that: In the I-line theoretical calculation in step 3, an EXCEL table is compiled based on the associated integral function of the surface movement deformation under the influence of mining, and the integral calculation is completed by the EXCEL table; in the slope stability calculation in step 6, the slope stability is calculated using the implicit solution method, and an EXCEL table is compiled based on the implicit solution association formula. The simulation analysis module of the EXCEL table performs a single variable solution, and the optimal value of the slope stability coefficient is simulated by setting the residual sliding force of the last block to zero.

8. The method for evaluating slope stability under the influence of coal mining according to claim 1, characterized in that: The slope stability is calculated using the following formula: ； ； ； Where, is the slope stability coefficient, which is used to characterize the slope stability; The subscript i is used to distinguish bars. is the anti-sliding force caused by gravity and other external forces per unit width of the i-th block, in kN / m; is the inclination angle of the sliding surface of the i-th block; is the internal friction angle of the i-th block; is the residual sliding force per unit width between the i-th block and the i+1-th block, in kN / m; is the residual sliding force per unit width of the nth block, in kN / m; ( ) ; is the transfer coefficient of the i-1th block to the i-th block; Ti is the sliding force per unit width of the i-th block caused by gravity and other external forces, and the unit is kN / m.

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