Slope stability evaluation method under influence of coal mine mining

Abstract

The invention relates to the technical field of slope stability analysis, and discloses a slope stability evaluation method under the influence of coal mine mining, comprising the following steps: step 1, acquiring terrain parameters and rock-soil body parameters; 2, obtaining coal mine underground mining related calculation parameters; step 3, determining surface movement deformation by adopting double-line calculation; the double-line calculation comprises I-line theoretical calculation and II-line numerical calculation; step 4, comparing the earth surface movement deformation under the mining influence obtained in the double-line calculation, and selecting the earth surface movement deformation according to a preset condition; 5, calculating the slope stability under the mining influence by adopting a limit equilibrium method; and 6, comprehensively analyzing and evaluating the stability of the mining slope. According to the method, numerical simulation and a limit equilibrium method are combined for calculation and analysis, the analysis dimension is comprehensive, and high calculation accuracy can be achieved; and an effective and reliable basis can be provided for stability evaluation, construction and utilization, reclamation and repair and the like of the goaf in the mountainous and hilly areas.

Description

Technical Field

[0001] The 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, the characteristics of my country's energy structure are "lack of oil, little gas, and relatively rich in coal". Coal, as the "ballast stone" of my country's energy, accounts for up to 70% of primary energy production and 56% of primary energy consumption. As one of my country's important energy bases, the southwest region not only has rich coal resources, but also has certain potential for hydropower development. However, the region has complex geological structures, many mountains and hills, and the terrain is undulating, which brings unique challenges to underground coal mining activities.

[0003] During the mining process of coal mines, collapse zones, fault zones and bending zones will be formed in the rock mass above the ore layer. These phenomena will destroy 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. In addition, mining activities also destroy the original stress distribution, leaving the slope in a new stress state, which is often not conducive to the stability of the slope, thereby increasing the risk of geological disasters such as landslides.

[0004] At present, the research on the impact of coal mining activities on the ground environment is mainly concentrated in plain areas, and most of the research is 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 of the slope is complex and changeable, the stress distribution state is uneven and unstable, and it is greatly affected by time and space effects and environmental factors. Its stability correlation factors are complex, which makes the traditional method insufficient in evaluating the stability of the slope under the influence of mining. For example, the existing patent with the publication number CN118171494B discloses a mining slope stability analysis method. The patent technology uses the mining slope critical sliding surface model to search for the mining slope critical sliding surface. The theory is not perfect enough, there are many human factors, and the theoretical calculation is not combined with numerical simulation; or all numerical simulations are used to calculate the slope stability coefficient, and its analysis reliability and analysis accuracy are lacking. For example, the "Slope Stability Analysis Combining Numerical Simulation and Limit Equilibrium Method" published in the journal "Modern Mining" proposed a slope stability analysis method combining numerical simulation with limit equilibrium method, but it did not fully consider the adverse effects of mining on the slope, does not belong to mining slopes, and cannot solve the stability assessment problems existing in mining slopes. Therefore, it is urgent to develop and improve the evaluation system 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 technology and geostatistics to improve prediction accuracy, and formulate more scientific and reasonable mining plans and safety protection measures to ensure environmental safety and social stability during mining. Summary of the invention

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

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

[0007] Step 1, obtaining terrain parameters and rock and soil parameters;

[0008] Step 2, obtaining calculation parameters related to underground coal mining;

[0009] Step 3, using double-line calculation to determine the surface movement deformation; the double-line calculation includes: I-line theoretical calculation and II-line numerical calculation;

[0010] In the I-line theoretical calculation, the calculation parameters of surface movement and deformation 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 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; 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 ε in the surface movement deformation under the influence of mining are derived;

[0012] Step 4, comparing the ground movement deformation under the influence of mining obtained by theoretical calculation of line I and numerical calculation of line II, and selecting the ground movement deformation according to 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 scheme combines numerical simulation and limit equilibrium method for calculation and 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 then 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 accuracy of numerical simulation. Then, the double-line calculation is used to obtain the surface movement deformation under the influence of mining and take values ​​from it, which can analyze more practical deformation conditions under the influence of mining and provide reliable basic data for stability assessment. Then, it is 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 the errors caused by parameter uncertainty. It is suitable for the 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 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 the slope shape of an embodiment of a slope stability evaluation method under the influence of coal mining in the present invention;

[0020] Figure 3 The figure is a schematic diagram of the strip-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 slope stability evaluation method 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 c 1 、Internal friction angle of structural surface Normal stiffness of structural surface 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, using double-line calculation to determine the surface movement deformation; the double-line calculation includes: I-line theoretical calculation and II-line numerical calculation.

[0028] In the I-line theoretical calculation, the calculation parameters of surface movement and deformation 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 deformation calculation parameters, an analogy method is used to determine (it can also be obtained based on field measured data), including the following steps:

[0030] The surface movement deformation calculation parameters are comprehensively determined based on the coal seam overburden properties, regional experience and test results. The surface movement deformation calculation parameters include the sinking coefficient q, the horizontal movement coefficient b, the strike movement angle δ, the uphill movement angle γ, the downhill movement angle β, the strike boundary angle δ 0 , uphill boundary angle γ 0 , downhill boundary angle β 0 , main influence angle tangent tanβ, mining influence propagation angle θ 0 , 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, and 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 sinking 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 movement coefficient b is corrected using the following formula:

[0043]

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

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

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

[0047] (3) Strike movement angle δ, uphill movement angle γ, downhill movement angle β, strike boundary angle δ 0 , Uphill moving angle γ 0 , downhill moving angle β 0 The size of the main influencing angle tangent tanβ is mainly determined by the structure and properties of the overlying rock.

[0048] The weaker and more broken the overburden is (such as the presence of faults, joints, bedding and other structures), the greater the strike movement angle δ, uphill movement angle γ, downhill movement angle β, and strike boundary angle δ. 0, uphill boundary angle γ 0 and the downhill boundary angle β 0 The smaller it is, the larger the main influence angle tangent tanβ is.

[0049] (4) Mining affects the propagation angle θ 0 The size of the coal seam is mainly determined by the nature of the overlying rock and the inclination of the coal seam.

[0050] The softer the overburden, the more mining affects the propagation angle θ 0 The larger the coal seam inclination, the greater the mining impact propagation angle θ 0 The smaller.

[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 softer 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 the 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 relevant parameters of underground coal mining, 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 ground movement 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 deformation according to preset conditions.

[0072] In this embodiment, the preset conditions for analysis refer to the most unfavorable conditions, that is, the situation where the ground surface 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 respectively to calculate the slope stability. Here, the width of each strip is set between 2 and 4 meters, which can 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 by implicit solution, and 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 formula. In particular, when using the EXCEL table for solution, the simulation analysis module is also used to simulate and analyze in advance the setting of the residual sliding force cell of the nth block to 0 to simulate the optimal value of the stability coefficient cell. 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 strip, 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 strip 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] In addition, 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 strips; Ti is the sliding force caused by the unit width gravity and other external forces of the i-th strip, and the unit is kN / m. i is the anti-sliding 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 force generated by the seepage pressure of the i-th block; T Di =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 soil height 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 ith 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 sWhen 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 of the slope.

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

[0089] P m is the slope mining degree coefficient; Among them, M d H is the normal mining thickness of the coal seam below the slope; 0 is the average mining depth below the slope; D W is the width of the working face within the influence range of slope mining. The influence range of mining is divided according to the surface movement angle, such as D W ≥1.5H 0 When D W =1.5H 0 β s is the slope angle; F is the lithology coefficient, and its 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 ~ 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 using 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 characterize the slope stability; α i is the inclination angle of the sliding surface of the i-th block; φ iis the internal friction angle of the i-th block; P n is the remaining sliding force per unit width of the n-th block, with the unit of kN / m; when P i <0 (i < n), take P i = 0; ψ i-1 is the transfer coefficient of the (i - 1)-th block to the i-th block.

[0097] Step 6, based on numerical calculation and theoretical calculation (i.e., based on the analysis content of Steps 1 - 5), comprehensively analyze and evaluate the stability of the mining-induced slope. The slope stability coefficient F s obtained from the comprehensive analysis, according to the provisions of the Technical Code for Building Slope Engineering (GB50330 - 2013), judge the stability state of the slope, that is:

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

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

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

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

[0102] Among them, F st is the slope stability safety factor. Considering the general working conditions of permanent slopes, when the safety grade of the slope project is grade I, the slope stability safety factor F st takes 1.35; when the safety grade of the slope project is grade II, the slope stability safety factor F st takes 1.30; when the safety grade of the slope project is grade III, the slope stability safety factor F st takes 1.25.

[0103] The slope stability evaluation method under the influence of coal mining provided in this embodiment combines numerical simulation and the limit equilibrium method for calculation and analysis, which can fully consider the constitutive relationship of the slope and the complex structure of the slope under the influence of coal mining, achieving a high calculation accuracy; it can provide effective and reliable basis for the stability assessment, construction utilization, reclamation and restoration of goafs in mountainous and hilly areas, helping to effectively reduce the subsequent treatment costs, effectively utilize the abandoned subsidence land, and ensure the sustainable development of local economic construction.

[0104] The key points are: first, this scheme obtains the potential sliding surface of the slope through numerical analysis. The numerical analysis method can take into account the constitutive relationship of the rock and soil (i.e., the stress-strain relationship) in the slope stability analysis, and then 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 higher numerical simulation accuracy.

[0105] Second, this scheme uses dual-line calculation to obtain the surface movement deformation under the influence of mining and extract values ​​from it, which can analyze the special terrain environment of mountainous hills and more practical slope surface deformation under the influence of mining, and can provide reliable basic data for stability assessment. Among them, in the I-line calculation, for the determination of the horizontal movement coefficient, the slope rock and soil properties, slope angle and horizontal position of the calculation point are comprehensively considered, and the slope correction horizontal movement coefficient is proposed, which solves the difficulty in calculating the surface movement deformation value of the mountain mining slope.

[0106] Third, this scheme combines numerical simulation and limit equilibrium method for calculation and analysis. Based on the determination of sliding surface based on numerical simulation and the acquisition of calculation parameters required for slope by double-line calculation (which also includes numerical simulation), the limit equilibrium method is combined to perform stability calculation with fewer precise parameters, which can reduce the error caused by parameter uncertainty and is suitable for complex analysis scenarios of slopes under the influence of coal mining in mountainous and hilly areas, making the calculation more efficient and the calculation results more reasonable and accurate.

[0107] Fourth, this solution has adopted an implicit solution to solve the slope stability coefficient in a breakthrough way, and overcomes the problem of cumbersome calculation steps in the implicit solution. In the current specifications, the calculation of the stability coefficient of the mining slope is often obtained by explicit solution using the transfer coefficient method. This solution has the problem of a large safety factor. In response to this, this solution proposes a calculation formula for the stability of the mining slope using the implicit solution of the transfer coefficient method. Among them, the solution result of the implicit solution is derived based on strict force balance conditions, which is more accurate than the calculation result of the explicit solution. At the same time, in order to solve the problem of cumbersome steps caused by iterative calculations in the implicit solution, this solution prepares an EXCEL table, and uses the simulation analysis module of the EXCEL table to perform single variable solutions, that is, by setting the residual sliding force of the last block to zero, to simulate the optimal value of the slope stability coefficient. The calculation steps and difficulty are simplified, and the calculation efficiency is improved.

[0108] Fifth, the analysis dimension of this solution is more comprehensive. In the calculation of slope stability under mining, the influence of groundwater level is specially considered (mining may change the flow path and pressure distribution of groundwater, further affecting the mechanical properties of rock and soil). It is suitable for slope stability calculation under various working conditions and has strong versatility.

[0109] Sixth, finally, based on numerical calculations and theoretical calculations (i.e., based on the analysis content of steps 1-5), a comprehensive analysis and evaluation of the stability of the mining slope is carried out. The two methods verify each other and the conclusions obtained are more reliable.

[0110] The above is only an embodiment of the present invention. The common sense such as the known specific structure and characteristics in the scheme is not described in detail here. The ordinary technicians in the relevant field are aware of all the common technical knowledge in the technical field to which the invention belongs before the application date or priority date, can obtain all the existing technologies in the field, and have the ability to apply the conventional experimental means before that date. The ordinary technicians in the relevant field can improve and implement the scheme in combination with their own abilities under the enlightenment given by this application. Some typical known structures or known methods should not become obstacles for the ordinary technicians in the relevant field to implement this application. It should be pointed out that for the technicians in this field, without departing from the structure of the present invention, several deformations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and 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, obtaining terrain parameters and rock and soil parameters; Step 2, obtaining 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 calculation parameters of surface movement and deformation 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; 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; 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 ε in the surface movement deformation under the influence of mining are derived; Step 4, comparing the ground movement deformation under the influence of mining obtained by theoretical calculation of line I and numerical calculation of line II, and selecting the ground movement deformation according to 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.

2. The slope stability evaluation method under the influence of coal mining according to claim 1 is characterized in that: In step 1, the terrain parameters include the slope angle β s , slope width B, slope height H s 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 Normal stiffness of structural surface K n , Structural surface tangential stiffness K s .

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

4. The slope stability evaluation method under the influence of coal mining according to claim 1 is characterized in that: In the I-line theoretical calculation of step 3, the analogy method is used to determine the calculation parameters of surface movement deformation, including the following steps: The surface movement deformation calculation parameters are comprehensively determined according to the properties of the coal seam overburden, regional experience and test results, and 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 influence angle tangent tanβ, mining influence propagation angle θ0, and inflection point offset distance s.

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

6. The slope stability evaluation method under the influence of coal mining according to claim 1 is characterized in that: In step 3, the potential sliding surfaces of the mining slopes 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 step 6, it also includes: drawing a slope stability calculation cross-section diagram based on the potential sliding surface of the slope; in the slope stability calculation cross-section diagram, the slope is divided into a number of strips along the corresponding potential sliding surface of the slope; and then for each strip, the sliding force and anti-sliding force are calculated respectively, so as to calculate the slope stability.

8. The method for evaluating slope stability under the influence of coal mining according to claim 7, 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 solves the problem with a single variable, that is, by setting the residual sliding force of the last block to zero, the optimal value of the slope stability coefficient is simulated.

9. The method for evaluating slope stability under the influence of coal mining according to claim 7, characterized in that: 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: R i =(W i ((1-th i )cosα i -(A+P m (l(e i +e i ′)+ξ(i i +i i ′)))sina i )-N wi -R Di )tanφ i -(ηcosα i tanf i -(1-th i ))c i L i ; The sliding force is calculated using the following formula: T i =W i ((1+n) i )sina i +(A+P m (l(e i +e i ′)+ξ(i i +i i ′)))cosα i )+T Di +n i c i L i Sinai i In the formula, the subscript i is used to distinguish bars, R i is the anti-sliding force caused by gravity and other external forces per unit width of the i-th block, in kN / m; W i is the weight of the i-th block; 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; H i H is the vertical height from the top of the slope to the bottom of the mined coal seam; s is the vertical distance from the top of the slope to the foot of the slope; α i is the inclination angle of the sliding surface of the ith block; A is the comprehensive horizontal seismic coefficient of the slope; c i is the cohesion of the ith block; P m is the slope mining degree coefficient; λ is the lateral pressure coefficient; ε and ε' are the final horizontal deformation value and dynamic horizontal deformation value of the slope top edge respectively; ξ is the second calculation coefficient, ξ i That is, the first calculation coefficient of the i-th block. When H i <H s When ξ=1.0, when H i ≥H s hour, i and i' are the final inclination value and dynamic inclination value of the slope top edge; is the pore water pressure of the i-th block; 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; is the vertical sliding surface force generated by the seepage pressure of the i-th block; φ i is the internal friction angle of the ith block.

10. The method for evaluating slope stability under the influence of coal mining according to claim 7, characterized in that: The slope stability is calculated using the following formula: P n ＝0； P i =P i-1 ψ i-1 +T i -R i / F s ; In the formula, F s is the slope stability coefficient, which is used to characterize the slope stability; the subscript i is used to distinguish strips and blocks, R i is the anti-sliding force caused by gravity and other external forces per unit width of the i-th block, in kN / m; α i is the inclination angle of the sliding surface of the i-th block; φ i is the internal friction angle of the ith block; P i is the remaining sliding force per unit width between the i-th block and the (i + 1)-th block, with the unit of kN / m; P n is the remaining sliding force per unit width of the n-th block, with the unit of kN / m; when P i <0 (i < n), take P i = 0; ψ i-1 is the transfer coefficient of the (i - 1)-th block to the i-th block; Ti is the sliding force caused by the gravity and other external forces per unit width of the i-th block, with the unit of kN / m.

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