A method for determining the layout position of a roadway under a residual coal pillar of a close coal seam group

Abstract

The present application relates to the technical field of mining engineering, and discloses a method for determining the layout position of a roadway under a residual coal pillar in a close-distance coal seam group, which obtains the geological and mining parameters of a target mining area, calculates the initial self-weight stress of the floor, equivalent to a two-dimensional strip uniform load on the surface of a semi-infinite plane body, calculates the additional stress of the floor and superimposes it with the self-weight stress to obtain the equivalent stress tensor before excavation, extracts the principal stress deflection angle and the principal stress ratio parameters in accordance with the foregoing, conducts polar coordinate implicit solving in combination with the rock mass yield criterion to obtain the boundary data of the plastic zone of the roadway surrounding rock, and finally, constructs a comprehensive evaluation constraint condition set containing the plastic zone radius, the stress concentration coefficient and the roof rock property in combination with different horizontal positions and interlayer rock properties to determine the final roadway layout position. The present application comprehensively analyzes the combined action of high stress, principal stress direction adjustment and rock property on the surrounding rock, and realizes the scientization and refinement of the roadway site selection under a complex superimposed coal pillar.

Description

Technical Field

[0001] This invention relates to the field of mining engineering technology, specifically a method for determining the location of roadways under coal pillars left in close proximity to coal seams. Background Technology

[0002] In recent years, with the gradual depletion of shallow coal resources, the proportion of mining in close proximity to coal seams has increased. After the upper coal seam is mined, a large number of coal pillars are often left behind due to geological structure or mining continuity requirements. When it is necessary to arrange mining roadways in the underlying coal seam, the overlying coal pillars will transmit highly concentrated support pressure to the floor, causing drastic changes in the stress field within the floor strata. Current technologies often rely solely on the vertical stress peak value or stress concentration factor of a single coal seam when determining the location of roadways below the coal pillars, lacking a comprehensive consideration of the complex spatial stress environment. Under the action of multiple superimposed coal pillars, the stress response within the floor strata not only exhibits a dramatic increase in numerical nonlinearity but also generates principal stress differences and severe deflections of principal stress directions. This torsion of the principal stress axis directly leads to asymmetric deep distortion and damage in the plastic zone of the roadway surrounding rock. Traditional roadway location assessment methods fail to construct analytical models encompassing the characteristics of principal stress deflection angles and principal stress ratios. Furthermore, they neglect the control of different interlayer lithologies on stress transmission paths and the degree of plasticity development in the surrounding rock, thus failing to comprehensively reflect the coupled disaster-causing mechanism of complex stress environments and multidimensional factors such as rock mass strength. This single-dimensional approach easily leads to the final determined roadway location being situated in a high stress gradient or strong deflection failure zone. Consequently, under mining disturbances, this can trigger severe dynamic disasters such as deep indentation on one side of the roadway, large-scale roof collapse, and even rockbursts, making it difficult to meet the engineering requirements for safe roadway layout in modern complex geological and mining conditions. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for determining the location of roadways under coal pillars in closely spaced coal seam groups.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for determining the location of roadways under coal pillars in closely spaced coal seam groups, comprising the following steps: Obtain the mining and geological parameters of the target mining area, as well as the corresponding physical and mechanical parameters, and calculate the initial self-weight stress data of the target base plate; The force exerted by the overlying coal pillar on the floor is equivalent to a two-dimensional strip uniformly distributed load on the surface of a semi-infinite plane. Based on the two-dimensional strip uniformly distributed load, the additional stress data inside the target base plate is calculated and obtained; The additional stress data is superimposed with the initial self-weight stress data to obtain the equivalent stress tensor before excavation. Based on the equivalent stress tensor before excavation, the principal stress deflection angle and principal stress ratio parameters are extracted. The implicit solution is then performed by combining the yield criterion corresponding to the physical and mechanical parameters to calculate and obtain the boundary data of the plastic zone of the surrounding rock of the roadway. Based on the boundary data of the plastic zone of the surrounding rock of the roadway under different horizontal location information and different interlayer lithological conditions, a comprehensive evaluation constraint set is constructed to determine the final roadway layout location.

[0005] The above method obtains the physical and mechanical parameters and lithological parameters of the multi-coal-seam space, establishes an analytical model of the plastic zone boundary including the principal stress deflection angle and principal stress ratio characteristics, and mathematically integrates and calculates the mechanical characteristic data such as the local high stress environment of the target floor, the increasing principal stress difference, and the principal stress direction deflection, directly outputting the roadway safety coordinates that meet the specified multi-dimensional mechanical constraints. This provides a quantitative decision-making mechanism for roadway layout that is adapted to complex multi-coal-seam environments.

[0006] As a preferred embodiment, the steps of equating the force exerted by the overlying residual coal pillar on the floor slab to a two-dimensional strip-shaped uniformly distributed load on the surface of a semi-infinite plane, and calculating and obtaining the additional stress data inside the target floor slab, specifically include: Define the load intensity variable of the two-dimensional strip uniformly distributed load as the vertical absolute compressive stress value at the center line position of the bottom surface of the remaining coal pillar in the unexcavated state of the roadway; calculate the first boundary direction angle pointing from the center point of the target roadway to the left boundary of the remaining coal pillar, and the second boundary direction angle pointing to the right boundary position. Using the load intensity variable, the first boundary direction angle, and the second boundary direction angle as input parameters, the corresponding additional vertical stress, additional horizontal stress, and additional shear stress are calculated and extracted as the additional stress data.

[0007] The above steps convert the complex local non-uniform boundary compressive stress gradient into a constant boundary condition that can be directly analyzed, thereby realizing the geometric dimensionality reduction of the mechanical response under the eccentric loading of multi-layer coal pillars.

[0008] As a preferred embodiment, the steps of obtaining the equivalent stress tensor before excavation and extracting feature parameters specifically include: Extract the initial vertical self-weight stress from the initial self-weight stress data, add the initial vertical self-weight stress to the additional vertical stress, and obtain the equivalent vertical stress data before excavation; Multiply the initial vertical self-weight stress by the original rock lateral pressure coefficient, and add the additional horizontal stress to obtain the equivalent horizontal stress data before excavation; set the additional shear stress as the equivalent shear stress data before excavation; The above three equivalent stress data are subjected to coordinate matrix transformation, and the maximum principal stress value and minimum principal stress value corresponding to the equivalent stress data are calculated and extracted. The principal stress ratio parameter is calculated based on the maximum and minimum principal stress values, and the principal stress deflection angle parameter is calculated based on the equivalent shear stress data before excavation.

[0009] The above steps extract key feature parameters based on the plane stress state transformation theory, quantify the deflection characteristics of the actual principal stress field inside the target floor space, and construct the core numerical conditions for judging the geometric shape of the extended boundary of the plastic zone of the roadway surrounding rock.

[0010] As a preferred embodiment, the step of implicitly solving for the yield criterion corresponding to the physical and mechanical parameters to calculate and obtain the boundary data of the plastic zone of the roadway surrounding rock specifically includes: Establish a polar coordinate system with the center point of the target roadway as the origin, and define the dimensionless polar radius parameter and the polar angle variable corresponding to different calculation directions; The stress state combination coefficient is calculated using the principal stress ratio parameter, and the relative polar angle parameter is obtained by subtracting the polar angle variable from the principal stress deflection angle parameter. Substitute the maximum principal stress value, the stress state combination coefficient, the relative polar angle parameter, and the dimensionless polar diameter parameter into the polar coordinate stress field analytical expression of the unbounded plane with a circular hole to calculate the boundary radial stress component, the boundary tangential stress component, and the boundary polar coordinate shear stress component. Based on the Mohr-Coulomb yield criterion, an implicit equation in polar coordinates is constructed, and the three boundary stress components mentioned above, as well as the cohesion and internal friction angle values ​​in the physical and mechanical parameters, are input into the implicit equation as known function terms. The implicit equation is solved by traversal, and the corresponding dimensionless polar radius (polar radius is not dimensionless) parameter numerical solution set is obtained. The actual plastic zone boundary polar radius data corresponding to each polar angle direction is calculated, and the roadway surrounding rock plastic zone boundary data is combined and output.

[0011] As a preferred implementation, the comprehensive evaluation constraint set specifically includes: First constraint: The maximum plastic zone radius data obtained from the parsing of the plastic zone boundary data of the surrounding rock of the roadway shall not exceed the preset first safety threshold. Second constraint: The vertical stress concentration factor extracted based on the equivalent vertical stress data before excavation shall not exceed the preset second safety threshold. The third constraint is that the direct top lithology classification data obtained based on the geological parameters does not belong to hard rock or rock strata with a strong tendency to impact.

[0012] In one preferred embodiment, determining the final tunnel layout location includes performing a region exclusion operation: If the ratio of the single-sided butterfly polar diameter corresponding to the candidate coordinate point to the equivalent radius of the roadway is greater than the preset distortion factor safety threshold, then the projection area corresponding to the candidate coordinate point is designated as a first-level restricted area and is removed. If the maximum plastic zone diameter corresponding to the candidate coordinate point intrudes into the effective anchorage section of the theoretically supported anchor cable, then the projection area corresponding to the candidate coordinate point is designated as a second-level restricted area and is eliminated.

[0013] The above steps, by introducing a plastic zone expansion deformation asymmetry assessment mechanism, forcibly eliminate the risk of unilateral rock mass deep slippage caused by principal stress field deflection and extreme spatial regions that lose overall self-bearing capacity.

[0014] As a preferred implementation, after performing the area exclusion operation, the final roadway layout location is determined, and a condition optimization strategy is further executed: Within the remaining selectable area after eliminating the first and second level restricted zones, the additional stress integral results of the candidate coordinate points directly below the goaf are extracted; the core coordinate system positioning point with the smallest envelope area corresponding to the maximum plastic zone radius data and whose direct roof lithology classification data satisfies the third constraint condition is selected as the final roadway layout location.

[0015] As a preferred implementation, if there are double or multiple superimposed coal pillar features above the target mining area, the equivalent transformation and additional stress analysis process are performed respectively, and the additional vertical stress, additional horizontal stress and additional shear stress corresponding to each layer are linearly scalarly added to output the absolute total additional stress tensor data.

[0016] As a preferred implementation, the conditional optimization strategy further includes a nonlinear weight adjustment mechanism: If the obtained direct top lithology classification data is determined to be mudstone or extremely soft rock layer, the safety margin requirement for the plastic zone calculated at the corresponding coordinate point should be appropriately increased.

[0017] As a preferred embodiment, the method further includes a dynamic correction mechanism based on the actual situation on site: Real-time acquisition of actual interlayer spacing and local original rock stress lateral pressure coefficient during actual tunneling process; The actual interlayer spacing at the site is input as a variable into the implicit equation in the polar coordinate system, and the boundary of the butterfly-shaped plastic zone in front of the current tunnel face is solved iteratively again. If the real-time calculation results show that the distortion factor in the plastic zone exceeds the preset distortion factor safety threshold, an adjustment command to increase the horizontal avoidance offset and shift to the low-stress zone will be output in real time.

[0018] The above steps, by establishing a dynamic feedback loop, eliminate the deviation of prior parameters caused by encountering hidden geological anomalies during construction, and ensure that the safety assessment instructions remain effective throughout the entire tunneling cycle.

[0019] This invention provides a method for determining the location of roadways under coal pillars in closely spaced coal seam groups. It has the following beneficial effects: 1. This invention breaks through the limitations of traditional methods that rely solely on a single stress peak value to determine roadway instability. By extracting the principal stress deflection angle and principal stress ratio parameters, and incorporating the direct roof lithology classification data from geological parameters into the comprehensive evaluation constraint set, this invention comprehensively analyzes the combined effects of high-stress environment, high principal stress difference, principal stress direction adjustment, and roadway roof lithology on roadway deformation and damage. This method clarifies that interlayer lithological changes can affect the roadway damage range by altering the stress transmission mode and the degree of plastic development of the surrounding rock, making the selection of roadway location under superimposed coal pillar action more scientific and reasonable.

[0020] 2. This invention equates the force exerted by the overlying coal pillar on the floor to a two-dimensional strip-shaped uniformly distributed load on the surface of a semi-infinite plane, and substitutes it into the implicit equation of the yield criterion in polar coordinates for ergonomic solution. This solves the calculation problem of the irregular attenuation of vertical stress on the floor with burial depth and horizontal distance under the action of multiple superimposed coal pillars. This process transforms the complex local non-uniform compressive stress gradient into a directly analyzable constant boundary condition, revealing the evolution law of the stress of the surrounding rock and the plastic zone of the mining roadway affected by spatial location, and providing high-precision quantitative data support for site selection decision-making.

[0021] 3. This invention establishes engineering exclusion rules by calculating the distortion factor of the unilateral butterfly blade's extreme diameter and the intrusion depth of the maximum plastic zone extreme diameter. This forcibly excludes asymmetric sliding areas of rock mass caused by principal stress field deflection and high-pressure deep extension areas that have lost their self-bearing capacity. In conjunction with the introduction of a dynamic correction mechanism that obtains the actual interlayer spacing and lateral pressure coefficient at the tunneling site in real time and iteratively solves the boundary of the plastic zone, this invention eliminates the deviation of prior parameters caused by hidden geological anomalies during construction and ensures the continuous safety and effectiveness of the engineering execution. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 This is a schematic diagram of different locations of the tunnel in this invention; Figure 3 This is a schematic diagram comparing the boundaries of the plastic zone of the surrounding rock in the tunnel at different horizontal positions according to the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] See attached document Figure 1 This invention provides a method for determining the location of roadways under coal pillars in closely spaced coal seams, which may include the following steps: Execute step S100 to conduct on-site surveys, determine the location of overlying coal pillars, and obtain mining and geological parameters for the target mining area.

[0025] The aforementioned mining and geological parameters include the mining height of the multi-layered coal seam working face, the caving angle of the overlying strata, the burial depth of each coal seam, inter-layer lithological parameters, and physical and mechanical parameters. Using these mining and geological parameters, a spatial profile is drawn that includes the relative positional relationship between the overlying coal pillar and the lower working face.

[0026] In step S200, based on the obtained mining and geological parameters, a collapse model of the overlying strata is constructed, and the support pressure distribution data of the overlying residual coal pillars and goaf are calculated.

[0027] Using the above-mentioned overlying strata collapse model, we analyze the data patterns of stress transmission from the overlying strata and goaf to the lower part of the target mining area, and output the support pressure distribution load data corresponding to the bottom plate area of ​​each coal seam.

[0028] Execute step S300 to construct a stress transfer model for the goaf floor. Based on the above-mentioned support pressure distribution load data, calculate and obtain the initial self-weight stress data and additional stress data of the remaining coal pillar floor.

[0029] The load data of the bearing pressure distribution of the overlying residual coal pillar and the goaf are input into the stress transfer model of the goaf floor to calculate the additional vertical stress generated by the overlying residual coal pillar and the goaf on the target floor. By linearly superimposing the initial self-weight stress of the target floor with the additional vertical stress, the total stress tensor data containing the stress components of any spatial point of the target floor is obtained.

[0030] Execute step S400 to construct a mechanical model of deformation and failure of the surrounding rock of the working face roadway. Based on the acquired total stress tensor data, calculate the principal stress deflection angle and principal stress ratio corresponding to the center point of the target roadway, and calculate and obtain the boundary data of the plastic zone of the surrounding rock of the roadway based on the above principal stress deflection angle and principal stress ratio.

[0031] The equivalent stress tensor before excavation at the center point of the roadway under different preset working conditions is extracted. Using this equivalent stress tensor, the principal stress deflection angle and principal stress ratio parameters under the preset working conditions are calculated. These parameters are then substituted into the polar coordinate equation established based on the yield criterion for implicit solution, and the boundary data of the plastic zone of the roadway surrounding rock, representing the extent of surrounding rock failure, are calculated.

[0032] Step S500 is executed to determine the final roadway layout location based on the boundary data and stress distribution data of the plastic zone of the roadway surrounding rock under different horizontal location information and different interlayer lithological conditions.

[0033] The boundary data of the first plastic zone under different horizontal location information and the boundary data of the second plastic zone under different interlayer lithological conditions were extracted respectively. The above-mentioned horizontal location information includes below the goaf, below the edge of the coal pillar, and below the superimposed coal pillar; the above-mentioned interlayer lithological conditions include the initial interlayer lithology, interlayer hard rock, and interlayer soft rock.

[0034] By comparing the regional expansion dimension and principal stress direction data of the first plastic zone boundary data and the second plastic zone boundary data, the spatial coordinates of the non-stress concentration area and the non-hard rock roof lithology area are output, and the above spatial coordinates are determined as the final roadway layout location.

[0035] Existing technologies, when determining the location of roadways under residual coal pillars, only refer to the peak stress environment data of a single coal seam, without incorporating inter-layer lithology and superimposed coal pillar environmental parameters. The method provided in this embodiment establishes a plastic zone solution model that includes principal stress deflection angles and principal stress ratio characteristics by simultaneously collecting physical and mechanical parameters and lithological parameters from multiple coal seams. This method integrates and calculates the high-stress environment, high principal stress difference, and principal stress direction deflection data of the target floor, outputting roadway locations with specified mechanical constraints. This solves the problem of site selection calculation for roadway layout in the mining of double-layer superimposed residual coal pillars under complex geological and mining conditions.

[0036] This embodiment describes the specific execution process of step S100, which involves multi-source geological parameter exploration and multi-coal seam spatial model construction.

[0037] The original geological parameters of the target mining area were obtained through on-site core drilling and mine geological logging data. These parameters included the thickness of each of the upper, middle, and lower coal seams, the thickness of inter-layer strata, and lithological distribution data. Using this lithological distribution data, corresponding physical and mechanical parameters were obtained through rock mechanics experiments. These parameters included at least the average unit weight of the overlying rock mass, the original rock lateral pressure coefficient, the comprehensive internal friction angle of the rock mass, and the cohesion data of the corresponding strata.

[0038] By extracting the actual mining engineering plan of the mine and on-site laser ranging data, the actual mining parameters of the target mining area are obtained. These mining parameters include the mining height of each coal seam working face, the caving angle of the overlying strata, the location of the goaf boundary of the mined working face, and the geometric dimensions of the multiple overlying residual coal pillars. The geometric dimensions of the multiple overlying residual coal pillars include the width of the first residual coal pillar, the width of the second residual coal pillar, and the horizontal misalignment data between the centerlines of the multiple residual coal pillars.

[0039] Based on the geological and mining parameters obtained above, a spatial profile model of the relative positions of multiple coal seams is constructed in a computer device. A local two-dimensional rectangular coordinate system is established in the spatial profile model. The center point of the target lower roadway to be arranged is set as the origin of the local two-dimensional rectangular coordinate system. The horizontal rightward direction is set as the positive direction of the first coordinate axis, and the vertical downward direction is set as the positive direction of the second coordinate axis.

[0040] In the aforementioned local two-dimensional rectangular coordinate system, based on the obtained data on the thickness of interlayer rock strata and the burial depth of each stratum, the vertical coordinate data of the bottom plate of each coal seam are calibrated. Specifically, the first vertical distance data from the bottom surface of the first remaining coal pillar to the center point of the target roadway, and the second vertical distance data from the bottom surface of the second remaining coal pillar to the center point of the target roadway are extracted and recorded.

[0041] Based on the above-mentioned data on the location of the goaf boundary, the width of each layer of remaining coal pillars, and the horizontal offset, the horizontal range of action of the multiple layers of remaining coal pillars is marked in the aforementioned local two-dimensional rectangular coordinate system. Specifically, the first set of horizontal coordinates of the left and right boundaries of the first layer of remaining coal pillars, and the second set of horizontal coordinates of the left and right boundaries of the second layer of remaining coal pillars are calculated and recorded.

[0042] By mapping the aforementioned first vertical distance data, second vertical distance data, first horizontal coordinate set, and second horizontal coordinate set, a spatial profile map containing the relative positional relationship of the working faces and the staggered characteristics of the double-layered coal pillars is generated. The geometric dimension topology relationship dataset corresponding to the above spatial profile map is extracted and stored as the basic input parameters for the subsequent overlying strata collapse model and bearing pressure calculation process.

[0043] This embodiment describes the specific execution process of step S200, which involves performing analysis of the collapse mechanism of the overlying strata of the superimposed coal pillar and analysis of the supporting pressure.

[0044] Extract the mining and geological parameters obtained in step S100. Based on the obtained overlying strata caving angle and the mining height of each coal seam working face, delineate the caving area boundary of the overlying strata above the target working face in the spatial profile model. Combine the location of the goaf boundary of the already mined working face to determine the fracture span of the overlying strata.

[0045] The average unit weight data of the overlying rock mass within the boundary of the aforementioned collapse area were obtained. The interaction between the collapsed rock mass and the remaining coal pillar was analyzed, and the horizontal floor of the target mining area was divided into the goaf-affected section and the coal pillar bearing section. According to rock mechanics theory, the bearing pressure generated by the overlying rock mass in the goaf and coal pillar areas exhibits a discontinuous, segmented, and nonlinear distribution characteristic.

[0046] Based on the defined goaf influence section and coal pillar bearing section, an analytical model of the support pressure distribution in the coal pillar and goaf is constructed. The support pressure distribution load data in the vertical direction of the above analytical model is calculated and extracted. The above support pressure distribution load data is calculated and solved using the following piecewise exponential function formula: ; In the formula, Represents horizontal distribution coordinates The corresponding vertical support pressure data; This represents the horizontally distributed coordinates established with the origin of a local two-dimensional rectangular coordinate system; Indicates the horizontal boundary coordinates between the goaf-affected section and the coal pillar bearing section; This indicates the horizontal coordinates of the boundary of the coal pillar bearing section. This represents the initial load boundary parameters located at the origin of the coordinate system; This represents the interfacial friction coefficient between the coal seam roof and the overlying strata. Indicates the overall internal friction angle of the target rock stratum; The correlation coefficient represents the cohesion at the interface of the overlying strata. This represents the stress concentration factor of the coal pillar region in the calculated stratigraphic level; This represents the average unit weight of the overlying rock mass; This indicates the burial depth data of the target stratum; Indicates the lateral pressure transmission coefficient of the overlying strata; The base of the natural logarithm, Sine function.

[0047] Substituting the obtained basic parameters such as the interfacial friction coefficient, comprehensive internal friction angle, cohesion correlation coefficient, unit weight, and burial depth into the above-mentioned analytical model of support pressure distribution, point-by-point numerical calculations are performed to generate a model covering the horizontal coordinate interval. Discrete dataset of vertical support pressure distribution within a given range.

[0048] The generated discrete dataset of vertical support pressure distribution is stored in a data structure format. This discrete dataset of vertical support pressure distribution reflects the boundary load characteristics of gravity and fracture structural forces transmitted downwards from the overlying strata and goaf, and is configured as the input boundary condition for the subsequent floor stress transfer model.

[0049] This embodiment describes the specific execution process of step S300, which involves performing the deduction of stress transfer law and the calculation of stress tensor of the semi-infinite planar plate.

[0050] Obtain the support pressure distribution load data output in step S200. Based on rock mechanics principles, the absolute total stress inside the target coal seam floor is composed of the initial self-weight stress data and the additional stress data generated by the mining movement of the overlying strata. Calculate and obtain the initial self-weight stress data of the target mining area unaffected by mining.

[0051] To achieve analytical calculation of the additional stress in the base plate, the discontinuous support pressure distribution load data obtained above is subjected to data dimensionality reduction and feature extraction. On the horizontal distribution coordinates, the complex support pressure curve is discretized and equivalent to multiple continuous linear load distribution segments. The characteristic load peak data and load valley data of each boundary point are extracted respectively, and piecewise linear functions corresponding to each linear load distribution segment are constructed.

[0052] Based on the analytical theory of semi-infinite planar bodies in elasticity, an integral equation for the additional stress generated at any spatial point inside the target base plate is constructed using piecewise linear functions. For any infinitesimal linear load acting on the horizontal boundary of the base plate surface, the additional stress component induced at any target point inside the base plate space is solved by integration using the following core formula: ; In the formula, , , These represent the additional vertical stress component, additional horizontal stress component, and additional shear stress component caused by the linear load of the infinitesimal element at the target point, respectively. This indicates the vertical depth coordinates of the target point within the base plate. This indicates the horizontal coordinate of the target point inside the base plate; This represents the positional integral variable of the distributed load on the horizontal boundary; This represents the piecewise linear function expression for each linear load distribution segment constructed above; and These represent the lower and upper bounds of the horizontal integral for the corresponding linear load distribution segment, respectively.

[0053] Using the aforementioned core formula, definite integral operations are performed on the divided segments of continuous linear loads to obtain the dataset of underlying stress components generated when each load segment acts independently. During this calculation, considering the internal stress unloading characteristics caused by the double-layered coal pillars, a process of eliminating the intermediate stress-constant region is implemented. Specifically, the linear load input data corresponding to the middle region of the overlapping surface of the superimposed coal pillars is forcibly set to zero, and the stress integral transfer calculation for that region is stopped.

[0054] The underlying stress component datasets obtained from the segmented calculations of the remaining effective loads after removing the unloading area are superimposed using tensors to obtain the total additional stress data for a spatial point on the target base plate. This total additional stress data is then added to the initial self-weight stress data of that spatial point using a scalar operation to output the total stress tensor data for any spatial point within the target base plate.

[0055] The total stress tensor data mentioned above reflects the actual mechanical state of the floor after the eccentric load transfer from the overlying coal pillar. The total stress tensor data is fully recorded and output, and configured as the basic numerical parameter for solving the failure boundary of the plastic zone of the surrounding rock in the subsequent roadway.

[0056] This embodiment describes in detail the conversion process of the equivalent two-dimensional strip uniformly distributed load in step S400. This process performs equivalent dimension reduction and additional stress analysis operations on the mechanical response of multi-layer coal pillars under eccentric load.

[0057] Extract the total stress tensor data obtained in step S300. Establish a local rectangular coordinate system in the floor area where the target roadway is located. Set the theoretical center point of the target roadway as the origin of this local rectangular coordinate system, set the horizontal rightward direction as the positive direction of the x-axis, and set the vertical downward direction as the positive direction of the y-axis.

[0058] For the multi-layered residual coal pillar structure above the target area, its impact on the uneven concentrated load in the underlying roadway is mathematically equivalently treated. The first... The force exerted by the remaining coal pillar on the floor is equivalent to a two-dimensional uniformly distributed strip load acting on the surface of a semi-infinite plane. The load intensity variable of this two-dimensional uniformly distributed strip load is defined, and its value is set to the value of the first load in the unexcavated state of the roadway. The absolute compressive stress value in the vertical direction corresponding to the centerline position of the bottom surface of the coal seam pillar. The above operation transforms the complex local non-uniform stress gradient into an analytical constant boundary condition.

[0059] Obtain the horizontal offset data of the centerline of each layer of remaining coal pillars relative to the center point of the target roadway, as well as the width data of the corresponding remaining coal pillars. Based on geometric addition and subtraction operations, calculate and obtain the first layer in a local rectangular coordinate system. The horizontal coordinates of the left and right boundaries of the coal pillar remaining in the stratum.

[0060] Extract the first The vertical distance data from the bottom surface of the remaining coal pillar in the first layer to the center point of the target roadway is obtained. Using the arctangent trigonometric function, the vertical distance from the center point of the target roadway to the first layer is calculated. The first boundary direction angle at the left boundary of the coal pillar remaining in the stratum, and the second boundary direction angle pointing to the right boundary.

[0061] Based on the plane elastic analytical theory of semi-infinite body surface strip loads, the above-mentioned load intensity variable, the first boundary direction angle, and the second boundary direction angle are used as input parameters to calculate the... The additional stress components generated at the center point of the target roadway when a residual coal pillar acts alone. These additional stress components include additional vertical stress, additional horizontal stress, and additional shear stress, which are calculated using the following formula: ; In the formula, , , They represent the first Additional vertical stress, additional horizontal stress and additional shear stress generated by the coal pillar left in the seam at the center point of the target roadway; Indicates the first The load intensity of the equivalent two-dimensional strip uniformly distributed load of the coal pillar left in the layer; Indicates that the center point of the target tunnel points to the first The first boundary direction angle of the left boundary of the coal pillar remaining in the layer; Indicates that the center point of the target tunnel points to the first The second boundary direction angle of the right boundary of the coal pillar remaining in the stratum; It represents pi (π).

[0062] For target mining areas with double or multiple superimposed coal pillars, the aforementioned equivalent transformation and additional stress analysis processes are performed to obtain the additional stress component datasets corresponding to each individual coal seam. By linearly summing the additional vertical stress, additional horizontal stress, and additional shear stress corresponding to each layer, the absolute total additional stress tensor data of the target roadway location in the local Cartesian coordinate system is output. The above absolute total additional stress tensor data is recorded and used as the basic values ​​for subsequent solutions to the principal stress deflection characteristics.

[0063] This embodiment elaborates on the derivation of the equivalent far-field stress tensor and the calculation of key characteristic parameters before excavation in step S400. This process performs a quantitative extraction operation of the principal stress field deflection state.

[0064] Extract the absolute total additional stress tensor data and the original rock lateral pressure coefficient data at the location of the target roadway. Based on the principle of linear superposition, calculate the equivalent far-field stress tensor components at the center point of the target roadway before the excavation simulation operation is performed.

[0065] The specific operating steps include: adding the initial vertical self-weight stress at the target depth to the aforementioned absolute total additional vertical stress to obtain the equivalent vertical stress data before excavation; multiplying the aforementioned initial vertical self-weight stress by the original rock lateral pressure coefficient, and then adding the aforementioned absolute total additional horizontal stress to obtain the equivalent horizontal stress data before excavation; directly setting the obtained absolute total additional shear stress data as the equivalent shear stress data before excavation. Recording the positive and negative signs of the aforementioned equivalent shear stress data, when the value is positive, indicates that the location is in a right-side eccentric loading working environment, and the maximum principal stress axis will undergo a physical process of rightward deflection.

[0066] Based on the plane stress state transformation theory of elasticity, the equivalent vertical stress data, equivalent horizontal stress data, and equivalent shear stress data obtained before excavation are transformed by coordinate matrix, and the maximum principal stress value and minimum principal stress value under this stress state are calculated and extracted.

[0067] Based on the obtained maximum and minimum principal stress values, two key characteristic parameters determining the geometry of the extended boundary of the plastic zone in the target roadway surrounding rock are calculated and extracted. These key characteristic parameters are the principal stress ratio parameter and the principal stress deflection angle parameter, which are analytically solved using the following core formula: ; ; In the formula, This indicates the extracted principal stress ratio parameter; This represents the calculated maximum principal stress value; This represents the calculated minimum principal stress value. The parameter represents the principal stress deflection angle relative to the local vertical coordinate axis; This represents the calculated equivalent shear stress data obtained before excavation. This represents the equivalent vertical stress data before excavation; This represents the equivalent horizontal stress data before excavation. Arctangent function.

[0068] The aforementioned principal stress ratio parameter and principal stress deflection angle parameter constitute the response characteristic index of the stress environment of the floor strata under superimposed coal pillar action. The attenuation of the aforementioned principal stress ratio parameter indicates an increase in the principal stress difference in the target area, while the generation of the aforementioned principal stress deflection angle parameter indicates directional torsion of the local stress field. The acquired data of the aforementioned two characteristic parameters are configured together as constraints and input into the subsequent solution module to perform implicit equation solving operations on the geometric range of the plastic zone boundary.

[0069] This embodiment elaborates on the process of solving the boundary of the plastic zone of the surrounding rock based on the yield criterion in step S400. This process performs a numerical calibration operation on the physical range of the surrounding rock failure under multi-field stress coupling.

[0070] Extract the design geometric parameters of the target tunnel and the shear strength parameters of the corresponding interlayer rock mass. The design geometric parameters include the equivalent circle radius after equivalent processing of the target tunnel cross-section; the shear strength parameters include the cohesion and internal friction angle of the surrounding rock in the target stratum.

[0071] A polar coordinate system is established with the center point of the target tunnel as the origin, and polar radius variables and polar angle variables corresponding to different calculation directions are defined. To achieve dimensionality reduction transformation for analytical calculations, a dimensionless polar radius parameter is defined based on the above equivalent circle radius value and polar radius variables.

[0072] Extract the maximum principal stress value, principal stress ratio parameter, and principal stress deflection angle parameter obtained in the preliminary calculation steps. Calculate the stress state combination coefficient using the obtained principal stress ratio parameter; simultaneously, perform a difference operation between the set polar angle variables for each calculation direction and the extracted principal stress deflection angle parameter to obtain the relative polar angle parameter reflecting the actual stress direction.

[0073] Substituting the aforementioned maximum principal stress values, stress state combination coefficients, relative polar angle parameters, and dimensionless polar diameter parameters into the analytical expression of the polar coordinate stress field for an unbounded plane with a circular hole, the three boundary stress components of the rock mass surrounding the target tunnel at the boundary of the plastic zone are calculated. These three boundary stress components specifically include: the boundary radial stress component, the boundary tangential stress component, and the boundary polar coordinate shear stress component.

[0074] A rock mass failure mechanics assessment model is obtained. An implicit equation in polar coordinates is constructed based on the classical Mohr-Coulomb yield criterion. The obtained boundary radial stress components, boundary tangential stress components, and boundary polar coordinate shear stress components are input into this implicit equation as known function terms. The core implicit equation formula for determining the boundary of the plastic zone is expressed as follows: ; In the formula, This represents the calculated boundary radial stress components; This represents the calculated boundary tangential stress components; This represents the calculated boundary polar coordinate shear stress components; This represents the cohesion value of the surrounding rock. This represents the numerical value of the internal friction angle of the surrounding rock. sine function, Cosine function.

[0075] The above formula establishes an equation relating the complex stress tensor at critical failure to the shear strength index of the rock mass itself. Since the three boundary stress components all contain nested dimensionless polar radius parameters to be solved, a numerical iterative calculation program is initiated to perform a comprehensive solution to the above implicit equations.

[0076] exist Within the polar angle variable range, obtain the corresponding dimensionless polar diameter parameter numerical solution set. Perform an inverse conversion between the obtained dimensionless polar diameter parameter numerical solution set and the set equivalent circle radius value to calculate the actual plastic zone boundary polar diameter data corresponding to each polar angle direction.

[0077] The actual polar diameter data of the plastic zone boundary are scatter-connected in a polar coordinate system to output the target roadway surrounding rock plastic zone boundary dataset. This plastic zone boundary dataset exhibits a four-lobed expansion morphology with central symmetry in planar coordinates, forming mapping data of the directional expansion area of ​​non-uniform rock failure. This dataset is recorded and stored as a final judgment parameter for subsequent evaluation of roadway surrounding rock structural stability and determination of the final layout location.

[0078] This embodiment describes the specific execution process of step S500, which involves performing a comprehensive evaluation operation that integrates multiple factors to determine the optimal location of the roadway.

[0079] Extract the boundary dataset of the plastic zone of the roadway surrounding rock and the dataset of key feature parameters generated in step S400 for different preset working conditions. Set multiple analysis working conditions at different horizontal positions. The above analysis working conditions include at least the following: the first horizontal position working condition, which aligns the center line of the target roadway with the center line of the goaf in the vertical direction; the second horizontal position working condition, which aligns the center line of the target roadway with the edge of the overlying coal pillar in the vertical direction; and the third horizontal position working condition, which aligns the center line of the target roadway with the stress concentration core area of ​​the double-layer superimposed coal pillar in the vertical direction.

[0080] For each of the aforementioned horizontal positions and analysis conditions, the corresponding first plastic zone boundary dataset is extracted. From this dataset, the maximum plastic zone radius and the symmetry axis deflection angle of the plastic zone expansion morphology are extracted for each condition. These two indicators are recorded and compared at different horizontal positions to quantitatively assess the impact of changes in the roadway's horizontal position on the extent and direction of surrounding rock failure.

[0081] Under the determined critical horizontal position conditions, multiple analysis conditions with different interlayer lithologies are set. The above-mentioned lithological analysis conditions include at least: the first interlayer lithological condition, using the physical and mechanical parameters of the initial interlayer lithology; the second interlayer lithological condition, using the physical and mechanical parameters of the interlayer hard rock; and the third interlayer lithological condition, using the physical and mechanical parameters of the interlayer soft rock.

[0082] For each interlayer lithological analysis condition specified above, the corresponding second plastic zone boundary dataset is extracted. From the second plastic zone boundary dataset, the maximum plastic zone radius data under each lithological condition is parsed. The above indicators under different lithological conditions are recorded and compared to quantitatively evaluate the control effect of interlayer lithological changes on the instability range of the surrounding rock.

[0083] Based on the above multi-dimensional comparative analysis results, a comprehensive set of evaluation constraints for the location of roadways is established. This comprehensive set of constraints includes: a first constraint, the radius of the maximum plastic zone of the roadway surrounding rock must not exceed the first safety threshold determined according to the support design; a second constraint, the vertical stress concentration coefficient of the roadway roof surrounding rock must not exceed the second safety threshold determined according to the rock strata stability; and a third constraint, the lithology classification data of the immediate roof of the roadway must not belong to hard rock or rock strata with a strong tendency to impact.

[0084] The process iterates through all preset horizontal position conditions, comparing the calculated maximum plastic zone radius data, vertical stress concentration factor data, and interlayer lithology classification data with the aforementioned comprehensive evaluation constraint set. A set of horizontal position coordinates that simultaneously satisfies all three constraints is then selected.

[0085] From the selected set of horizontal coordinates, choose the coordinate point with the minimum and maximum plastic zone radius and the lowest vertical stress concentration factor, and determine this coordinate point as the final roadway layout location. Output the geometric coordinate data of the final roadway layout location as the positioning basis for mine roadway excavation engineering.

[0086] This embodiment uses the actual geological conditions of a certain mine as a background and verifies the reliability of the aforementioned model and calculation method through specific numerical mapping.

[0087] This example is for mine 9. -2 The spatial mining relationship between the coal seam and the underlying No. 19 coal seam was analyzed. (Overlying No. 9) -2 The coal seam has been mined out, leaving a 30m wide inclined coal pillar at the working face boundary, as shown in the attached figure. Figure 2 As shown, a mining roadway is planned to be arranged in the lower No. 19 coal seam (19105 working face area).

[0088] Based on the basic data obtained in step S100: 9 -2 Interlayer distance (bottom depth) between coal seam and coal seam No. 19 The average burial depth of the overlying strata is 20m. The depth is 350m. Rock mechanical parameters were determined through laboratory testing: surrounding rock cohesion. internal friction angle Original rock lateral pressure coefficient .

[0089] The 30m coal pillar width and interlayer spacing were input into the analytical system to construct a stress transfer model of the semi-infinite planar body floor. The system automatically identified three typical areas (red, blue, and purple) in the attached diagram, each corresponding to a different stress influence environment, serving as a comparative condition for subsequent site selection assessment.

[0090] By executing steps S200 and S300, the distribution of the additional stress field generated by the 30m residual coal pillar in the underlying strata is calculated. (Combined with...) Figure 2 Extract the core stress characteristic parameters from three preset locations: Red area (condition 1): located at 9 -2 Directly below the goaf. Due to its distance from the remaining coal pillars, this area is mainly affected by the residual stress at the edge of the goaf. Calculation results show that the principal stress ratio at this location is higher than that at the edge of the goaf. Approaching 1.0, the maximum principal stress deflection angle The stress field approaches 0°. This indicates that the stress field distribution in this region is close to the original rock state, with no obvious stress concentration or directional torsion.

[0091] Blue area (Condition 2): Located at 9 -2 The projected area at the edge of the remaining coal pillar. Influenced by the drastically changing support pressure gradient at the edge of the 30m coal pillar, the equivalent shear stress at this location... The peak value was reached. The calculated maximum principal stress axis was deflected ( (Approximately between 25° and 35°), and the principal stress ratio A significant decrease. This high gradient and strong deflection characteristic indicates a serious risk of shear failure at this location.

[0092] Purple area (condition 3): located at 9 -2 Directly below the center of the remaining coal pillar. This area is located within the vertical stress superposition zone of the 30m coal pillar's bearing core. The calculated equivalent vertical stress... Much higher than the original rock's self-weight stress, principal stress ratio It drops below 0.45. Although the principal stress deflection angle Due to its relatively low symmetry, the extremely high deviatoric stress environment indicates that the surrounding rock will experience large-scale compaction failure.

[0093] Based on the stress components of the above three types of regions, the geometric boundary data of the plastic zone of the surrounding rock in the roadway are calculated by substituting them into the implicit equations of the polar coordinate system constructed in step S400: In the red area (below the goaf), the calculated boundary of the plastic zone exhibits a uniform circular or elliptical shape, and the maximum failure radius is only 1.1 times the equivalent radius of the roadway. This means that arranging roadways in this area requires only conventional support strength to ensure stability.

[0094] In the blue area (coal pillar edge), the plastic zone exhibits typical asymmetric butterfly-shaped distortion. Due to the deflection of the principal stress axis, the butterfly's blades rapidly expand towards the direction of maximum stress gradient, with the maximum failure radius (butterfly diameter) surging to over 3.5m. This asymmetric failure can lead to unilateral roof collapse or asymmetric intrusion of both sides, posing a significant challenge to directional support.

[0095] In the purple area (directly below the coal pillar), the plastic zone evolves into a large-sized symmetrical butterfly shape. Although the shape returns to symmetry, due to the extreme deviatoric stress, the depth of the four butterfly blades expands, which can easily induce penetrating fractures in the deep rock strata of the roadway.

[0096] Based on the comprehensive evaluation system of step S500, the final decision on the location of the mining roadway for the 19105 working face is made: Based on the calculated maximum plastic zone radius and stress concentration factor, the purple and blue areas are automatically excluded by the system because their failure radii exceed the safety threshold (set to 2.0m in this example).

[0097] Final decision: Prioritize the red area (9) -2 The projected area below the goaf is used as the roadway layout point. At this location, the additional stress generated by the 30m residual coal pillar has decayed to a negligible level, and the plastic zone of the surrounding rock is in a low-stress stable state.

[0098] Furthermore, based on the inter-layer lithology detection data of the mine, it was confirmed that the immediate roof of coal seam No. 19 is medium-hard sandy mudstone, which does not have a strong tendency to impact, thus meeting the third constraint condition. Through the extrapolation and calculation power of the above typical examples, this invention provides accurate numerical logic and safety judgment basis for the accurate positioning of mine roadways under complex superimposed coal pillars.

[0099] See attached document Figure 2 This embodiment provides a specific implementation strategy for tunnel layout decision-making based on the aforementioned physical model and calculation results. This strategy couples multi-dimensional stress characteristic parameters, plastic zone evolution morphology, and rock mass physical and mechanical properties to construct a closed-loop engineering execution procedure that includes regional exclusion, condition optimization, and dynamic correction.

[0100] The primary execution logic of this strategy is to establish engineering boundary lines, eliminating areas prone to severe surrounding rock damage from the candidate coordinate set. (Extracting attached data...) Figure 2 The three partition coordinate datasets defined in the document specify the following two categories of high-risk areas that must be excluded: The first category is the high-gradient, strong-deflection forbidden zone (see attached document). Figure 2 (The blue area in the image).

[0101] The system extracts this region (9) 2The stress characteristics (below the edge of the remaining coal pillar) are mechanically fingerprinted as follows: principal stress deflection angle. The values ​​rise sharply, and there is an extremely high shear stress gradient within the region. This mechanical environment directly leads to severe asymmetric butterfly distortion in the plastic zone of the surrounding rock in the calculation output.

[0102] During implementation, the system defines a distortion factor safety threshold (e.g., the ratio of the single-sided butterfly blade diameter to the equivalent radius of the roadway must not exceed 2.5). When the butterfly blade diameter calculated for any candidate coordinate point within the blue area exceeds this threshold, it means that excavation at that location will lead to deep slippage and asymmetric intrusion of the rock mass on one side, which conventional homogeneous support cannot resist. Therefore, the system issues an instruction to the execution terminal to forcibly designate the blue projection area and its horizontal buffer zone as a first-level restricted area.

[0103] The second category is the restricted area for deep propagation of high-pressure stress (corresponding appendix) Figure 2 (The purple area in the image).

[0104] The system extracts this region (9) 2 The stress characteristics (directly below the center of the remaining coal pillar) exhibit mechanical fingerprints as follows: principal stress deflection angle. It is close to zero, but the ratio of the equivalent vertical stress to the initial original rock stress (stress concentration factor) reaches its peak.

[0105] In this environment, although the plastic zone remains symmetrical, the expansion depth of the four leaflets reaches its global maximum. The system sets a second-level safety constraint: when the maximum plastic zone diameter of the candidate coordinates intrudes into the effective anchorage section of the theoretical support anchor cable, the surrounding rock is determined to be in a high-stress fractured state and lose its self-bearing capacity. Accordingly, the system designates the purple projection area as a second-level restricted area.

[0106] After eliminating the high-risk areas mentioned above, the system then examines the remaining candidate coordinate system spaces (mainly concentrated in the adjacent areas). Figure 2 The red area shown is 9 2 The optimal conditions for starting the goaf (directly below the goaf) are selected.

[0107] The first-level selection is based on the principle of low-stress steady state.

[0108] Within the red optional area, the system iterates through the additional stress integration results at each coordinate point. Due to the influence of the support pressure far from the 30m coal pillar, the principal stress ratio in this area is higher than that in the red optional area. Maintaining a high value (close to equilibrium), the plastic zone morphology degenerates into a conventional near-circular shape, with the smallest maximum failure radius. The system prioritizes marking the coordinate points with the smallest plastic zone envelope area as primary candidate points.

[0109] The second-level selection is based on the principle of lithological hazard constraints. For the marked first-level candidate points, the system retrieves engineering geological borehole data at that depth and extracts the lithological physical parameters of the immediate top and the basic top of the target stratum.

[0110] Here, a nonlinear weight adjustment mechanism is introduced: if the direct top is determined to be mudstone or extremely soft rock layer, because it is prone to rheological expansion under long-term static load, the system will appropriately increase the safety margin requirement of the plastic zone calculated at that coordinate point. If the immediate roof is determined to be high-strength brittle hard rock such as fine sandstone, and possesses strong impact tendency indicators, the system will execute a veto decision. This is because even if the point is in a low-stress zone, under the disturbance of surrounding mining, the high elastic energy accumulated in the hard rock cannot be released through appropriate plastic deformation, which can easily induce sudden floor rockbursts or roof rockbursts.

[0111] The final optimal site was precisely located within the core coordinate system of the red area, which satisfies the dual conditions of minimizing the expansion radius of the plastic zone and ensuring that the lithology of the top and bottom plates does not belong to the impact hazard source.

[0112] After optimization, the system converts the selected theoretical coordinates into absolute three-dimensional coordinates under the mine measurement and control network, and generates digital construction instructions that include tunneling azimuth, horizontal offset and support design strength.

[0113] Meanwhile, the system is equipped with a dynamic correction and error prevention mechanism that is tailored to the actual site conditions. During the actual tunnel excavation, if the drilling parameters of the roadheader or the data fed back by the advanced detection radar indicate that the actual interlayer spacing suddenly thins, or that an unforeseen local abnormal geological structure zone (such as a concealed fault) has been crossed, the actual local original rock stress lateral pressure coefficient and rock mass shear strength parameters will undergo abrupt changes, deviating from the initial set values.

[0114] Upon triggering an anomaly alarm, the system will capture new on-site detection parameters in real time and input them as variables into the aforementioned implicit equations in the polar coordinate system to iteratively solve the boundary of the butterfly-shaped plastic zone in front of the current working face. If the real-time calculation results show that the plastic zone distortion factor exceeds the safety threshold, the system will immediately output an adjustment command: requiring the construction unit to increase the horizontal avoidance offset (shifting deeper into the red low-stress zone), and simultaneously output a high-order asymmetric support parameter scheme matching the anomaly state, thereby forming a complete safety closed loop of prediction, evaluation, feedback, and correction at the engineering execution level.

[0115] Specific application examples: A certain mine faces complex operating conditions involving the mining of multiple coal seams in close proximity. Overlying 9... -2 The coal seam has been completely mined, leaving a 30m wide inclined coal pillar. It is now proposed to construct a mining roadway in coal seam No. 19, 20m deep beneath the underlying floor.

[0116] The obtained rock mechanics parameters are as follows: average burial depth of overlying strata Cohesion of surrounding rock internal friction angle Original rock lateral pressure coefficient .

[0117] First, an analytical model of the bearing pressure distribution in the coal pillar and goaf is constructed. This model includes bearing pressure distribution load data generated by the overlying strata. It exhibits piecewise nonlinear characteristics: ; Subsequently, the complex load described above is converted into an equivalent two-dimensional strip uniformly distributed load, and the first... The additional stress component generated by the remaining coal pillar at the center point of the target roadway. This is the additional vertical stress. For example: ; After calculating the equivalent stress tensor, the principal stress ratio parameters that determine the failure mode of the surrounding rock in the roadway are extracted. With principal stress deflection angle parameters : ; ; The calculated maximum principal stress values ​​and stress state combination coefficients are substituted into the polar coordinate stress field of the unbounded plane with a circular hole to obtain the boundary stress components, and then input into the implicit equations based on the Mohr-Coulomb yield criterion for traversal solving: ; The actual plastic zone boundary is obtained by solving the set of dimensionless polar radius parameters.

[0118] To verify the effectiveness of this solution, three sets of comparative verification conditions were set up, and a comprehensive evaluation was conducted using traditional methods and the method of this invention: Traditional site selection method: Only refers to vertical stress distribution data. The traditional method assumes that the vertical stress below the edge of the coal pillar is lower than that directly below the coal pillar and is far from the water accumulation area of ​​the goaf. Therefore, it recommends to arrange the roadway below the edge of the coal pillar (blue area). In actual tunneling experiments, it was found that the roadway in this area experienced severe unilateral asymmetric floor heave and roof shear displacement, resulting in large-scale failure of support equipment and a repair rate of 85%.

[0119] The site selection method of this invention: introducing principal stress deflection angle The distortion characteristics of the plastic zone. Calculations in this invention indicate the equivalent shear stress below the edge of the coal pillar. Reaching peak value, principal stress axis deflection angle about This leads to severe unilateral butterfly-shaped distortion in the plastic zone, intruding into the anchorage section of the anchor cable, which is a high-risk restricted area; while the principal stress ratio directly below the goaf (red area) is close to equilibrium, and the stress field is not deflected. This invention mandates that this area be designated as the optimal placement point. Field experiments show that in roadways positioned using the method of this invention, the deformation of the surrounding rock is reduced by 72%, no asymmetric compression failure occurs, and the support equipment remains intact.

[0120] See attached document Figure 3 , attached Figure 3 It clearly shows the expansion dimension and geometric shape of the plastic zone of the surrounding rock under different horizontal working conditions of the tunnel.

[0121] Solid line outline (directly below the goaf): corresponds to the aforementioned first-level candidate point. Figure 3 The data shows that under this condition, the plastic zone is a gently sloping, near-circular shape, with a very small maximum diameter, and no obvious butterfly-shaped expansion. This indicates that in this area, the additional eccentric stress caused by the remaining coal pillar has been largely dissipated, and the roadway is in a low-stress, steady-state environment. Conventional support can ensure the stability of the surrounding rock, confirming the rationality of selecting this point as the optimal roadway location in this invention.

[0122] Dashed outline (below the edge of the coal pillar): corresponds to the aforementioned high gradient strong deflection restricted area. Figure 3 The data shows that due to intense shear stress, the maximum principal stress axis deflected downwards and to the right. The plastic zone evolved into a distorted, asymmetrical butterfly shape, with the butterfly blades rapidly expanding towards the lower right and upper left corners, and its unilateral extreme diameter far exceeding the safety threshold. This morphological feature intuitively explains the physical mechanism by which unilateral bulging and eccentric damage are highly likely to occur at this location.

[0123] The dotted-line outline (directly below the coal pillar): corresponds to the aforementioned high-pressure stress deep expansion restricted area. Figure 3 The data shows that although the plastic zone maintains a symmetrical distribution (with the principal stress deflection angle close to zero), the extremely high vertical principal stress causes the butterfly-shaped sections infiltrate deep into the surrounding rock in all four directions. This indicates that the top and bottom plates in this area are severely fractured, and the anchor cable support system will be unable to provide an effective anchoring foundation, necessitating its removal.

Claims

1. A method for determining the location of roadways under coal pillars remaining in closely spaced coal seams, characterized in that, Includes the following steps: Obtain the mining and geological parameters of the target mining area, as well as the corresponding physical and mechanical parameters, and calculate the initial self-weight stress data of the target base plate; The force exerted by the overlying coal pillar on the floor is equivalent to a two-dimensional strip uniformly distributed load on the surface of a semi-infinite plane. Based on the two-dimensional strip uniformly distributed load, the additional stress data inside the target base plate is calculated and obtained; The additional stress data is superimposed with the initial self-weight stress data to obtain the equivalent stress tensor before excavation. Based on the equivalent stress tensor before excavation, the principal stress deflection angle and principal stress ratio parameters are extracted. The implicit solution is then performed by combining the yield criterion corresponding to the physical and mechanical parameters to calculate and obtain the boundary data of the plastic zone of the surrounding rock of the roadway. Based on the boundary data of the plastic zone of the surrounding rock of the roadway under different horizontal location information and different interlayer lithological conditions, a comprehensive evaluation constraint set is constructed to determine the final roadway layout location.

2. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 1, characterized in that, The steps of equating the force exerted by the overlying residual coal pillar on the floor plate to a two-dimensional strip-shaped uniformly distributed load on the surface of a semi-infinite plane, and calculating and obtaining the additional stress data inside the target floor plate, specifically include: The load intensity variable of the two-dimensional strip uniformly distributed load is defined as the absolute compressive stress value in the vertical direction at the center line position of the bottom surface of the left coal pillar in the unexcavated state of the roadway. Calculate the first boundary direction angle pointing from the center point of the target roadway to the left boundary of the remaining coal pillar, and the second boundary direction angle pointing to the right boundary. Using the load intensity variable, the first boundary direction angle, and the second boundary direction angle as input parameters, the corresponding additional vertical stress, additional horizontal stress, and additional shear stress are calculated and extracted as the additional stress data.

3. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 2, characterized in that, The steps of obtaining the equivalent stress tensor before excavation and extracting feature parameters specifically include: Extract the initial vertical self-weight stress from the initial self-weight stress data, add the initial vertical self-weight stress to the additional vertical stress, and obtain the equivalent vertical stress data before excavation; Multiply the initial vertical self-weight stress by the original rock lateral pressure coefficient, and add the additional horizontal stress to obtain the equivalent horizontal stress data before excavation; The additional shear stress is set to the equivalent shear stress data before excavation; The above three equivalent stress data are subjected to coordinate matrix transformation, and the maximum principal stress value and minimum principal stress value corresponding to the equivalent stress data are calculated and extracted. The principal stress ratio parameter is calculated based on the maximum and minimum principal stress values, and the principal stress deflection angle parameter is calculated based on the equivalent shear stress data before excavation.

4. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 3, characterized in that, The step of implicitly solving for the yield criterion corresponding to the physical and mechanical parameters to calculate and obtain the boundary data of the plastic zone of the surrounding rock in the roadway specifically includes: Establish a polar coordinate system with the center point of the target roadway as the origin, and define the dimensionless polar radius parameter and the polar angle variable corresponding to different calculation directions; The stress state combination coefficient is calculated using the principal stress ratio parameter, and the relative polar angle parameter is obtained by subtracting the polar angle variable from the principal stress deflection angle parameter. Substitute the maximum principal stress value, the stress state combination coefficient, the relative polar angle parameter, and the dimensionless polar diameter parameter into the polar coordinate stress field analytical expression of the unbounded plane with a circular hole to calculate the boundary radial stress component, the boundary tangential stress component, and the boundary polar coordinate shear stress component. Based on the Mohr-Coulomb yield criterion, an implicit equation in polar coordinates is constructed, and the three boundary stress components mentioned above, as well as the cohesion and internal friction angle values ​​in the physical and mechanical parameters, are input into the implicit equation as known function terms. The implicit equation is solved by traversal, and the corresponding numerical solution set of dimensionless polar diameter parameter is obtained. The actual plastic zone boundary polar diameter data corresponding to each polar angle direction is calculated, and the boundary data of the plastic zone of the roadway surrounding rock is output by combination.

5. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 4, characterized in that, The comprehensive evaluation constraint set specifically includes: First constraint: The maximum plastic zone radius data obtained from the parsing of the plastic zone boundary data of the surrounding rock of the roadway shall not exceed the preset first safety threshold. Second constraint: The vertical stress concentration factor extracted based on the equivalent vertical stress data before excavation shall not exceed the preset second safety threshold. The third constraint is that the direct top lithology classification data obtained based on the geological parameters does not belong to hard rock or rock strata with a strong tendency to impact.

6. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 5, characterized in that, Determining the final tunnel layout includes performing an area exclusion operation: If the ratio of the single-sided butterfly polar diameter corresponding to the candidate coordinate point to the equivalent radius of the roadway is greater than the preset distortion factor safety threshold, then the projection area corresponding to the candidate coordinate point is designated as a first-level restricted area and is removed. If the maximum plastic zone diameter corresponding to the candidate coordinate point intrudes into the effective anchorage section of the theoretically supported anchor cable, then the projection area corresponding to the candidate coordinate point is designated as a second-level restricted area and is eliminated.

7. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 6, characterized in that, After determining the final tunnel layout location and performing the area exclusion operation, a condition optimization strategy is further implemented: In the remaining selectable area after removing the first-level and second-level restricted areas, the additional stress integral results of the candidate coordinate points directly below the goaf are extracted; The core coordinate system positioning point with the smallest envelope area corresponding to the maximum plastic zone radius data and whose direct roof lithology classification data satisfies the third constraint condition is selected as the final roadway layout location.

8. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 2, characterized in that, If there are double or multiple superimposed coal pillars above the target mining area, the equivalent transformation and additional stress analysis processes are performed respectively, and the additional vertical stress, additional horizontal stress and additional shear stress corresponding to each layer are linearly scalarly added to output the absolute total additional stress tensor data.

9. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 7, characterized in that, The conditional optimization strategy also includes a nonlinear weight adjustment mechanism: If the obtained direct top lithology classification data is determined to be mudstone or extremely soft rock layer, the safety margin requirement for the plastic zone calculated at the corresponding coordinate point should be appropriately increased.

10. The method for determining the location of roadways under coal pillars in closely spaced coal seams according to claim 4, characterized in that, It also includes a dynamic correction mechanism based on the actual situation on site: Real-time acquisition of actual interlayer spacing and local original rock stress lateral pressure coefficient during actual tunneling process; The actual interlayer spacing at the site is input as a variable into the implicit equation in the polar coordinate system, and the boundary of the butterfly-shaped plastic zone in front of the current tunnel face is solved iteratively again. If the real-time calculation results show that the distortion factor in the plastic zone exceeds the preset distortion factor safety threshold, an adjustment command to increase the horizontal avoidance offset and shift to the low-stress zone will be output in real time.

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