Impact prevention-based section coal pillar width determination method

Abstract

The invention relates to the technical field of mining engineering and rock stratum control, and discloses a section coal pillar width determination method based on scour prevention, and the method comprises the steps: constructing a whole-process mining numerical model, and determining a first optimal interval according to stress evolution characteristics; extracting the maximum vertical stress value of the advance area of the working face, dynamically correcting the stress concentration coefficient in the limit equilibrium theory, calculating the width of the limit equilibrium area of the coal pillar, and determining the width as a theoretical hardness lower limit; based on a mine burial depth matching engineering case library, performing statistics to obtain a second optimal interval; and performing intersection operation on the dual optimization interval to obtain a preliminary feasible region, performing one-way inequality truncation by using a theoretical hardness lower limit, and selecting an optimal width in an effective decision space. According to the method, through triangular verification of numerical simulation, theoretical calculation and engineering analogy, systematic deviation of a single method is eliminated, and coal pillar parameters meeting the dual requirements of anti-impact safety and high resource recovery rate are accurately positioned.

Description

A method for determining the width of a section coal pillar based on anti-scour Technical Field

[0001] This invention relates to the fields of mining engineering and rock strata control technology, specifically a method for determining the width of a coal pillar in a section based on rock erosion prevention. Background Technology

[0002] Leaving coal pillars is a primary technical means of maintaining the stability of pre-mining roadways in coal mining, and the setting of its geometric parameters directly affects the prevention and control of rockburst disasters. In deep, high-stress mining environments, to reduce the risk of dynamic disasters, traditional rockburst prevention theories tend to design coal pillars with smaller widths, aiming to promote the coal pillar cross-section to enter the plastic yield state to the greatest extent possible. By eliminating or reducing the internal elastic core area, the accumulation of high elastic potential energy is suppressed, thereby reducing the frequency and intensity of rockbursts.

[0003] However, the reduction in coal pillar width is strictly constrained by the control capacity of the surrounding rock. Excessively narrow coal pillars are highly susceptible to structural instability or collapse under continuous overburden loads, failing to provide necessary lateral support for the mining roadway and leading to severe roadway deformation or even abandonment. Conversely, adopting a wide coal pillar roadway protection scheme, typically exceeding 50 meters in width, solely to ensure stability, while mitigating instability risks, results in significant waste of coal resources and severely reduces the mining area's recovery rate.

[0004] Furthermore, during actual mining, the coal pillar section is situated in a complex stress field environment. It not only bears the combined lateral support pressure from the goaf on both sides but may also be affected by concentrated stress transmitted downwards from the upper coal pillar, with the impact depth often exceeding 100 meters. Existing technologies, when determining the width of the coal pillar, often struggle to quantify the specific impact of these multiple stress superpositions on coal body stability. They also find it difficult to find a precise balance between ensuring roadway support safety, reducing the risk of rockburst, and improving resource recovery. A parameter determination mechanism that comprehensively considers mechanical mechanisms, stress evolution characteristics, and engineering empirical experience is lacking. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for determining the width of a section coal pillar based on anti-rockburst, which solves the problem of accurately determining the width of a section coal pillar in deep, high-stress mining environments that can effectively eliminate the risk of rockburst while balancing the stability of the surrounding rock in the roadway and maximizing the recovery of coal resources.

[0006] To achieve the above objectives, the present invention provides a method for determining the width of a section coal pillar based on anti-scour, which integrates full-process mining numerical simulation, limit equilibrium theory calculation based on field measured data correction, and multi-mine engineering analogy experience. Through the logical constraints and fusion of multi-source data, the method achieves accurate determination of the width of the anti-scour coal pillar under deep mining conditions.

[0007] The method specifically includes the following steps: First, a numerical model of the target mine is constructed and the entire mining process is simulated. By analyzing the vertical stress distribution characteristics around the longwall face, the first preferred range for the coal pillar width is initially determined based on the stress peak location and the stress reduction zone range. Second, in the numerical model, the distribution curve of the advance support pressure in the direction of the longwall face advance is traversed and tracked to extract the maximum vertical stress value in the solid coal area in front of the coal wall of the longwall face, which is used as the key correction source data. Subsequently, the stress concentration coefficient in the limit equilibrium theory is dynamically corrected using the key correction source data, and the corrected coefficient and the width of the plastic zone of the coal pillar are used to calculate... The model calculates the width of the limit equilibrium zone and establishes it as the theoretical hard lower limit of the section coal pillar width. Simultaneously, a case database containing historical engineering data from multiple mines is established. Using mine depth as a benchmark, engineering analogy matching is performed to screen successful cases under similar geological conditions and conduct statistical analysis, deriving an empirical range of coal pillar widths as the second preferred interval. Finally, the intersection operation is performed on the first and second preferred intervals to obtain a preliminary feasible region. The theoretical hard lower limit is used to truncate the preliminary feasible region using a one-way inequality constraint, eliminating values ​​smaller than the theoretical hard lower limit. The final section coal pillar width is then selected within the remaining effective decision space.

[0008] In one possible implementation, the determination of the first preferred interval follows the principle of stress release and load balance. Specifically, a width range in a plastically softened state with residual strength is selected to ensure that the vertical stress distribution within this range is gentle, without high static load accumulation, and can effectively release elastic energy, thereby eliminating the static source of rockburst.

[0009] To ensure the accuracy of key correction source data, when extracting the maximum vertical stress value in the solid coal area in front of the working face, monitoring lines are laid out in the leading area of ​​the working face in the numerical model. The density of data monitoring points on the monitoring lines is increased in the estimated stress concentration area to accurately capture the actual stress extreme points and prevent the omission of peak values ​​due to excessively large data sampling intervals.

[0010] The core innovation of this invention at the theoretical calculation level lies in the dynamic correction of the stress concentration factor. The specific steps for dynamically correcting the stress concentration factor in the limit equilibrium theory include: obtaining the maximum vertical stress value in the advanced region of the working face, and simultaneously obtaining the original rock vertical stress determined by the average unit weight of the overlying strata and the working face burial depth; calculating the ratio of the maximum vertical stress value to the original rock vertical stress, and using this ratio as the corrected stress concentration factor to replace the preset empirical constant in traditional calculations. This step realizes the parameter transfer from the numerical simulation solution to the analytical model solution, enabling theoretical calculations to reflect the actual mining stress level of a specific mine.

[0011] Furthermore, the calculation model for the width of the limiting equilibrium zone is an analytical model constructed based on the primary extraction thickness of the coal seam, the lateral pressure coefficient, the internal friction angle of the coal-rock interface, the cohesion of the coal-rock interface, the average unit weight of the overlying strata, the mining depth of the working face, and the corrected stress concentration coefficient. The constraint condition of the theoretical hard lower limit is that the actual width of the coal pillar in the section must be greater than or equal to the width of the limiting equilibrium zone to ensure that there is an elastic core zone inside the coal pillar that can withstand the supporting pressure.

[0012] In the engineering analogy phase, the engineering analogy matching utilizes mine depth as a core indicator for measuring ground stress level and rockburst risk, and retrieves deep well cases with similar depths to the target mine from the case database. The case database includes data dimensions for mine depth, coal seam height, and actual coal pillar width. The second preferred interval is determined by performing discrete statistics and convergence analysis on the coal pillar width values ​​of the selected similar cases where rockburst disasters have not occurred and the deformation of the surrounding rock in the roadway is controllable, selecting a range of values ​​with concentrated distribution.

[0013] In the final decision-making stage, the specific operation of truncating the preliminary feasible region using the theoretical hard lower limit includes: taking the overlapping part of the first preferred interval and the second preferred interval as the preliminary feasible region; if there are numerical segments within the preliminary feasible region that are less than the theoretical hard lower limit, they are forcibly removed, and only the intervals greater than or equal to the theoretical hard lower limit are retained. When selecting the final section coal pillar width within the remaining effective decision space, the upper limit integer or half-integer value within the effective decision space is selected as the final design parameter, based on the premise of maximizing safety and resource recovery rate, and combined with the parameter standardization requirements of underground roadway excavation construction.

[0014] This invention provides a method for determining the width of a coal pillar in a section based on anti-rockburst technology. It has the following advantages: 1. This invention extracts the maximum vertical stress value of the working face from numerical simulation and dynamically corrects the stress concentration factor in the limit equilibrium theory, replacing the empirical constant in traditional methods. This feature ensures that the calculated width of the plastic zone of the coal pillar truly reflects the overburden load transfer law under specific geological conditions in the target mine, thereby establishing a theoretically hard lower limit with physical significance. This ensures that a stable elastic bearing core zone is always maintained inside the coal pillar, effectively preventing coal pillar instability-type rockbursts caused by improper parameter selection.

[0015] 2. This invention performs an intersection operation on the numerical simulation interval characterizing the stress evolution law and the engineering analogy interval characterizing successful field experience, and introduces a theoretical hard lower limit for unidirectional inequality truncation. This multi-dimensional integrated decision-making logic not only eliminates the idealization error of pure theoretical analysis, but also eliminates the potential safety hazards of blindly copying experience, ensuring that the final determined coal pillar width satisfies the mechanical mechanism while having mature engineering practice backing, significantly improving the reliability of anti-scour design.

[0016] 3. This invention accurately locates the minimum safe width that falls into the low-stress zone and meets the requirements of standardized construction within the effective decision space locked after intersection operation and theoretical lower limit truncation. While minimizing the ineffective loss of coal pillars in sections and improving the coal resource recovery rate, it effectively avoids the accumulation of high static loads inside the coal pillars, thereby reducing the risk of rockburst in the mining roadway and the subsequent maintenance costs from the source. Attached Figure Description

[0017] Figure 1 is a flowchart of an embodiment of the present invention; Figure 2 is a structural diagram of a numerical model for mining two adjacent sections of a coal mine according to an embodiment of the present invention; Figure 3 is a vertical stress curve in a coal pillar according to an embodiment of the present invention; Figure 4 is an axial stress curve of a parallel roadway in a coal pillar according to an embodiment of the present invention; Figure 5 is an axial curve of a vertical roadway in a coal pillar according to an embodiment of the present invention. Detailed Implementation

[0018] 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.

[0019] Referring to Figure 1, this invention provides a method for determining the width of a coal pillar in a section based on anti-scour, characterized by the following steps: Step S1: Constructing a numerical model of the target mine and simulating the entire mining process, analyzing the vertical stress distribution characteristics around the longwall face, and preliminarily determining the first preferred interval for the coal pillar width based on the stress peak location and the stress reduction zone range; Step S2: In the numerical model, traversing and tracking the advance support pressure distribution curve in the direction of the longwall face advance, extracting the maximum vertical stress value in the solid coal area in front of the longwall face coal wall as key correction source data; Step S3: Using the key correction source data to dynamically correct the stress concentration factor in the limit equilibrium theory, and then applying the corrected system... Step S4: Substitute the values ​​into the coal pillar plastic zone width calculation model to calculate the limit equilibrium zone width, and establish it as the theoretical hard lower limit of the section coal pillar width; Step S5: Establish a case database containing historical engineering data from multiple mines, perform engineering analogy matching based on mine burial depth, screen out successful cases under similar geological conditions, and statistically analyze to obtain the empirical value range of coal pillar width, and establish it as the second preferred interval; Step S6: Perform an intersection operation on the first preferred interval and the second preferred interval to obtain the preliminary feasible region; Use the theoretical hard lower limit to perform a one-way inequality constraint truncation on the preliminary feasible region, eliminate values ​​smaller than the theoretical hard lower limit, and select the final section coal pillar width within the remaining effective decision space.

[0020] In the embodiments of the present invention, it is first necessary to clarify the geological environment and spatial geometric relationship of the research object, which is the prerequisite for establishing an accurate numerical model and conducting theoretical calculations.

[0021] A deep mining area of ​​a rockburst-prone mine was selected as the specific implementation target. The mine has a relatively complex geological structure, and the stress level increases significantly with increasing mining depth. The width of the coal pillar in the section directly affects the stability and rockburst prevention safety of the mining roadway. To obtain accurate calculation input parameters, the following geological exploration and data acquisition work was mainly carried out.

[0022] Mining depth ( Determination of the target working face: Based on the mine's geological exploration report and borehole columnar section data, the average burial depth of the target working face is determined. In this embodiment, the target area is located deep underground, and its average burial depth is measured. The depth is 600m. This burial depth data will be directly used to calculate the vertical stress of the original rock. ( ) is a basic indicator for assessing the impact hazard level of a mine.

[0023] Coal seam occurrence characteristics Measurement of thickness: The thickness variation of the main coal seam was determined through underground measurements and ground-penetrating radar detection. In this embodiment, the main coal seam is a thick seam with a relatively simple structure, and it is mineable throughout the entire area. The thickness of the coal seam extracted in a single operation was measured. It is 4.82m. This parameter ( The result will be directly substituted into the limit equilibrium theory formula as a geometric height factor that affects the width of the plastic zone. The thicker the coal seam, the easier it is to induce a wider plastic failure zone under the same stress conditions.

[0024] Working face layout (geometric boundary): The study area includes two adjacent working faces, namely working face ① (first mining face) and working face ② (continuing face). A section of coal pillar is left between the two working faces to isolate the goaf and maintain the return air or transport roadway of working face ②. Measuring lines are arranged in the coal pillar area to monitor the stress response characteristics under different pillar widths.

[0025] Roof and floor lithological characteristics: The lithological assemblage of the coal seam's roof and floor was confirmed by consulting the mine's comprehensive geological columnar section. In this embodiment, the roof of the coal seam is mainly composed of interbedded fine sandstone and siltstone, while the floor is mudstone. This geological characteristic determines the direction of the assignment of rock material properties in subsequent numerical simulations, ensuring that the simulation environment accurately reflects the mechanical response of the coal and rock assemblage.

[0026] To construct a numerical model that accurately reflects the response of underground engineering and provide a basis for precise theoretical calculations, systematic physical and mechanical property tests were conducted on the coal and rock mass in the target area. A combination of in-situ sampling and standard laboratory tests was used to obtain key mechanical parameters of the coal seam and its roof and floor rocks.

[0027] First, core samples of the coal seam, immediate roof, main roof, and floor are drilled from the underground working face and roadways, and then processed into standard cylindrical specimens in strict accordance with rock mechanics testing standards. Uniaxial compression tests, triaxial compression tests, and Brazilian splitting tests are then conducted using an electro-hydraulic servo rock mechanics testing system (such as an MTS or RMT system).

[0028] The key calculation parameters measured and selected in this embodiment include: the average unit weight of the overlying strata ( By weighted calculation of the densities of the overlying rock strata, the average unit weight of the overlying rock strata was determined to be: =2.5t / m 3 This parameter characterizes the intensity of the gravity exerted by the overlying strata and is used to calculate the vertical stress of the original rock. () is a direct factor.

[0029] Interface shear strength parameters ( Considering that the failure mode of a coal pillar under load is often controlled by the weak surface structure within the coal and rock mass, the shear strength tests were primarily conducted on the bedding planes and interfaces of the coal and rock mass itself. Through regression analysis of multiple shear tests, the cohesion at interfaces such as the bedding planes of the coal and rock mass was determined. =2.51MPa, internal friction angle =35°. These two parameters directly determine the ease with which the plastic zone at the edge of the coal pillar extends deeper, and are the core resistance indicators in the subsequent limit equilibrium equations.

[0030] Lateral pressure coefficient ( In-situ stress measurements are performed downhole using hydraulic fracturing or hollow inclusion stress relief methods to obtain the ratio of the maximum horizontal principal stress to the vertical principal stress. This embodiment measures and uses the lateral pressure coefficient. (Note: Based on the aforementioned calculation logic, the following is set) (Specific measured values, such as between 1.0 and 1.5, are used to characterize the lateral restraining effect of horizontal tectonic stress on the coal pillar).

[0031] Referring to Figure 2, in order to quantitatively invert the evolution law of the surrounding rock stress field under different coal pillar widths, a three-dimensional numerical calculation model that can reflect the real stratigraphic structure is constructed based on the geological borehole columnar section and rock mechanical parameters obtained in step one.

[0032] The model is discretized and solved using the finite difference method or the finite element method (FLAC3D program is used in this embodiment). The rock strata structure of the model is strictly established based on the actual geological stratification of the mine. The strata, from bottom to top, include fine-grained sandstone, sandy mudstone, medium-grained sandstone, coal, and upper coal seam. Each rock stratum unit is assigned corresponding physical and mechanical properties such as density, bulk modulus, shear modulus, cohesion, internal friction angle, and tensile strength to characterize the elastoplastic deformation characteristics of the rock mass. The Mohr-Coulomb criterion is used for the material constitutive relation, which can accurately describe the mechanical behavior of rock and soil materials after shear failure.

[0033] To eliminate the interference of artificial boundary conditions on the stress distribution in the core mining area, the model's geometry is set according to the following principles: Dip direction (perpendicular to the mining advance direction): The model covers two adjacent working faces and the coal pillars left between them. The dip length of the two working faces in the model is set to be no less than 1 / 2 of the actual dip length of the working faces. This scale setting ensures that during the simulated mining process, the overlying strata above the goaf can form a complete spatial structure movement, thereby applying realistic support pressure to the coal pillars.

[0034] Strike direction (along the mining advance direction): The strike length of the two working faces is set to be no less than 100m. In this embodiment, the strike length of the model is specifically set to 200m. This length ensures that a fully mined zone is formed in the middle area of ​​the model after the working face advances, avoiding the end effect of the model's front and rear boundaries from affecting the accuracy of stress monitoring data.

[0035] In terms of mesh generation, a non-uniform discretization strategy is adopted. The main study area (i.e., the coal seam and section coal pillar area) is divided into a high-density fine mesh to ensure that the mesh cell size is smaller than the distribution gradient of the stress peak area, so as to accurately capture the stress concentration phenomenon inside the coal pillar; for the roof and floor surrounding rock far from the mining-affected area, a gradually sparse mesh generation method is adopted to optimize the computational efficiency.

[0036] The boundary conditions of the model are set as follows: Vertical displacement constraints are applied to the bottom boundary of the model to limit its settlement; normal displacement constraints are applied to the lateral boundaries around the model to limit its horizontal displacement; the top boundary of the model is a stress boundary, applying an force equivalent to the gravity of the overlying strata. A vertically uniformly distributed load is applied to simulate the geostress environment under actual burial depth conditions.

[0037] Based on the aforementioned geological model, a comparative simulation scheme was designed with the width of the coal pillar in the section as a single independent variable. To comprehensively reveal the stress evolution law inside coal pillars of different sizes, multiple sets of numerical calculation models were established. The preset coal pillar width sequence covers the size range of small, medium, and wide coal pillars, with specific width values ​​set as 3m, 5m, 8m, 10m, 12m, 15m, 20m, 25m, and 30m.

[0038] For each model with a specific width, a step-by-step mining simulation was performed strictly following the actual engineering sequence of the mine to ensure that the load history and stress path of the coal pillar were consistent with the actual working conditions. The simulation calculation process consisted of the following two consecutive stages: The first stage simulated the mining process of the first mining face (face ①). Coal seam units in the corresponding area were removed, and the calculation program was run until the unbalanced force ratio detected by the model was lower than a set threshold (e.g., 1×10). -5 This process brings the model to a state of mechanical equilibrium. This stage simulates the stress redistribution characteristics of the coal pillar under the influence of unilateral mining.

[0039] The second stage simulates the mining process of the adjacent working face (Working Face ②). Based on the equilibrium stress field established in the first stage, the coal seam units in the Working Face ② area are removed, and the calculation is run again until the model reaches mechanical equilibrium again. This process reproduces the dynamic mechanical response of the coal pillar as it transitions from unilateral to bilateral loading, thereby obtaining the final stress distribution and plastic failure range of the coal pillar under the superimposed influence of secondary strong mining. After the secondary mining simulation calculation is completed, key data reflecting the loading state of the coal pillar are extracted for each coal pillar width scheme. Monitoring lines are laid at the geometric center of the coal pillar, with the line trajectory perpendicular to the coal pillar strike and running through the entire width of the coal pillar to completely capture the stress distribution gradient from the roadway sidewall to the depth of the coal pillar.

[0040] To ensure the accuracy of stress peak capture, the data monitoring point density on the measurement line is set to be no less than one measurement point per 0.5m. In the estimated stress concentration area, the density is increased to one measurement point per 0.2m to prevent local stress extreme points from being missed due to excessively large data sampling intervals, and to ensure that the generated stress distribution curve has sufficient smoothness and feature resolution.

[0041] Export the triaxial principal stress data at the survey line nodes using the post-processing program. ), and focused on visual analysis of vertical stress components.

[0042] Referring to Figure 3, which illustrates the distribution and numerical characteristics of vertical stress within the coal pillar under different continuity schemes, based on the mechanical mechanism of rockbursts—namely, dynamic instability induced by high static load accumulation—the following criteria were established to screen the preset width sequence: Crushed zone elimination: It was observed that when the coal pillar width was 3m, the overall vertical stress values ​​on the measuring line were at extremely low levels, and the distribution curve had no obvious peak. This characteristic indicates that the coal pillar has entered a fully plastic yielding state under strong mining action, the coal structure has undergone through-through failure, and it has lost its effective bearing capacity for the overlying strata, making it difficult to meet the surrounding rock control requirements of the mining roadway. Therefore, this width range was eliminated.

[0043] High stress concentration zone elimination: When the coal pillar width is between 10m and 12m, the vertical stress distribution curve shows a significant steep rise, with the peak stress rapidly increasing to over 130MPa. This characteristic indicates the existence of a large elastic core region within the coal pillar, accumulating extremely high elastic deformation energy. This high-stress environment constitutes the static load basis for rockbursts, and once subjected to external disturbances, it is highly susceptible to inducing dynamic disasters. Therefore, this width range exhibiting high stress concentration is eliminated.

[0044] The first preferred range was determined: when the coal pillar width is between 5m and 8m, the vertical stress distribution curve exhibits unique mechanical characteristics. Its stress peak is significantly lower than the aforementioned high stress concentration zone, and the stress distribution gradient along the coal pillar width is relatively small and the shape is relatively gentle. This indicates that the main body of the coal pillar at this size is in a state of equilibrium between plastic softening and residual strength support. It releases accumulated elastic energy through moderate deformation, eliminating the high stress source triggered by impact, while retaining the necessary residual bearing capacity to maintain the macroscopic stability of the roadway.

[0045] Referring to Figures 4 and 5, based on the qualitative and quantitative analysis of the stress field evolution law described above, the range of 5m to 8m, where the vertical stress level is relatively low and the distribution pattern is gentle, is determined as the first preferred interval. This range is directly derived from numerical simulation and reflects the true response characteristics of surrounding rock stress under specific geological and mining conditions.

[0046] Based on the establishment of the first preferred interval, in order to overcome the lack of specificity in the selection of key parameter values ​​in the traditional limit equilibrium theory calculation, it is necessary to further extract mechanical indicators that can characterize the specific mining disturbance intensity of the mine from the numerical simulation results, so as to realize the linkage between numerical simulation and theoretical calculation.

[0047] Based on the principles of rock mechanics in mining, the development range of the plastic zone around the longwall face is directly controlled by the peak intensity of the bearing pressure. Therefore, in the above numerical model, the area affected by the advance bearing pressure in the direction of face advancement (i.e., the solid coal area in front of the coal face wall) is identified. The stress peak in this area objectively reflects the maximum vertical load borne by the coal and rock mass under the combined action of the gravity of the overlying strata and the mining-induced tectonic movement.

[0048] Using the post-processing function of numerical simulation software, the working face advanced support pressure distribution curve under the corresponding working condition in the first preferred interval is traversed and tracked to capture the maximum value point of its vertical stress. In this embodiment, the maximum vertical stress value of the working face advanced region is extracted through numerical inversion. Approximately 45 MPa. This value is an exact physical quantity calculated based on the actual burial depth, rock strata structure, and constitutive relationship of the target mine. The value, in its physical essence, characterizes the ultimate peak value of the mining-induced support pressure at the edge of the elastic core zone. Its magnitude directly maps the degree of concentration of the overlying strata load transmitted to the coal seam. Therefore, this value can be used to calculate... The coefficient can accurately eliminate the systematic errors introduced by traditional empirical values ​​due to the failure to consider the differences in the fracture structure of the top strata, thus... The value serves as a key correction source data, passed to subsequent theoretical calculation steps, and is used to replace the estimated parameters in traditional empirical formulas, thereby correcting the stress concentration factor caused by mining. Perform dynamic calibration.

[0049] Within the framework of limit equilibrium theory, the stress concentration factor caused by mining This is a core mechanical parameter that determines the width of the plastic zone in coal. Traditional calculation methods often ignore the differences in specific mine conditions and rely solely on experience to select a fixed value (usually 3), leading to theoretical calculation results that often deviate from engineering reality. To overcome this deficiency, a physical mapping relationship is established between numerical simulation results and theoretical analytical models, and dynamic corrections are implemented for this parameter based on the actual stress response.

[0050] The correction logic is determined based on the ratio between the peak stress obtained from numerical inversion and the original rock stress field. Specifically, it utilizes the maximum vertical stress value of the advanced region of the working face extracted in the preceding numerical calculation stage. Divide by the average unit weight of the overlying strata With burial depth By determining the original rock vertical stress, the stress concentration factor under specific geological and mining conditions can be calculated. The revised calculation formula is as follows: This formula condenses the complex boundary conditions and nonlinear response characteristics of materials contained in the macroscopic numerical model into a dimensionless stress concentration factor, realizing parameter transfer from numerical solution to analytical solution. Substituting the specific physical parameters in this embodiment into the above formula: the peak value of the advance support pressure extracted by numerical simulation. The pressure is 45 MPa, and the average unit weight of the overlying strata is... Converted to 0.025MN / m 3， working face burial depth For 600 The corrected stress concentration factor is calculated as follows: Through this correction process, the parameters Instead of being a constant predetermined by experience, it is a dynamic variable jointly determined by the actual burial depth of the mine, the properties of the rock strata, and the level of mining-induced stress. This approach ensures that the boundary conditions subsequently substituted into the limit equilibrium equations strictly conform to the actual stress state of the mine, providing a reliable mechanical input for accurately calculating the width of the plastic zone of the coal pillar.

[0051] Based on the limit equilibrium theory of coal pillar stability, the width of the plastic zone of the coal body This characterizes the physical range within which the edge of a coal pillar enters a state of plastic failure under supporting pressure. Within this range, the coal body loses its original elastic bearing capacity and retains only residual strength. To accurately define the minimum geometric dimensions required for the coal pillar to maintain the elastic bearing capacity of the core area, theoretical calculations are performed using modified mechanical parameters.

[0052] Select the stress concentration factor obtained through prior dynamic correction The thickness of the coal seam extracted in a single mining operation was obtained by combining geological exploration and mechanical testing. Lateral pressure coefficient Internal friction angle of coal-rock interface Cohesion Average unit weight of overlying strata and mining depth Based on fundamental parameters, an analytical calculation model for the width of the lateral plastic zone of the coal seam in the longwall mining face was constructed. This analytical model is based on the Mohr-Coulomb failure criterion in limit equilibrium theory, assuming that the coal and rock mass is an isotropic elastoplastic medium, and that shear failure at the interface between the coal seam and the roof and floor follows the linear friction law. Based on this, the equation for the width of the limit equilibrium zone, including stress concentration effects, was derived. The calculation formula is as follows: ;in, Indicates the width of the plastic zone of the coal body. This indicates the thickness of the coal seam extracted in a single operation, and is taken as 4.82m. This represents the lateral pressure coefficient, characterizing the ratio of horizontal stress to vertical stress, and has a value of 1.2. The internal friction angle represents the interface between bedding planes and other surfaces of a coal-rock mass, and is taken as 35°. This represents the cohesion at interfaces such as bedding planes in coal and rock mass, and is taken as 2.51 MPa. The stress concentration factor, corrected for peak stress levels based on numerical simulation, is set to 3. This represents the average unit weight of the overlying rock strata, taken as 0.025MN / m³. 3 , This indicates the depth of the working face, with a value of 600m.

[0053] The physical parameters characterizing the specific geological environment and stress state of the mine are substituted into the analytical formula for calculation. This calculation process comprehensively considers the deep high-stress environment (…). Local stress concentration caused by mining () ) and the shear strength characteristics of the coal and rock medium itself ( Calculations yielded the width of the plastic zone in the coal under this working condition. =5.69m. This value provides a theoretical hard boundary for maintaining the stability of the coal pillar core area from the perspective of rock mechanics.

[0054] According to the strength criterion of limit equilibrium theory, the mechanical prerequisite for the long-term stability of a coal pillar section is the existence of an elastic core region capable of withstanding high support pressure. The width of the plastic zone calculated previously... The value of 5.69m, in a physical sense, defines the minimum geometric range within which coal seams will undergo irreversible plastic yielding under specific stress conditions. If the width of the coal pillar is less than this critical value, the coal and rock mass will undergo full-section yielding under the superposition of bidirectional mining support pressure, resulting in the complete disappearance of the elastic bearing core, and thus the loss of effective support capacity for the roof strata and the function of blocking dynamic loads from rockbursts.

[0055] Therefore, 5.69m is established as the theoretical hard lower limit for the width of the coal pillar in the section. This lower limit constitutes the mechanical rigid constraint for the anti-rockfall coal pillar design in this technical solution, that is, it requires the final determined coal pillar width. Must strictly meet An inequality relationship of ≥5.69m. This judgment logic directly excludes any under-design scheme that attempts to sacrifice safety boundaries for resource recovery rate, ensuring that the subsequently selected parameter range has sufficient safety margin at the level of basic mechanical mechanism, and providing an insurmountable bottom line basis for multi-source data fusion decision-making.

[0056] To verify the engineering applicability of numerical simulation and theoretical calculation results, and to introduce empirical constraints from field measured data, an engineering case database containing successful practice samples from multiple mines was constructed. This database uses a summary table of coal pillar retention in smaller sections as its core, systematically collecting and recording key engineering parameters from different mines under similar mining conditions.

[0057] The data entry dimensions cover the core indicators that determine the stress environment of the surrounding rock and the characteristics of overburden movement: the first is the mine depth ( This parameter directly maps to the original rock stress level and the risk level of rockburst; secondly, it relates to the coal seam mining height. This parameter affects the severity of mining disturbance and the range of plastic failure; finally, it represents the actual width of the coal pillar. Through standardized cleaning and structured storage of the aforementioned historical engineering data, an empirical dataset for retrieval and comparative analysis is formed. This dataset covers successful cases of surrounding rock control under different geological conditions, providing quantitative data support and a benchmark for subsequent engineering analogies based on geological condition similarity.

[0058] Using mine depth as a core physical indicator for measuring ground stress level and impact risk, feature matching retrieval was performed on the engineering case database. Given that the actual depth of the target mine is 600m, a similarity threshold was set for the search conditions, focusing on selecting similar deep well cases with depths between 400m and 800m.

[0059] The search program traversed the database entries, identifying successful engineering examples that shared high similarities with the target mine in terms of geological structure complexity, coal seam thickness, and mining technology. After screening, several similar mine data with direct reference value were extracted from the summary table. Statistical analysis showed that in similar deep-well fully mechanized longwall mining operations at a depth of approximately 600m, the width of the coal pillar in sections that effectively controlled roadway surrounding rock deformation and prevented rockbursts generally fell within the range of 5.0m to 6.0m.

[0060] These selected benchmark cases, after experiencing similar high-stress environments and intense mining disturbances, did not experience rockburst dynamic disasters, and the roadway cross-sectional convergence rate was controlled within the allowable range, confirming the engineering adaptability of this size range in deep and complex geological environments. This matching process eliminated data interference from low-stress conditions in shallow-buried deep mines, ensuring that the reference dimensions of empirical data were highly consistent with the deep mechanical environment of the target mine, thus providing objective evidence based on field verification for the determination of final design parameters.

[0061] Based on the feature matching and screening results of the aforementioned engineering analogies, discrete statistics and convergence analysis were performed on the key parameters in highly correlated cases. The data aggregation results show that in deep mining engineering practices that are highly similar to the geological environment of the target mine, the width of the coal pillar in the section that can successfully maintain the long-term stability of the mining roadway and avoid rockburst disasters is mainly concentrated in the range of 5.0m to 6.0m.

[0062] Within this width range, on-site mine pressure monitoring data from multiple mines confirms that the deformation of the surrounding rock in the roadway, the stress condition of the anchor bolts (cables), and the indicators detected by the drill cuttings method are all within a safe and controllable range. This indicates that these dimensional parameters have passed the dual test of deep high-stress environment and strong mining disturbance on an engineering scale, and possess mature on-site adaptability.

[0063] Therefore, 5.0m to 6.0m is established as the second preferred range. This interval is essentially a physical mapping of existing support technology capabilities and deep surrounding rock control experience, providing empirically constrained boundaries for the design scheme based on engineering evidence. In subsequent multi-source data fusion decision-making, this interval will be used to verify the engineering rationality of the numerical simulation results, prevent idealization deviations that may arise from purely theoretical calculations, and ensure that the finally selected coal pillar parameters are operable and safe in actual production operations.

[0064] Quantitative conclusions obtained through three independent technical paths—numerical simulation inversion, theoretical mechanics analysis, and engineering statistical analogy—are combined to construct a set of characteristic parameters for final decision-making. This parameter set encompasses numerical solutions reflecting the evolution of the surrounding rock stress field, analytical solutions characterizing the limit equilibrium stability of the coal pillar, and empirical solutions based on field measurement data, forming a triangular verification system where physical mechanisms and engineering empirical evidence mutually support each other. Specific summarized data are as follows: Numerical simulation domain ( Based on the smoothness and peak level of the vertical stress distribution pattern in the full-process mining simulation, the width range of the coal pillar in a state of equilibrium between plastic softening and residual strength is identified as the first preferred interval, denoted as . =[5m, 8m]. This interval represents the geometric range within which a coal pillar can effectively release elastic energy without high static load accumulation under a specific geological model.

[0065] Theoretical mechanics domain ( Based on the corrected stress concentration factor: And based on the limit equilibrium criterion, the minimum critical size for maintaining the existence of the elastic core region at the center of the coal pillar is calculated, and the theoretical hard lower limit is established, denoted as . =5.69m. This value defines the physical baseline for preventing full-section plastic yielding of a coal pillar under deep, high-stress conditions.

[0066] Engineering experience domain Through feature matching and convergence analysis of the deep mine case database, a range of analogous parameters, proven safe and reliable through on-site mine pressure monitoring, was selected and established as the second preferred interval, denoted as . =[5.0m, 6.0m]. This range reflects the proven engineering safety range in similar geological conditions under existing support technology.

[0067] These three sets of data represent the constraints in three dimensions: stress response, mechanism limit, and empirical experience, respectively, providing a complete input foundation for accurately identifying the unique optimal solution through multi-source data fusion algorithms.

[0068] A decision model based on multi-source data fusion is constructed, and a constraint intersection logic based on set theory is used to filter and lock heterogeneous parameters. This logic aims to find a unique solution set that can simultaneously accommodate the stress evolution characteristics of numerical simulation, the stability limits of theoretical calculation, and the safety experience of engineering analogy, thereby eliminating the systematic bias that may exist in a single method.

[0069] First, the first preferred interval characterizing the low stress level of the surrounding rock. (5m~8m) and the second preferred range representing mature on-site support experience (5.0m~6.0m) Perform mathematical intersection operation: The intersection interval In a physical sense, a preliminary feasible domain is defined that has both a reasonable stress relief environment (no accumulation of high static load) and historical engineering practice as a basis.

[0070] Subsequently, a theoretical hard lower limit was introduced. (5.69m) is used as an absolute veto criterion to construct a one-way inequality constraint. Using this constraint, the preliminary feasible region is... A safety truncation is implemented, forcibly removing numerical segments smaller than 5.69m within the interval. This operation, from a mechanistic perspective, eliminates potential risk areas that, while conforming to empirical statistical laws, lack sufficient theoretical safety reserves, thus precisely compressing the effective decision space to a closed interval of [5.69m, 6.0m].

[0071] Ultimately, ensuring compliance with both the aforementioned mechanical mechanisms and engineering empirical constraints, and adhering to the principle of maximizing the recovery rate of deep coal resources, while also considering the technological requirements for parameter standardization (usually taking integer or half-integer values) in underground roadway excavation, an upper limit integer value was selected as the final parameter within the effective decision space. Specifically, considering that the spacing of underground anchor-mesh-cable support systems is typically based on a module of 0.8m or 1.0m, selecting 6.0m as the final width achieves optimal matching with existing support construction process parameters. This avoids waste from cutting support mesh or difficulties in adjusting anchor (cable) spacing due to non-standard dimensions, thus ensuring construction efficiency while meeting mechanical safety requirements, i.e., determining the section coal pillar width for the target mine. It is 6.0m.

[0072] The design value of 6.0m exceeds the lower limit of the theoretical plastic zone width by 0.31m, ensuring the existence of a stable elastic bearing core zone inside the coal pillar. At the same time, this value falls completely within the low stress zone determined by numerical simulation and the safety verification zone of engineering analogy, achieving a multi-dimensional balance between safety, economy and engineering applicability.

[0073] Using the 6.0m section coal pillar width determined by this multi-source data fusion decision model, a surrounding rock control system with multiple safety redundancies was constructed in a deep, high-stress fully mechanized longwall mining environment.

[0074] From a mechanical stability perspective, the design dimensions strictly exceed the theoretically calculated lower limit of the plastic zone, which is 5.69m. This geometric margin ensures that the coal pillar center always retains a continuous and stable elastic bearing core zone. This core zone effectively bears the supporting pressure transmitted from the roof, physically preventing the overall instability of the coal pillar caused by the connection of the plastic zones on both sides, and providing a rigid support foundation for the mining roadway.

[0075] From the perspective of rockburst prevention, this width falls entirely within the low stress gradient range revealed by numerical simulation. The vertical stress distribution within the coal body remains in a gentle pattern, effectively suppressing the non-uniform accumulation of high static loads within the coal pillar and eliminating the static source core that induces rockburst. The coal body dissipates the accumulated elastic energy through moderate plastic deformation, achieving source control of dynamic disaster risks.

[0076] From the perspective of resource efficiency and engineering adaptability, compared with the traditional conservative design of wide coal pillars, this parameter, while meeting safety constraints, maximizes the compression of the non-mining area and significantly improves the coal resource recovery rate of the mining area. At the same time, this dimension highly matches the mature support experience range of deep mines, verifying the control capability of existing anchor-mesh-cable support technology for this width of coal pillar. This avoids a surge in support costs or increased construction difficulty due to aggressive parameters, achieving a systematic optimization of safe mining, precise resource extraction, and engineering economy under complex deep conditions.

[0077] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0078] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0079] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing custom logic functions or processes, and the scope of the preferred embodiments of this application includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as should be understood by those skilled in the art to which embodiments of this application pertain.

[0080] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0081] It should be understood that various parts of this application can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0082] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0083] Furthermore, the functional units in the various embodiments of this application can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0084] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of this application.

Claims

1. A method for determining the width of a section coal pillar based on anti-scour, characterized in that, include: Step S1: Construct a numerical model of the target mine and simulate the entire mining process. Analyze the vertical stress distribution characteristics around the longwall face. Based on the stress peak location and stress reduction zone range, preliminarily determine the first preferred range for the coal pillar width. Step S2: In the numerical model, traverse and track the advance support pressure distribution curve in the face advance direction, and extract the maximum vertical stress value in the solid coal area in front of the coal wall of the longwall face as key correction source data. Step S3: Dynamically correct the stress concentration coefficient in the limit equilibrium theory using the key correction source data, and substitute the corrected coefficient into the coal pillar plastic zone width calculation model to calculate the limit equilibrium zone width, which is then established as the theoretical hard lower limit of the section coal pillar width; Step S4: Establish a case database containing historical engineering data from multiple mines, perform engineering analogy matching based on mine burial depth, screen out successful cases under similar geological conditions, statistically analyze and derive the empirical value range of the coal pillar width, which is then established as the second preferred interval; Step S5: Perform an intersection operation on the first preferred interval and the second preferred interval to obtain the preliminary feasible region; use the theoretical hard lower limit to truncate the preliminary feasible region using a one-way inequality constraint, eliminate values ​​smaller than the theoretical hard lower limit, and select the final section coal pillar width within the remaining effective decision space.

2. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S1, the first preferred range for initially determining the width of the coal pillar includes: selecting a width range that is in a plastic softening state and has residual strength, ensuring that the vertical stress distribution within this range is gentle, there is no accumulation of high static load, and the elastic energy can be released.

3. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S2, in order to extract the maximum vertical stress value in the solid coal area in front of the coal face, monitoring lines are laid out in the leading area of ​​the working face in the numerical model. The data monitoring point density of the monitoring lines is increased in the estimated stress concentration area to capture the real stress extreme points.

4. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S3, the step of dynamically correcting the stress concentration factor in the limit equilibrium theory includes: obtaining the maximum vertical stress value in the advanced region of the working face; obtaining the original rock vertical stress determined by the average unit weight of the overlying strata and the burial depth of the working face; calculating the ratio of the maximum vertical stress value to the original rock vertical stress, and using this ratio as the corrected stress concentration factor to replace the empirical constant.

5. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S3, the calculation model for the width of the limit equilibrium zone is an analytical model constructed based on the primary extraction thickness of the coal seam, the lateral pressure coefficient, the internal friction angle of the coal-rock interface, the cohesion of the coal-rock interface, the average unit weight of the overlying strata, the mining depth of the working face, and the corrected stress concentration coefficient.

6. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S3, the constraint condition of the theoretical hard lower limit is: the actual width of the coal pillar in the section must be greater than or equal to the width of the limit equilibrium zone.

7. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S4, the engineering analogy matching includes: using the mine depth as a core indicator to measure the level of ground stress and the risk of impact, and searching the case database for deep well cases with a similar depth to the target mine; the case database contains data dimensions such as mine depth, coal seam mining height and actual coal pillar width.

8. The method for determining the width of a section coal pillar based on anti-scouring according to claim 7, characterized in that, In step S4, the second preferred interval is determined by performing discrete statistics and convergence analysis on the coal pillar width values ​​of the selected similar cases where no rockburst disaster has occurred and the deformation of the surrounding rock of the roadway is controllable, and selecting the concentrated distribution range of values ​​as the second preferred interval.

9. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S5, the step of truncating the preliminary feasible region using the theoretical hard lower limit includes: taking the overlapping part of the first preferred interval and the second preferred interval as the preliminary feasible region; if there are numerical segments in the preliminary feasible region that are less than the theoretical hard lower limit, they are forcibly removed, and only the intervals that are greater than or equal to the theoretical hard lower limit are retained.

10. The method for determining the width of a section coal pillar based on anti-scouring according to claim 1, characterized in that, In step S5, selecting the final section coal pillar width within the remaining effective decision space includes: under the premise of maximizing safety and resource recovery rate, and in combination with the parameter standardization requirements of underground roadway excavation construction, selecting the upper limit integer value or half-integer value within the effective decision space as the final design parameter.

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