Method for arranging small coal pillar grouting hole based on genetic algorithm in large deformation gob-side entry driving

Abstract

The application discloses a large deformation gob-side entry driving small coal pillar grouting hole arrangement method based on a genetic algorithm, adopts a borehole peeping technology to detect distribution characteristics of internal deformation fissure and broken zone of the small coal pillar, and delimits a grouting reinforcement target area; the side wall of the coal pillar is simplified into a regular plane model, a safety coefficient is introduced to convert an effective diffusion radius in combination with actual diffusion characteristics of the slurry, then the minimum slurry diffusion range overlap degree and the maximum overall effective coverage area of adjacent grouting holes are taken as optimization targets, an intelligent optimization algorithm is used to iteratively solve optimal slurry diffusion radius and grouting hole arrangement parameters, and the hole diameter, hole depth, spacing and arrangement form are determined; a tilt grouting hole is additionally arranged in the deep broken zone, and peeping rechecking and additional hole drilling are carried out after construction. The application can accurately adapt to the reinforcement requirements of the broken small coal pillar, avoids grouting blank areas, reduces invalid slurry overlap, improves slurry utilization and coal pillar integrity, and is suitable for various small coal pillar grouting reinforcement engineering of gob-side entry driving.

Description

Technical Field

[0001] This invention relates to the field of coal mine roadway surrounding rock support and reinforcement technology, and in particular to a method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on a genetic algorithm. Background Technology

[0002] To ensure roadway stability, narrow protective coal pillars, or small coal pillars, are typically reserved in engineering projects. However, due to the combined effects of mining stress and surrounding rock tectonic stress, small coal pillars excavated along the goaf are prone to compression deformation, internal fissure development, and rock mass fracturing and loosening, leading to a significant decrease in the coal pillar's bearing capacity. This, in turn, can cause safety hazards such as spalling, air leakage, and surrounding rock instability, seriously restricting safe production in coal mines.

[0003] Currently, the industry commonly uses grouting reinforcement to improve the mechanical properties of broken coal pillars. This involves injecting grout into the coal pillar to fill fissures and cement the broken coal mass, thereby enhancing the pillar's integrity and load-bearing strength. However, existing grouting hole arrangement technology has the following significant drawbacks:

[0004] First, the layout of grouting holes relies heavily on construction experience, lacking precise detection of the deformation and fracturing range within small coal pillars. This leads to a high degree of haphazard drilling and the creation of reinforcement blind spots. Second, the adsorption and seepage loss of grout by the fractured coal body are not fully considered; the natural diffusion radius is directly used for borehole layout, resulting in insufficient actual reinforcement area. Third, the unreasonable borehole spacing design leads to excessive overlap of grout diffusion between adjacent grouting holes, causing grout waste, extended construction period, and significantly higher reinforcement costs. Fourth, the uniform layout method used for areas with different degrees of fracturing results in poor adaptability and inconsistent reinforcement effects.

[0005] In existing publicly available patents and literature, most grouting layout schemes only fix the borehole spacing and arrangement, without dynamically optimizing them based on the deformation and fracturing characteristics of the coal pillar, and lack intelligent solution methods. Relying on manual experience to determine the diffusion radius and borehole position results in low optimization accuracy and a lack of quantitative optimization logic centered on minimum overlap and maximum coverage area, making it difficult to specifically address the problems of inefficient coal pillar grouting reinforcement and frequent blind spots.

[0006] Therefore, there is an urgent need to develop a method that can accurately detect the characteristics of coal pillar breakage, reasonably calculate the slurry diffusion radius, and introduce intelligent optimization algorithms to optimize the layout of grouting holes. Summary of the Invention

[0007] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a method for arranging grouting holes in small coal pillars during large deformation goaf excavation based on genetic algorithms. This method can solve the technical pain points of existing methods for arranging grouting holes in small coal pillars during goaf excavation, such as blind arrangement, large amount of diffusion and overlap, many reinforcement blind areas, low grout utilization rate, and poor coal pillar reinforcement effect. Through a process of detection and analysis, model simplification, radius calculation, and optimized arrangement, this method can achieve scientific and precise arrangement of grouting holes, taking into account both reinforcement integrity and construction economy.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0009] This invention provides a method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on a genetic algorithm, comprising the following steps:

[0010] S1. Obtain the deformation and fragmentation distribution characteristics inside the small coal pillar, and delineate the target area for grouting reinforcement accordingly;

[0011] S2. The reinforced sidewall of the small coal pillar is equivalent to a regular plane model. The natural diffusion radius R of the slurry is measured, and the natural diffusion radius R is converted into an effective diffusion radius r based on the deformation level of the coal pillar, where r = K × R.

[0012] S3. Using the grouting hole layout parameters as optimization variables, within the regular plane model, draw a circle with each grouting hole as the center and the effective diffusion radius as the radius. Use an intelligent optimization algorithm to iteratively solve the problem with the fitness function of minimizing the overlap of the grout diffusion range of adjacent grouting holes and maximizing the effective coverage area, and determine the optimal grouting hole layout parameters.

[0013] S4. Match the drilling depth, borehole diameter, and drilling inclination angle of the grouting hole according to the fracture depth and coal hardness of the target area for grouting reinforcement.

[0014] S5. Integrate the layout parameters, drilling depth, drilling diameter and drilling inclination angle to form a grouting hole layout plan, and carry out drilling construction and grouting reinforcement operations accordingly.

[0015] Preferably, in step S1, when obtaining the deformation and breakage distribution characteristics inside the small coal pillar, a borehole inspection instrument is used to lay out detection boreholes at equal intervals along the side wall of the coal pillar for in-situ detection. The spacing between detection boreholes is 2~3m, the borehole depth is not less than the maximum depth of the coal pillar breakage zone, the number of detections is not less than 3, and after removing abnormal data, the average value of the data at each measuring point is taken.

[0016] Preferably, in step S1, the deformation of the surrounding rock, the degree of fracture development, the density of fracture development, and the distribution range of the fracture zone at different depths of the coal pillar are collected. Combined with the stress monitoring data of the surrounding rock in the roadway, the coal pillar is divided into intact area, micro-fracture area, and severely fractured area. The intact area that does not need reinforcement is eliminated, and the micro-fractured area and the severely fractured area are merged and designated as the grouting reinforcement target area. The boundary, thickness, and fracture level of the grouting reinforcement target area are clearly defined.

[0017] Preferably, in step S2, when the sidewall of the small coal pillar is simplified to a regular (rectangular) planar model, the slight unevenness and deformation of the surface of the small coal pillar are ignored, and the rectangular plane is used as the reference plane for the arrangement of grouting holes. Grouting tests are conducted at the construction site with constant grouting pressure and grout water-cement ratio to determine the natural diffusion radius of the grout in the crushed coal body.

[0018] Preferably, in step S2, the safety factor ranges from 0.75 to 0.9, and is graded according to the amount of coal pillar deformation: when the coal pillar deformation is less than 100 mm, the safety factor is 0.85 to 0.9; when the coal pillar deformation is 100 to 300 mm, the safety factor is 0.8 to 0.85; and when the coal pillar deformation is greater than 300 mm, the safety factor is 0.75 to 0.8.

[0019] Preferably, in step S3, the converted effective diffusion radius is used as the initial optimization variable, and a genetic algorithm optimization model is built in the MATLAB optimization platform. The model strictly follows the dual optimization principle of minimizing the overlap of diffusion ranges and maximizing the effective coverage area of ​​a single pore. A multi-objective fitness function is constructed, with minimizing the total overlap area as the primary optimization objective and maximizing the overall effective coverage area as the secondary optimization objective.

[0020] The preferred intelligent optimization algorithm is a genetic algorithm.

[0021] The constraints of the intelligent optimization algorithm include: the overlap coverage of grout diffusion between adjacent grouting holes does not exceed 15%; the horizontal spacing between adjacent grouting holes is 1.4 to 1.7 times the effective diffusion radius; and the vertical spacing between rows is 1.5 to 1.8 times the effective diffusion radius. The intelligent optimization algorithm's iterative convergence condition is that the fitness function difference is less than 0.01, with a population size of 20 to 50, a crossover probability of 0.7 to 0.9, a mutation probability of 0.01 to 0.05, and 50 to 100 iterations until the function converges. The intelligent optimization algorithm automatically selects the optimal diffusion radius and matches the arrangement form according to the crack distribution state of the reinforced area.

[0022] Preferably, in step S3, based on the obtained fracture development density at each measuring point (i.e., the number of fractures within a unit hole depth), the coefficient of variation of fracture density along the coal pillar direction is calculated, and the arrangement is automatically matched based on the comparison result of the coefficient of variation and the preset threshold: the arrangement of grouting holes output by the intelligent optimization algorithm includes rectangular arrangement and five-petal arrangement.

[0023] When the coefficient of variation is less than or equal to a preset threshold, the crack distribution is determined to be uniform, and the intelligent optimization algorithm outputs a rectangular arrangement; when the coefficient of variation is greater than the preset threshold, the crack distribution is determined to be disordered or there are severely broken areas in some areas, and the intelligent optimization algorithm outputs a pentagonal arrangement, ultimately outputting the optimal hole spacing and row spacing parameters to minimize invalid overlap and improve the overall coverage area.

[0024] Preferably, in step S4, the borehole diameter is set to 42~56mm, the borehole depth in the shallow fractured zone is 2~4m, and the borehole depth in the deep fractured zone is 5~8m; for the deep fractured zone, an inclined grouting hole is added, which is inclined toward the goaf side with an inclination angle of 15°~30°.

[0025] Preferably, in step S5, the above-mentioned layout, hole spacing, row spacing, hole diameter, hole depth, and inclination angle parameters are integrated to formulate a standardized grouting hole layout construction plan; during the construction process, drilling, sealing, and grouting are carried out strictly in accordance with the plan; after the grouting reinforcement operation is completed, no less than 5 grouting holes are randomly selected for secondary inspection. If there are blind spots where the grout is not covered, additional grouting holes should be added in the center of the blind spot. The spacing of the additional grouting holes is 0.5 to 0.7 times that of the conventional grouting hole spacing, and the holes need to be re-inspected after being added to completely eliminate the reinforcement blank areas.

[0026] Beneficial effects:

[0027] 1. Drilling inspection technology is used to conduct in-situ detection of deformation, fractures, and broken zones within the coal pillar, quantitatively dividing the micro-fracture zone and the severely broken zone, and accurately delineating the target area for grouting reinforcement. This method abandons the traditional experience-based borehole layout, avoids ineffective drilling, and significantly reduces construction workload and material waste.

[0028] 2. The natural diffusion radius of the grout was determined through on-site grouting tests, and the effective diffusion radius was obtained by introducing a graded safety factor based on the deformation level of the coal pillar. The adsorption and seepage losses of the grout by the crushed coal body were fully considered, correcting the deviation of the theoretical diffusion radius and ensuring that the calculated grouting diffusion range more closely matches the actual working conditions.

[0029] 3. An intelligent optimization algorithm is introduced, with the dual optimization objectives of minimizing grout overlap area and maximizing effective reinforcement coverage area, to establish a multi-objective fitness function. The optimal effective diffusion radius and grouting hole layout parameters (hole spacing, row spacing, and layout form) are automatically solved through iterative convergence, eliminating the need for manual calculations, significantly improving parameter matching accuracy, reducing grout overlap loss at the source, and increasing grout utilization.

[0030] 4. The grouting arrangement is adaptively matched to the distribution of internal fractures in the coal pillar: a rectangular arrangement is used when the fractures are uniformly distributed, and a pentagonal arrangement is used when the fractures are disordered or severely fractured in certain areas. Simultaneously, inclined grouting holes are added for deep fractured areas, tilted towards the goaf side to ensure that the boreholes completely penetrate the fractured zone. This method is widely applicable to grouting and reinforcement projects for small coal pillars in various goaf-side excavations.

[0031] 5. After construction, grouting holes were randomly selected for secondary inspection to identify unconsolidated grout areas and to supplement and densify the grouting holes, completely eliminating any unreinforced areas. Actual engineering verification showed that coal pillar deformation decreased from 280mm to less than 35mm, the rock mass was completely consolidated, and there were no air leaks or spalling, effectively ensuring the long-term stability of the roadway along the goaf. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 A flowchart illustrating a method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on a genetic algorithm, provided for an embodiment of the present invention; Detailed Implementation

[0034] The technical solutions of 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.

[0035] This embodiment takes a small coal pillar in the working face of the 2205# goaf tunnel of a state-owned coal mine as the object of reinforcement. The coal pillar is 8m wide and has undergone significant deformation due to mining, with a deformation of 280mm. It has developed internal fissures and broken rock mass, and there are hidden dangers of air leakage and rock spalling.

[0036] like Figure 1 As shown, this embodiment of the invention provides a method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on a genetic algorithm, including the following steps:

[0037] S1. Obtain the deformation and fragmentation distribution characteristics inside the small coal pillar, and delineate the target area for grouting reinforcement accordingly;

[0038] Detection boreholes were installed on the side of the small coal pillar in the working face of No. 2205 coal mine. The boreholes were spaced 2.5m apart, with a diameter of 50mm and a depth of 7m. A borehole inspection instrument was used to detect each borehole. The monitoring data showed that: 0~2.5m was a shallow and severely fractured zone with continuous fractures and loose coal; 2.5~5.5m was a medium-sized micro-fractured zone with developed but not continuous fractures; and above 5.5m was intact coal. The area from 0~5.5m was determined to be the target area for grouting reinforcement.

[0039] S2. The reinforced sidewall of the small coal pillar is equivalent to a regular planar model with a height of 4.2m and a length of 50m. The natural diffusion radius of the grout is determined to be R=1.8m by the on-site grouting test. The deformation of this coal pillar is 280mm, which is a medium-level deformation. The safety factor K is taken as 0.82. The effective diffusion radius is calculated as r=0.82×1.8=1.476m.

[0040] S3. Using the grouting hole layout parameters as optimization variables, within the regular plane model, draw circles with each grouting hole as the center and the effective diffusion radius as the radius. Use a genetic algorithm to iteratively solve the problem with the fitness function of minimizing the overlap of the grout diffusion range of adjacent grouting holes and maximizing the effective coverage area, and determine the optimal grouting hole layout parameters.

[0041] In this embodiment, the effective diffusion radius of 1.476m is used as the initial input variable, the population size is set to 30, the crossover probability is 0.8, the mutation probability is 0.02, and the maximum number of iterations is 80. The optimization objective is to minimize the overlapping area and maximize the coverage area, with a constraint that the overlap coverage rate is ≤15%. After the genetic algorithm converges iteratively, the optimal five-flower arrangement is automatically selected, and the optimal horizontal hole spacing of 2.3m (1.56 times the effective diffusion radius) and vertical row spacing of 2.5m (1.69 times the effective diffusion radius) are output. After the arrangement, the coverage area of ​​a single hole is maximized, and the overall overlap rate is controlled at 12.3%, which meets the design requirements.

[0042] S4. Match the drilling depth, borehole diameter, and drilling inclination angle of the grouting hole according to the fracture depth and coal hardness of the target area for grouting reinforcement.

[0043] In this embodiment, the drilling depth in the shallow fractured zone is 3.5m, and the drilling depth in the middle micro-fractured zone is 5.5m; the uniform borehole diameter is 50mm; an inclined borehole with an inclination angle of 22° and a depth of 6m is added on the side near the goaf, penetrating the deep fractured transition zone.

[0044] S5. Integrate the layout parameters, drilling depth, drilling diameter and drilling inclination angle to form a grouting hole layout plan, and carry out drilling construction and grouting reinforcement operations accordingly.

[0045] In this embodiment, the final layout scheme was determined as follows: a five-petal pattern with a horizontal spacing of 2.3m and a vertical spacing of 2.5m. The depth of the straight holes was 3.5~5.5m, and the inclination of the inclined holes was 22° with a depth of 6m and a diameter of 50mm. The drilling and grouting construction was completed according to the scheme. After construction, 6 boreholes were randomly selected for inspection and verification. Only one small blind spot was found. The additional holes were then installed with a spacing of 1.3m. After the reinforcement was completed, the deformation of the coal pillar was reduced to less than 35mm, the rock mass was completely consolidated, and there was no air leakage or spalling. The reinforcement effect was excellent.

[0046] Example 2:

[0047] Example of optimized layout of grouting holes for small coal pillars in goaf excavation roadway under large deformation of 3102 working face;

[0048] 1. Project Overview;

[0049] The 3102 working face of a certain coal mine is a goaf-side excavation roadway with 7m wide small coal pillars reserved between sections. The working face is affected by the combined stress of mining from both the working face and the adjacent goaf, resulting in severe compression deformation of the coal pillar sides. The maximum cumulative deformation of the coal pillar measured on-site reached 360mm. The coal body exhibits dense and interconnected internal fissures and large-area breakage and loosening, posing safety hazards such as side spalling, air leakage from the goaf, and surrounding rock instability in the roadway. Grouting reinforcement of the small coal pillars is necessary. This example utilizes the method disclosed in this invention, encompassing the entire process of detection zoning, diffusion radius calculation, multi-objective iterative optimization using a genetic algorithm, borehole parameter matching, and construction review and hole replenishment. Detailed values ​​of the genetic algorithm's iterative fitness and monitoring data of the coal pillar deformation over 30 days after grouting are simultaneously provided.

[0050] 2. Complete implementation steps and measured / calculated data, specifically as follows:

[0051] S1. Obtain the internal deformation and fracturing characteristics of the small coal pillar and delineate the target area for grouting reinforcement;

[0052] Detection and construction parameters: Detection boreholes are arranged at equal intervals along the coal pillar, with a borehole spacing of 2m, a borehole diameter of 48mm, and a borehole depth of 6m (greater than the maximum depth of the fracture zone); four in-situ inspections are carried out in sections of the roadway, and the average value of each measuring point is taken after removing abnormal measuring points such as collapsed holes and water seepage.

[0053] Actual test results of coal pillar stratification and crushing:

[0054] 0~1m: Shallow severely fractured zone, with completely continuous fissures and loose coal body;

[0055] 1–3m and 3.8–6m: Central micro-fracture zone, with high density of fractures but no interconnection;

[0056] 3.2~3.8m: Intact coal body with very few cracks, no need for grouting reinforcement.

[0057] Surrounding rock stress monitoring: The stress concentration factor of the surrounding rock within the range of 0 to 6m is 1.78, indicating significant stress concentration and a substantial decrease in the bearing capacity of the coal pillar.

[0058] Reinforcement zone delineation: Combining the severely fractured zone and the micro-fractured zone, the 0-6m area was determined as the target area for grouting reinforcement; the coal pillar reinforcement sidewall was equivalent to a regular rectangular plane with a length of 60m and a vertical height of 4.5m, and a total area of ​​[missing information]. .

[0059] S2. Equivalent plane modeling, graded calculation of effective diffusion radius of slurry;

[0060] On-site grouting test: The water-cement ratio of the grout was uniformly controlled at 0.7, and the grouting pressure was kept constant at 3 MPa. The natural diffusion radius of the grout was measured in the fractured coal seam. .

[0061] The safety factor is selected based on the following: the measured deformation of the coal pillar is 360mm > 300mm, and the corresponding safety factor range is 0.75 to 0.8. In this case, K = 0.78 is selected.

[0062] Effective diffusion radius calculation: ;

[0063] S3. Iteratively solve the optimal grouting hole layout parameters based on genetic algorithm;

[0064] 3.1 Basic settings for genetic algorithms;

[0065] Optimized model: Using a 4.5m×60m rectangular reinforced plane as the calculation base, the single-hole slurry diffusion range is drawn as a circular coverage area with the effective diffusion radius (r=1.56m);

[0066] Algorithm parameters: population size 40, crossover probability 0.85, mutation probability 0.03, maximum number of iterations 90; convergence criterion: difference in fitness function between two adjacent generations < 0.01;

[0067] Constraints: Grout diffusion overlap coverage ≤15%; horizontal spacing of grouting holes 1.4~1.7r; vertical spacing of rows 1.5~1.8r;

[0068] Arrangement pattern determination: The measured coefficient of variation of the fracture density along the direction of the coal pillar is 0.37, which is greater than the preset threshold of 0.25. It is determined that the fracture distribution is disordered and the local breakage is severe. The algorithm automatically selects a five-petaled arrangement.

[0069] Multi-objective integrated fitness function: ;

[0070] In the formula: α and β are weighting coefficients, and α + β = 1, where α = 0.7 (overlap area weight, prioritizing control of slurry waste), and β = 0.3 (coverage area weight); S overlap S represents the total overlapping area of ​​the slurry. total S represents the total diffusion area of ​​all grouting holes. cover The effective reinforcement coverage area of ​​the plane; the smaller the overall adaptability F value, the better the hole layout scheme.

[0071] 3.2. Refine the numerical values ​​throughout the entire iterative process (key iteration nodes), see Table 1 below; Table 1:

[0072]

[0073] 3.3 The algorithm outputs the optimal layout parameters;

[0074] The horizontal grouting hole spacing is 2.52m, which is 1.62 times the effective diffusion radius, satisfying the 1.4~1.7r constraint.

[0075] Vertical row spacing: 2.74m, which is 1.76 times the effective diffusion radius, satisfying the 1.5~1.8r constraint;

[0076] The overall average overlap coverage of the grout was 13.1%, which is lower than the upper limit of 15%; the effective coverage area of ​​the reinforced plane was 246.92㎡, and the blind area was only 23.08㎡, accounting for 8.55%.

[0077] S4. Match the borehole diameter, depth, and inclination angle according to the breaking depth;

[0078] Drill hole diameter: 52mm (within the standard range of 42~56mm);

[0079] Straight hole partition depth:

[0080] Shallow severely fractured zone (0~1m): Straight hole depth 3.8m;

[0081] Central micro-fracture zone (1~6m): Straight hole depth 6.0m;

[0082] Laterally inclined grouting holes in deep goaf areas: arranged inclined towards the goaf area at an angle of 26° (15°~30° range), with a hole depth of 6.0m, connecting the transition zone between the broken zone and the intact coal body.

[0083] S5. Integrate parameters to form a construction plan, including grouting construction, inspection and re-inspection, and densification of holes;

[0084] Summary of complete grouting hole layout scheme: The layout is in a five-petal shape, with a horizontal hole spacing of 2.52m and a vertical row spacing of 2.74m; the borehole diameter is 52mm; the straight holes are available in two specifications: 3.8m and 6.0m.

[0085] Construction process: Roadway layout and hole positioning → Drilling → Sealing pipe installation → Constant pressure grouting;

[0086] Post-grouting inspection: Seven grouting holes were randomly selected for borehole inspection.

[0087] Blind spot filling treatment: A narrow and long reinforcement blind spot was found at the 42m position of the roadway, and denser grouting holes were laid out; the spacing between the denser holes was 0.6 times that of the conventional hole spacing; after the filling grouting was completed, a second inspection was carried out and no reinforcement blank area was left on the plane.

[0088] 3. Monitoring data of coal pillar deformation over the entire 30-day period after grouting reinforcement;

[0089] Using the completion time of grouting as the baseline (0d), multiple displacement gauges were arranged in the middle of the coal pillar, and deformation data were collected every 12 hours. The cumulative convergence deformation of the coal pillar (unit: mm) was recorded, and the original unreinforced stable deformation was 360 mm. See Table 2 below; Table 2:

[0090]

[0091] 4. Quantitative analysis of reinforcement effect;

[0092] Deformation control effect: The original deformation was 360mm, the stable deformation after 30 days was 32.8mm, the total deformation was reduced by 327.2mm, and the deformation control reduction reached 90.89%;

[0093] The deformation characteristics in stages are as follows: the deformation decreased by 144.3 mm from 0 to 10 days, accounting for 44.1% of the total decrease; the deformation decreased by 182.9 mm from 10 to 30 days, accounting for 55.9% of the total decrease. This indicates that the bearing capacity of the coal pillar continued to improve after the slurry was completely solidified, and the long-term support effect was excellent.

[0094] Economic and Efficiency Comparison: Under the same geological conditions, the traditional empirical borehole layout method resulted in a stable deformation of 89 mm over 30 days. The optimized scheme of this invention improved deformation control by 63.1%; ineffective grout overlap was significantly reduced, and grout material consumption was reduced by 21% compared to the traditional scheme.

[0095] Visual results on site: After 30 days of reinforcement, the coal wall is flat, with no spalling, bulging, or air leakage in the goaf. The integrity and structural stability of the coal pillars are significantly improved, meeting the long-term safe production requirements for roadway excavation along the goaf.

[0096] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithms, characterized in that, Includes the following steps: S1. Obtain the deformation and fragmentation distribution characteristics inside the small coal pillar, and delineate the target area for grouting reinforcement accordingly; S2. The reinforced sidewall of the small coal pillar is equivalent to a regular plane model. The natural diffusion radius R of the slurry is measured, and the natural diffusion radius R is converted according to the deformation level of the coal pillar by introducing a safety factor K to obtain the effective diffusion radius r, r=K×R; S3. Using the grouting hole layout parameters as optimization variables, within the regular plane model, draw a circle with each grouting hole as the center and the effective diffusion radius as the radius. Use an intelligent optimization algorithm to iteratively solve the problem with the fitness function of minimizing the overlap of the grout diffusion range of adjacent grouting holes and maximizing the effective coverage area, and determine the optimal grouting hole layout parameters. S4. Match the drilling depth, borehole diameter, and drilling inclination angle of the grouting hole according to the fracture depth and coal hardness of the target area for grouting reinforcement. S5. Integrate the layout parameters, drilling depth, drilling diameter and drilling inclination angle to form a grouting hole layout plan, and carry out drilling construction and grouting reinforcement operations accordingly.

2. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm according to claim 1, characterized in that... In step S1, when obtaining the deformation and breakage distribution characteristics inside the small coal pillar, a borehole inspection instrument is used to lay out detection boreholes at equal intervals along the side wall of the coal pillar for in-situ detection. The spacing between detection boreholes is 2~3m, the borehole depth is not less than the maximum depth of the coal pillar breakage zone, the number of detections is not less than 3, and after removing abnormal data, the average value of the data at each measuring point is taken.

3. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm as described in claim 1, characterized in that... In step S1, data on the deformation of the surrounding rock, the degree of fracture development, the density of fracture development, and the distribution range of the fracture zone at different depths of the coal pillar are collected. Combined with the stress monitoring data of the surrounding rock in the roadway, the coal pillar is divided into intact area, micro-fracture area, and severely fractured area. The micro-fractured area and the severely fractured area are merged and designated as the grouting reinforcement target area.

4. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm according to claim 1, characterized in that, In step S2, the safety factor ranges from 0.75 to 0.9, and is graded according to the amount of coal pillar deformation: when the coal pillar deformation is less than 100 mm, the safety factor is 0.85 to 0.9; when the coal pillar deformation is 100 to 300 mm, the safety factor is 0.8 to 0.85; when the coal pillar deformation is greater than 300 mm, the safety factor is 0.75 to 0.

8.

5. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm according to claim 1, characterized in that, In step S3, the constraints of the intelligent optimization algorithm include: the grout diffusion overlap coverage of adjacent grouting holes does not exceed 15%, the horizontal spacing between adjacent grouting holes is 1.4 to 1.7 times the effective diffusion radius, and the vertical spacing is 1.5 to 1.8 times the effective diffusion radius; the iterative convergence condition of the intelligent optimization algorithm is that the fitness function difference is less than 0.01, and the number of iterations is not less than 50.

6. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm according to claim 3, characterized in that, In step S3, based on the obtained fracture development density at each measuring point, the coefficient of variation of fracture density along the coal pillar direction is calculated, and the arrangement pattern is automatically matched according to the comparison result of the coefficient of variation and the preset threshold. When the coefficient of variation is less than or equal to a preset threshold, the crack distribution is determined to be uniform, and the intelligent optimization algorithm outputs a rectangular arrangement; when the coefficient of variation is greater than the preset threshold, the crack distribution is determined to be disordered or there are locally severely fractured areas, and the intelligent optimization algorithm outputs a quincunx arrangement.

7. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm according to claim 1, characterized in that, In step S4, the borehole diameter is set to 42~56mm, the borehole depth in the shallow fractured zone is 2~4m, and the borehole depth in the deep fractured zone is 5~8m; for the deep fractured zone, an inclined grouting hole is added, which is inclined toward the goaf side with an inclination angle of 15°~30°.

8. The method for arranging grouting holes for small coal pillars in large deformation goaf excavation based on genetic algorithm according to claim 1, characterized in that, In step S5, after the grouting reinforcement operation is completed, at least 5 grouting holes are randomly selected for secondary inspection. If there are blind areas where the grout is not covered, additional grouting holes should be added in the center of the blind area. The spacing of the additional grouting holes is 0.5 to 0.7 times that of the conventional grouting hole spacing, and the holes need to be inspected again after being added.

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