A seepage path variable weight fusion mining floor water blocking performance evaluation method

Abstract

The application discloses a kind of seepage path variable weight fusion's mining floor water-blocking performance evaluation method, the method is first obtained target working face basic parameter, constructs and checks numerical calculation model;Determine the change characteristics of permeability of floor strata after mining;Permeability ratio threshold is set, search from the top interface of pressure-bearing aquifer to the potential dominant seepage path of the bottom interface of goaf;Calculate overall equivalent permeability and the equivalent permeability of each dominant seepage path, and determine contribution weight according to relative size;Variable weight fusion is carried out according to contribution weight, and the equivalent permeability of mining floor is calculated;Again conversion is equivalent water-blocking thickness, compared with the total interval of coal seam and pressure-bearing aquifer, determine whether water conservation mining can be realized.The application can highlight the control effect of a few dominant seepage paths on the overall water-conducting capacity of floor, avoid weakening the influence of local through channel by traditional averaging equivalent method, and improve the accuracy of floor water-blocking performance evaluation and water conservation mining discrimination.

Description

Technical Field

[0001] This invention relates to the field of water-retaining mining technology in coal mines, and in particular to a method for evaluating the water-blocking performance of the mining floor based on the fusion of seepage path weights. Background Technology

[0002] Mining activities cause deformation and damage to the floor rock mass, significantly increasing permeability and creating dominant seepage channels, which can lead to water inrush accidents and damage groundwater resources. The water-conserving mining concept requires the safe extraction of coal without disrupting the regional groundwater resource balance or causing catastrophic water inrushes. Its core lies in accurately assessing the water-blocking performance of the mining floor.

[0003] Currently, methods for assessing the water-blocking performance of the floor slab are mainly divided into three categories. The first category is the inrush coefficient method and its improved versions. These methods are simple to calculate and widely used, but they primarily focus on the relationship between macroscopic water pressure and the thickness of the aquitard, making it difficult to reflect processes such as floor slab rock damage, fracture propagation, sudden increases in permeability, and non-uniform development of dominant seepage paths under mining conditions. The second category is evaluation methods based on the evolution of floor slab permeability during mining. These methods obtain changes in permeability before and after mining through numerical simulation or field testing. However, existing technologies typically use overall equivalent permeability, layered averaging, or simple series-parallel equivalence methods, failing to distinguish the differences in the contribution of different seepage units and different seepage paths to the overall water-conducting capacity. For floor slab rock masses, inrush is often dominated by a few high-permeability units or localized through-paths. Averaging equivalence methods weaken or even eliminate the contribution of localized dominant channels, leading to an overestimation of the floor slab's water-blocking performance. The third category is multi-factor comprehensive evaluation methods. While these can incorporate many influencing factors, they mainly rely on index superposition or empirical weighting, making it difficult to quantitatively characterize water-blocking performance from the perspective of seepage path contribution.

[0004] To address the aforementioned issues, Chinese patent CN110749533B discloses a method for identifying water-retaining coal mining based on the equivalent aquitard thickness. This method is applicable to situations with widespread roof fractures, but for water inrushes controlled by dominant seepage channels in the floor, the averaging equivalent approach struggles to highlight the dominant role of the penetration path. Chinese patent application CN121024534A involves calculating the equivalent permeability tensor of discrete fractures, but it relies on flow simulation results and is an equivalent correction method based on a known flow field. It does not establish an analytical evaluation method centered on dominant path identification and contribution allocation for confined water inrushes in the floor. Chinese patent application CN119761256A proposes a method for calculating the full equivalent permeability tensor based on EDFM, but this still involves known numerical flow field inversion and is difficult to directly reflect the differentiated contributions of different paths in rapid assessments.

[0005] In summary, existing technologies have the following shortcomings: First, evaluations often use thickness, water pressure, or overall permeability indicators, which are insufficient to accurately reflect the formation and connectivity of dominant seepage paths. Second, equivalent permeability calculations employ averaging or fixed series-parallel processing, failing to consider variable weighting and fusion based on path connectivity and the degree of permeability surges. Third, existing methods for equivalent fracture media largely rely on flow simulation or inversion calculations, lacking a path contribution-based theoretical analytical method for identifying dominant seepage paths in the confined water of mining-induced floor slabs. Therefore, there is an urgent need for a method to assess the water-blocking performance of mining-induced floor slabs that can identify dominant seepage paths, dynamically assign weights based on the water-conducting contribution of each path, and perform variable weighting and fusion. Summary of the Invention

[0006] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a method for evaluating the water-blocking performance of the mining floor by merging seepage paths with variable weights. This method identifies potential dominant seepage paths in the mining floor that connect the confined aquifer and the bottom interface of the goaf. It assigns dynamic weights to each path based on its equivalent permeability, connectivity, and contribution to the overall water-conducting capacity. By merging multiple dominant seepage paths with variable weights, it achieves quantitative evaluation of the equivalent water-blocking performance of the mining floor and accurate identification of water-retaining mining conditions.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] This invention provides a method for evaluating the water-blocking performance of mining-induced floor slabs based on variable weight fusion of seepage paths, comprising the following steps:

[0009] S1. Obtain the basic parameters of the target working face, and construct and verify the numerical calculation model of fluid-structure interaction in high-pressure water-bearing coal seam mining;

[0010] S2. Based on the verified numerical calculation model, determine the permeability change characteristics of the bottom rock strata after mining;

[0011] S3. Set a threshold based on the permeability change characteristics, and search for potential advantageous seepage paths from the top interface of the confined aquifer to the bottom interface of the goaf based on the threshold.

[0012] S4. Determine the region to be solved, and calculate the equivalent permeability of the dominant seepage path and the overall equivalent permeability of the rock mass other than the dominant seepage path in the region to be solved. Then, determine the contribution weight of each of the dominant seepage paths to the overall water conductivity based on the relative size of the overall equivalent permeability and the equivalent permeability of each dominant seepage path.

[0013] S5. Based on the contribution weights, the equivalent permeability of each advantageous seepage path is fused with the overall equivalent permeability using a weighted method to calculate the equivalent permeability of the mining-induced floor.

[0014] S6. Determine the critical permeability based on the water inflow control conditions of the working face, and calculate the equivalent water-blocking thickness from the equivalent permeability of the mining floor. Compare the equivalent water-blocking thickness with the total distance between the coal seam and the confined aquifer to determine whether water-conserving mining can be achieved.

[0015] Preferably, the basic parameters of the target working face include burial depth, lithology, rock layer thickness, density, bulk modulus, shear modulus, internal friction angle, cohesion, tensile strength, porosity, initial permeability, thickness of the confined aquifer, pressure, and recharge rate.

[0016] Preferably, in step S1, constructing and verifying the numerical calculation model for fluid-structure interaction in high-pressure water-bearing coal seam mining includes:

[0017] S11. Determine the geometric dimensions of the numerical calculation model based on the geological conditions of the target working face. Apply an equivalent load to the top of the numerical calculation model according to the burial depth of the target working face and the height of the numerical calculation model. Apply the pressure of the confined aquifer to the bottom of the numerical calculation model and use fixed constraints. Set roller supports on both sides of the numerical calculation model.

[0018] S12. Divide the numerical calculation model into several numerical units according to the rock strata distribution of the target working face, and assign the corresponding basic parameters of the target working face to each numerical unit;

[0019] S13. Simulate the coal seam mining process and obtain the advance support pressure, rock subsidence and / or surrounding rock deformation under mining conditions as model output values;

[0020] The steps for verifying the numerical calculation model include: obtaining the output value of the numerical calculation model and comparing the output value with the field measured value; the output value includes one or more parameters such as advance support pressure, rock stratum settlement, and surrounding rock deformation.

[0021] Preferably, in step S2, when determining the permeability change characteristics of the bottom rock strata after mining, the elastic-plastic state of the rock strata is considered;

[0022] If the numerical unit is in an elastic state, the permeability ratio is calculated using the formula. calculate;

[0023] If the numerical unit is in a plastic state, the permeability ratio is calculated using the formula. calculate;

[0024] In the formula, , Let m be the current permeability and the initial permeability of the numerical unit. 2 ; For volumetric strain; Initial porosity; This is the influence coefficient; For plastic strain; the subscript ij represents the numerical unit corresponding to the unit layer in the j-th column of the i-th geological layer below the coal seam.

[0025] Preferably, the influence coefficient Determined based on lithology and the ratio of vertical stress before and after mining: When the lithology is sandstone and the ratio of vertical stress before and after mining is ≥0.5, 15≤ ≤20; when the ratio <0.5, 10 < <15; when the ratio is ≥1, 1≤ ≤10; When the lithology is mudstone and the ratio of vertical stress before and after mining is ≥0.5, 10≤ ≤15; when the ratio <0.5, 5 < <10; when the ratio is ≥1, 1≤ ≤5; When the lithology is limestone and the ratio of vertical stress before and after mining is ≥0.5, 20≤ ≤25; when the ratio <0.5, 15 < <20; when the ratio is ≥1, 1≤ ≤15.

[0026] Preferably, the specific method for searching for potential advantageous seepage paths in step S3 is as follows:

[0027] A threshold is set for the ratio of rock permeability after mining to rock permeability before mining, and numerical units with a permeability ratio greater than the threshold are identified as candidate seepage-conducting units;

[0028] Starting from each unit at the top interface of the confined aquifer, and following the bottom-up and left-right neighbor search principle, among the candidate adjacent units that meet the threshold requirements, the unit with the largest permeability ratio is selected as the next path unit. After the search is completed, the search is backtracked to the previous unit and the second-best candidate unit is selected to continue the search until the continuous unit sequence connects the top interface of the confined aquifer and the bottom interface of the goaf. Then, the continuous unit sequence is determined as a dominant seepage path.

[0029] Preferably, in step S4, the method for determining the region to be solved is as follows:

[0030] Using the central axis of the goaf as a reference, take the points on the left and right sides that are farthest from the central axis as the location of the dominant seepage path, and draw vertical lines to intersect the coal seam and the confined aquifer respectively. The area enclosed by these lines is the area to be solved.

[0031] Preferably, in step S4, the overall equivalent permeability of the rock mass within the region to be solved, excluding the dominant seepage path, is... The calculation method is as follows:

[0032] , The distance between the coal seam and the confined aquifer is in meters (m). , where is the thickness of each rock stratum between the coal seam and the confined aquifer, in meters; This represents the total number of intermediate rock layers; This represents the average permeability of all numerical units in the region to be solved, excluding the dominant seepage path.

[0033] The equivalent permeability calculation method for the dominant seepage path is as follows: , The number of numerical units along the dominant seepage path; The unit size is in meters (m). m represents the permeability of a numerical cell along the dominant seepage path. 2 The contribution weights are determined as follows:

[0034] ; ;

[0035] The weights of numerical units other than the dominant seepage path; Let m be the equivalent permeability of the i-th dominant seepage path. 2 ; This represents the total number of dominant seepage paths;

[0036] The weight of a numerical cell along a dominant seepage path is the sum of the weights of all paths if a numerical cell is located on multiple dominant seepage paths.

[0037] Preferably, in step S5, the equivalent permeability of the mining base plate is... The calculation method is as follows:

[0038] ;

[0039] in, The distance between the coal seam and the confined aquifer is in meters (m). , where is the thickness of each rock stratum between the coal seam and the confined aquifer, in meters; This represents the total number of intermediate rock layers; Let m be the permeability of the numerical unit corresponding to the j-th unit layer in the i-th row of geological strata below the coal seam. 2 ; is the weight of the numerical unit corresponding to the unit layer in the j-th column of the i-th row of geological layers below the coal seam; M is the number of numerical units corresponding to each lithology layer in the region to be solved.

[0040] Preferably, the critical permeability mentioned in step S6 The calculation formula is:

[0041] ;

[0042] in, The distance between the coal seam and the confined aquifer is in meters (m). The aquifer recharge rate is expressed in m / s. The thickness of the confined water level is in meters (m). The hydrodynamic viscosity coefficient is 1×10⁻⁶. -3 Pa·s; Let be the length of the base plate of the region to be solved, in meters. To determine the acceptable percentage of losses relative to replenishment, Adjustments are made dynamically based on ecological water demand.

[0043] Equivalent water-blocking thickness of mining strata The calculation formula is:

[0044] ;

[0045] like If so, it is determined that water-conserving extraction can be achieved; if If so, it is determined that water-conserving extraction cannot be achieved.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. Traditional methods, which use averaging or fixed series-parallel equivalent methods to process the permeability of the floor strata, easily weaken or even cancel the contribution of a few high-permeability pathways, leading to an overestimation of the floor's water-blocking performance. This invention achieves variable-weight fusion of dominant seepage paths by setting a permeability ratio threshold, searching for potential dominant seepage paths from the top interface of the confined aquifer to the bottom interface of the goaf, and assigning dynamic weights based on the equivalent permeability of each dominant seepage path and its contribution to the overall water conductivity. This method highlights the controlling effect of a few dominant paths on the overall water conductivity of the floor, avoids the bias caused by averaging, and significantly improves the accuracy of assessing the water-blocking performance of the mining-induced floor.

[0048] 2. This invention converts the equivalent permeability of the mining floor into an equivalent water-blocking thickness and compares it with the actual total distance from the coal seam to the confined aquifer. Using a set condition that the water inflow at the working face does not exceed the aquifer recharge rate as the critical condition, a clear criterion for determining water-conserving mining is provided. Verification through examples shows that traditional non-variable weighting methods may misjudge water-conserving mining as feasible, while the method of this invention determines it as not feasible, consistent with the actual situation where a high-permeability dominant path has formed on-site. Therefore, this invention can more reliably determine water-conserving mining conditions, effectively prevent floor water inrush disasters, and protect groundwater resources.

[0049] 3. Existing methods for calculating equivalent permeability in fractured media often rely on flow simulation or numerical flow field inversion, which are computationally complex and difficult to directly reflect the differentiated contributions of different paths in rapid evaluation. This invention, based on the permeability distribution output by a numerical calculation model, directly provides analytical expressions for the equivalent permeability and equivalent water-blocking thickness of the mining floor through explicit path search, weight allocation, and variable weight fusion formulas. The calculation process is clear, the physical meaning of the parameters is explicit, and there is no need for repeated iterations or flow field inversion, making it easy to promote and apply in engineering projects.

[0050] 4. In calculating the permeability of the floor after mining, this invention distinguishes between elastic and plastic states, and sets the range of values ​​for the plasticity influence coefficient in segments based on lithology (sandstone, mudstone, limestone) and the ratio of vertical stress before and after mining. This fully reflects the controlling effect of different rock strata and different stress loading and unloading paths on permeability changes under mining conditions, making the permeability evolution results more consistent with engineering practice, and providing reliable basic data for subsequent dominant path identification and equivalent permeability calculation.

[0051] 5. This invention introduces a proportionality coefficient β into the critical permeability calculation formula. This coefficient can be dynamically adjusted according to the aquifer recharge and regional ecological water demand, so that the water-retaining mining judgment conditions can adapt to the hydrogeological conditions and ecological environmental protection requirements of different mining areas, and have good flexibility and applicability. Attached Figure Description

[0052] 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.

[0053] Figure 1 A flowchart illustrating a method for evaluating the water-blocking performance of mining-induced floor slabs based on the fusion of seepage path weights, provided in an embodiment of the present invention;

[0054] Figure 2 A schematic diagram of the numerical calculation model provided in an embodiment of the present invention;

[0055] Figure 3 A comparison and verification diagram of the pre-support pressure simulated by numerical simulation in step S1 and the pre-support pressure measured on site.

[0056] Figure 4 The rock strata permeability between the coal seam and the confined aquifer provided in the embodiments of the present invention;

[0057] Figure 5 The ratio of post-mining to pre-mining permeability of the rock strata between the coal seam and the confined aquifer is provided in the embodiments of the present invention.

[0058] Figure 6 This is a schematic diagram of the dominant seepage path found in step S3. Detailed Implementation

[0059] 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.

[0060] Taking a mine in the Permian coalfield of the Carboniferous region of North China, which is affected by floor water hazards, as an example, the main coal seam is No. 5. The coal seam base is a thick Ordovician karst aquifer with strong water content, and the hydrogeological conditions are extremely complex. Therefore, assessing the floor water-blocking performance is crucial for floor water hazard prevention and water-conserving mining. This embodiment provides a method for assessing the floor water-blocking performance of mining operations by incorporating variable seepage path weights, specifically including:

[0061] S1. Through on-site investigation and laboratory testing, obtain the geological and hydrogeological conditions and coal and rock physical and mechanical parameters of the target working face, including burial depth, lithology, rock layer thickness, density, bulk modulus, shear modulus, internal friction angle, cohesion, tensile strength, porosity, initial permeability, thickness of confined aquifer, pressure, and recharge rate. -4 m / s, specific parameters are shown in Table 1.

[0062] The coal seam is 500m deep and 8m thick, with a confined water pressure of 5MPa, a confined aquifer thickness of 30m, and a recharge rate of 2.01×10⁻⁶. -4 m / s.

[0063] Table 1:

[0064]

[0065] Based on the geological and hydrogeological conditions and coal and rock physical and mechanical parameters of the target working face, a numerical calculation model of the target working face (hereinafter referred to as the model) is constructed and verified. Figure 2 As shown, the model measures 150×73m (length×height), with a 1×1m mesh element. A 5MPa water pressure is applied to the bottom of the model, with fixed constraints. The model is supported by rollers on both sides, and an equivalent load is applied to the top according to the burial depth. The pre-support pressure is compared and verified using numerical simulation and on-site measured pre-support pressure. Figure 3 As shown, the error rate of the advanced support pressure is less than 5%, which verifies the rationality of the model.

[0066] S2. Based on the verified numerical calculation model, the ratio of vertical stress and elastoplastic state at different locations after and before coal seam mining are determined. Considering the influence of the elastoplastic state and loading / unloading state of the rock strata on permeability, the permeability calculation principle is as follows:

[0067] If the numerical unit is in an elastic state, the permeability is expressed as follows: calculate;

[0068] If the numerical unit is in a plastic state, the permeability is expressed as follows: calculate.

[0069] In the formula, , Let m be the current permeability and the initial permeability of the numerical unit. 2 ; For volumetric strain; Initial porosity; This is the influence coefficient; For plastic strain; the subscript ij represents the numerical unit corresponding to the unit layer in the j-th column of the i-th geological layer below the coal seam.

[0070] When the lithology is sandstone and the ratio of vertical stress before and after mining is ≥0.5, 15≤ ≤20; when the ratio <0.5, 10 < <15; when the ratio is ≥1, 1≤ ≤10; When the lithology is mudstone and the ratio of vertical stress before and after mining is ≥0.5, 10≤ ≤15; when the ratio <0.5, 5 < <10; when the ratio is ≥1, 1≤ ≤5; When the lithology is limestone and the ratio of vertical stress before and after mining is ≥0.5, 20≤ ≤25; when the ratio <0.5, 15 < <20; when the ratio is ≥1, 1≤ ≤15.

[0071] Calculate the permeability of rock strata at different locations after coal seam mining, such as Figure 4 As shown, this mainly illustrates the rock strata between the coal seam and the confined aquifer, determining the ratio of floor permeability after mining to rock strata permeability before mining at different locations, such as... Figure 5 As shown.

[0072] S3. Determine the threshold for the ratio of rock stratum permeability after mining to floor permeability before mining, set this threshold to 5, and search for potential advantageous seepage paths from the top interface of the confined aquifer to the bottom interface of the goaf based on the threshold.

[0073] Starting with each unit of the confined water top interface, and following the bottom-up and left-right neighbor search principle, among the candidate adjacent units that meet the threshold requirements, the unit with the largest permeability ratio is selected as the next path unit. After the search is completed, the search is backtracked to the previous unit and the second-best candidate unit is selected to continue the search. This process is repeated.

[0074] When a continuous unit sequence connects the top interface of the confined aquifer in Ordovician limestone and the bottom interface of the goaf, this continuous unit sequence is determined as the dominant seepage path, such as... Figure 6 As shown, a total of 6 dominant seepage paths were found, namely dominant seepage path 1, dominant seepage path 2, dominant seepage path 3, dominant seepage path 4, dominant seepage path 5 and dominant seepage path 6.

[0075] S4. Taking the central axis of the goaf as the benchmark, take the location of the dominant seepage path farthest from the central axis on the left and right sides, and draw vertical lines to intersect the coal seam and the confined aquifer respectively. The area enclosed by these lines is the area to be solved. The rectangular area is 23m away from the left and right boundaries of the model. Calculate the overall equivalent permeability of the numerical units in the area to be solved, excluding the dominant seepage path.

[0076] Substitute the data from the numerical computation unit into the calculation formula. Determine the overall equivalent permeability of the numerical cells in the region to be solved, excluding the dominant seepage path. =3.35×10 -13 m 2 ;

[0077] Similarly, substitute the data from the numerical calculation unit into the formula. The equivalent permeability of the dominant seepage path can be obtained, as shown in Table 2;

[0078] Following the approach of combining the overall equivalent permeability with the equivalent permeability of the dominant seepage path in parallel, we substitute the overall equivalent permeability and the equivalent permeability of the dominant seepage path into the equation:

[0079] ; ;

[0080] The weights of numerical units other than the dominant seepage path; Let m be the equivalent permeability of the i-th dominant seepage path. 2 ; This represents the total number of dominant seepage paths;

[0081] The overall equivalent permeability of the numerical units other than the dominant seepage path and the contribution ratio of each dominant seepage path to the equivalent permeability were determined, and the weights of different numerical units were determined. The calculation results are shown in Table 2.

[0082] The weight of a cell that is in both dominant seepage path 2 and dominant seepage path 3 is the sum of the two weights, which is 0.354. The weight of a cell that is in both dominant seepage path 4 and dominant seepage path 5 is the sum of the two weights, which is 0.338.

[0083] Table 2:

[0084]

[0085] S5. Combining the weights of different numerical units and their corresponding permeability values, the number of numerical units in each layer of the solution area is 810. The thickness of each rock layer between the coal seam and the confined aquifer is 10m, and the distance between the coal seam and the confined aquifer is 50m. Substituting these values ​​into the formula for calculating the equivalent permeability of the mining floor along the dominant seepage path using weighted fusion... ;

[0086] The permeability of each rock layer from the coal seam to the confined aquifer can be determined to be 5.83 × 10⁻⁶. -13 m 2 2.30×10 -12 m 2 1.17×10 -11 m 2 2.14×10 -12 m 2 4.47×10 -13 m 2 The equivalent permeability of the mining base plate can be obtained. 1.01×10 -12 m 2 .

[0087] Meanwhile, the equivalent permeability of the mining-induced floor was also calculated using the traditional non-variable weighting method, and the result was 3.45 × 10⁻⁶. -13 m 2 To verify the rationality of the variable weight calculation, the permeability with a solution range was derived, and a numerical calculation model with the same size as the region to be solved was constructed. Water pressure was applied to the upper surface, and the equivalent permeability numerical solution was calculated by inversely applying Darcy's law. The calculation result was 1.07 × 10⁻⁶. -12 m 2 The numerical solution and the solution proposed in this invention have an error of less than 5.61%, while the numerical solution and the solution proposed in this invention have an error of more than 67.7%, which verifies the rationality of the proposed method.

[0088] S6. A certain set ratio of the water inflow at the working face to the aquifer recharge is the critical condition for achieving water-conserving coal mining. The length of the floor plate in the area to be solved is... It is 81m, and the proportionality coefficient is... Set to 0.8, aquifer recharge rate 2.01×10 -4 m / s, thickness of confined water The hydrodynamic viscosity coefficient is 30m. 1×10 -3 Pa·s, solve for the corresponding critical permeability It is 5.96×10 -13 m 2 ,

[0089] The equivalent water-blocking thickness of the mined rock strata is 1.69m, making water-retaining mining impossible. However, if the equivalent water-blocking thickness of the mined rock strata is determined using the traditional non-variable weighting method, it is 0.58m, allowing for water-retaining mining. This demonstrates that the results obtained using the traditional method do not match the established high-permeability dominant pathway, further proving the effectiveness of the method proposed in this invention.

[0090] 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 evaluating the water-blocking performance of mining-induced floor slabs based on variable weight fusion of seepage paths, characterized in that, Includes the following steps: S1. Obtain the basic parameters of the target working face, and construct and verify the numerical calculation model of fluid-structure interaction in high-pressure water-bearing coal seam mining; S2. Based on the verified numerical calculation model, determine the permeability change characteristics of the bottom rock strata after mining; S3. Set a threshold based on the permeability change characteristics, and search for potential advantageous seepage paths from the top interface of the confined aquifer to the bottom interface of the goaf based on the threshold. S4. Determine the region to be solved, and calculate the equivalent permeability of the dominant seepage path and the overall equivalent permeability of the rock mass other than the dominant seepage path in the region to be solved. Then, determine the contribution weight of each of the dominant seepage paths to the overall water conductivity based on the relative size of the overall equivalent permeability and the equivalent permeability of each dominant seepage path. Among them, the overall equivalent permeability of the rock mass in the region to be solved, excluding the dominant seepage path. The calculation method is as follows: , The distance between the coal seam and the confined aquifer is in meters (m). , where is the thickness of each rock stratum between the coal seam and the confined aquifer, in meters; This represents the total number of intermediate rock layers; This represents the average permeability of all numerical units in the region to be solved, excluding the dominant seepage path. The equivalent permeability calculation method for the dominant seepage path is as follows: , The number of numerical units along the dominant seepage path; The unit size is in meters (m). m represents the permeability of a numerical cell along the dominant seepage path. 2 The contribution weights are determined as follows: ； ； The weights of numerical units other than the dominant seepage path; Let m be the equivalent permeability of the i-th dominant seepage path. 2 ; This represents the total number of dominant seepage paths; The weight of a numerical cell along a dominant seepage path is the sum of the weights of all paths if a numerical cell is located on multiple dominant seepage paths. S5. Based on the aforementioned contribution weights, the equivalent permeability of each advantageous seepage path is weighted and fused with the overall equivalent permeability to calculate the mining-induced floor equivalent permeability; the mining-induced floor equivalent permeability... The calculation method is as follows: ； in, The distance between the coal seam and the confined aquifer is in meters (m). , where is the thickness of each rock stratum between the coal seam and the confined aquifer, in meters; This represents the total number of intermediate rock layers; Let m be the permeability of the numerical unit corresponding to the j-th unit layer in the i-th row of geological strata below the coal seam. 2 ; is the weight of the numerical unit corresponding to the unit layer in the j-th column of the i-th row of geological layers below the coal seam; M is the number of numerical units corresponding to each lithology layer in the region to be solved. S6. Determine the critical permeability based on the water inflow control conditions at the working face, and calculate the equivalent water-blocking thickness from the equivalent permeability of the mining floor. Compare the equivalent water-blocking thickness with the total distance between the coal seam and the confined aquifer to determine whether water-conserving mining can be achieved; Critical permeability The calculation formula is: ； in, The distance between the coal seam and the confined aquifer is in meters (m). The aquifer recharge rate is expressed in m / s. The thickness of the confined water level is in meters (m). The hydrodynamic viscosity coefficient is 1×10⁻⁶. -3 Pa·s; Let be the length of the base plate of the region to be solved, in meters. To determine the acceptable percentage of losses relative to replenishment, Adjustments are made dynamically based on ecological water demand. Equivalent water-blocking thickness of mining strata The calculation formula is: ； like If so, it is determined that water-conserving extraction can be achieved; if If so, it is determined that water-conserving extraction cannot be achieved.

2. The method for evaluating the water-blocking performance of mining-induced floor slabs based on seepage path weight fusion according to claim 1, characterized in that, The basic parameters of the target working face include burial depth, lithology, rock layer thickness, density, bulk modulus, shear modulus, internal friction angle, cohesion, tensile strength, porosity, initial permeability, thickness of the confined aquifer, pressure, and recharge rate.

3. The method for evaluating the water-blocking performance of mining-induced floor slabs based on seepage path weight fusion according to claim 1, characterized in that, In step S1, the numerical calculation model for fluid-structure interaction in high-pressure water-bearing coal seam mining is constructed and verified, including: S11. Determine the geometric dimensions of the numerical calculation model based on the geological conditions of the target working face. Apply an equivalent load to the top of the numerical calculation model according to the burial depth of the target working face and the height of the numerical calculation model. Apply the pressure of the confined aquifer to the bottom of the numerical calculation model and use fixed constraints. Set roller supports on both sides of the numerical calculation model. S12. Divide the numerical calculation model into several numerical units according to the rock strata distribution of the target working face, and assign the corresponding basic parameters of the target working face to each numerical unit; S13. Simulate the coal seam mining process and obtain the advance support pressure, rock subsidence and / or surrounding rock deformation under mining conditions as model output values; The steps for verifying the numerical calculation model include: obtaining the output value of the numerical calculation model and comparing the output value with the field measured value; the output value includes one or more parameters such as advance support pressure, rock stratum settlement, and surrounding rock deformation.

4. The method for evaluating the water-blocking performance of mining-induced floor slabs based on seepage path weight fusion according to claim 3, characterized in that, In step S2, when determining the permeability change characteristics of the bottom rock strata after mining, the elastic-plastic state of the rock strata is considered; If the numerical unit is in an elastic state, the permeability ratio is calculated using the formula. calculate; If the numerical unit is in a plastic state, the permeability ratio is calculated using the formula. calculate; In the formula, , Let m be the current permeability and the initial permeability of the numerical unit. 2 ; For volumetric strain; Initial porosity; This is the influence coefficient; For plastic strain; the subscript ij represents the numerical unit corresponding to the unit layer in the j-th column of the i-th geological layer below the coal seam.

5. The method for evaluating the water-blocking performance of mining-induced floor slabs based on seepage path weight fusion according to claim 4, characterized in that, The influence coefficient Determined based on lithology and the ratio of vertical stress before and after mining: When the lithology is sandstone and the ratio of vertical stress before and after mining is ≥0.5, 15≤ ≤20; when the ratio is <0.5, < <15; when the ratio is ≥1, ≤ ≤10; When the lithology is mudstone and the ratio of vertical stress before and after mining is ≥0.5, 10≤ ≤15; when the ratio <0.5, 5 < <10; When the ratio is ≥1, 1≤ ≤5; When the lithology is limestone and the ratio of vertical stress before and after mining is ≥0.5, 20≤ ≤25; when the ratio <0.5, 15 < <20; when the ratio is ≥1, 1≤ ≤15.

6. The method for evaluating the water-blocking performance of mining-induced floor slabs based on seepage path weight fusion according to claim 1, characterized in that, The specific method for searching for potential advantageous seepage paths in step S3 is as follows: A threshold is set for the ratio of rock permeability after mining to rock permeability before mining, and numerical units with a permeability ratio greater than the threshold are identified as candidate seepage-conducting units; Starting from each unit at the top interface of the confined aquifer, and following the bottom-up and left-right neighbor search principle, among the candidate adjacent units that meet the threshold requirements, the unit with the largest permeability ratio is selected as the next path unit. After the search is completed, the search is backtracked to the previous unit and the second-best candidate unit is selected to continue the search until the continuous unit sequence connects the top interface of the confined aquifer and the bottom interface of the goaf. Then, the continuous unit sequence is determined as a dominant seepage path.

7. The method for evaluating the water-blocking performance of mining-induced floor slabs based on seepage path weight fusion according to claim 1, characterized in that, In step S4, the method for determining the region to be solved is as follows: Using the central axis of the goaf as a reference, take the points on the left and right sides that are farthest from the central axis as the location of the dominant seepage path, and draw vertical lines to intersect the coal seam and the confined aquifer respectively. The area enclosed by these lines is the area to be solved.

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