A method for determining a high permeability area of overburden strata of mining

Abstract

The application discloses a kind of high permeation area determination methods of mining overburden rock, it is related to coal mine gas extraction technical field, specifically includes steps, S1, gas migration area determination: the fracture characteristic parameter is obtained by physical similar simulation experiment, the range of gas migration area range in fracture field is determined from horizontal and vertical, wherein horizontal is the direction of parallel coal seam advancement, vertical is the direction of vertical coal seam advancement;S2, high permeation area determination: obtain the gas emission of coal mining, calculate model gas mass source item, carry out numerical simulation experiment, determine high permeation area;The application realizes the accurate identification of high permeation area of pressure-relief gas, improves the extraction efficiency of pressure-relief gas, realizes gas prevention and control, by determining the high permeation area of mining overburden rock, further optimizes resource utilization, avoids the waste of extraction resources, reduces extraction energy consumption, ensures extraction efficiency, improves the safety of coal mining.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of coal mine gas extraction, in particular to a method for determining a high-permeability area of overburden strata subjected to mining. BACKGROUND

[0002] Coal seam gas is not only a disaster gas, but also a unique resource of coal mines. Realizing gas extraction during coal seam mining can not only prevent and control gas disasters and reduce environmental pollution, but also increase energy utilization rate, achieving multiple effects such as mine safety production, environmental protection, and new energy supply.

[0003] The existing patent with the patent number CN118273763A discloses a gas sub-domain coordinated efficient extraction method for thick coal seam fully mechanized caving face area, which constructs a "low+high" multi-layer pressure relief gas extraction spatial layout, fully considers the pressure relief gas extraction conditions, reasonably divides the extraction area, forms a gas sub-domain extraction method suitable for thick coal seam fully mechanized caving mining, effectively improves the gas extraction flow, extraction concentration and on-site gas extraction effect, realizes the thick coal seam gas extraction system comprehensive evaluation result standard, and ensures safe and efficient mining.

[0004] However, the invention patent still has the following problems: the gas sub-domain extraction method is only suitable for thick coal seams, and is not suitable for other coal seams with other occurrence conditions, such as thin coal seams and inclined thick coal seams; secondly, the gas extraction area is not accurately divided, but only divided into multiple sub-regions, which does not realize accurate identification of the gas extraction area, resulting in resource waste and low extraction efficiency. SUMMARY

[0005] The purpose of the present application is to provide a method for determining a high-permeability area of overburden strata subjected to mining.

[0006] To solve the above technical problems, the present application specifically provides the following technical solutions:

[0007] A method for determining a high-permeability area of overburden strata subjected to mining, specifically comprising the steps of,

[0008] S1, determining the gas migration area: obtaining the fracture characteristic parameters through physical similar simulation experiment, and determining the range of the gas migration area in the fracture field from the horizontal and vertical directions, wherein the horizontal direction is parallel to the coal seam advancement direction, and the vertical direction is perpendicular to the coal seam advancement direction;

[0009] S2, determining the high-permeability area: obtaining the total gas emission amount of coal mining, calculating the model gas mass source term, carrying out numerical simulation experiment, and determining the high-permeability area;

[0010] S3, field inversion of high-permeability area: carrying out microseismic monitoring and borehole peeping experiment on site, and inverting the high-permeability area of overburden strata subjected to mining according to the microseismic events and fracture conditions.

[0011] As a preferred scheme of the present application, in the S1, the specific method of the gas migration zone area determination comprises:

[0012] S101, collecting field materials, and analyzing the coal seam occurrence conditions, hydrogeological conditions, and overburden rock types based on the field materials, and carrying out a two-dimensional physical similar simulation test based on the field materials to obtain overburden rock fracture characteristic parameters, the overburden rock fracture characteristic parameters including separation amount, broken fracture density, penetration degree, and surface fracture rate;

[0013] S102, constructing a gas migration zone discrimination criterion based on the overburden rock fracture characteristic parameters;

[0014] S103, dividing the specific range of the gas migration zone from the physical similar simulation test results according to the gas migration zone determination criterion.

[0015] As a preferred scheme of the present application, in the S101, the two-dimensional physical similar simulation test is carried out by using a physical similar model, the physical similar model uses dry river sand as the aggregate of simulated rock strata, and gypsum and putty powder as the cementing agent, the aggregate and the cementing agent are mixed uniformly, and then the model is built, and the specific batching formula is as follows:

[0016]

[0017] Wherein, G is the total mass of the material required for each lithology of the rock stratum; l is the length of the physical similar model, in meters; m is the thickness of the physical similar model, in meters; h is the height of the bedding division in the physical similar model, in meters; and g is the acceleration of gravity.

[0018] As a preferred scheme of the present application, in the step S102, the gas migration zone discrimination criterion is specifically:

[0019] Lateral boundary: dividing the lateral boundary of the lateral area of the gas migration zone in the fracture field according to the surface fracture rate (10 < B < 20, B is the surface fracture rate) and the separation amount (>1.5);

[0020] Vertical boundary: dividing the vertical boundary of the gas migration zone in the fracture field according to the broken fracture density (>6.5 pieces / m) and the penetration degree (>0.2);

[0021] Area range: finally determining the area range of the gas migration zone in the fracture field according to the lateral boundary and the vertical boundary.

[0022] As a preferred scheme of the present application, in the S2, the specific steps of the high permeability zone area determination are as follows:

[0023] S201, crack identification and delineation are carried out on the physical similar simulation experiment result, then are introduced into a numerical simulation software to carry out numerical modeling, and a model gas mass source term is obtained;

[0024] S202, the total gas emission amount and the model gas mass source term are input into the model to carry out numerical simulation experiment, the migration law of the pressure relief gas in the gas migration zone is obtained, and the distribution of the gas pressure is obtained;

[0025] S203, based on the distribution of the gas pressure, the gas migration zone is divided into a diffusion zone and a high permeation zone.

[0026] As a preferred scheme of the present application, in the S202, the total gas emission amount is calculated based on field gas emission amount detection data, and a model gas mass source term is further calculated, the total gas emission amount detection includes goaf residual coal gas emission amount, adjacent seam gas emission and working face gas emission amount, the model gas mass source term is a source term of released gas in numerical simulation, and the total gas emission amount and the model gas mass source term are calculated according to a formula.

[0027] As a preferred scheme of the present application, the calculation formula of the total gas emission amount and the model gas mass source term is as follows:

[0028] Total gas emission amount:

[0029] Gas mass source term:

[0030] Wherein, Q1 is the total gas emission amount, Q d is the bottom coal body gas emission amount, the unit is m 3 / min; Q2 is the adjacent seam relative gas emission amount, the unit is m 3 / min; Q3 is the goaf gas extraction amount, the unit is m 3 / min;

[0031] Q s is the model gas mass source term, the unit is kg / (m 3 / s); Q g is the gas emission amount, the unit is m 3 / s, obtained by field test; ρ g is the gas density, ρ g =0.7167 kg / m 3 ; V is the total volume occupied by the gas mass source term, the unit is m 3 .

[0032] As a preferred scheme of the present application, in the S3, the specific steps of field inversion of the high permeation zone are as follows:

[0033] S301, a high permeation zone is circled through a field microseismic test, and the microseismic test distinguishes the high permeation zone based on the density of microseismic events;

[0034] S302, a gas enrichment area in the coal seam is further determined through borehole peeping, and the fracture condition and the broken degree of the rock stratum in the borehole are observed, and the stereoscopic distribution rule of the high permeation zone is analyzed;

[0035] S303, the development of the high permeation zone is understood through the microseismic data obtained through the microseismic test and the borehole peeping, the arrangement of the gas extraction borehole is guided, and the determination criterion of the high permeation zone of the mining overburden rock is obtained according to the test results.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] The present application can not only extract gas from coal seams with different occurrence conditions, but also improve the extraction efficiency of the pressure-relief gas, realize gas prevention and control, further optimize resource utilization by determining the high permeation zone of the mining overburden rock, avoid waste of extraction resources, reduce extraction energy consumption, ensure extraction efficiency, improve the safety of coal mining, and reduce the probability of accidents such as gas outburst. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only exemplary, and for those skilled in the art, other drawings can be obtained without creative labor on the basis of the provided drawings.

[0039] Figure 1 A flowchart of a determination method of a high permeation zone of mining overburden rock is provided for the embodiments of the present application;

[0040] Figure 2 A flowchart of a determination criterion of a gas migration zone is provided for the embodiments of the present application;

[0041] Figure 3 A schematic diagram of a gas migration zone is provided for the embodiments of the present application;

[0042] Figure 4 A schematic diagram of the distribution of a high permeation zone is provided for the embodiments of the present application;

[0043] Figure 5 A schematic diagram of a microseismic event is provided for the embodiments of the present application;

[0044] Figure 6 A schematic diagram of a borehole arrangement area is provided for the embodiments of the present application;

[0045] Figure 7 A flowchart of a first high-permeability zone determination method for overburden strata affected by mining is provided for the embodiments of the present application.

[0046] Figure 8 An effect diagram of single-hole extraction provided for the embodiments of the present application;

[0047] Figure 9 An effect diagram of gas prevention and control provided for the embodiments of the present application;

[0048] Figure 10 A borehole peeping diagram provided for the embodiments of the present application. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of the present application.

[0050] As shown in Figures 1 to 7 The present application provides a high-permeability zone determination method for overburden strata affected by mining, specifically comprising the steps of,

[0051] S1, determination of a gas migration zone: obtaining fracture characteristic parameters through physical simulation experiments, and determining the range of the gas migration zone in the fracture field from the horizontal and vertical directions, wherein the horizontal direction is parallel to the direction of coal seam advancement, and the vertical direction is perpendicular to the direction of coal seam advancement;

[0052] S2, determination of a high-permeability zone: obtaining the total gas emission amount of coal mining, calculating the gas mass source term of the model, and determining the high-permeability zone through numerical simulation experiments;

[0053] S3, inversion of a high-permeability zone in the field: conducting microseismic monitoring and borehole peeping experiments in the field, and inverting the high-permeability zone of overburden strata affected by mining according to microseismic events and fracture conditions.

[0054] In the S1, the specific method for determining the gas migration zone comprises:

[0055] S101, collecting field materials, analyzing the coal seam occurrence conditions, hydrogeological conditions, and overburden types based on the field materials, and conducting two-dimensional physical simulation experiments based on the field materials to obtain overburden fracture characteristic parameters, including separation amount, broken fracture density, connectivity, and surface fracture rate;

[0056] S102, constructing a gas migration zone determination criterion based on the overburden fracture characteristic parameters;

[0057] S103, the specific range of the gas migration zone is divided according to the gas migration zone determination criterion.

[0058] In the step S101, the two-dimensional physical similar simulation experiment is carried out by using a physical similar model. The physical similar model uses dry river sand as the aggregate of the simulated rock stratum, and uses gypsum and putty powder as the cementing agent. After the aggregate and the cementing agent are uniformly mixed, the model is built. The specific formula of the ingredients is as follows:

[0059]

[0060] Wherein, G is the total mass of the material required for the rock stratum where each lithology is located; l is the length of the physical similar model, and the unit is m; m is the thickness of the physical similar model, and the unit is m; h is the height of the bedding division in the physical similar model, and the unit is m; and g is the acceleration of gravity.

[0061] In the step S102, the gas migration zone determination criterion is as follows:

[0062] The lateral limit: the lateral area lateral limit of the gas migration zone is divided in the fracture field according to the surface fissure rate (10 < B < 20, B is the surface fissure rate) and the separation amount (> 1.5);

[0063] The longitudinal limit: the longitudinal limit of the gas migration zone is divided in the fracture field according to the broken fracture density (> 6.5 pieces / m) and the penetration degree (> 0.2);

[0064] The area range: the area range of the gas migration zone in the fracture field is finally determined according to the lateral limit and the longitudinal limit.

[0065] After the physical similar model is built, the whole model needs to be dried for a period of time before mining. In order to simulate the mining effect on site, the model mining adopts 2cm and 3cm interactive propulsion. The state of the overburden rock after each mining is recorded by using a high-definition camera, which is convenient for subsequent data processing. Subsequently, the fracture identification software (for example, PCAS software can be used) is relied on to analyze the fracture characteristic parameters of the overburden rock.

[0066] As shown in Figure 2 The gas migration zone determination criterion divides the overburden rock into the gas migration zone and the compaction zone (i.e. Figure 2In the determination of the gas migration zone, the lateral limit determination and the longitudinal limit determination are divided, and finally the lateral limit and the longitudinal limit are comprehensively determined to determine the gas migration zone. First, the surface fissure rate and the separation amount are determined. When the values of the two meet the range requirements, the lateral limit of the gas migration zone is determined. When one or both of the values of the surface fissure rate and the separation amount do not meet the range requirements, the overburden compaction zone or the original rock is determined. Then, the range requirements of the broken fissure density and the penetration degree are determined. When the values of the two meet the range requirements, the longitudinal limit of the gas migration zone is determined. When one or both of the values of the broken fissure density and the penetration degree do not meet the range requirements, the overburden compaction zone or the original rock is determined.

[0067] wherein, Figure 2 B in the formula (1) represents the surface fissure rate, D i represents the penetration degree.

[0068] In the embodiment, the specific method of the physical similar simulation experiment refers to the physical similar simulation experiment device and experimental research method disclosed in the patent publication No. CN115267060B.

[0069] In the S2, the specific steps of the high-permeability zone region determination are as follows:

[0070] S201, the physical similar simulation experiment results are subjected to fissure identification and drawing, and then are imported into a numerical simulation software for numerical modeling to obtain a model gas mass source;

[0071] S202, the total gas emission amount and the model gas mass source are input into the model to carry out numerical simulation experiment, to obtain the migration rule of the pressure-relief gas in the gas migration zone and the distribution of the gas pressure;

[0072] S203, based on the distribution of the gas pressure, the gas migration zone is divided into a diffusion zone and a high-permeability zone.

[0073] In the S202, the total gas emission amount is calculated based on the field gas emission detection data, and the model gas mass source is further calculated. The total gas emission detection includes the goaf residual coal gas emission amount, the adjacent coal seam gas emission and the working face gas emission amount. The model gas mass source is the source term of the released gas in the numerical simulation. The total gas emission amount and the model gas mass source are calculated according to the formula.

[0074] The calculation formula of the total gas emission amount and the model gas mass source is as follows:

[0075] Total gas emission amount:

[0076] Gas mass source:

[0077] Q1 = Q2 + Q3 + Q4 d Q1 is the total gas emission amount, Q 3 Q2 is the adjacent layer relative gas emission amount, Q 3 Q3 is the gas extraction amount of the goaf, Q 3

[0078] Q1 = Q2 + Q3 + Q4 S Q1 is the total gas emission amount, Q 3 Q2 is the adjacent layer relative gas emission amount, Q g Q is the gas emission amount, m 3 / s, obtained by field testing; p g is the gas density, p g = 0.7167 kg / m 3 ; V is the total volume occupied by the gas mass source, m 3 .

[0079] In the process of numerical simulation, the upper stress condition, surrounding rock stress, model influence range and other parameters need to be fully considered, so as to finally obtain the distribution of gas pressure. In the embodiment, the numerical simulation software is the prior art, for example, COMSOL Multiphysics can be used.

[0080] Based on the numerical simulation test results, the distribution characteristics of the gas pressure in the overlying strata are obtained. The overlying strata are divided according to the gas pressure distribution. The area with a gas pressure less than 1 x 10 5 Pa is a compaction zone, the area with a gas pressure greater than 1 x 10 5 Pa and less than 3.5 x 10 5 Pa is a high permeability zone, and the area with a gas pressure greater than 3.5 x 10 5 Pa is a diffusion zone. The diffusion zone is mainly located in the caving zone, and the high permeability zone is mainly located in the fractured zone. The caving zone and the fractured zone are a regional division made by scholars according to the characteristics of rock strata collapse in the process of coal mining. The caving zone is a region above the goaf where the rock strata are broken and collapsed after losing support. The fractured zone is a region above the caving zone where the rock strata have a large number of fractures but have not completely collapsed, also known as the fracture zone. In the diffusion zone, the fracture opening is large, the fracture distribution is chaotic, and the gas mainly migrates horizontally in the form of diffusion. In the high permeability zone, the fracture distribution is mainly broken fracture, and the gas mainly rises and floats upward, mainly vertically migrates by seepage. The gas flows fast and has high concentration in the high permeability zone, and the rock strata are more stable than the diffusion zone in the caving zone, so the high permeability zone is set as the gas extraction area.

[0081] In the S3, the specific steps of inverting the high permeability zone on site are as follows: ​

[0082] S301, circumscribe the high permeability zone by field microseismic test, which distinguishes the high permeability zone based on the intensity of microseismic events;

[0083] S302, further determine the gas enrichment area in the coal seam by borehole peeping, and observe the fissure condition and the broken degree of the rock stratum in the borehole, and analyze the stereoscopic distribution rule of the high permeability zone;

[0084] S303, obtain the development of the high permeability zone by the microseismic data obtained by the microseismic test and the understanding of the high permeability zone by borehole peeping, guide the arrangement of the gas extraction borehole, and obtain the determination criterion of the high permeability zone of the overburden rock subjected to mining according to the test results.

[0085] Since the fissures in the high permeability zone are highly developed, microseismic events are prone to occur, so the intensity of the microseismic events in the high permeability zone is much higher than that in the compaction zone, as shown in FIG. 2; therefore, the gas enrichment area in the coal seam is further determined by borehole peeping. Figure 5

[0086] The development of the high permeability zone refers to the spatial position of the high permeability zone changing and the width and height of the high permeability zone changing in the process of mining the coal seam, because the rock stratum above the coal seam collapses continuously due to the mining of the coal seam, and the development of the high permeability zone is adjusted after the microseismic data and the borehole peeping results are obtained, the parameters such as the interval, height and angle of the borehole are adjusted according to the development of the high permeability zone, and thus the position of the gas extraction borehole can be guided, as shown in FIG. 3. Figure 6

[0087] In step S302, the broken degree determines the stability of the borehole, and the fissure condition determines the flowability of the gas.

[0088] According to the above method of the present application, the pressure-relief gas high permeability zone can be accurately identified, which can be applied to coal seams with different occurrence conditions, widens the application range, improves the extraction efficiency of the pressure-relief gas, realizes gas prevention and control, further optimizes resource utilization, avoids waste of extraction resources, reduces extraction energy consumption, and ensures extraction efficiency.

[0089] In the present embodiment:

[0090] 1. The determination method of the gas migration zone can be replaced according to other laboratory methods, and the fissure characteristic parameters in the mentioned area criterion can be replaced by other fissure characteristic parameters.

[0091] 2. The determination method of the high permeability zone can be replaced according to other numerical simulation means, and the mentioned area division criterion can be replaced by other characteristic parameters.

[0092] 3. The extraction mode based on the gas high permeability zone can be replaced according to the actual mining conditions of the coal mine.​​

[0093] Test example

[0094] As Figures 8 to 10 shown, the test mine takes the working face (9-15) 08 of the Changji Liuhuangou coal mine in Xinjiang as the engineering background, the working face (9-15) 08 uses high-position drilling to control the gas in the goaf, and at the same time, due to the large thickness of the main mining coal seam, the high-permeability area of the overburden gas is high, and it is determined to use directional drilling technology to construct directional long-distance high-position drilling in the open-off cut direction, because the high-permeability area of the gas will change continuously, the drilling is arranged in the working face, that is, within 20-45 m from the coal seam floor, and the specific arrangement parameters are shown in the following table:

[0095] Table 1 Drilling arrangement parameters

[0096]

[0097] According to the distribution of the high-permeability area, the drilling arrangement is carried out, and the gas extraction effect of one of the drillings is shown in Figure 8 , the overall gas extraction effect is shown in Figure 9 , according to Figure 8 , the pressure relief gas extraction concentration gradually decreases with the deepening of the working face advancing distance, and the extraction volume first increases and then decreases within a certain range with the deepening of the working face advancing distance, which shows that the high-permeability area changes with the mining of the coal seam. In Figure 9 , the arrangement of the extraction drilling, the absolute gas emission first increases and then decreases with the increase of the cumulative advancing distance of the working face, and finally remains stable, the air exhaust gas quantity decreases and remains stable, the total amount of gas extraction first increases and then decreases slightly and remains stable, which shows that the drilling has high-efficiency gas extraction concentration and maintains stable continuous extraction state. In summary, the present application can accurately identify the high-permeability area of the pressure relief gas, improve the extraction efficiency of the pressure relief gas, realize gas prevention and control, and reduce the extraction energy consumption and ensure the extraction efficiency.

[0098] The above examples are only exemplary embodiments of the present application and are not used to limit the present application, the protection scope of the present application is defined by the claims. Those skilled in the art can make various modifications or equivalent replacements to the present application within the spirit and protection scope of the present application, and such modifications or equivalent replacements are also regarded as falling within the protection scope of the present application.

Claims

1. A method for determining a high permeability zone in a mining overburden, characterized in that, Specifically comprising steps, S1, gas migration zone area determination: fracture characteristic parameters are obtained through physical similar simulation experiment, and the gas migration zone area range in the fracture field is determined comprehensively from the horizontal direction and the vertical direction, wherein the horizontal direction is the direction parallel to the coal seam advancement, and the vertical direction is the direction vertical to the coal seam advancement; S2, high permeability zone area determination: the total gas emission amount of the coal mine is obtained, the model gas mass source term is calculated, numerical simulation experiment is carried out, and the high permeability zone is determined; S3, field inversion of high permeability zone: microseismic monitoring and borehole peeping experiment are carried out in the field, and the high permeability zone of the mining overburden is inverted according to the microseismic events and the fracture conditions; In the S1, the specific method of gas migration zone area determination comprises: S101, collecting field materials, analyzing the coal seam occurrence conditions, hydrogeological conditions and overburden types based on the field materials, and carrying out two-dimensional physical similar simulation experiment based on the field materials to obtain overburden fracture characteristic parameters, wherein the overburden fracture characteristic parameters comprise separation amount, broken fracture density, penetration degree and surface fracture rate; S102, constructing a gas migration zone determination criterion based on the overburden fracture characteristic parameters; S103, dividing the specific range of the gas migration zone from the physical similar simulation experiment results according to the gas migration zone determination criterion; In the step S102, the gas migration zone determination criterion is specifically: Horizontal limit: the horizontal limit of the gas migration zone in the fracture field is divided according to the surface fracture rate, 10 < B < 20, B is the surface fracture rate, and the separation amount > 1.5; Vertical limit: the vertical limit of the gas migration zone in the fracture field is divided according to the broken fracture density > 6.5 pieces / m and the penetration degree > 0.2; Regional range: the regional range of the gas migration zone in the fracture field is finally determined according to the horizontal limit and the vertical limit; In the S2, the specific steps of high permeability zone area determination are as follows: S201, fracture identification and depiction are carried out on the physical similar simulation experiment results, then numerical modeling is carried out in the numerical simulation software to obtain the model gas mass source term; S202, the total gas emission amount and the model gas mass source term are input into the model to carry out numerical simulation experiment, the migration law of the pressure relief gas in the gas migration zone is obtained, and the distribution of the gas pressure is obtained; S203, based on the distribution of the gas pressure, the gas migration zone is divided into diffusion zone and high permeability zone; In the S3, the specific steps of field inversion of high permeability zone are as follows: S301, the high permeability zone is circled through the field microseismic experiment, wherein the microseismic experiment determines the high permeability zone based on the density of the microseismic events; S302, the gas enrichment area in the coal seam is further determined through borehole peeping, the fracture conditions and the broken degree of the rock stratum in the borehole are observed, and the three-dimensional distribution law of the high permeability zone is analyzed and obtained; S303, the development of the high permeability zone is understood through the microseismic data obtained by the microseismic experiment and the borehole peeping, the arrangement of the gas extraction borehole is guided, and the determination criterion of the mining overburden high permeability zone is obtained according to the above experiment results.

2. The method according to claim 1, characterized in that, In the S101, the two-dimensional physical similarity simulation test is carried out by using a physical similarity model, the physical similarity model uses dry river sand as aggregate for simulating rock stratum, uses gypsum and putty powder as cementing agent, and builds the model after mixing the aggregate and the cementing agent uniformly, and a specific batching formula is as follows: ； Wherein, G is the total mass of the material required for the rock stratum where each lithology is located; l is the length of the physical similarity model, in meters; m is the thickness of the physical similarity model, in meters; h is the height of the layering division in the physical similarity model, in meters; and g is the acceleration of gravity.

3. The method according to claim 1, characterized in that, In the S202, the total gas emission amount is calculated based on the field gas emission detection data, and a model gas mass source term is further calculated, the total gas emission detection includes the goaf residual coal gas emission, the adjacent coal seam gas emission and the working face gas emission, the model gas mass source term is a source term of released gas in numerical simulation, and the total gas emission amount and the model gas mass source term are calculated according to the formula.

4. The method according to claim 3, characterized in that, The calculation formula of the total gas emission amount and the model gas mass source term is as follows: Total gas emission: ; Gas mass source term: ; Wherein, Q1 is the total gas emission, Q d is the gas emission of the bottom coal, with the unit of m 3 / min; Q2 is the relative gas emission of the adjacent layer, with the unit of m 3 / min; Q3 is the gas extraction of the goaf, with the unit of m 3 / min; Q s is the model gas mass source term, with the unit of kg / (m 3 / s); Q g is the gas emission, with the unit of m 3 / s, obtained by field test; p g is the gas density, p g = 0.7167 kg / m 3 ; V is the total volume occupied by the gas mass source term, with the unit of m 3 .

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