A water hazard risk assessment method for overburden isolation grouting filling technology

Abstract

The present invention provides a method for assessing water hazard risk of overburden isolation grouting filling technology, which relates to the field of overburden isolation grouting data processing technology, and specifically includes the following steps: establishing a basic data set for overburden isolation grouting of coal seams; using the basic data set for overburden isolation grouting to analyze the movement law of overburden strata in coal seams and estimate the height of water-conducting fracture zones; drawing a water hazard analysis profile of the overburden isolation grouting working face, and conducting a preliminary judgment on the water hazard of overburden isolation grouting; establishing an overburden isolation grouting spatial evolution model to simulate the entire process of real overburden isolation grouting; conducting overburden isolation grouting water hazard risk assessment from multiple angles of engineering analogy, semi-empirical formula judgment and theoretical analysis; and optimizing the grouting design according to the water hazard risk of overburden isolation grouting filling. The technical solution of the present invention overcomes the problem that the prior art cannot scientifically and effectively assess the water hazard risk of overburden isolation grouting filling.

Description

Technical Field

[0001] The invention relates to the technical field of overburden rock isolation grouting data processing, and in particular to a water hazard risk assessment method for overburden rock isolation grouting filling technology. Background Art

[0002] As an emerging green mining technology, overburden isolation grouting filling technology has gradually become the preferred solution to difficult problems such as building compression coal mining, gangue emission reduction, shock absorption and impact prevention.

[0003] At present, the main method used for the risk assessment of water hazards in overburden isolation grouting is the improved water inrush coefficient method, which evaluates the water hazard risk by considering the deadweight of the underlying rock layer under the isolation grouting and the size of the grouting pressure. The standard used retains the evaluation index for the bottom plate water inrush coefficient method, that is, for simple structural areas, when the water inrush coefficient is <0.1Pa / m, the grouting project is considered safe. However, due to the influence of various factors such as slurry properties and grouting layer, overburden isolation grouting will not flow continuously and maintain pressure like groundwater, so the evaluation standard of the improved water inrush coefficient method will cause significant errors. The second commonly used method is the comprehensive evaluation method of water hazard risk in overburden isolation grouting, that is, the main influencing factors of overburden isolation grouting, including grouting pressure, slurry properties, grouting depth, underlying rock layer thickness, rock mechanical properties and other indicators, establish an evaluation system, and use a variety of comprehensive evaluation methods, such as analytic hierarchy process, entropy weight method, etc. to predict and partition the results, so as to achieve the purpose of water hazard risk assessment. However, since this method only uses statistical data for mathematical analysis, it lacks scientificity and cannot provide effective support for actual engineering.

[0004] Therefore, a scientific and effective water hazard risk assessment method for overburden isolation grouting filling technology is needed. Summary of the invention

[0005] The main purpose of the present invention is to provide a water hazard risk assessment method for overburden isolation grouting filling technology, so as to solve the problem that the water hazard risk assessment of overburden isolation grouting filling cannot be carried out scientifically and effectively in the prior art.

[0006] To achieve the above object, the present invention provides a water hazard risk assessment method for overburden isolation grouting filling technology, which specifically includes the following steps:

[0007] S1, collect mine data and analyze hydrogeological data to establish a basic data set for coal seam overburden isolation grouting.

[0008] S2, using the basic data set of overburden isolation grouting in step S1, analyze the movement law of coal seam overburden and estimate the height of water-conducting fracture zone.

[0009] S3, based on step S2, draw a water hazard analysis profile of the overburden isolation grouting working face, and conduct a preliminary assessment of the water hazard of the overburden isolation grouting.

[0010] S4, establish the spatial evolution model of overburden isolation grouting, simulate the whole process of real overburden isolation grouting, and clarify the real-time changes of overburden isolation grouting space grouting parameters and rock mass stress.

[0011] S5, conduct water hazard risk assessment of overburden isolation grouting from multiple angles from engineering analogy, semi-empirical formula judgment and theoretical analysis.

[0012] S6. Optimize the grouting design according to the water hazard risk of overburden isolation grouting filling to ensure the safety of the grouting project.

[0013] Furthermore, step S2 specifically includes the following steps:

[0014] S2.1, using the basic data set of overburden isolation grouting, based on the rock stratum control key layer theory, calculate and analyze the development position, lithology, thickness, fracture distance and other parameters of each key layer of the coal seam roof, clarify the development position of the overburden separation layer of the coal seam roof, and record all possible overburden isolation grouting layers of the coal seam roof, and determine the distance between each grouting layer and the coal seam roof .

[0015] S2.2, based on the measured data of water-conducting fracture zones in other working faces of the mine, obtain the ratio of the development height of the water-conducting fracture zones in the mine, combine the coal seam thickness data revealed by each borehole of the overburden isolation grouting working face, calculate the development height of the water-conducting fracture zone at each borehole location, and use the Kriging interpolation method to calculate the development height of the water-conducting fracture zone at different positions of the overburden isolation grouting working face.

[0016] Furthermore, step S3 specifically includes the following steps:

[0017] S3.1. Based on the exploration, supplementary exploration and hydrogeological drilling data within the working face, draw a cross-section of the aquiclude and impermeable layers of the overburden isolation grouting working face, and add the top boundary interface curve of the water-conducting fracture zone development height; based on the overburden isolation grouting design data of the mine and the mine water-conducting channel analysis data, draw the grouting drilling information, fault information, poorly sealed boreholes and oil and gas well information on the cross-section to form a water hazard analysis cross-section of the overburden isolation grouting working face.

[0018] S3.2, conduct preliminary water hazard analysis based on the water hazard analysis profile of the overburden isolation grouting working face.

[0019] Furthermore, step S3.2 specifically includes the following steps:

[0020] S3.2.1. Analyze the position relationship between the overburden isolation grouting layer and the water-conducting fracture zone of the working face. If the overburden isolation grouting layer is located within the water-conducting fracture zone, it will cause roof water damage and overburden isolation grouting water damage, and grouting work should not be carried out.

[0021] S3.2.2, if the grouting layer is located above the water-conducting fracture zone, the relationship between the position of the aquifer above the water-conducting fracture zone and the overburden isolation grouting layer should be analyzed. When there is a water-rich aquifer below the overburden isolation layer and no stable impermeable layer, grouting should not be carried out. When there is a stable impermeable layer below the overburden isolation grouting layer, the position relationship between the grouting borehole and the fault, poorly sealed borehole, and water-conducting channels of oil and gas wells should be further clarified to ensure that the grouting borehole is located outside the coal pillars protected by each water-conducting channel.

[0022] Furthermore, step S4 specifically includes the following steps:

[0023] S4.1, select the design layer of overburden isolation grouting that meets the conditions of step S3, and further clarify the overburden movement law near the overburden isolation grouting layer in combination with the overburden movement law analysis in S2; obtain the displacement deformation of the upper and lower layers of the overburden isolation grouting space according to the Ritz method, and obtain the maximum height of the overburden isolation grouting space According to the “inverted funnel” shape of the overburden isolation grouting space, the overburden isolation grouting space evolution model was established and imported into the COMSOL software; the calculation formula for the geometric dimensions of the overburden isolation grouting space is as follows:

[0024] (1);

[0025] In the formula, is the working face advancement distance; is the oblique length of the working surface; is the rock fracture angle, is the length of the overburden isolation grouting space, It is the width of the grouting space for overburden isolation.

[0026] The calculation formula for the maximum height of the overburden isolation grouting space is as follows:

[0027] (2);

[0028] In the formula, , are coordinates, respectively between (0, ) (0, )between, , are the lateral uniform loads on the upper and lower strata of the grouting space, , are the compressive stiffness of the rock strata above and below the grouting space, is the flexural stiffness of the rock formation.

[0029] S4.2, carry out simulation of the whole process of overburden isolation grouting to obtain specific information on the slurry diffusion process, stress field change law, and stress change process of the upper and lower rock layers in the grouting space during the overburden isolation grouting process.

[0030] S4.3, according to the depth of the overburden isolation grouting layer, grouting materials, grouting pressure and other parameter changes, the corresponding overburden isolation grouting slurry diffusion simulation is carried out in turn, and the pressure change law of the grouting space under various working conditions with time is recorded, and the maximum grouting pressure value during the grouting process is selected. Used as the calculated value for water hazard evaluation of overburden isolation grouting.

[0031] Furthermore, step S4.2 specifically includes the following steps:

[0032] S4.2.1, the Navier-Stokes equation is used as the governing equation for slurry-water flow, and the formula is:

[0033] (3);

[0034] In the formula, is the fluid velocity, is the fluid pressure, is the fluid density, is the fluid dynamic viscosity, is the unit tensor, is the interfacial tension term, is the acceleration due to gravity, is the Laplace operator.

[0035] S4.2.2, in order to make the slurry-water two-phase flow process in the overburden isolation grouting space satisfy the law of conservation of mass, the continuity equation is used for description, the formula is:

[0036] (4).

[0037] S4.2.3, in order to describe the real-time change process of the slurry-water two-phase displacement interface, the interface tracking method Level set is used to mark the slurry-water two-phase interface, and the control equation is expressed as:

[0038] (5);

[0039] In the formula, is the initialization parameter, is the interface thickness control parameter; is the level set variable, is the level set function.

[0040] S4.2.4, Corresponding Interfacial Tension Terms in the Navier-Stokes Equations It is expressed as:

[0041] (6);

[0042] in, is the surface tension coefficient, is the interface normal vector, for The transpose of is the non-zero Diktola function at the fluid interface.

[0043] S4.2.5, based on the built-in meshing tool and transient solver of COMSOL numerical simulation software, the computational solution and description of the entire process of grouting and slurry-water displacement in the overburden isolation grouting space are realized, and the slurry diffusion process, stress field change law, stress change process of the upper and lower rock layers in the grouting space and other specific information during the overburden isolation grouting process are obtained.

[0044] Furthermore, step S5 specifically includes the following steps:

[0045] S5.1, Critical value The area is defined as a serious danger zone with the risk of overburden isolation grouting water damage. The specific formula is:

[0046] (7);

[0047] In the formula, is the water hazard risk factor of overburden isolation grouting, and are the bulk density and thickness of each rock layer between the bottom boundary of the grouting space and the top boundary of the fracture zone, The depth of coal seam, is the bottom depth of the grouting space, It is the height of development of water-conducting fracture zone.

[0048] S5.2, evaluate the water hazard risk of overburden isolation grouting based on the key layer identification method.

[0049] S5.3. According to the “inverted funnel” shape of the overburden isolation grouting space, the lower isolation layer of the overburden isolation grouting space is regarded as a curved elastic thin plate. Based on the geometric characteristics of the rock formation and the fracture criterion, the fracture critical value of the lower isolation layer of the overburden isolation grouting is calculated.

[0050] S5.4, based on the three types of overburden separation grouting water inrush risk identification results, in order to ensure the grouting safety of the overburden isolation grouting working face, the evaluation results should at least meet the safety requirements of two identification methods. When the safety requirements cannot be met, proceed to step S6.

[0051] Furthermore, step S5.3 specifically includes the following steps:

[0052] S5.3.1, based on the basic data set of overburden isolation grouting and the key layer identification theory, obtain the position of the overburden key layer under normal conditions.

[0053] S5.3.2. The height estimation method of the water-conducting fracture zone at the key layer position is used for calculation. When the distance between the main key layer position and the top boundary of the coal seam is less than 7 to 10 times the thickness of the coal seam, the height of the through-fractures in the roof will be equal to the thickness of the bedrock. When the distance between the main key layer position and the top boundary of the coal seam is greater than 7 to 10 times the thickness of the coal seam, the height of the through-fractures in the roof will be equal to the position of the first key layer whose height is greater than 7 to 10 times the thickness of the coal seam.

[0054] S5.3.3, the maximum grouting pressure value during grouting It is regarded as an additional load and applied entirely on the bottom interface of the overburden isolation space. The key layer theory is then used to recalculate the position of the overburden key layer under the overburden isolation grouting condition.

[0055] S5.3.4, compared with the position of the key layer before overburden isolation grouting, if the position of the key layer of the overburden changes, the height of the water-conducting fracture zone will increase accordingly, indicating that the overburden isolation grouting conditions have caused the overburden to break and penetrate, and there is a risk of water damage caused by overburden isolation grouting; if the position of the key layer has not changed, it indicates that the height of the water-conducting fracture zone has not changed under the overburden isolation grouting conditions.

[0056] Furthermore, step S5.4 specifically includes the following steps:

[0057] S5.4.1, based on formulas (1) and (2), calculate the geometric dimensions of the lower isolation layer of the overburden isolation grouting space and , and calculate the thickness of the isolation layer .

[0058] S5.4.2, based on the thin plate theory, taking into account the deadweight of the rock layer, the isolation grouting pressure of the overburden rock and the rock layer support force, calculate the deflection of the isolation rock layer , the formula is as follows:

[0059] (8);

[0060] In the formula, is the support coefficient, ranging from 0 to 1, is the thickness of the isolating rock layer.

[0061] S5.4.3, calculate the maximum and minimum principal stresses at the neutral plane height z = h / 2 of the isolation rock layer under the maximum overburden isolation grouting pressure as follows:

[0062] (9);

[0063] in, and represent the maximum principal stress and the minimum principal stress respectively, and Respectively represent Direction and The normal stress in the direction, represents the xy plane shear stress, and Represents a variable.

[0064] in, and It is expressed as:

[0065] (10);

[0066] in, represents the elastic modulus, Represents the parameters, .

[0067] S5.4.4, Based on the Mohr-Coulomb criterion, establish the rock formation failure criterion:

[0068] (11);

[0069] In the formula, is the rock cohesion, is the internal friction angle.

[0070] S5.4.5, the formula for determining the failure of the isolation layer filled with grouting in the overburden separation layer is as follows:

[0071] (12);

[0072] in, and As parameters, , , As the damage judgment index, =1, it indicates that the isolation layer is broken, indicating that there is a risk of water inrush in the overburden isolation grouting under this grouting condition.

[0073] Furthermore, step S6 specifically includes the following steps:

[0074] S6.1, adjust the grouting materials, reduce the slurry self-weight load by reducing the slurry density, so that the load on the lower isolation layer of the overburden isolation grouting space is reduced.

[0075] S6.2, reduce the grouting pressure, and reduce the load on the lower isolation layer of the overburden isolation grouting space by reducing the final grouting pressure of the overburden isolation grouting project.

[0076] S6.3, adjust the grouting layer upward, reduce the grouting depth, increase the thickness of the isolation layer, and improve the damage resistance of the isolation layer.

[0077] The present invention has the following beneficial effects:

[0078] The present invention mainly proposes a water hazard risk assessment method under overburden isolation grouting filling conditions, which solves the problems of lack of quantitative assessment, limitations, ambiguity and the like in the current water hazard risk assessment of overburden isolation grouting filling. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to more clearly illustrate the specific implementation of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the specific implementation or the prior art description. Obviously, the drawings described below are some implementations of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0080] Figure 1 A flow chart of a water hazard risk assessment method for overburden isolation grouting filling technology of the present invention is shown. DETAILED DESCRIPTION

[0081] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0082] like Figure 1 A water hazard risk assessment method for overburden isolation grouting filling technology is shown, which specifically includes the following steps:

[0083] S1, collect mine data and analyze hydrogeological data to establish a basic data set for coal seam overburden isolation grouting.

[0084] S2, using the basic data set of overburden isolation grouting in step S1, analyze the movement law of coal seam overburden and estimate the height of water-conducting fracture zone.

[0085] S3, based on step S2, draw a water hazard analysis profile of the overburden isolation grouting working face, and conduct a preliminary assessment of the water hazard of the overburden isolation grouting.

[0086] S4, establish the spatial evolution model of overburden isolation grouting, simulate the whole process of real overburden isolation grouting, and clarify the real-time changes of overburden isolation grouting space grouting parameters and rock mass stress.

[0087] S5, conduct water hazard risk assessment of overburden isolation grouting from multiple angles from engineering analogy, semi-empirical formula judgment and theoretical analysis.

[0088] S6. Optimize the grouting design according to the water hazard risk of overburden isolation grouting filling to ensure the safety of the grouting project.

[0089] Specifically, in step S1, basic data such as mine geology, hydrogeology, drilling, overburden isolation grouting design, etc. are collected to establish a basic data set for coal seam overburden isolation grouting, and to clarify the lithology of each rock layer group and the thickness of the isolation layer in the coal seam mining roof. , mechanical properties (compressive strength, elastic modulus), water richness (unit water yield, permeability coefficient and water richness level (weak water richness, medium water richness, strong water richness, extremely strong water richness) and other basic parameters. Specifically, step S2 specifically includes the following steps:

[0090] S2.1, using the basic data set of overburden isolation grouting, based on the rock stratum control key layer theory, calculate and analyze the development position, lithology, thickness, fracture distance and other parameters of each key layer of the coal seam roof, clarify the development position of the overburden separation layer of the coal seam roof, and record all possible overburden isolation grouting layers of the coal seam roof, and determine the distance between each grouting layer and the coal seam roof .

[0091] S2.2, based on the measured data of water-conducting fracture zones in other working faces of the mine, obtain the ratio of the development height of the water-conducting fracture zones in the mine, combine the coal seam thickness data revealed by each borehole of the overburden isolation grouting working face, calculate the development height of the water-conducting fracture zone at each borehole location, and use the Kriging interpolation method to calculate the development height of the water-conducting fracture zone at different positions of the overburden isolation grouting working face.

[0092] Specifically, step S3 includes the following steps:

[0093] S3.1. Based on the exploration, supplementary exploration and hydrogeological drilling data within the working face, draw a cross-section of the aquiclude and impermeable layers of the overburden isolation grouting working face, and add the top boundary interface curve of the water-conducting fracture zone development height; based on the mine overburden isolation grouting design data and the mine water-conducting channel analysis data, draw the grouting drilling information (location, burial depth), fault information (location, cut-through stratum), poorly sealed boreholes (location, burial depth) and oil and gas wells (location, burial depth) on the cross-section to form a cross-section of water hazard analysis of the overburden isolation grouting working face.

[0094] S3.2, conduct preliminary water hazard analysis based on the water hazard analysis profile of the overburden isolation grouting working face.

[0095] Specifically, step S3.2 includes the following steps:

[0096] S3.2.1. Analyze the position relationship between the overburden isolation grouting layer and the water-conducting fracture zone of the working face. If the overburden isolation grouting layer is located within the water-conducting fracture zone, it will cause roof water damage and overburden isolation grouting water damage, and grouting work should not be carried out.

[0097] S3.2.2, if the grouting layer is located above the water-conducting fracture zone, the relationship between the position of the aquifer above the water-conducting fracture zone and the overburden isolation grouting layer should be analyzed. When there is a water-rich aquifer below the overburden isolation layer and no stable impermeable layer, grouting should not be carried out. When there is a stable impermeable layer below the overburden isolation grouting layer, the position relationship between the grouting borehole and the fault, poorly sealed borehole, and water-conducting channels of oil and gas wells should be further clarified to ensure that the grouting borehole is located outside the coal pillars protecting each water-conducting channel, and a detailed analysis of the overburden isolation grouting should be carried out.

[0098] Specifically, step S4 includes the following steps:

[0099] S4.1, select the design layer of overburden isolation grouting that meets the conditions of step S3, and combine the analysis of overburden movement law in S2 to specifically clarify the overburden movement law near the overburden isolation grouting layer; obtain the displacement deformation of the upper and lower layers of the overburden isolation grouting space according to the Ritz method, and obtain the maximum height of the overburden isolation grouting space According to the “inverted funnel” shape of the overburden isolation grouting space, the overburden isolation grouting space evolution model was established and imported into the COMSOL software; the calculation formula for the geometric dimensions of the overburden isolation grouting space is as follows:

[0100] (1);

[0101] In the formula, is the working face advancement distance; is the oblique length of the working surface; is the rock fracture angle, is the length of the overburden isolation grouting space, It is the width of the grouting space for overburden isolation.

[0102] The calculation formula for the maximum height of the overburden isolation grouting space is as follows:

[0103] (2);

[0104] In the formula, , are coordinates, respectively between (0, ) (0, )between, , are the lateral uniform loads on the upper and lower strata of the grouting space, , are the compressive stiffness of the rock strata above and below the grouting space, S4.2, carry out simulation of the whole process of overburden isolation grouting, obtain the specific information of slurry diffusion process, stress field change law, and stress change process of rock layers above and below the grouting space during overburden isolation grouting, and provide data support for the risk assessment of water hazards caused by overburden isolation grouting.

[0105] S4.3, according to the depth of the overburden isolation grouting layer, grouting materials, grouting pressure and other parameter changes, the corresponding overburden isolation grouting slurry diffusion simulation is carried out in turn, and the pressure change law of the grouting space under various working conditions with time is recorded, and the maximum grouting pressure value during the grouting process is selected. Used as the calculated value for water hazard evaluation of overburden isolation grouting.

[0106] Specifically, step S4.2 includes the following steps:

[0107] S4.2.1, in order to accurately describe the two-phase flow process of slurry and groundwater (slurry-water) in the overburden isolation grouting space, the Navier-Stokes equation is used as the control equation of slurry-water flow, the formula is:

[0108] (3);

[0109] In the formula, is the fluid velocity, is the fluid pressure, is the fluid density, is the fluid dynamic viscosity, is the unit tensor, is the interfacial tension term, is the acceleration due to gravity, is the Laplace operator.

[0110] S4.2.2, in order to make the slurry-water two-phase flow process in the overburden isolation grouting space satisfy the law of conservation of mass, the continuity equation is used for description, the formula is:

[0111] (4).

[0112] S4.2.3, in order to describe the real-time change process of the slurry-water two-phase displacement interface, the interface tracking method Level set is used to mark the slurry-water two-phase interface, and the control equation is expressed as:

[0113] (5);

[0114] In the formula, is the initialization parameter, is the interface thickness control parameter; is the level set variable, is the level set function.

[0115] S4.2.4, Corresponding Interfacial Tension Terms in the Navier-Stokes Equations It is expressed as:

[0116] (6);

[0117] in, is the surface tension coefficient, is the interface normal vector, for The transpose of is the non-zero Diktola function at the fluid interface.

[0118] In summary, by combining the above formulas (3) to (6), we can obtain the level set-Navier-Stokes coupling mathematical model of the slurry and water two-phase flow in the overburden isolation grouting space.

[0119] S4.2.5, based on the built-in meshing tool and transient solver of COMSOL numerical simulation software, the computational solution and description of the entire process of grouting and slurry-water displacement in the overburden isolation grouting space are realized, and the slurry diffusion process, stress field change law, stress change process of the upper and lower rock layers in the grouting space and other specific information during the overburden isolation grouting process are obtained.

[0120] Specifically, step S5 includes the following steps:

[0121] S5.1, the engineering analogy method is used to evaluate the water hazard risk of overburden isolation grouting. The water inrush risk assessment coefficient is used as the evaluation index in the evaluation process. The critical value of the water hazard risk coefficient of overburden isolation grouting is It should be determined based on the overburden isolation grouting work surface that has been carried out in the adjacent mine or the mine. Critical value The area is defined as a serious danger zone with the risk of overburden isolation grouting water damage. The specific formula is:

[0122] (7);

[0123] In the formula, is the water hazard risk factor of overburden isolation grouting, and are the bulk density and thickness of each rock layer between the bottom boundary of the grouting space and the top boundary of the fracture zone, The depth of coal seam, is the bottom depth of the grouting space, It is the height of development of water-conducting fracture zone.

[0124] S5.2, evaluate the water hazard risk of overburden isolation grouting based on the key layer identification method.

[0125] S5.3. According to the "inverted funnel" shape of the overburden rock isolation grouting space, the lower isolation layer of the overburden rock isolation grouting space (the rock layer between the bottom boundary and the water-conducting fracture zone) is regarded as a curved elastic thin plate. Based on the geometric characteristics of the rock layer and the breaking criterion, the breaking critical value of the lower isolation layer of the overburden rock isolation grouting is calculated.

[0126] S5.4, based on the three types of overburden separation grouting water inrush risk identification results in steps S5.1 to S5.3, in order to ensure the safety of grouting in the overburden isolation grouting working face, the evaluation results should at least meet the safety requirements of two identification methods. When the safety requirements cannot be met, proceed to step S6.

[0127] Specifically, step S5.3 includes the following steps:

[0128] S5.3.1, based on the basic data set of overburden isolation grouting and the key layer identification theory, obtain the position of the overburden key layer under normal conditions.

[0129] S5.3.2. The height estimation method of the water-conducting fracture zone at the key layer position is used for calculation. When the distance between the main key layer position and the top boundary of the coal seam is less than 7 to 10 times the thickness of the coal seam, the height of the through-fractures in the roof will be equal to the thickness of the bedrock. When the distance between the main key layer position and the top boundary of the coal seam is greater than 7 to 10 times the thickness of the coal seam, the height of the through-fractures in the roof will be equal to the position of the first key layer whose height is greater than 7 to 10 times the thickness of the coal seam.

[0130] S5.3.3, the maximum grouting pressure value during grouting It is regarded as an additional load and applied entirely on the bottom interface of the overburden isolation space. The key layer theory is then used to recalculate the position of the overburden key layer under the overburden isolation grouting condition.

[0131] S5.3.4, compared with the position of the key layer before overburden isolation grouting, if the position of the key layer of the overburden changes, the height of the water-conducting fracture zone will increase accordingly, indicating that the overburden isolation grouting conditions have caused the overburden to break and penetrate, and there is a risk of water damage caused by overburden isolation grouting; if the position of the key layer has not changed, it indicates that the height of the water-conducting fracture zone has not changed under the overburden isolation grouting conditions.

[0132] Specifically, step S5.4 includes the following steps:

[0133] S5.4.1, based on formulas (1) and (2), calculate the geometric dimensions of the lower isolation layer of the overburden isolation grouting space and , and calculate the thickness of the isolation layer .

[0134] S5.4.2, based on the thin plate theory, taking into account the deadweight of the rock layer, the isolation grouting pressure of the overburden rock and the rock layer support force, calculate the deflection of the isolation rock layer , the formula is as follows:

[0135] (8);

[0136] In the formula, is the support coefficient, ranging from 0 to 1, is the thickness of the isolating rock layer.

[0137] S5.4.3, calculate the maximum and minimum principal stresses at the neutral plane height z = h / 2 of the isolation rock layer under the maximum overburden isolation grouting pressure as follows:

[0138] (9);

[0139] in, and represent the maximum principal stress and the minimum principal stress respectively, and Respectively represent Direction and The normal stress in the direction, represents the xy plane shear stress, and Represents a variable.

[0140] in, and It is expressed as:

[0141] (10);

[0142] in, represents the elastic modulus, Represents the parameters, .

[0143] S5.4.4, Based on the Mohr-Coulomb criterion, establish the rock formation failure criterion:

[0144] (11);

[0145] In the formula, is the rock cohesion, is the internal friction angle.

[0146] S5.4.5, the formula for determining the failure of the isolation layer filled with grouting in the overburden separation layer is as follows:

[0147] (12);

[0148] in, and As parameters, , , As the damage judgment index, =1, it indicates that the isolation layer is broken, indicating that there is a risk of water inrush in the overburden isolation grouting under this grouting condition.

[0149] Specifically, when the overburden isolation grouting evaluation results cannot meet the safety requirements in step S5.4, the importance of grouting parameters should be considered and adjustments should be made from four aspects: grouting materials, grouting pressure, grouting layer or grouting position.

[0150] Step S6 specifically includes the following steps:

[0151] S6.1, adjust the grouting materials, reduce the slurry deadweight load by lowering parameters such as slurry density, so that the load on the lower isolation layer of the overburden isolation grouting space is reduced.

[0152] S6.2, reduce the grouting pressure, and reduce the load on the lower isolation layer of the overburden isolation grouting space by reducing the final grouting pressure of the overburden isolation grouting project.

[0153] S6.3, adjust the grouting layer upward, reduce the grouting depth, increase the thickness of the isolation layer, and improve the damage resistance of the isolation layer.

[0154] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A water hazard risk assessment method for overburden isolation grouting filling technology, characterized in that: The specific steps include: S1, collect mine data and analyze hydrogeological data to establish a basic data set for coal seam overburden isolation grouting; S2, using the basic data set of overburden isolation grouting in step S1, analyzing the movement law of overburden in the coal seam and estimating the height of the water-conducting fracture zone; S3, based on step S2, draw a water hazard analysis profile of the overburden isolation grouting working face, and conduct a preliminary assessment of the water hazard of the overburden isolation grouting; S4, establish the spatial evolution model of overburden isolation grouting, simulate the whole process of real overburden isolation grouting, and clarify the real-time changes of overburden isolation grouting space grouting parameters and rock mass stress; S5, conduct water hazard risk assessment of overburden isolation grouting from multiple perspectives, including engineering analogy, semi-empirical formula judgment and theoretical analysis; S6, optimize the grouting design according to the water hazard risk of overburden isolation grouting filling to ensure the safety of grouting engineering; Step S5 specifically includes the following steps: S5.1, Critical value The area is defined as a serious danger zone with the risk of overburden isolation grouting water damage. The formula is specifically expressed as: （7）； In the formula, is the water hazard risk factor of overburden isolation grouting, and are the bulk density and thickness of each rock layer between the bottom boundary of the grouting space and the top boundary of the fracture zone, The depth of coal seam, is the bottom depth of the grouting space, It is the height of development of water-conducting fracture zone; S5.2, evaluate the water hazard risk of overburden isolation grouting based on the key layer identification method; S5.3, according to the "inverted funnel" shape of the overburden rock isolation grouting space, the lower isolation layer of the overburden rock isolation grouting space is regarded as a curved elastic thin plate, and the fracture critical value of the lower isolation layer of the overburden rock isolation grouting is calculated based on the geometric characteristics of the rock formation and the fracture criterion; S5.4, based on the three types of overburden separation grouting water inrush risk identification results, in order to ensure the grouting safety of the overburden isolation grouting working face, the evaluation results should at least meet the safety requirements of the two identification methods. If the safety requirements cannot be met, proceed to step S6; Step S5.3 specifically includes the following steps: S5.3.1, based on the basic data set of overburden isolation grouting and the key layer identification theory, obtain the position of the overburden key layer under normal conditions; S5.3.2, based on the method of estimating the height of the water-conducting fracture zone at the key layer position, when the distance between the main key layer position and the top boundary of the coal seam is less than 7 to 10 times the thickness of the coal seam, the height of the through-fracture of the roof will be equal to the thickness of the bedrock; when the distance between the main key layer position and the top boundary of the coal seam is greater than 7 to 10 times the thickness of the coal seam, the height of the through-fracture of the roof will be equal to the position of the first key layer whose height is greater than 7 to 10 times the thickness of the coal seam; S5.3.3, the maximum grouting pressure value during grouting It is regarded as an additional load and applied entirely to the bottom interface of the overburden isolation space. Then the key layer theory is used to recalculate the position of the overburden key layer under the overburden isolation grouting condition. S5.3.4, compared with the position of the key layer before the overburden isolation grouting, if the position of the key layer of the overburden changes, the height of the water-conducting fracture zone will increase accordingly, indicating that the overburden isolation grouting conditions have led to the breaking and penetration of the overburden, and there is a risk of water damage caused by the overburden isolation grouting; if the position of the key layer has not changed, it means that the height of the water-conducting fracture zone has not changed under the overburden isolation grouting conditions; Step S5.4 specifically includes the following steps: S5.4.1, based on formulas (1) and (2), calculate the geometric dimensions of the lower isolation layer of the overburden isolation grouting space and , and calculate the thickness of the isolation layer ; S5.4.2, based on the thin plate theory, taking into account the deadweight of the rock layer, the isolation grouting pressure of the overburden rock and the rock layer support force, calculate the deflection of the isolation rock layer , the formula is as follows: （8）； In the formula, is the support coefficient, ranging from 0 to 1, is the thickness of the isolating rock layer; S5.4.3, calculate the maximum and minimum principal stresses at the neutral plane height z = h / 2 of the isolation rock layer under the maximum overburden isolation grouting pressure as follows: （9）； in, and represent the maximum principal stress and the minimum principal stress, respectively. and Respectively represent Direction and The normal stress in the direction, represents the xy plane shear stress, and represents a variable; in, and It is expressed as: （10）； in, represents the elastic modulus, Represents the parameters, ; S5.4.4, Based on the Mohr-Coulomb criterion, establish the rock formation failure criterion: （11）； In the formula, is the rock cohesion, is the internal friction angle; S5.4.5, the formula for determining the failure of the isolation layer filled with grouting in the overburden separation layer is as follows: （12）； in, and As parameters, , , As the damage judgment index, =1, it indicates that the isolation layer is broken, indicating that there is a risk of water inrush in the overburden isolation grouting under this grouting condition.

2. A water hazard risk assessment method for overburden isolation grouting filling technology according to claim 1, characterized in that: Step S2 specifically includes the following steps: S2.1, using the basic data set of overburden isolation grouting, based on the rock stratum control key layer theory, calculate and analyze the development position, lithology, thickness, fracture distance and other parameters of each key layer of the coal seam roof, clarify the development position of the overburden separation layer of the coal seam roof, and record all possible overburden isolation grouting layers of the coal seam roof, and determine the distance between each grouting layer and the coal seam roof ; S2.2, based on the measured data of water-conducting fracture zones in other working faces of the mine, obtain the ratio of the development height of the water-conducting fracture zones in the mine, combine the coal seam thickness data revealed by each borehole of the overburden isolation grouting working face, calculate the development height of the water-conducting fracture zone at each borehole location, and use the Kriging interpolation method to calculate the development height of the water-conducting fracture zone at different positions of the overburden isolation grouting working face.

3. A water hazard risk assessment method for overburden isolation grouting filling technology according to claim 1, characterized in that: Step S3 specifically includes the following steps: S3.

1. Based on the exploration, supplementary exploration and hydrogeological drilling data within the working face, draw the profile of the aquiclude and water-proof layer of the overburden isolation grouting working face, and add the top boundary interface curve of the water-conducting fracture zone development height; based on the overburden isolation grouting design data of the mine and the analysis data of the mine water-conducting channel, draw the grouting drilling information, fault information, poorly sealed boreholes and oil and gas wells on the profile to form a water hazard analysis profile of the overburden isolation grouting working face; S3.2, conduct preliminary water hazard analysis based on the water hazard analysis profile of the overburden isolation grouting working face.

4. A water hazard risk assessment method for overburden isolation grouting filling technology according to claim 3, characterized in that: Step S3.2 specifically includes the following steps: S3.2.1, analyze the position relationship between the overburden isolation grouting layer and the water-conducting fracture zone of the working face. If the overburden isolation grouting layer is located within the water-conducting fracture zone, it will cause roof water damage and overburden isolation grouting water damage, and grouting work should not be carried out; S3.2.2, if the grouting layer is located above the water-conducting fracture zone, the relationship between the position of the aquifer above the water-conducting fracture zone and the overburden isolation grouting layer should be analyzed. When there is a water-rich aquifer below the overburden isolation layer and no stable impermeable layer, grouting should not be carried out. When there is a stable impermeable layer below the overburden isolation grouting layer, the position relationship between the grouting borehole and the fault, poorly sealed borehole, and water-conducting channels of oil and gas wells should be further clarified to ensure that the grouting borehole is located outside the coal pillars protected by each water-conducting channel.

5. A water hazard risk assessment method for overburden isolation grouting filling technology according to claim 1, characterized in that: Step S4 specifically includes the following steps: S4.1, select the design layer of overburden isolation grouting that meets the conditions of step S3, and further clarify the overburden movement law near the overburden isolation grouting layer in combination with the overburden movement law analysis in S2; obtain the displacement deformation of the upper and lower layers of the overburden isolation grouting space according to the Ritz method, and obtain the maximum height of the overburden isolation grouting space According to the "inverted funnel" shape of the overburden isolation grouting space, the overburden isolation grouting space evolution model was established and imported into the COMSOL software; the calculation formula for the geometric dimensions of the overburden isolation grouting space is as follows: （1）； In the formula, is the working face advancement distance; is the oblique length of the working surface; is the rock fracture angle, is the length of the overburden isolation grouting space, The width of the overburden isolation grouting space; The calculation formula for the maximum height of the overburden isolation grouting space is as follows: （2）； In the formula, , are coordinates, respectively between (0, ) (0, )between, , are the lateral uniform loads on the upper and lower strata of the grouting space, , are the compressive stiffness of the rock strata above and below the grouting space, is the flexural stiffness of the rock formation; S4.2, conduct simulation of the whole process of overburden isolation grouting to obtain specific information on the slurry diffusion process, stress field change law, and stress change process of the upper and lower rock layers in the grouting space during the overburden isolation grouting process; S4.3, according to the depth of the overburden isolation grouting layer, grouting materials, grouting pressure and other parameter changes, the corresponding overburden isolation grouting slurry diffusion simulation is carried out in turn, and the pressure change law of the grouting space under various working conditions with time is recorded, and the maximum grouting pressure value during the grouting process is selected. Used as the calculated value for water hazard evaluation of overburden isolation grouting.

6. A water hazard risk assessment method for overburden isolation grouting filling technology according to claim 5, characterized in that: Step S4.2 specifically includes the following steps: S4.2.1, the Navier-Stokes equation is used as the governing equation for slurry-water flow, and the formula is: （3）； In the formula, is the fluid velocity, is the fluid pressure, is the fluid density, is the fluid dynamic viscosity, is the unit tensor, is the interfacial tension term, is the acceleration due to gravity, is the Laplace operator; S4.2.2, in order to make the slurry-water two-phase flow process in the overburden isolation grouting space satisfy the law of conservation of mass, the continuity equation is used for description, the formula is: （4）； S4.2.3, in order to describe the real-time change process of the slurry-water two-phase displacement interface, the interface tracking method Level set is used to mark the slurry-water two-phase interface, and the control equation is expressed as: （5）； In the formula, is the initialization parameter, is the interface thickness control parameter; is the level set variable, is the level set function; S4.2.4, Corresponding Interfacial Tension Terms in the Navier-Stokes Equations It is expressed as: （6）； in, is the surface tension coefficient, is the interface normal vector, for The transpose of is the non-zero Diktral function at the fluid interface; S4.2.5, based on the built-in meshing tool and transient solver of COMSOL numerical simulation software, the computational solution and description of the entire process of grouting and slurry-water displacement in the overburden isolation grouting space are realized, and the slurry diffusion process, stress field change law, stress change process of the upper and lower rock layers in the grouting space and other specific information during the overburden isolation grouting process are obtained.

7. A water hazard risk assessment method for overburden isolation grouting filling technology according to claim 1, characterized in that: Step S6 specifically includes the following steps: S6.1, adjust the grouting materials, reduce the grouting deadweight load by reducing the grouting density, so that the load on the lower isolation layer of the overburden isolation grouting space is reduced; S6.2, reduce the grouting pressure, by reducing the final grouting pressure of the overburden isolation grouting project, and reduce the load on the lower isolation layer of the overburden isolation grouting space; S6.3, adjust the grouting layer upward, reduce the grouting depth, increase the thickness of the isolation layer, and improve the damage resistance of the isolation layer.

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