Method for constructing coal mine gob-out water accumulation change relation model

Abstract

The invention provides a coal mine goaf ponding change relation model construction method, which utilizes a numerical method to establish a three-dimensional hydrogeological model of a heterogeneous anisotropic aquifer, and solves the problem that a traditional analytical method can only be used for solving a homogeneous isotropic aquifer with a regular geometrical shape. The change process of the dynamic supply goaf of the aquifer is successfully simulated, the established model is identified and verified to be more suitable for the real hydrogeological environment of a research area, technical support is provided for successfully solving goaf water disasters for a coal mine, safe stoping of a working face is achieved, and the working efficiency is improved. And a method reference is provided for coal mine water prevention and control engineering in mining areas with similar hydrogeological conditions in China.

Description

Technical Field

[0001] The invention relates to the technical field of mining area housing reconstruction, in particular to a method for constructing a coal mine goaf water accumulation change relationship model. Background Art

[0002] The Bojianghaizi Mine in Mengxi Mining Area is located in the Bojianghaizi small watershed in the northern part of the Ordos Basin. It mines the Mesozoic Jurassic Yan'an Formation coal seam at a depth of more than 500m, but is threatened by water hazards in the middle and lower Jurassic and Cretaceous sandstones and goaf water hazards. Due to the influence of the sedimentary environment and structural geological superposition, the overlying sandstone aquifer has an irregular geometry and is heterogeneous and anisotropic during the mining process. Its permeability and water-richness vary greatly in space. The formation mechanism and change relationship of goaf water accumulation are unclear, resulting in extremely uneven water inflow during the mining process of the working face, affecting the safe production of the mine.

[0003] The groundwater system in coal mining areas is affected by both natural and human activities. For the study of the changing relationship of water accumulation in coal mine goaf areas, the main solution methods are analytical methods and numerical methods. However, analytical methods are mostly used for aquifers with regular geometric shapes and homogeneous isotropic, while numerical methods can solve complex hydrogeological conditions due to their flexibility and strong adaptability. Numerical methods include finite difference method and finite element method. The present invention uses GMS (three-dimensional groundwater simulation) software to simulate the process of dynamic recharge of groundwater in the goaf area by the non-homogeneous anisotropic confined water aquifer of Bojiang Haizi Mine, revealing the changing relationship between the water level drop of the aquifer and the water accumulation in the goaf area, providing technical support for the successful solution of goaf water hazards in coal mines.

[0004] The current shortcomings of the existing technology are: for the construction of the relationship model of coal mine goaf water accumulation, traditional analytical methods are mostly used for aquifers with regular geometric shapes and homogeneous isotropic aquifers. For aquifers with irregular geometric shapes or in the presence of heterogeneous anisotropic aquifers, the analytical method has large errors and is not applicable, and cannot correctly simulate the change process of goaf water accumulation.

[0005] In view of the shortcomings of the prior art, the present invention solves the problem of establishing a three-dimensional hydrogeological model of a heterogeneous anisotropic aquifer using a numerical method to simulate the changing process of the aquifer dynamically recharging the goaf. Summary of the invention

[0006] The technical problem to be solved by the present invention is how.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] A method for constructing a coal mine goaf water accumulation change relationship model comprises the following steps:

[0009] Step 1: Generalize the simulation area, aquifer structure, boundary conditions, spatial distribution of corresponding parameters and source-sink processing of the groundwater system in the study area to establish a conceptual model of heterogeneous and anisotropic confined non-steady flow groundwater.

[0010] Step 2: Based on the established hydrogeological conceptual model and the study of the hydraulic properties of the aquifer, the groundwater flow in the simulation area is generalized into a heterogeneous, anisotropic, and unstable three-dimensional groundwater flow system according to Darcy's law and the principle of water balance, and the corresponding mathematical model is established.

[0011] Step 3: Based on the thickness variation characteristics of the Middle Jurassic confined aquifer in the study area and the internal structure characteristics of the aquifer, and considering the dynamic changes of its water level, a corresponding numerical model is established in the GMS software, and the spatial discretization is performed to determine the initial conditions.

[0012] Step 4: According to the characteristics of the actual flow field that the mathematical model should reflect, the model is identified and verified before application to improve the model accuracy. The simulation period is selected, the water level dynamics in the area where the observation hole is located are calculated, and the initial parameters and boundary conditions of the aquifer are adjusted accordingly according to the degree of fit between the calculated water level and the measured water level.

[0013] Step 5, use the identified and verified numerical model to simulate and obtain the groundwater flow field diagram of the study area at different mining periods, and study the changing relationship of the mined-out water accumulation.

[0014] Furthermore, the step 1 comprises the following steps:

[0015] Step 1.1, the scope of the simulation area, combined with the groundwater flow characteristics of the study area, is determined to be the coal mine goaf and the upper and lower aquicludes, aquicludes, a total of seven layers.

[0016] Step 1.2, the aquifer structure is divided into seven layers from top to bottom based on the hydrogeological characteristics of the study area, namely: Quaternary loose layer groundwater aquifer, Lower Cretaceous Zhidan Group pore fissure groundwater-confined water aquifer, Cretaceous and Jurassic aquifer, Middle Jurassic confined water aquifer, impermeable layer between Middle Jurassic and Middle and Lower Jurassic, Middle and Lower Jurassic Yan'an Formation confined water aquifer, and Middle and Lower Jurassic Yan'an Formation bottom impermeable layer.

[0017] Step 1.3, the boundary conditions, according to the analysis of the structural characteristics of the aquifers in the area, generalize the Middle Jurassic confined aquifer to have a certain hydraulic connection with the Cretaceous System in the upper part (weak recharge boundary), an impermeable boundary in the lower part, and constant head boundaries on all sides.

[0018] Step 1.4, the spatial distribution of the corresponding parameters, the main hydrogeological parameters involved are: permeability coefficient (K), elastic water release coefficient (S), rainfall infiltration recharge coefficient (a), and groundwater evaporation conversion coefficient (C). The values ​​of each parameter are obtained by analyzing the hydrogeological data of the study area, and the values ​​are assigned to different regions according to the spatial distribution characteristics of each parameter.

[0019] Step 1.5, the source and sink items are processed. In the study area, the source and sink items mainly include atmospheric precipitation infiltration, groundwater evaporation, artificial mining, etc.

[0020] Furthermore, the step 2 comprises the following steps:

[0021] Step 2.1, the mathematical model, since the Middle Jurassic confined aquifer is a heterogeneous anisotropic confined aquifer, its parameters are spatially heterogeneous, so it is discretized into several homogeneous aquifers using the difference method.

[0022] Step 2.2, the mathematical model has the following characteristics: the parameters of the entire aquifer system are spatially heterogeneous, which can be generalized into a heterogeneous, anisotropic aquifer three-dimensional flow with a single-layer structure; the drainage of the Middle Jurassic aquifer and the recharge of the Cretaceous system vary with time, which is a non-stable flow; the thickness distribution of the aquifer in the area is relatively stable, and the groundwater flow is laminar, which is a Darcy flow.

[0023] Step 2.3, the mathematical model is a heterogeneous anisotropic unsteady three-dimensional groundwater flow mathematical model, and the formula is as follows:

[0024]

[0025] Where: Kxx, Kyy, Kzz—permeability coefficients on x, y, z axes (m / d);

[0026] H.H0—groundwater head elevation and initial head elevation (m);

[0027] W—Cretaceous aquifer recharge;

[0028] P—water discharge volume;

[0029] Ss—elastic water release rate of porous media (1 / m);

[0030] t—time (d);

[0031] Γ1—a type of boundary;

[0032] Ω—Simulation area.

[0033] Furthermore, the step 3 comprises the following steps:

[0034] Step 3.1, the spatial discretization, based on the thickness variation characteristics of the Middle Jurassic (J2) confined aquifer and the internal structure characteristics of the aquifer, and considering the dynamic changes of its water level, the study area is gridded in the GMS software, divided into 100*100 grids, a total of 10,000 units, and the waterlogged area is displayed on the grid.

[0035] Step 3.2, the initial conditions, the initial conditions, use the water levels of each observation well on January 10, 2020 as the initial values.

[0036] Furthermore, the step 4 comprises the following steps:

[0037] Step 4.1, the simulation period is selected from 12:00 on March 10, 2021 to 12:00 on September 10, 2021 as the model identification period; and from 12:00 on January 10, 2023 to 12:00 on March 30, 2023 is selected as the model verification period.

[0038] Step 4.2, the model identification and verification, aims to make the simulated calculated water level of the observation well consistent with the observed water level by adjusting the hydrogeological parameters, source and sink terms and boundary conditions, and then establish a numerical model that meets the hydrogeological conditions of the study area, so as to provide a reference for the subsequent simulation of groundwater flow movement and quantitative simulation of water balance in the study area.

[0039] Step 4.3, the model identification and verification, abides by the following principles: the dynamic process of simulated groundwater is basically similar to the measured dynamic process, requiring the shapes of simulated and measured groundwater process lines to be similar; the simulated groundwater flow field is basically consistent with the measured groundwater flow field, and the calculated flow field can objectively reflect the trend of groundwater flow; the identified hydrogeological parameters should conform to the actual hydrogeological conditions.

[0040] Step 4.4, the model identification and verification, selects Hydrology 1#, Water J9-1, Water J11 and Water J15 as the model identification and verification observation wells, and repeatedly fits the water levels of the existing observation wells of the Middle Jurassic confined aquifer, and conforms to the water balance relationship of the entire groundwater flow field. After model identification and verification, the parameters that meet the different blocks of the aquifer within the study area are finally obtained.

[0041] Furthermore, the step 5 comprises the following steps:

[0042] Step 5.1, the numerical simulation, based on the established model, simulates the flow field for 10 days, 50 days and 100 days according to the drainage of the goaf in the verification phase;

[0043] Step 5.2, the change relationship of the goaf water accumulation, analysis of the numerical simulation results shows that: 3-1 After the first area of ​​the coal seam is mined, a cavity is formed at the working face. The water-conducting fracture zone formed after the collapse of the coal seam roof communicates with the upper Middle Jurassic confined aquifer, providing a water filling channel for replenishing the goaf area; during the mining construction process, the collapse of the roof causes the original confined area on the upper part of the working face to be transformed into a pressure-free area. Under the influence of the hydraulic gradient difference, the water from the surrounding confined aquifers converges to the goaf, and then forms a local drop funnel in the groundwater flow field; after the coal seam is mined, the working face of the mining area is closed, leaving a certain scale of goaf space. Under the continuous replenishment of the upper confined water, the original coal seam area space forms goaf water accumulation with a certain scale of water, which gradually affects the safe production of other mining areas.

[0044] The advantages of the present invention are:

[0045] The technology of the present invention uses numerical methods to establish a three-dimensional hydrogeological model of a heterogeneous anisotropic aquifer, which solves the problem that the traditional analytical method can only be used for geometric shape rules and can only solve homogeneous isotropic aquifers. It successfully simulates the changing process of the aquifer dynamically replenishing the goaf area. The established model has been identified and verified, and is more in line with the actual hydrogeological environment of the study area. It provides technical support for the successful solution of goaf water hazards in coal mines, realizes safe mining of the working face, and also provides a method reference for coal mine water prevention and control projects in domestic mining areas with similar hydrogeological conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a spatial discrete stereogram of a numerical model according to an embodiment of the present invention.

[0047] Figure 2 is a discrete plane diagram of the numerical model space according to an embodiment of the present invention.

[0048] Figure 3 is an initial flow field diagram of the study area according to an embodiment of the present invention.

[0049] Figure 4 100th day groundwater flow field diagram of the study area according to an embodiment of the present invention.

[0050] Figure 5 It is a flow chart of a method for constructing a coal mine goaf water accumulation change relationship model according to an embodiment of the present invention. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are 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.

[0052] A method for constructing a coal mine goaf water accumulation change relationship model comprises the following steps:

[0053] Step 1: Generalize the simulation area, aquifer structure, boundary conditions, spatial distribution of corresponding parameters and source-sink processing of the groundwater system in the study area to establish a conceptual model of heterogeneous and anisotropic confined non-steady flow groundwater.

[0054] Step 2: Based on the established hydrogeological conceptual model and the study of the hydraulic properties of the aquifer, the groundwater flow in the simulation area is generalized into a heterogeneous, anisotropic, and unstable three-dimensional groundwater flow system according to Darcy's law and the principle of water balance, and the corresponding mathematical model is established.

[0055] Step 3: Based on the thickness variation characteristics of the Middle Jurassic confined aquifer in the study area and the internal structure characteristics of the aquifer, and considering the dynamic changes of its water level, a corresponding numerical model is established in the GMS software, and the spatial discretization is performed to determine the initial conditions.

[0056] Step 4: According to the characteristics of the actual flow field that the mathematical model should reflect, the model is identified and verified before application to improve the model accuracy. The simulation period is selected, the water level dynamics in the area where the observation hole is located are calculated, and the initial parameters and boundary conditions of the aquifer are adjusted accordingly according to the degree of fit between the calculated water level and the measured water level.

[0057] Step 5, use the identified and verified numerical model to simulate and obtain the groundwater flow field diagram of the study area at different mining periods, and study the changing relationship of the mined-out water accumulation.

[0058] Furthermore, the step 1 comprises the following steps:

[0059] Step 1.1, the scope of the simulation area, combined with the groundwater flow characteristics of the study area, is determined to be the coal mine goaf and the upper and lower aquicludes, aquicludes, a total of seven layers.

[0060] Step 1.2, the aquifer structure is divided into seven layers from top to bottom based on the hydrogeological characteristics of the study area, namely: Quaternary loose layer groundwater aquifer, Lower Cretaceous Zhidan Group pore fissure groundwater-confined water aquifer, Cretaceous and Jurassic aquifer, Middle Jurassic confined water aquifer, impermeable layer between Middle Jurassic and Middle and Lower Jurassic, Middle and Lower Jurassic Yan'an Formation confined water aquifer, and Middle and Lower Jurassic Yan'an Formation bottom impermeable layer.

[0061] Step 1.3, the boundary conditions, according to the analysis of the structural characteristics of the aquifers in the area, generalize the Middle Jurassic confined aquifer to have a certain hydraulic connection with the Cretaceous System in the upper part (weak recharge boundary), an impermeable boundary in the lower part, and constant head boundaries on all sides.

[0062] Step 1.4, the spatial distribution of the corresponding parameters, the main hydrogeological parameters involved are: permeability coefficient (K), elastic water release coefficient (S), rainfall infiltration recharge coefficient (a), and groundwater evaporation conversion coefficient (C). The values ​​of each parameter are obtained by analyzing the hydrogeological data of the study area, and the values ​​are assigned to different regions according to the spatial distribution characteristics of each parameter.

[0063] Step 1.5, the source and sink items are processed. In the study area, the source and sink items mainly include atmospheric precipitation infiltration, groundwater evaporation, artificial mining, etc.

[0064] Furthermore, the step 2 comprises the following steps:

[0065] Step 2.1, the mathematical model, since the Middle Jurassic confined aquifer is a heterogeneous anisotropic confined aquifer, its parameters are spatially heterogeneous, so it is discretized into several homogeneous aquifers using the difference method.

[0066] Step 2.2, the mathematical model has the following characteristics: the parameters of the entire aquifer system are spatially heterogeneous, which can be generalized into a heterogeneous, anisotropic aquifer three-dimensional flow with a single-layer structure; the drainage of the Middle Jurassic aquifer and the recharge of the Cretaceous system vary with time, which is a non-stable flow; the thickness distribution of the aquifer in the area is relatively stable, and the groundwater flow is laminar, which is a Darcy flow.

[0067] Step 2.3, the mathematical model is a heterogeneous anisotropic unsteady three-dimensional groundwater flow mathematical model, and the formula is as follows:

[0068]

[0069] Where: Kxx, Kyy, Kzz—permeability coefficients on x, y, z axes (m / d);

[0070] H.H0—groundwater head elevation and initial head elevation (m);

[0071] W—Cretaceous aquifer recharge;

[0072] P—water discharge volume;

[0073] Ss—elastic water release rate of porous media (1 / m);

[0074] t—time (d);

[0075] Γ1—a type of boundary;

[0076] Ω—Simulation area.

[0077] Furthermore, the step 3 comprises the following steps:

[0078] Step 3.1, the spatial discretization, based on the thickness variation characteristics of the Middle Jurassic (J2) confined aquifer and the internal structure characteristics of the aquifer, and considering the dynamic changes of its water level, the study area is gridded in the GMS software, divided into 100*100 grids, a total of 10,000 units, and the waterlogged area is displayed on the grid.

[0079] Step 3.2, the initial conditions, the initial conditions, use the water levels of each observation well on January 10, 2020 as the initial values.

[0080] Furthermore, the step 4 comprises the following steps:

[0081] Step 4.1, the simulation period is selected from 12:00 on March 10, 2021 to 12:00 on September 10, 2021 as the model identification period; and from 12:00 on January 10, 2023 to 12:00 on March 30, 2023 is selected as the model verification period.

[0082] Step 4.2, the model identification and verification, aims to make the simulated calculated water level of the observation well consistent with the observed water level by adjusting the hydrogeological parameters, source and sink terms and boundary conditions, and then establish a numerical model that meets the hydrogeological conditions of the study area, so as to provide a reference for the subsequent simulation of groundwater flow movement and quantitative simulation of water balance in the study area.

[0083] Step 4.3, the model identification and verification, abides by the following principles: the dynamic process of simulated groundwater is basically similar to the measured dynamic process, requiring the shapes of simulated and measured groundwater process lines to be similar; the simulated groundwater flow field is basically consistent with the measured groundwater flow field, and the calculated flow field can objectively reflect the trend of groundwater flow; the identified hydrogeological parameters should conform to the actual hydrogeological conditions.

[0084] Step 4.4, the model identification and verification, selects Hydrology 1#, Water J9-1, Water J11 and Water J15 as the model identification and verification observation wells, and repeatedly fits the water levels of the existing observation wells of the Middle Jurassic confined aquifer, and conforms to the water balance relationship of the entire groundwater flow field. After model identification and verification, the parameters that meet the different blocks of the aquifer within the study area are finally obtained.

[0085] Furthermore, the step 5 comprises the following steps:

[0086] Step 5.1, the numerical simulation, based on the established model, simulates the flow field for 10 days, 50 days and 100 days according to the drainage of the goaf in the verification phase;

[0087] Step 5.2, the change relationship of the goaf water accumulation, analysis of the numerical simulation results shows that: 3-1 After the first area of ​​the coal seam is mined, a cavity is formed at the working face. The water-conducting fracture zone formed after the collapse of the coal seam roof communicates with the upper Middle Jurassic confined aquifer, providing a water filling channel for replenishing the goaf area; during the mining construction process, the collapse of the roof causes the original confined area on the upper part of the working face to be transformed into a pressure-free area. Under the influence of the hydraulic gradient difference, the water from the surrounding confined aquifers converges to the goaf, and then forms a local drop funnel in the groundwater flow field; after the coal seam is mined, the working face of the mining area is closed, leaving a certain scale of goaf space. Under the continuous replenishment of the upper confined water, the original coal seam area space forms goaf water accumulation with a certain scale of water, which gradually affects the safe production of other mining areas.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a relationship model of water accumulation in coal mines, characterized in that: The following steps are involved: Step 1: Generalize the simulation area, aquifer structure, boundary conditions, spatial distribution of corresponding parameters and source-sink processing of the groundwater system in the study area, and establish a conceptual model of heterogeneous and anisotropic confined unsteady flow groundwater; Step 2: Based on the established hydrogeological conceptual model and the study of hydraulic properties of aquifers, the groundwater flow in the simulation area is generalized into a heterogeneous, anisotropic, and unstable three-dimensional groundwater flow system according to Darcy's law and water balance principle, and the corresponding mathematical model is established; Step 3: Based on the thickness variation characteristics of the Middle Jurassic confined aquifer in the study area and the internal structure characteristics of the aquifer, and considering the dynamic changes of its water level, a corresponding numerical model is established in the GMS software, and the spatial discretization is performed to determine the initial conditions; Step 4: According to the characteristics of the actual flow field that the mathematical model should reflect, the model is identified and verified before being applied to improve the model accuracy; the simulation period is selected, the water level dynamics in the area where the observation hole is located are calculated, and the initial parameters and boundary conditions of the aquifer are adjusted accordingly according to the degree of fit between the calculated water level and the measured water level; Step 5, use the identified and verified numerical model to simulate and obtain the groundwater flow field diagram of the study area at different mining periods, and study the changing relationship of the mined-out water accumulation.

2. A method for constructing a coal mine goaf water accumulation change relationship model according to claim 1, characterized in that: The step 1 comprises the following steps: Step 1.1, the simulation area is determined to be the coal mine goaf and the upper and lower aquifers and impermeable layers, a total of seven layers, in combination with the groundwater flow characteristics of the study area; Step 1.2, the aquifer structure is divided into seven layers from top to bottom based on the hydrogeological characteristics of the study area, namely: Quaternary loose layer phreatic aquifer, lower Cretaceous Zhidan Group pore fissure phreatic-confined water aquifer, Cretaceous and Jurassic impermeable layer, Middle Jurassic confined water aquifer, impermeable layer between Middle Jurassic and Lower Jurassic, Middle Jurassic Yan'an Formation confined water aquifer, and Middle Jurassic Yan'an Formation bottom impermeable layer; Step 1.3, the boundary conditions are analyzed according to the characteristics of the aquifer structure in the area. The Middle Jurassic confined aquifer is generalized as having a certain hydraulic connection with the Cretaceous System in the upper part (weak recharge boundary), a water-isolating boundary in the lower part, and a constant head boundary around it; Step 1.4, the spatial distribution of the corresponding parameters, the main hydrogeological parameters involved are: permeability coefficient (K), elastic water release coefficient (S), rainfall infiltration recharge coefficient (a), and groundwater evaporation conversion coefficient (C). The values ​​of each parameter are obtained by analyzing the hydrogeological data of the study area, and the values ​​are assigned to different regions according to the spatial distribution characteristics of each parameter; Step 1.5, the source and sink items are processed. In the study area, the source and sink items mainly include atmospheric precipitation infiltration, groundwater evaporation, artificial mining, etc.

3. A method for constructing a coal mine goaf water accumulation change relationship model according to claim 1, characterized in that: The step 2 comprises the following steps: Step 2.1, the mathematical model, since the Middle Jurassic confined aquifer is a heterogeneous anisotropic confined aquifer, its parameters are spatially heterogeneous, so it is discretized into several homogeneous aquifers using the difference method; Step 2.2, the mathematical model has the following characteristics: the parameters of the entire aquifer system are heterogeneous with space, which can be generalized into a heterogeneous, anisotropic aquifer three-dimensional flow with a single-layer structure; the drainage of the Middle Jurassic aquifer and the recharge of the Cretaceous system vary with time, which is an unsteady flow; the thickness distribution of the aquifer in the area is relatively stable, and the groundwater flow is laminar, which is a Darcy flow; Step 2.3, the mathematical model is a heterogeneous anisotropic unsteady three-dimensional groundwater flow mathematical model, and the formula is as follows: Where: Kxx, Kyy, Kzz—permeability coefficients on x, y, z axes (m / d); H.H0—groundwater head elevation and initial head elevation (m); W—Cretaceous aquifer recharge; P—water discharge volume; Ss—elastic water release rate of porous media (1 / m); t—time (d); Γ1—a type of boundary; Ω—Simulation area.

4. A method for constructing a coal mine goaf water accumulation change relationship model according to claim 1, characterized in that: The step 3 comprises the following steps: Step 3.1, the spatial discretization, based on the thickness variation characteristics of the confined aquifer in the Middle Jurassic (J2) and the internal structure characteristics of the aquifer, and considering the dynamic change of its water level, the study area is gridded in the GMS software, divided into 100*100 grids, a total of 10,000 units, and the waterlogged area is displayed on the grid; Step 3.2, the initial conditions, the initial conditions, use the water levels of each observation well on January 10, 2020 as the initial values.

5. The method for constructing a coal mine goaf water accumulation change relationship model according to claim 1, characterized in that: The step 4 comprises the following steps: Step 4.1, the selected simulation period is selected from 12:00 on March 10, 2021 to 12:00 on September 10, 2021 as the model identification period; and from 12:00 on January 10, 2023 to 12:00 on March 30, 2023 as the model verification period; Step 4.2, the model identification and verification, aims to make the simulated water level of the observation well consistent with the observed water level by adjusting the hydrogeological parameters, source and sink terms and boundary conditions, and then establish a numerical model that meets the hydrogeological conditions of the study area, so as to provide a reference for the later simulation of groundwater flow and quantitative simulation of water balance in the study area; Step 4.3, the model identification and verification, abides by the following principles: the dynamic process of simulated groundwater is basically similar to the measured dynamic process, requiring the simulated and measured groundwater process lines to be similar in shape; the simulated groundwater flow field is basically consistent with the measured groundwater flow field, and the calculated flow field can objectively reflect the trend of groundwater flow; the identified hydrogeological parameters should conform to the actual hydrogeological conditions; Step 4.4, the model identification and verification, selects Hydrology 1#, Water J9-1, Water J11 and Water J15 as the model identification and verification observation wells, and repeatedly fits the water levels of the existing observation wells of the Middle Jurassic confined aquifer, and conforms to the water balance relationship of the entire groundwater flow field. After model identification and verification, the parameters that meet the different blocks of the aquifer within the study area are finally obtained.

6. A method for constructing a coal mine goaf water accumulation change relationship model according to claim 1, characterized in that: The step 5 comprises the following steps: Step 5.1, the numerical simulation, based on the established model, simulates the flow field for 10 days, 50 days and 100 days according to the drainage of the goaf in the verification phase; Step 5.2, the change relationship of the goaf water accumulation, analysis of the numerical simulation results shows that: after the 3-1 coal seam is mined in a plate area, a cavity is formed in the working face. The water-conducting fracture zone formed after the coal seam roof collapses communicates with the upper Jurassic Middle System confined aquifer, providing a water filling channel for replenishing the goaf area; during the mining construction process, the roof collapses, causing the original confined area on the upper part of the working face to be transformed into a pressure-free area. Under the influence of the hydraulic gradient difference, the water from the surrounding confined aquifers converges to the goaf, and then forms a local drop funnel in the groundwater flow field; after the coal seam is mined, the working face of the mining area is closed, leaving a certain scale of goaf space. Under the continuous replenishment of upper confined water, the original coal seam area space forms goaf water accumulation with a certain scale of water, which gradually affects the safe production of other mining areas.

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