Mine pit water inflow prediction method based on numerical model

Abstract

The invention discloses a numerical simulation-based mine pit water inflow prediction method, which comprises the following steps of: firstly, constructing a hydrogeological conceptual model of a research area, and determining the range and boundary conditions of the research area, a hydrogeological structure, hydrogeological parameters and groundwater supply and drainage items; establishing a three-dimensional unsteady flow underground water flow numerical model by adopting underground water simulation software GMS, carrying out space-time discrete processing on the model, and configuring initial conditions at the same time; performing parameter identification and effect verification on the underground water flow numerical model by using field water pumping test data and hydrogeological parameters, so that a model calculation result is consistent with an actual hydrogeological condition; and finally, based on the verified underground water flow numerical model, calculating and outputting a mine pit water inflow prediction result. According to the method, the water inflow of the mining area is predicted through the software program GMS applied to underground water flow mathematical simulation, and then guarantee is provided for safe production of the mining area.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mine hydrogeology, and particularly relates to a mine water inflow prediction method based on numerical simulation. BACKGROUND

[0002] Groundwater is a very thorny problem in the production process of open-pit mines. Groundwater is a key component of global water resource reserves, which can meet the construction needs and water needs of life of factories, but the water inflow of a mining area can greatly affect the safety of the mining area, and greatly fluctuates. Therefore, accurate water inflow prediction is of great significance to construction safety and economic benefits.

[0003] At present, with the development of science and technology and the rise of electronic information industry, the research on groundwater simulation software in the world is becoming more and more professional. The GMS software is a graphical interface software established on the basis of the existing groundwater models such as Visual MODFLOW, MT3DMS, PEST, MODPATH, FMWATER, AQUA3D, etc. The working principle of the MODFLOW calculation module of the GMS software is to divide the grid as the basis, supplemented by the finite difference method to simulate the order of groundwater movement. First, the selected research area is discretely processed in time and space dimensions, then the divided grid is separately analyzed and deduced for water flow equation, and then the equation set of the entire research area is derived by comprehensively deducing all the equations, and then the water level value of each individual grid is calculated by the iterative solution method. Through the above steps, the solution of the equation set is obtained. SUMMARY

[0004] The purpose of the application is to provide a mine water inflow prediction method based on numerical simulation, which predicts the water inflow of a mining area by using the GMS software program applied in the mathematical simulation of groundwater flow, thereby providing protection for the safe production of the mining area.

[0005] The technical scheme adopted by the application is a mine water inflow prediction method based on numerical simulation, comprising the following steps: Step 1, constructing a hydrogeological conceptual model of the research area, the model clearly defines the research area range and boundary conditions, hydrogeological structure, hydrogeological parameters, and groundwater recharge and discharge items; Step 2, based on the hydrogeological conceptual model, using the groundwater simulation software GMS to establish a three-dimensional non-steady flow groundwater flow numerical model, and performing time and space discretization processing on the model, and configuring initial conditions; Step 3, using field pumping test data and hydrogeological parameters to identify parameters and verify the effect of the groundwater flow numerical model, so that the model calculation results are consistent with the actual hydrogeological conditions; Step 4, based on the verified groundwater flow numerical model, the Drain module in GMS is used to simulate the mine drainage process, and the mine water inflow prediction result is calculated and output.

[0006] The application is also characterized in that, The boundary conditions in step 1 include lateral boundaries and vertical boundaries, the lateral boundaries are divided according to the hydrogeological unit boundary, watershed, and terrain height, and are divided into zero-flow boundaries and lateral outflow boundaries; The upper part of the vertical boundary is the top plate of the Quaternary aquifer as the infiltration-evaporation boundary, and the lower part of the specific coal seam roof confined aquifer bottom is the water-resisting boundary.

[0007] The hydrogeological structure divides the water-bearing rock group and the water-resisting layer, the water-bearing rock group includes the Quaternary aquifer, the Cretaceous aquifer, the Jurassic aquifer and the Triassic aquifer, the water-resisting layer includes the weak permeable layer between the Quaternary and the Cretaceous, the water-resisting layer between the Cretaceous and the coal seam roof aquifer, and the coal seam floor water-resisting layer, and the vertical of the study area is generalized as a multi-layer structure system.

[0008] The hydrogeological parameters include the permeability coefficient of the water-bearing medium, the specific yield, the atmospheric precipitation infiltration coefficient and the groundwater limit evaporation depth; The groundwater recharge and discharge items include atmospheric precipitation infiltration amount, lateral runoff recharge, outflow, mining amount and evaporation amount.

[0009] The atmospheric precipitation infiltration amount is calculated by the following formula: ; In the formula, is the precipitation infiltration recharge amount of the i-th partition in the k-th month, and the unit is m³; is the corresponding precipitation infiltration coefficient of the i-th area; is the precipitation of the i-th area in the k-th month, and the unit is mm; is the calculation area of the i-th area, and the unit is km²; The lateral runoff recharge amount and the lateral outflow are calculated by using the Darcy formula, and are specifically shown in the following formula: ; In the formula, indicates the lateral runoff recharge amount, the inflow is positive, K indicates the permeability coefficient near the cross section of the aquifer, I indicates the hydraulic gradient perpendicular to the cross section, B indicates the length of the cross section, and M indicates the thickness of the aquifer where the cross section is located; The evaporation amount is calculated by using the following formula: ; In the formula, is the water surface evaporation intensity; H is the phreatic water depth; is the limit depth of groundwater evaporation; n is an empirical constant related to soil texture and vegetation, and its value is 1-3.

[0010] The expression of the three-dimensional unsteady flow groundwater flow numerical model in step 2 is as follows: ; In the formula, Ω is the range of the research area, h is the groundwater level elevation, S is the water storage rate of the aquifer, K l is the horizontal permeability coefficient of the aquifer, K z is the vertical permeability coefficient of the aquifer, and ε is the source and sink term of the aquifer.

[0011] The boundary condition of the three-dimensional unsteady flow groundwater flow numerical model is a second-class boundary condition, and the expression is as follows: ; In the formula, Γ1 is the lateral and bottom boundary of the aquifer; n is the internal normal direction of the aquifer; Kn is the normal permeability coefficient of the aquifer boundary; q is the inflow and outflow per unit area, the inflow is positive, the outflow is negative, and the zero is the impermeable boundary; The initial condition of the groundwater flow when the groundwater is in unsteady flow is as follows: ; In the formula, h0 is the initial groundwater level value of the aquifer.

[0012] In step 2, the model is discretized in space and time, and the initial condition is specifically discretized in space by using a structured grid, and the grid size is set to 200m×200m. The simulation period covers more than 10 years, and the natural month is used as the stress period, and one time step is set for each stress period.

[0013] Step 3 specifically includes the following steps: Step 3.1, the hydrogeological parameters obtained from the field pumping test and the hydrogeological report are used as the initial input, and the groundwater flow numerical model is run to obtain the groundwater flow field, groundwater level dynamic data and aquifer storage; Step 3.2, the groundwater flow field, groundwater level dynamic data and aquifer storage obtained by simulation calculation are compared with the actual groundwater flow field, groundwater level change trend and groundwater recharge and discharge difference data, and the two are consistent, which meets the verification criterion; Step 3.3, if the verification criterion is not met, adjust the hydrogeological parameters and boundary condition settings, and repeat the model running until the verification criterion is met, and complete the model calibration.

[0014] The mine pit drainage process in step 4 is simulated by using the Drain module in GMS, and the mine pit water inflow prediction result is calculated and output, specifically, in GMS, the Drain module is enabled, the drainage area is accurately defined as the mining section of the target coal seam, and the drainage elevation is set as the bottom elevation of the overburden aquifer of the target coal seam, so as to simulate the convergence process of groundwater to the goaf during the mining process of the mine pit; The groundwater flow numerical model that passes the verification of the prediction cycle is set again; the total amount of groundwater drainage in the drainage area during the simulation period is quantitatively calculated by using the Zone budget water balance module of GMS, and the specific numerical value of the mine pit water inflow is finally output; based on the analysis result of the Zone budget water balance module, the source composition proportion of the water inflow is disassembled and output.

[0015] The beneficial effects of the present application are: The present application comprehensively constructs a hydrogeological conceptual model, systematically and clearly studies the boundary conditions, hydrogeological structure, core parameters and groundwater recharge and discharge items of the research area, avoids the problems of missing or disconnection of model basic parameters in traditional prediction, provides a reliable basis for subsequent numerical simulation that fits the actual hydrogeological conditions, and makes the prediction direction more targeted.

[0016] By using GMS software to establish a three-dimensional unsteady flow groundwater flow numerical model, combining time and space discrete processing and professional module configuration, the motion law of groundwater in a complex aquifer system is accurately reproduced, compared with the traditional simplified model, the dynamic change characteristics of groundwater can be better captured, and the scientificity and accuracy of the prediction of the mine pit water inflow are significantly improved.

[0017] In addition, the model is parameter-identified and effect-verified in combination with field pumping test data, hydrogeological reports and long-term monitoring data, and is calibrated through flow field, water level dynamics, recharge and discharge balance and other multi-dimensional indicators, so that the problems of blind setting of traditional model parameters and inconsistency with actual hydrological conditions are solved, and the reliability and credibility of the model output result are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a flowchart of the mine pit water inflow prediction method based on numerical simulation of the present application; Figure 2 is an aquifer generalization diagram in embodiment 6 of the present application; Figure 3 is a precipitation infiltration coefficient initial value zoning diagram in embodiment 6 of the present application; Figure 4 is a Quaternary-Cretaceous system flow field fitting diagram in embodiment 6 of the present application; Figure 5 is a "2 coal roof" aquifer flow field fitting diagram in embodiment 6 of the present application; Figure 6is a fitting graph of the aquifer of the "6 coal roof" in Example 6 of the present application; Figure 7 is a distribution graph of the observation points in Example 6 of the present application; Figure 8a is a fitting graph of the XJ24 observation hole of the aquifer of the "6 coal roof" in Example 6 of the present application; Figure 8b is a fitting graph of the XJ31 observation hole of the aquifer of the "6 coal roof" in Example 6 of the present application; Figure 9a is a fitting graph of the XJ26 observation hole of the Quaternary-Cretaceous aquifer in Example 6 of the present application; Figure 9b is a fitting graph of the XJ44 observation hole of the Quaternary-Cretaceous aquifer in Example 6 of the present application; Figure 10a is a fitting graph of the XJ6 observation hole of the "2 coal roof" aquifer in Example 6 of the present application; Figure 10b is a fitting graph of the XJ14 observation hole of the "2 coal roof" aquifer in Example 6 of the present application; Figure 11 is a horizontal permeability coefficient zoning map of the Quaternary-Cretaceous aquifer in Example 6 of the present application Figure 12 is a horizontal permeability coefficient zoning map of the "2 coal roof" in Example 6 of the present application; Figure 13 is a horizontal permeability coefficient zoning map of the "6 coal roof" in Example 6 of the present application. DETAILED DESCRIPTION

[0019] 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 some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0020] Embodiment 1 The present application is based on a numerical simulation mine water inflow prediction method, as shown in Figure 1 , comprising the following steps: Step 1, constructing a hydrogeological conceptual model of the study area, the model clearly defines the study area range and boundary conditions, hydrogeological structure, hydrogeological parameters, and groundwater recharge and discharge items; Step 2, based on the hydrogeological conceptual model, using the groundwater simulation software GMS to establish a three-dimensional unsteady flow groundwater flow numerical model, and performing time and space discretization processing on the model, and configuring initial conditions; Step 3, using field pumping test data and hydrogeological parameters, the groundwater flow numerical model is parameter identified and effect verified, so that the model calculation results are consistent with the actual hydrogeological conditions; Step 4, based on the verified groundwater flow numerical model, the Drain module in GMS is used to simulate the mine drainage process, and the mine water inflow prediction results are calculated and output.

[0021] Embodiment 2 Based on the above embodiment 1, the boundary conditions in step 1 of the application include lateral boundary and vertical boundary, the lateral boundary is divided according to the hydrogeological unit boundary, watershed, and terrain height, and is divided into zero flow boundary and lateral outflow boundary; the upper part of the Quaternary aquifer roof is the infiltration-evaporation boundary, and the lower part of the specific coal seam roof confined aquifer bottom is the water-resisting boundary.

[0022] Further, the hydrogeological structure divides the water-bearing rock group and the water-resisting layer, the water-bearing rock group includes the Quaternary aquifer, the Cretaceous aquifer, the Jurassic aquifer and the Triassic aquifer, and the water-resisting layer includes the weak permeable layer between the Quaternary and the Cretaceous, the water-resisting layer between the Cretaceous and the coal seam roof aquifer, and the coal seam floor water-resisting layer, and the vertical of the study area is generalized as a multi-layer structure system.

[0023] Further, the hydrogeological parameters include the permeability coefficient of the water-bearing medium, the specific yield, the atmospheric precipitation infiltration coefficient and the groundwater limit evaporation buried depth; The groundwater recharge and discharge items include atmospheric precipitation infiltration amount, lateral runoff recharge, outflow amount, mining amount and evaporation amount.

[0024] Embodiment 3 Based on the above embodiment 2, the atmospheric precipitation infiltration amount of the application is calculated by the following formula (1): (1); In the formula, is the precipitation recharge amount of the i-th partition in the k-th month, and the unit is m³; is the corresponding precipitation infiltration coefficient of the i-th area; is the precipitation of the i-th area in the k-th month, and the unit is mm; is the calculation area of the i-th area, and the unit is km²; The lateral runoff recharge and lateral outflow are calculated by using Darcy formula, and are specifically shown in the following formula (2): (2); In the formula, represents the lateral runoff recharge, the inflow is positive, K represents the permeability coefficient near the cross section of the aquifer, I represents the hydraulic gradient perpendicular to the cross section, B represents the length of the cross section, and M represents the thickness of the aquifer where the cross section is located; Evaporation amount is calculated by using the following formula (3): (3); In the formula, Evaporation intensity of water surface; H is the depth of the underground water; Limiting evaporation depth of underground water; n is an empirical constant related to soil texture and vegetation, and the value is 1-3.

[0025] Example 4 Based on the above-mentioned example 3, the expression of the three-dimensional unsteady flow groundwater flow numerical model in step 2 of the present application is shown in the following formula (4): (4); In the formula, Ω is the range of the research area, h is the groundwater level elevation, S is the water storage rate of the aquifer, K l is the horizontal permeability coefficient of the aquifer, K z is the vertical permeability coefficient of the aquifer, and ε is the source-sink term of the aquifer.

[0026] Further, the boundary condition of the three-dimensional unsteady flow groundwater flow numerical model adopts a second-type boundary condition, and the expression is shown in the following formula (5): (5); In the formula, Γ1 is the lateral and bottom boundary of the aquifer; n is the internal normal direction of the aquifer; Kn is the normal permeability coefficient of the aquifer boundary; q is the inflow and outflow per unit area, positive for inflow, negative for outflow, and zero for the water-resistant boundary; For the unsteady flow of groundwater, the initial condition of groundwater flow is shown in the following formula (6): (6); In the formula, h0 is the initial groundwater level value of the aquifer.

[0027] Further, the model is subjected to space-time discrete processing, and the initial condition is specifically configured by using structured grid for space discretization, and the grid size is set to 200m*200m. The simulation period covers more than 10 years, and the natural month is used as the stress period, and one time step is set for each stress period.

[0028] Example 5 Based on the above-mentioned example 4, step 3 of the present application specifically includes the following steps: Step 3.1, the hydrogeological parameters obtained from the field pumping test and the hydrogeological report are used as initial input, and the groundwater flow numerical model is run to calculate the groundwater flow field, groundwater level dynamic data and aquifer storage capacity; Step 3.2, compare the simulated groundwater flow field, groundwater level dynamic data and aquifer storage with the actual groundwater flow field, groundwater level change trend and groundwater recharge and discharge difference data. If the two are consistent, the verification criterion is met; Step 3.3, if the verification criterion is not met, adjust the hydrogeological parameters and boundary condition settings, and repeat the model until the verification criterion is met to complete the model calibration.

[0029] Further, in step 4, the Drain module in GMS is used to simulate the mine drainage process, and the mine water inflow prediction results are calculated and output. Specifically, in GMS, the Drain module is enabled, the drainage area is accurately defined as the target coal seam mining area, and the drainage elevation is set as the bottom elevation of the target coal seam roof confined aquifer, to simulate the convergence process of groundwater to the goaf during mining. Then, set the groundwater flow numerical model that passes the prediction period operation verification; use the Zone budget water balance module in GMS to quantitatively calculate the total amount of groundwater drainage in the drainage area during the simulation period, and finally output the specific numerical value of the mine water inflow. Based on the analysis results of the Zone budget water balance module, the source composition ratio of the water inflow is also output.

[0030] Example 6 This example takes Xingjie Taigemiao mine area as the research area. The mine area is located in the Dongsheng mine area of the national large coal base, Shendong coal base. The northern boundary is the eastern Wulu railway and Ganzhu Temple water source protection area boundary, the northern slope of the Loess Plateau soil and water conservation ecological protection red line, and the Genghis Khan National Forest Park, adjacent to Gaotouyao mine area; the western boundary is the western boundary of Taigemiao mine area, adjacent to Hujiert mine area; the southern boundary is the southern boundary of Taigemiao mine area, adjacent to Hujiert mine area; the eastern boundary is the dynamic boundary of Taigemiao mine area, adjacent to Xingjie mine area. The east-west width of the mine area is 13.5km-22.7km, the south-north length is 37.2km-41.0km, and the area is 800.77km 2 The total planning scale of the mine area is 56Mt / a.

[0031] The main simulation range of this time is the area where San and Si wells are located, but the mine area boundary is artificially defined. In order to more accurately simulate the groundwater flow field, the model range is defined to the hydrogeological boundary.

[0032] Step 1, build a hydrogeological conceptual model of the research area. The model clearly defines the research area range and boundary conditions, hydrogeological structure, hydrogeological parameters, and groundwater recharge and discharge items; Among them, the lateral boundary is defined as follows: The south side of the model is divided by the Suobenmao- Hongjianmao third-level groundwater system and the Wudinghe third-level groundwater system as the model boundary, which is treated as a zero-flow boundary. The southeast side of the model is divided by the intermediate ridge of Gaolih River and Jiasake River as the model boundary, which is treated as a zero-flow boundary. The southeast corner is divided by the west boundary of Hongjianmao, which is treated as a lateral outflow boundary. The northeast side of the model is divided by the Suobenmao-Hongjianmao third-level groundwater system and the Wulanchunhe third-level groundwater system as the boundary, The south side is divided by the Bahannao fourth-level groundwater system and the Hongjianmao fourth-level groundwater system as the boundary, which is treated as a zero-flow boundary; the north side is delineated along the ridge terrain, which is treated as a zero-flow boundary. The southwest side of the model is divided by the Bahannao fourth-level groundwater system and the Hongjianmao fourth-level groundwater system as the boundary, which is treated as a zero-flow boundary, and the northwest side is divided by the lower terrain on the west side of the mining area as the boundary, which is treated as a lateral outflow boundary.

[0033] The main rivers and lakes in the simulation area, such as Tonggelang River, Gaolih River, Yuetashu Reservoir, Dazhagannao, and Xiaozhagannao, are treated as outflow boundaries.

[0034] The vertical boundary is defined as the top boundary of the Quaternary aquifer, which accepts atmospheric precipitation recharge and is generalized as an infiltration-evaporation boundary; the coal and 6 coal roof confined aquifer in the north of the study area accepts recharge, and groundwater flows from north to south and finally discharges into the same layer aquifer in the south of the study area, and the east and west sides can be considered as zero-flow boundaries; the bottom of the 6 coal roof confined aquifer is the lower boundary of the model, which is generalized as a water-resisting boundary.

[0035] The hydrogeological structure is divided into water-bearing rock group and water-resisting layer, and the scope of water-bearing rock layer is as follows: 1. Quaternary aquifer The Quaternary aquifer is widely distributed in the whole area. The sand layer is loose, with good permeability and generally not thick, providing good conditions for atmospheric precipitation infiltration recharge to the underlying Cretaceous aquifer. The unit water inflow is between 0.435~2.607 L / s·m, and the water-richness grade is medium~strong. In the higher places, the Cretaceous weathered sandstone seeps downward to supply the Cretaceous groundwater, forming an important recharge source. In the low-lying areas, the thick Quaternary aquifer accepts the leakage recharge of Cretaceous confined water, becoming a groundwater-rich area.

[0036] 2. Cretaceous aquifer Cretaceous sandstone is sporadically exposed on the surface of the mining area, with a unit yield of 0.0788~0.3506 L / s·m. The water quality is generally good, and the aquifer is shallow, making it easy to develop. The lithology consists of sandstone of various grain sizes, gravelly coarse-grained sandstone interbedded with sandy mudstone. The lithology is uniform, the structure is loose, and the pores are well-developed. The main sources of recharge are lateral runoff, vertical recharge from atmospheric precipitation in the exposed Cretaceous areas in the central and peripheral parts of the mining area, and vertical infiltration from Quaternary aquifers. In the southern part of the mining area, the Cretaceous water level is higher than the Quaternary groundwater level, resulting in gravity flow. In the north and northeast, the Cretaceous water level is lower than the Quaternary groundwater level. During the rainy season, the abundant Quaternary groundwater can recharge the Cretaceous water, while during the dry season, it creates a backwater effect on the Quaternary groundwater. Controlled by the surface watershed in the central part of the mining area, the general direction of groundwater runoff in the southern part of the mining area is from northwest to southeast; while the runoff direction in the northern part is from southeast to northwest. The hydraulic gradient is generally 1.1 to 2.4‰. Cretaceous strata are mainly discharged through lateral runoff, followed by artificial mining.

[0037] 3. Jurassic aquifer 1) Aquifer group on the roof of the first coal seam The aquifers on the roof of the first coal seam mainly consist of the lower part of the Anding Formation, the Zhiluo Formation, and the upper part of the Yan'an Formation. The lithology is primarily coarse-grained sandstone, medium-grained sandstone, fine-grained sandstone, and sandy mudstone. Groundwater flows from northwest to southeast, consistent with the regional water flow direction. The hydraulic gradient in the north is 0.5‰, with relatively good flow conditions; the hydraulic gradient in the south is greater (0.7-1.6‰), with larger water level fluctuations, reflecting weaker fracture development, poorer connectivity, and worse flow conditions.

[0038] 2) Aquifer between the first coal seam and the No. 6 coal seam This aquifer is a coal-bearing stratum of the Middle-Lower Jurassic Yan'an Formation, distributed throughout the region. The aquifer is mainly composed of medium- to coarse-grained sandstone, primarily cemented by argillaceous material, with poorly developed fractures but relatively well-developed porosity. Groundwater flows from northwest to southeast with a gentle hydraulic gradient. In the northern edge of the Husiliang area and the border zone between Inner Mongolia and Shaanxi, parts of the Middle Jurassic strata are exposed, directly receiving recharge from atmospheric precipitation.

[0039] 4. Triassic aquifers The Triassic aquifers are buried deep, and the lithology is mainly grayish-green medium- to fine-grained sandstone with weak water-bearing capacity.

[0040] The specific scope of the waterproof layer is as follows: 1. Aquitard between Quaternary and Cretaceous aquifers One to several layers of water-blocking rock, mainly composed of sandy mudstone and siltstone, were discovered at the top of the Cretaceous system. These layers are spatially discontinuous, have poor stability, and high sand content, and are weakly permeable layers located between the Cretaceous and Quaternary aquifers.

[0041] 2. Aquitard between the Cretaceous aquifer and the roof aquifer of coal seam No. 2 This aquitard consists of the Anding Formation aquitard and the upper aquitard of the Zhiluo Formation, and is distributed throughout the region, gradually thinning from south to north.

[0042] The Anding Formation's aquitard lithology consists of purplish-red or brownish-red fine- to coarse-grained sandstone interbedded with thin layers of purplish-red and grayish-green mudstone and sandy mudstone. The sandstone contains numerous bluish-gray mud inclusions, predominantly horizontally bedding, providing good water-blocking performance and serving as an effective aquitard between the Cretaceous and coal-bearing strata. The Anding Formation is basically developed throughout the entire area, with its thickness gradually increasing from northwest to south. Significant variations in thickness are observed between the north and south of the mining area; it is more stable in the south, while locally thinner in the north, exhibiting poor water-blocking properties. The upper aquitard of the Zhiluo Formation consists of alternating layers of grayish-green sandy mudstone and siltstone. This aquitard is more developed in the central part of the mining area, with a thickness of more than 30m, but the thickness is thinner in some local sections in the north and south.

[0043] 3. Water-resistant layer of the bottom plate of coal seam 2 The bottom of the No. 2 coal seam has a water-retaining layer mainly composed of sandy mudstone and mudstone. This water-retaining layer blocks the hydraulic connection between the aquifer in the water-conducting fracture zone of the first coal seam and the aquifer in the roof of the No. 6 coal seam.

[0044] Based on previous hydrogeological work and the understanding of the hydrogeological conditions in the study area from this study, such as Figure 2 As shown, the study area is generalized into four layers vertically, from top to bottom: Quaternary-Cretaceous unconfined aquifer, Anding Formation and Zhiluo Formation top weakly permeable layer, No. 2 coal seam confined aquifer, and No. 6 coal seam confined aquifer.

[0045] Hydrogeological parameters include the following parameters: Permeability coefficient: Based on topography, stratigraphy and hydrogeological conditions, the permeability coefficient of the unconfined aquifer is initially divided into several zones. Referring to pumping tests, relevant reports and empirical values ​​of permeability coefficients of various lithologies in hydrogeological manuals, a permeability coefficient zone map of the simulation area is given, which is then applied to the model and fitted and adjusted according to the actual situation.

[0046] Water yield: The zoning and initial values ​​of water yield in the model are mainly determined based on the changes in lithology and the lithological characteristics of the water level fluctuation zone.

[0047] Atmospheric precipitation infiltration coefficient: The magnitude of the precipitation infiltration coefficient is mainly affected by topography, rainfall characteristics, vadose zone lithology and structure, and groundwater depth. The initial value of the precipitation infiltration coefficient in this embodiment is as follows: Figure 3 As shown.

[0048] The limiting evaporation depth of groundwater: The natural evaporation of groundwater is closely related to the lithology of the vadose zone, the depth of the groundwater level, air saturation, and surface evaporation. Based on the Avyanov formula, the evaporation process of groundwater at different depths is described by a linear equation. Referring to relevant literature, the conversion factor between land surface evaporation and water surface evaporation is taken as 0.62. In this example, the limiting evaporation depth of groundwater in the study area is taken as 2.15m based on previous data.

[0049] Groundwater recharge and discharge items include atmospheric precipitation infiltration, lateral runoff recharge and outflow, extraction and evaporation.

[0050] Step 2: Based on the hydrogeological conceptual model, a three-dimensional unsteady flow groundwater numerical model is established using the groundwater simulation software GMS, and the model is spatiotemporally discretized, while initial conditions are configured. In this embodiment, spatial discretization is performed using structured mesh generation (GMS). The basic mesh size of the model is 200m × 200m, and the model is divided into 33,510 meshes, as shown in the figure. Based on available data, the simulation period is initially determined to be from January 2013 to December 2024, a total of 144 months. Each calendar month corresponds to a stress period, and each stress period has one time step. Within each stress period, the intensity of all given source and sink terms remains constant.

[0051] Furthermore, this embodiment also requires processing of various boundaries and refill amounts, as shown in Table 1 below: Table 1 Boundary Conditions and Arrangement Item Processing Table

[0052] As shown in the table above, atmospheric precipitation infiltration: atmospheric precipitation recharge is input into the model in the form of isometric recharge, precipitation infiltration coefficient is divided into zones using GIS software, and precipitation data is processed into a format that GMS can recognize using EXCEL.

[0053] Lateral replenishment: handled by the General Head Boundary subpackage; Mine drainage: The Drain module is used for processing, the drainage area is set as Drain, and the drainage elevation is set as the bottom plate of the No. 2 coal seam aquifer.

[0054] Evaporation and discharge: Evaporation module (EVT) is used for treatment. The evaporation module includes the maximum evaporation rate, evaporation surface and limit burial depth. The evaporation surface is set to the same elevation as the ground, and the limit burial depth is set to 2.15m.

[0055] Mining areas: The Chagannao water source and the Ganzhumiao water source were both simulated using the Wells module; agricultural irrigation and forestry irrigation were processed in GMS using the RCH package as a surface, and then imported into an EXCEL format that the software could recognize.

[0056] Lakes and Rivers: The area of ​​lakes within the simulation area was statistically analyzed, and its product with the annual water surface evaporation rate of the study area was used as a reference value for lake discharge to correct the model equilibrium term. Major rivers and lakes within the study area were processed using DRN.

[0057] Step 3: Using field pumping test data and hydrogeological parameters, perform parameter identification and effect verification on the groundwater flow numerical model to ensure that the model calculation results are consistent with the actual hydrogeological conditions. Specifically, the criteria for identification and verification are as follows: the calculated groundwater flow field should be basically consistent with the actual groundwater flow field, and the groundwater level contour lines of the two should basically match; the groundwater level change trend calculated during the simulation period should be consistent with the actual change trend, and the dynamic process of groundwater level of the two should basically match; the actual groundwater recharge and discharge difference should be close to the calculated change value of aquifer storage; and the identified hydrogeological parameters, aquifer structure and boundary conditions should conform to the actual hydrogeological conditions.

[0058] Once these criteria are met, the model can be used to predict subsequent water inflow.

[0059] Running the calculation program yields the spatiotemporal distribution of groundwater level under given hydrogeological parameters and various source-sink conditions. By fitting the historical curves of long-term observation wells and the groundwater flow field during the same period, hydrogeological parameters, boundary values, and other source-sink conditions are identified, making the established model more consistent with the hydrogeological conditions of the study area. This allows for a more accurate quantitative study of the recharge and discharge in the simulated area, providing data support for groundwater flow prediction models.

[0060] The model validation phase utilized borehole data from 2014 and groundwater level monitoring data from 2024. A water level flow field map was created using GIS, which served as the basis for simulation verification. Comparisons between simulated water levels at each layer and existing water level flow fields are shown below. Figure 4 , 5 6, such as Figure 7 As shown, the observation wells for the water level flow field are set, and the water level fitting effect of each observation well is as follows. Figure 8a , 8b As shown in Figures 9a, 9b, 10a, and 10b, it can be seen that the groundwater flow field calculated by the model is basically consistent with the actual groundwater flow field. The simulated flow field basically reflects the flow characteristics of groundwater, showing good fitting and effectively reflecting the groundwater movement patterns in the study area. After model identification and verification, the hydrogeological parameters of the simulated area are zoned as follows: Figure 11 , 12 As shown in Figure 13.

[0061] Step 4: Based on the validated groundwater flow numerical model, the Drain module in GMS is used to simulate the mine drainage process, calculate and output the predicted mine water inflow.

[0062] Specifically, "normal conditions" refers to the predicted water inflow under the multi-year average precipitation conditions. The predicted coal seam is coal seam 2, in which the Cretaceous and Anding Formation aquifers have no direct hydraulic connection with the coal-bearing strata aquifers and are indirect water-bearing aquifers of the deposit. The Jurassic Middle Series Zhiluo Formation (J2z) is a pore-fracture confined aquifer, and the Jurassic Middle and Lower Series Yan'an Formation (J... 1-2 y) Confined aquifers are the directly water-bearing aquifers of mineral deposits.

[0063] The water inflow prediction for Wells 3 and 4 utilized the Drain module in GMS. By setting the water level and flow rate of the drainage wells, the process of groundwater flowing to the drainage wells was simulated to calculate the mine water inflow. The simulated mining location was located in the third layer of the model, namely the confined aquifer on the roof of Coal Mine 2. The area of ​​the initial mining section west of Well 3 was 38.84 km², and the area of ​​the initial mining section of Well 4 was 41.62 km². Drain boundaries were set in the mining sections of Wells 3 and 4, and the drainage elevation was set to the bottom of the confined aquifer on the roof of Coal Mine 2. The model was run for 20 years, and the dewatering volume was calculated based on the Zone budget of the water balance module. The output results are shown in Tables 2 and 3.

[0064] Table 2. Water Inflow Balance Table for the Initial Mining Area of ​​Mitsui

[0065] Table 3. Balance of Water Inflow in Four Wells

[0066] Based on the data analysis of the water inflow balance table in Table 2, the mine water inflow generated by the goaf formed in the early mining area of ​​Mitsui is 15445.15 m³ / d (643.55 m³ / h). Among the water inflow sources, lateral recharge accounts for 25.1%, crossflow recharge accounts for 21.8%, and reserves account for 53.1%.

[0067] Based on the data analysis of the water inflow balance table of the three wells in Table 3, the mine water inflow generated by the goaf formed in the early mining area of ​​the fourth well is 14864.6 m³ / d (611.86 m³ / h). Among the water inflow sources, lateral recharge accounts for 33.6%, crossflow recharge accounts for 23.4%, and reserves account for 43%.

[0068] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0069] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting mine water inflow based on numerical simulation, characterized in that, Includes the following steps: Step 1: Construct a hydrogeological conceptual model of the study area. The model clarifies the scope and boundary conditions of the study area, the hydrogeological structure, hydrogeological parameters, and groundwater recharge and discharge items. Step 2: Based on the hydrogeological conceptual model, a three-dimensional unsteady flow groundwater numerical model is established using the groundwater simulation software GMS, and the model is spatiotemporally discretized, while initial conditions are configured. Step 3: Using field pumping test data and hydrogeological parameters, perform parameter identification and effect verification on the groundwater flow numerical model to ensure that the model calculation results are consistent with the actual hydrogeological conditions. Step 4: Based on the validated groundwater flow numerical model, the Drain module in GMS is used to simulate the mine drainage process, calculate and output the predicted mine water inflow.

2. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, The boundary conditions in step 1 include lateral boundaries and vertical boundaries. The lateral boundaries are defined according to the hydrogeological unit boundaries, watersheds, and topographic elevations, and are divided into zero-flow boundaries and lateral outflow boundaries. The upper Quaternary aquifer roof above the vertical boundary serves as the infiltration-evaporation boundary, while the bottom of the confined aquifer under the specific coal seam roof below serves as the water-resistant boundary.

3. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, The hydrogeological structure is divided into aquifer groups and aquitards. The aquifer groups include Quaternary aquifers, Cretaceous aquifers, Jurassic aquifers and Triassic aquifers. The aquitards include a weakly permeable layer between the Quaternary and Cretaceous systems, an aquitard between the Cretaceous system and the aquifer on the roof of the coal seam, and an aquitard on the floor of the coal seam. The vertical structure of the study area is generalized into a multi-layered structural system.

4. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, The hydrogeological parameters include the permeability coefficient of the water-bearing medium, the specific yield, the atmospheric precipitation infiltration coefficient, and the groundwater evaporation depth. Groundwater recharge and discharge items include atmospheric precipitation infiltration, lateral runoff recharge and outflow, extraction and evaporation.

5. The method for predicting mine water inflow based on numerical simulation according to claim 4, characterized in that, The atmospheric precipitation infiltration rate is calculated using the following formula: ； In the formula, This represents the precipitation infiltration recharge in the i-th zone during the k-th month, in m³. Let be the precipitation infiltration coefficient corresponding to zone i; This represents the precipitation in region i for month k, in mm. Let be the area of ​​the computational region of region i, in km². The lateral runoff recharge and lateral outflow are calculated using Darcy's formula, as shown in the following equation: ； In the formula, The value represents the lateral runoff recharge, with inflow being positive. K represents the permeability coefficient near the aquifer cross section, I represents the hydraulic gradient perpendicular to the cross section, B represents the cross section length, and M represents the aquifer thickness where the cross section is located. The evaporation rate is calculated using the following formula: ； In the formula, H represents the water surface evaporation intensity; H represents the groundwater depth. denoted as the groundwater evaporation limit depth; n is an empirical constant related to soil texture and vegetation conditions, with a value ranging from 1 to 3.

6. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, The expression for the three-dimensional unsteady groundwater flow numerical model in step 2 is shown in the following equation: ； In the formula, Ω represents the study area, h represents the groundwater level, S represents the aquifer's water storage capacity, and K represents the water storage capacity of the aquifer. l K is the horizontal permeability coefficient of the aquifer. z ε is the vertical permeability coefficient of the aquifer, and ε is the source and sink term of the aquifer.

7. The method for predicting mine water inflow based on numerical simulation according to claim 6, characterized in that, The boundary conditions of the three-dimensional unsteady groundwater flow numerical model adopt two types of boundary conditions, as shown in the following expression: ； In the formula, Γ1 represents the lateral and bottom boundaries of the aquifer; n represents the inner normal direction of the aquifer; Kn represents the normal permeability coefficient of the aquifer boundary; q represents the inflow and outflow per unit area of ​​the boundary, with inflow being positive and outflow being negative, and zero for impermeable boundaries; For unsteady groundwater flow, the initial conditions for groundwater flow are as follows: ； In the formula, h0 is the groundwater level at the initial moment of the aquifer.

8. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, In step 2, the model is spatiotemporally discretized, and the initial conditions are configured as follows: spatial discretization is performed using a structured grid with a grid size of 200m×200m, the simulation period covers more than 10 years, the stress period is defined as a natural month, and one time step is set for each stress period.

9. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, Step 3 specifically includes the following steps: Step 3.1: Using the hydrogeological parameters obtained from the field pumping test and hydrogeological report as initial inputs, run the groundwater flow numerical model to calculate the groundwater flow field, groundwater level dynamic data and aquifer storage capacity. Step 3.2: Compare the simulated groundwater flow field, groundwater level dynamic data, and aquifer storage with the actual groundwater flow field, groundwater level change trend, and groundwater recharge and discharge difference data. If the two are consistent, the verification criteria are met. Step 3.3: If the verification criteria are not met, adjust the hydrogeological parameters and boundary conditions, and run the model repeatedly until the verification criteria are met, thus completing the model calibration.

10. The method for predicting mine water inflow based on numerical simulation according to claim 1, characterized in that, In step 4, the Drain module in GMS is used to simulate the mine drainage process and calculate and output the predicted mine water inflow. Specifically, the Drain module in GMS is enabled, the drainage area is accurately defined as the mining section of the target coal seam, and the drainage elevation is set as the bottom elevation of the pressure aquifer on the roof of the target coal seam, so as to simulate the process of groundwater flowing into the goaf during the mining process. Next, a groundwater flow numerical model that has passed the prediction cycle is set up; the total amount of groundwater drainage in the drainage area during the simulation period is quantitatively calculated using the Zone budget water balance module of GMS, and the specific value of mine pit water inflow is finally output. At the same time, based on the analysis results of the Zone budget water balance module, the composition ratio of water inflow sources is broken down and output.

Images