A method and system for predicting and evaluating the influence of coal mining on groundwater

Abstract

The present application relates to a kind of coal seam mining influence on groundwater prediction evaluation method and system, method includes: S1, for groundwater numerical model, set the time range of groundwater flow simulation period, space range and calculation grid and each source and sink item and boundary condition during simulation period;S2, according to mining plan, drainage scheme and water-conducting fractured zone development height and the permeability coefficient of different lithology rock in strain different stages of coal seam roof and floor rock, set corresponding parameters in groundwater numerical model;S3, run groundwater numerical model, obtain the groundwater dynamic parameter of different time step of simulation area;S4, according to the groundwater dynamic parameter of each time step of simulation area obtained and the threshold range corresponding to each type of groundwater dynamic parameter pre-set, assess the influence of the time step corresponding mine water inrush on groundwater flow field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of numerical simulation, in particular to a prediction and evaluation method and system for the influence of coal seam mining on groundwater. BACKGROUND

[0002] Coal seam mining may have multiple influences on the groundwater environment, however, the influence of coal seam mining on the groundwater environment is not comprehensive in the prior art, and the existing technology cannot quantitatively and accurately evaluate the influence of mine water inrush on the groundwater flow field, etc., therefore, there is an urgent need for a prediction and evaluation method and system for the influence of coal seam mining on groundwater. SUMMARY

[0003] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present application provides a prediction and evaluation method and system for the influence of coal seam mining on groundwater.

[0004] In order to achieve the above-mentioned purpose, the main technical scheme adopted by the present application includes:

[0005] In a first aspect, the present application provides a prediction and evaluation method for the influence of coal seam mining on groundwater, comprising:

[0006] S1, for a pre-established groundwater numerical model, setting the time range, spatial range and calculation grid during groundwater flow simulation, and the source and sink items and boundary conditions during simulation in the numerical model;

[0007] S2, according to the pre-acquired coal mining scheme, drainage scheme and development height of water-conducting fractured zone, and the pre-acquired permeability coefficients of different lithology rocks in the coal seam roof and floor at different strain stages, setting the corresponding parameters in the pre-established groundwater numerical model;

[0008] S3, according to the time range, spatial range and calculation grid during groundwater flow simulation, the source and sink items and boundary conditions during simulation, and the corresponding parameters set in the pre-established groundwater numerical model, running the groundwater numerical model to simulate the evolution of the groundwater flow field during the prediction period, and obtaining the groundwater dynamic parameters of the simulation area at different time steps;

[0009] S4, according to the obtained groundwater dynamic parameters of the simulation area at each time step and the pre-set threshold range of each type of groundwater dynamic parameter, evaluating the influence of the mine water inrush corresponding to the time step on the groundwater flow field.

[0010] Preferably,

[0011] In the S1, the source and sink items specifically include: precipitation source, evaporation source, irrigation and condensation water source, and residential water mining source.

[0012] The precipitation amount is set by multiplying the N-year average precipitation amount of the simulation area by a precipitation infiltration coefficient, and the precipitation amount is input into the numerical model by using a Recharge program package;

[0013] N is a preset value, and N is greater than or equal to 2;

[0014] The evaporation amount is the M-year average evaporation amount of the simulation area, and the evaporation amount is input into the numerical model by using an Evapotranspiration program package;

[0015] M is a preset value, and M is greater than or equal to 2;

[0016] The irrigation and condensation water sources are input into the numerical model by using a Recharge program package according to the data of the model identification period;

[0017] The domestic water extraction source is input into the numerical model by using a Wells subprogram package using the data of the model identification period;

[0018] The inflow and outflow boundaries are set using the data at the end of the model identification period.

[0019] Preferably,

[0020] The pre-acquired permeability coefficients of different lithologies of the coal seam roof and floor rocks at different strain stages include: a first permeability coefficient corresponding to each of a coarse sandstone layer, a medium sandstone layer, a fine sandstone layer, a siltstone layer, a sandy mudstone layer, and a mudstone layer, respectively;

[0021] The first permeability coefficient includes an initial permeability coefficient and a stable permeability coefficient, and a ratio of the initial permeability coefficient to the stable permeability coefficient.

[0022] Preferably, the corresponding parameters set in the S2 include:

[0023] Parameters corresponding to the coal mining scheme: spatial range and time sequence of the coal mining area, coal mining speed, coal mining height, and underground water level drop caused by coal mining;

[0024] Parameters corresponding to the drainage scheme: including the position, depth, width, and drainage efficiency of the drainage ditch;

[0025] The drainage efficiency is the amount of water removed by the drainage system, which is a parameter for simulating the regulation of the underground water level by drainage;

[0026] Parameters corresponding to the development height of the water flowing fractured zone: including the development height of the east wing and west wing water flowing fractured zones calculated according to the multiple of the coal mining thickness;

[0027] The stable permeability coefficients of the different lithological rocks in the simulation area are obtained by analogy of the ratio of the initial permeability coefficient to the stable permeability coefficient of the different lithological rocks of the coal seam roof and floor rocks at different strain stages and the ratio of the initial permeability coefficient to the stable permeability coefficient of the same rock stratum in the simulation area when the rock stratum is strained.

[0028] Preferably, the groundwater dynamic parameters include water level distribution, water flow velocity and water inflow.

[0029] Preferably, the S4 specifically includes:

[0030] S41, comparing the groundwater dynamic parameters of the simulation area at any time step with a pre-set threshold range to determine whether there is a case of exceeding the threshold range;

[0031] S42, if the groundwater dynamic parameters of the simulation area are not within the pre-set threshold range, determining the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter corresponding to the time step according to the groundwater dynamic parameters of the simulation area and the threshold range corresponding thereto.

[0032] Preferably, the S42 specifically includes:

[0033] If the groundwater dynamic parameters of the simulation area are greater than the maximum value of the pre-set threshold range, the formula (1) is used to determine the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter corresponding to the time step;

[0034] The formula (1) is:

[0035]

[0036] wherein, x i is the i th groundwater dynamic parameter;

[0037] a is the minimum value of the pre-set threshold range;

[0038] b is the maximum value of the pre-set threshold range;

[0039] c i is the pre-set coefficient corresponding to the groundwater dynamic parameter x i ;

[0040] y i is the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter;

[0041] If the groundwater dynamic parameters of the simulation area are less than the minimum value of the pre-set threshold range, the formula (2) is used to determine the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter corresponding to the time step;

[0042] wherein the formula (2) is:

[0043] Preferably, the method further comprises:

[0044] S5, according to the obtained groundwater dynamic parameters corresponding to the first time step and the last time step of the simulation area during the simulation period, the influence of the mine water inflow on the groundwater flow field during the simulation period is determined by using formula (3);

[0045] wherein the formula (3) is:

[0046]

[0047] wherein x i始 is the i-th groundwater dynamic parameter corresponding to the first time step of the simulation area during the simulation period;

[0048] x i终 is the i-th groundwater dynamic parameter corresponding to the last time step of the simulation area during the simulation period;

[0049] Q is the influence value of the mine water inflow on the groundwater flow field during the simulation period.

[0050] On the other hand, the embodiment also provides an evaluation system for the influence of coal seam mining in a mining area on a groundwater flow field, comprising:

[0051] a first processor; and a memory connected in communication with the first processor;

[0052] wherein the memory stores program instructions executable by the processor, and the processor calling the program instructions can execute the evaluation method for the influence of coal seam mining in a mining area on a groundwater flow field as described above.

[0053] Preferably, the system further comprises water level sensors respectively arranged at different water level monitoring points;

[0054] wherein each water level sensor is connected with the first processor;

[0055] The first processor is further configured to determine whether the groundwater is in a leakage state according to the water level information collected by each water level sensor.

[0056] The beneficial effects of the present application are: the coal seam mining influence on groundwater prediction and evaluation method and system, because the parameters are set in the pre-established groundwater numerical model according to the pre-obtained coal mining scheme, drainage scheme and water-conducting fracture zone development height, and the pre-obtained permeability coefficient of different lithology rocks in the strain different stage of coal seam roof and floor rock; then, according to the time range, space range and calculation grid during the simulation period, the source and sink items and boundary conditions during the simulation period, and the pre-established groundwater numerical model, the evolution of the groundwater flow field during the simulation period is simulated by setting the corresponding parameters in the pre-established groundwater numerical model, and the groundwater dynamic parameters of the simulation area at different time steps are obtained; finally, according to the obtained groundwater dynamic parameters of the simulation area at each time step and the pre-set threshold range of each type of groundwater dynamic parameter, the influence of the mine water inflow on the groundwater flow field corresponding to the time step is evaluated, and compared with the prior art, the method of the present application covers the establishment of the groundwater numerical model, the setting of the parameters, the running of the model and the evaluation of the water inflow, and considers many factors, so that the analysis is more comprehensive and comprehensive. Through the establishment and running of the numerical model, the method can provide quantitative groundwater dynamic parameters, which helps to more accurately evaluate the influence of mine water inflow on the groundwater flow field. By pre-setting the parameters, the method can flexibly adapt to different coal mining schemes, drainage schemes and geological conditions, so that the model can adapt to different actual situations. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 A coal seam mining influence on groundwater prediction and evaluation method flow chart of the present application;

[0058] Figure 2 A full stress-strain-permeability relationship curve of different lithology rocks in the present embodiment;

[0059] Figure 3 A water level observation point position schematic diagram in the present embodiment;

[0060] Figure 4 A phreatic aquifer equal water level line after one panel mining under the present mining method in the present embodiment;

[0061] Figure 5 A phreatic aquifer equal water level line after one panel mining under the present mining method in the present embodiment;

[0062] Figure 6 A phreatic aquifer equal water level line after one panel mining under the present mining method in the present embodiment;

[0063] Figure 7 A phreatic aquifer equal water level line after one panel mining under the present mining method in the present embodiment;

[0064] Figure 8 Fig. 6 is a phreatic water level contour line of the end of mining in the first and second panels under the current mining mode in the embodiment;

[0065] Figure 9 Fig. 7 is a phreatic aquifer water level contour line of the end of mining in the first panel under the height-limited mining mode in the embodiment;

[0066] Figure 10 Fig. 8 is a phreatic water level contour line of the end of mining in the first and second panels under the height-limited mining mode in the embodiment;

[0067] Figure 11 Fig. 9 is a schematic diagram of the phreatic water level change of the observation point during the mining period in the first panel under the height-limited mining mode in the embodiment;

[0068] Figure 12 Fig. 10 is a phreatic aquifer water level contour line of the end of mining in the first and second panels under the height-limited mining mode in the embodiment;

[0069] Figure 13 Fig. 11 is a phreatic water level contour line of the end of mining in the first and second panels under the height-limited mining mode in the embodiment. DETAILED DESCRIPTION

[0070] In order to better explain the present application, so as to be understood, the following will be described in detail by specific embodiments in combination with the drawings.

[0071] In order to better understand the above technical solutions, the following will describe the exemplary embodiments of the present application in more detail with reference to the drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided in order to enable a clearer, more thorough understanding of the present application and to enable the scope of the present application to be fully conveyed to those skilled in the art.

[0072] Referring to Figure 1 The embodiment provides a prediction and evaluation method for the influence of coal mining on underground water, comprising:

[0073] S1, for a pre-established numerical model of underground water, setting the time range, spatial range and calculation grid during the simulation of the underground water flow in the numerical model, and the source and sink items and boundary conditions during the simulation;

[0074] S2, according to the pre-acquired coal mining scheme, drainage scheme and development height of water-conducting fractured zone, and the pre-acquired permeability coefficients of different lithology rocks in the coal seam roof and floor at different stages of strain, setting the corresponding parameters in the pre-established numerical model of underground water;

[0075] S3, according to the time range, space range and calculation grid during the simulation of the groundwater flow, the source and sink items and boundary conditions during the simulation, and setting corresponding parameters in the pre-established numerical model of groundwater, running the numerical model of groundwater, simulating the evolution of the groundwater flow field during the prediction period, and obtaining the groundwater dynamic parameters of the simulation area at different time steps; in the embodiment, the groundwater dynamic parameters include water level distribution, water flow velocity and water inflow.

[0076] S4, according to the obtained groundwater dynamic parameters of the simulation area at each time step and the pre-set threshold range corresponding to each type of groundwater dynamic parameter, evaluating the influence of the mine water inflow corresponding to the time step on the groundwater flow field.

[0077] In the embodiment, S4 specifically includes:

[0078] S41, comparing the groundwater dynamic parameters of the simulation area at any time step with the pre-set threshold range, and determining whether there is a case of exceeding the threshold range;

[0079] S42, if the groundwater dynamic parameters of the simulation area are not within the pre-set threshold range, determining the influence degree value of the mine water inflow corresponding to the time step on the groundwater flow field in the groundwater dynamic parameter according to the groundwater dynamic parameters of the simulation area and the threshold range corresponding thereto.

[0080] Each time step in the embodiment refers to the time unit adopted by the numerical model when simulating the groundwater flow field. The dynamic change of the groundwater system is a process of evolution over time. In order to simulate this time evolution, the numerical model will divide the entire simulation time range into many small time steps. Each time step represents a small time unit in the simulation, usually in seconds, minutes or hours, depending on the time scale selection of the model. In each time step, the model will consider and update various parameters of the groundwater system to simulate the evolution of the groundwater flow field in a short time. By dividing the entire simulation time into many small time steps, the numerical model can more accurately capture the dynamic changes of the groundwater system, especially when facing complex geological conditions and mining activities. Therefore, "each time step" is the basic unit for discretizing time in the model.

[0081] The method in the embodiment covers multiple links such as establishing a numerical model of groundwater, setting parameters, running the model, and evaluating the influence of water inrush, and considers multiple factors, so that the analysis is more comprehensive and overall. Through the establishment and running of the numerical model, the method can provide quantitative dynamic parameters of groundwater, which helps to more accurately evaluate the influence of water inrush in the mine on the groundwater flow field. By pre-setting parameters, the method can flexibly adapt to different coal mining schemes, drainage schemes, and geological conditions, so that the model can adapt to different actual situations. By establishing a numerical model of groundwater and using the numerical simulation method, the method has a certain basis in science and can more accurately reflect the changes of the groundwater flow field. The method considers factors such as the time range, the spatial range, and the calculation grid, and can provide simulation results of high spatiotemporal resolution of the dynamic changes of groundwater to a certain extent. By evaluating the influence of water inrush in the mine on the groundwater flow field, the method provides practical insights into the groundwater problems that may be caused by coal mining activities and provides a basis for formulating corresponding countermeasures.

[0082] In actual application, the source-sink items set in the S1 specifically include: precipitation sources, evaporation sources, irrigation and condensed water sources, and residential water mining sources.

[0083] The precipitation amount is set by multiplying the N-year average precipitation amount of the simulation area by a precipitation infiltration coefficient; the precipitation amount is input into the numerical model by using a Recharge program package; N is a pre-set value, and N is greater than or equal to 2.

[0084] The evaporation amount is the M-year average evaporation amount of the simulation area, and the evaporation amount is input into the numerical model by using an Evapotranspiration program package; M is a pre-set value, and M is greater than or equal to 2.

[0085] The irrigation and condensed water sources are input into the numerical model by using the Recharge program package according to the data of the model identification period; the residential water mining sources are input into the numerical model by using the Wells sub-program package using the data of the model identification period; and the inflow and outflow boundaries are set using the data at the end of the model identification period.

[0086] In the embodiment, the pre-acquired permeability coefficients of different lithological rocks of the coal seam roof and floor at different strain stages include: first permeability coefficients of coarse sandstone, medium sandstone, fine sandstone, siltstone, sandy mudstone, and mudstone respectively.

[0087] The first permeability coefficients include initial permeability coefficients, stable permeability coefficients, and a ratio of the initial permeability coefficients to the stable permeability coefficients.

[0088] Specifically, the corresponding parameters set in the S2 include: parameters corresponding to the coal mining scheme: spatial range and time sequence of the coal mining area, coal mining speed, coal mining height, and underground water level drop caused by coal mining; parameters corresponding to the drainage scheme: including the position, depth, width, and drainage efficiency of the drainage ditch; the drainage efficiency is the water amount drained by the drainage system, which is a parameter for simulating the regulation effect of drainage on the underground water level; parameters corresponding to the development height of the water flowing fractured zone: including the development height of the water flowing fractured zone in the east wing and the west wing calculated according to the multiple of the coal mining thickness; the stable permeability coefficient of the rock of different lithology in the simulation area is obtained by analogy by taking the ratio of the initial permeability coefficient to the stable permeability coefficient of the rock of different lithology of the coal seam roof and floor rock in the simulation area at different strain stages.

[0089] Specifically, the specific examples of the method of the embodiment are the first and second panels of the Jinchitan minefield, and the specific coal mining period is set according to the Jinchitan Coal Mine Mineral Resources Development and Utilization Scheme-1700 million tons / year, that is, the first panel is mined out in the next 11 years, and the second panel is mined out in 12.9 years after the first panel is mined out.

[0090] The coal mining scheme in the embodiment is to set two coal mining methods of the current mining method and the limited height mining method to predict and evaluate their effects on the underground water flow field and underground water resources. The drainage scheme in the embodiment is to use the Drain drainage ditch module in the working face according to the Jinchitan Coal Mine Mining Connection Scheme, and to simulate the process of the water-filled aquifer discharging to the working face according to the mine working face connection mining plan.

[0091] In the embodiment, after the coal seam is mined, the stress balance of the overlying rock is broken, the rock breaks, the water flowing fractured zone is generated to connect the overlying aquifer, the hydrogeological parameters of the water flowing fractured zone development zone are reset, the development height of the water flowing fractured zone in the east wing is calculated according to 26.07 times the mining thickness, and the development height of the water flowing fractured zone in the west wing is calculated according to 25.18 times the mining thickness.

[0092] In addition, with the mining of the coal seam, the permeability coefficient around the water flowing fractured zone generated by the breakage of the overlying rock will change, and it is necessary to reassign values in the rock fracture zone. The permeability test of the rock sample of the coal seam roof and floor of the Jurassic Yan'an group in the Shendong mining area in the whole stress-strain process is studied, and the whole stress-strain-permeability evolution curve in the deformation and failure process of each group of rock samples is obtained, as shown in Figure 2 .

[0093] The permeability coefficients of the rock of different lithology of the coal seam roof and floor of the Jurassic Yan'an group in the Shendong mining area at different strain stages are shown in Table 1. Considering that the Shendong mining area is close to the simulation area and the stratum age is consistent with the simulation area, the ratio of the initial permeability coefficient to the stable permeability coefficient Ka The stable permeability coefficient of the strata in the simulation area is obtained by analogy with the ratio of the stable permeability coefficient to the initial permeability coefficient when the strata are strained.

[0094] Table 1

[0095]

[0096] The permeability coefficient values of the rocks in the Yan'an Formation and the Zhiluo Formation-Anding Formation are also calculated by analogy with the above ratio, and the stable permeability coefficients of the rocks in the Yan'an Formation and the Zhiluo Formation-Anding Formation in the water-conducting fractured zone are obtained. The permeability coefficients of the corresponding strata are input into the model at the positions of the corresponding strata.

[0097] The numerical simulation of the groundwater in the Jinjitan Coal Mine is carried out, and four observation points of the phreatic water level are set in the model area, i.e., the water level observation point G1, the water level observation point G2, the water level observation point G3, and the water level observation point G4, as shown in Figure 3 .

[0098] Under the current mining method, the phreatic water level contour lines and the phreatic water drawdown contour lines in the simulation area after the mining of the first panel are shown in Figure 4 and Figure 5 . It can be seen from Figure 4 and Figure 5 that the general pattern of the Quaternary groundwater flowing from the northeast to the southwest does not change after the mining of the first panel, the trend of the groundwater discharging into the Yuxi River does not change, and no local or regional groundwater drawdown funnel appears. The average drawdown of the Quaternary groundwater level is 1.87 m, and the maximum drawdown is 4.38 m. In the eastern mining area, the drawdown of the Quaternary water level is the most obvious due to the large thickness of the coal seam and the large subsidence of the strata. The change trend of the Quaternary groundwater level at the observation points during the mining of the first panel under the current mining method is shown in Figure 6 . From the water level duration curve, the water level of the phreatic water observation hole decreases to different degrees during the mining of the first panel, and the drawdown of the water level is 0.82-3.33 m. The water level of the observation point G4 outside the minefield also shows a downward trend, indicating that the drawdown of the phreatic water level caused by the mining of the mine will extend outside the minefield.

[0099] Under the current mining method, the phreatic water level contour lines and the phreatic water drawdown contour lines in the simulation area after the mining of the first and second panels are shown in Figure 7 and Figure 8 . It can be seen from Figure 7 and Figure 8It can be seen that after the mining of the first and second panels was completed, the general trend of Quaternary groundwater flowing from the northeast to the southwest will not change, the trend of groundwater discharge into the Yuxi River will not change, and there will be no local or regional groundwater drawdown cones. The changes in water level mainly occurred in the eastern wing of the first and second panels and the eastern wing of the first panel. During this period, the groundwater level dropped by 0.87 to 5.48 meters, with an average drop of 2.82 meters.

[0100] Under height-restricted mining conditions, after the completion of mining in panels 11 and 12, the simulated groundwater level contour lines and groundwater drawdown contour lines are as follows: Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 As shown. From Figure 9 , Figure 10 , Figure 11 , Figure 12 , Figure 13 It can be seen that under the height-restricted mining conditions, the groundwater level drop after the completion of mining in the first panel area was smaller than that under the current mining method, with an average drop of 1.01m. From the water level change curves of the monitoring points during the mining period of the first panel area, the water level drop at each monitoring point ranged from 0.39 to 2.28m, which was smaller than the water level change under the current mining scheme. After the completion of mining in the first and second panels areas, the groundwater level drop ranged from 0.87 to 3.23m, with an average drop of 1.64m.

[0101] In summary, with the continuous mining of the No. 1 and No. 2 mining faces of the Jinjitan Coal Mine, the resulting subsidence basin is expanding, leading to a significant drop in the ecological groundwater level of the sand layers in this area. Simulations show that by the completion of mining in the No. 1 and No. 2 mining faces, the maximum drop in groundwater level within the mining area is 5.48m, located in the eastern wing of the No. 1 mining face. The drop in groundwater level in the western wing of both the No. 1 and No. 2 mining faces is smaller. Coal seam mining methods affect the drop in groundwater level; under height-restricted mining conditions, the drop in groundwater level is significantly less than under current mining methods.

[0102] The water balance of the Quaternary unconfined aquifer and the impact of coal mining on the Quaternary aquifer during each prediction period are shown in Tables 2 to 7.

[0103] Table 2 shows the equilibrium of water volume in the unconfined aquifer after the completion of mining in the current mining mode.

[0104]

[0105]

[0106] Table 3 Current Mining Methods: Water Content in the Unconfined Aquifer After Mining in the First and Second Panels is Balanced

[0107]

[0108] Table 4 Water balance of phreatic aquifer at the end of mining in each panel under the limited height mining method

[0109]

[0110] Table 5 Water balance of phreatic aquifer at the end of mining in each panel under the limited height mining method

[0111]

[0112] Table 6 Water level drawdown of Quaternary aquifer at each predicted period under the current mining scheme

[0113]

[0114] Table 7 Water level drawdown of Quaternary aquifer at each predicted period under the limited height mining scheme

[0115]

[0116] From Tables 2 to 7, it can be seen that the phreatic aquifer in the simulation area is in negative balance during mining. With the continuous increase of mining range, the total groundwater recharge decreases, the downward flow increases, and the degree of groundwater negative balance intensifies. Under the current mining conditions, the Quaternary leakage discharge is greater than that under the limited height mining method, and the increase in groundwater balance difference is obvious. Under the current mining scheme, the maximum water level drawdown of the Quaternary aquifer after the mining of the first and second panels is 5.48 m, and under the limited height mining scheme, the maximum water level drawdown of the Quaternary aquifer after the mining of the first and second panels is 3.23 m. That is, the impact of limited height mining on Quaternary groundwater resources is much smaller than that of the current mining method. After the mining of the first and second panels under the limited height mining method, the water level drawdown is about 1 / 25 of the thickness of the aquifer.

[0117] The mine inflow of Jinjitan Coal Mine is mainly composed of groundwater from directly water-filled aquifers and Quaternary groundwater leakage. Determining the proportion of Quaternary groundwater in mine inflow is of great significance for mine water disaster prevention and the impact of coal mining on groundwater resources. The predicted results of the impact of coal mining on Quaternary groundwater under different mining schemes at each predicted period are shown in Tables 8 and 9.

[0118] Table 8 Impact of coal mining on Quaternary aquifer water under the current mining method (10,000 m3) 3 / a

[0119]

[0120] From Table 8, it can be seen that under the current mining method, the Quaternary groundwater leakage caused by coal mining in the first and second panels is the largest, with a value of 991.54 million m 3 / a, accounting for the largest proportion of 41.03% of the mine inflow.

[0121] Table 9 predicts the influence of coal mining on the water quantity of Quaternary aquifer under the limited height mining mode (million m) 3 / a

[0122]

[0123] As shown in Table 9, under the limited height mining mode, the maximum transmissive flow of Quaternary groundwater caused by coal mining in the first and second panels is 711.2 million m 3 / a, and the proportion of the largest mine water inflow is 36.39%.

[0124] In summary, compared with the current mining mode, under the limited height mining mode, the transmissive flow and its proportion of the mine water inflow have decreased to different degrees, and the limited height mining is of great significance for protecting the Quaternary aquifer.

[0125] Preferably, S42 specifically comprises:

[0126] If the groundwater dynamic parameter of the simulation area is greater than the maximum value of the pre-set threshold range, the formula (1) is used to determine the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter corresponding to the time step; wherein the formula (1) is:

[0127]

[0128] wherein x i is the i-th groundwater dynamic parameter; a is the minimum value of the pre-set threshold range; b is the maximum value of the pre-set threshold range; c i is the pre-set coefficient corresponding to the groundwater dynamic parameter x i ; y i is the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter;

[0129] If the groundwater dynamic parameter of the simulation area is less than the minimum value of the pre-set threshold range, the formula (2) is used to determine the influence degree value of the mine water inflow on the groundwater flow field at the groundwater dynamic parameter corresponding to the time step;

[0130] wherein the formula (2) is:

[0131] In the practical application of the embodiment, the method further comprises: S5, according to the obtained groundwater dynamic parameters of the first time step and the last time step of the simulation area during the simulation, the influence of the mine water inflow on the groundwater flow field during the simulation is determined by using formula (3);

[0132] wherein the formula (3) is:

[0133]

[0134] wherein, xi initial is the i th groundwater dynamic parameter corresponding to the first time step of the simulation area during the simulation period; xi final is the i th groundwater dynamic parameter corresponding to the last time step of the simulation area during the simulation period; Q is the influence value of the mine water inflow on the groundwater flow field during the simulation period.

[0135] In another aspect, the embodiment also provides a system for evaluating the influence of coal seam mining in a mining area on a groundwater flow field, comprising: a first processor; and a memory in communication connection with the first processor; wherein the memory stores program instructions executable by the processor, and the processor calling the program instructions can execute the method for evaluating the influence of coal seam mining in a mining area on a groundwater flow field as described in the embodiment.

[0136] wherein, the system further comprises: water level sensors respectively arranged at different water level monitoring points; wherein each water level sensor is connected with the first processor; and the first processor is further configured to determine whether the groundwater is in a leakage state according to the water level height information collected by each water level sensor.

[0137] The real-time water level height information collected by each water level sensor is continuously monitored. The real-time water level height is compared with the preset leakage state threshold range. There can be different leakage state indicators, such as the water level exceeding a certain percentage of the normal water level, reaching a set threshold or more, etc. If the water level height exceeds or equals the set leakage state threshold, the first processor will determine that the groundwater is in a leakage state. This can trigger an alarm system or related monitoring and management measures. According to the determination result, the first processor can output corresponding information, such as the alarm information of the leakage state, the time stamp of recording the abnormal event, etc. In addition, other systems or devices can be triggered to take corresponding measures, such as automatically starting the drainage system, sending an alarm signal, etc. The determination of the leakage state is continuously updated according to the measured data. This helps to understand the changes of the groundwater flow state in real time. Water level monitoring points are arranged around the mining area to monitor the changes of the groundwater level in real time. Through water level monitoring, it can be observed whether the groundwater is in a leakage state, i.e. whether the water level shows a continuous downward trend.

[0138] Specifically, the system further comprises: a geophysical device for imaging the caving zone and the water flowing fractured zone to obtain information of the underground structure; wherein the geophysical device is connected with the first processor.

[0139] The geophysical device includes: a power supply: provides a current source, usually a battery or a generator. Electrodes: introduce current into the ground, consisting of two or more electrodes. Current measurement equipment: measures the voltage between the electrodes, usually using a multimeter or a voltmeter. Data logger: records measured current and voltage data. Support equipment for laying electrodes: such as iron rods, used to insert electrodes into the ground. Alternatively, the geophysical device includes: a sound source: a device that generates sound waves, usually a seismic source or a vibrator. Receiver: used to record the reflected or transmitted sound wave signals in the ground, usually a seismometer or receiver group. Data logger: records data such as intensity, propagation time, etc. of sound wave signals.

[0140] The coal seam mining influence prediction and evaluation method and system of the embodiment, because the corresponding parameters are set in the pre-established groundwater numerical model according to the pre-obtained coal mining scheme, drainage scheme and development height of the water flowing fractured zone and the pre-obtained permeability coefficients of different lithology rocks in the strain different stages of the coal seam roof and floor rocks; then, the evolution of the groundwater flow field during the prediction period is simulated by running the pre-established groundwater numerical model according to the time range, space range and calculation grid during the simulation period, each source and sink item and boundary condition during the simulation period and the corresponding parameters set in the pre-established groundwater numerical model, and the groundwater dynamic parameters of the simulation area at different time steps are obtained; finally, the influence of the mine water inflow corresponding to each time step on the groundwater flow field is evaluated according to the obtained groundwater dynamic parameters of the simulation area at each time step and the threshold range corresponding to each type of groundwater dynamic parameter pre-set, compared with the prior art, the method covers multiple links such as establishing a groundwater numerical model, setting parameters, running a model and evaluating water inflow influence, considers multiple factors, and makes the analysis more comprehensive and comprehensive. Through the establishment and running of the numerical model, the method can provide quantitative groundwater dynamic parameters, which helps to more accurately evaluate the influence of mine water inflow on the groundwater flow field. By pre-setting parameters, the method can flexibly adapt to different coal mining schemes, drainage schemes and geological conditions, so that the model can adapt to different actual situations.

[0141] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "first", "second" can be explicitly or implicitly included one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0142] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connection", "fixed", "unfixed", and the like should be construed broadly, for example, can be fixed connection, can be detachable connection, or integral; can be mechanical connection, can be electrical connection; can be direct connection, can be indirect connection through an intermediate medium; can be internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0143] In the present application, unless specifically defined otherwise, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature is "above", "over" and "on" the second feature, which can be directly above or obliquely above the first feature, or only indicates that the first feature is higher than the second feature in horizontal height. The first feature is "below", "under" and "under" the second feature, which can be directly below or obliquely below the first feature, or only indicates that the first feature is lower than the second feature in horizontal height.

[0144] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0145] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can modify, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for predicting and evaluating the impact of coal seam mining on groundwater, characterized in that, include: S1. For the pre-established groundwater numerical model, set the time range, spatial range, and computational grid for the groundwater flow simulation, as well as the source and sink terms and boundary conditions during the simulation. S2. Based on the pre-obtained coal mining scheme, drainage scheme, and water-conducting fracture zone development height, as well as the pre-obtained permeability coefficients of different lithologies of the coal seam roof and floor rocks at different strain stages, set the corresponding parameters in the pre-established groundwater numerical model. S3. Based on the time range, spatial range, and computational grid of the groundwater flow simulation period, the source and sink terms and boundary conditions during the simulation period, and the corresponding parameters set in the pre-established groundwater numerical model, run the groundwater numerical model to simulate the evolution of the groundwater flow field during the prediction period and obtain the groundwater dynamic parameters at different time steps in the simulation area. S4. Based on the groundwater dynamic parameters of each time step in the simulation area and the threshold range corresponding to each type of groundwater dynamic parameter, evaluate the impact of mine water inflow on the groundwater flow field at that time step. S4 specifically includes: S41. Compare the groundwater dynamic parameters at any time step in the simulation area with the preset threshold range to determine whether there is a situation that exceeds the threshold range. S42. If the dynamic parameters of groundwater in the simulation area are not within the preset threshold range, then the influence of the mine water inflow on the groundwater flow field in the dynamic parameters of groundwater corresponding to the time step is determined based on the dynamic parameters of groundwater in the simulation area and its corresponding threshold range. S42 specifically includes: If the groundwater dynamic parameters in the simulation area are greater than the maximum value of the preset threshold range, then the influence of the mine water inflow on the groundwater flow field at the groundwater dynamic parameters corresponding to the time step is determined by formula (1). Wherein, formula (1) is: ； Where, x i Let i be the i-th dynamic parameter of groundwater; 'a' is the minimum value of a pre-defined threshold range; b is the maximum value within a pre-defined threshold range; c i For the pre-set dynamic parameter x of the groundwater i The corresponding coefficient; y i The value representing the degree of influence of mine water inflow on the groundwater flow field and the dynamic parameters of the groundwater. If the groundwater dynamic parameters in the simulation area are less than the minimum value of the preset threshold range, then formula (2) is used to determine the degree of influence of the mine water inflow on the groundwater flow field on the groundwater dynamic parameters corresponding to the time step. Formula (2) is as follows: .

2. The method for predicting and evaluating the impact of coal seam mining on groundwater according to claim 1, Its features are, in, The source and sink items set in S1 specifically include: precipitation source, evaporation source, irrigation and condensate water source, and residential water extraction source; The precipitation source is defined by multiplying the N-year average precipitation of the simulated area by the precipitation infiltration coefficient; the precipitation source is input into the numerical model through the Recharge package. N is a preset value, and N is greater than or equal to 2; Wherein, the evaporation source is the average evaporation of the simulated region over M years, and the evaporation source is input into the numerical model using the Evapotranspiration package; M is a preset value, and M is greater than or equal to 2; Irrigation and condensate water sources were input into the numerical model using the Recharge package, based on data from the model identification period. The source of residential water use is determined using data from the model identification period, and the Wells subroutine package is used as input to the numerical model. The inflow and outflow boundaries are set using data identified at the end of the model period.

3. The method for predicting and evaluating the impact of coal seam mining on groundwater according to claim 2, characterized in that, The permeability coefficients of different lithologies of the coal seam roof and floor rocks at different strain stages obtained in advance include: the first permeability coefficients corresponding to each of the coarse sandstone, medium sandstone, fine sandstone, siltstone, sandy mudstone, and mudstone layers. The first permeability coefficient includes the initial permeability coefficient, the stable permeability coefficient, and the ratio of the initial permeability coefficient to the stable permeability coefficient.

4. The method for predicting and evaluating the impact of coal seam mining on groundwater according to claim 3, characterized in that, in, The corresponding parameters set in S2 include: Parameters corresponding to the coal mining plan: spatial range and timing of the coal mining area, coal mining speed, coal mining height, and groundwater level drop caused by coal mining; Parameters corresponding to the drainage scheme include: the location, depth, width, and drainage efficiency of the drainage ditch; Among them, drainage efficiency is the amount of water discharged by the drainage system, which is used to simulate the regulatory effect of drainage on the groundwater level. Parameters corresponding to the development height of the water-conducting fracture zone: including the development height of the water-conducting fracture zone in the east and west wings calculated based on multiples of the coal mining thickness; The strain-stable permeability coefficient of different lithologies in the simulation area is obtained by analogy between the ratio of the initial permeability coefficient to the stable permeability coefficient of different lithologies in the roof and floor of the coal seam at different stages of strain and the ratio of the initial permeability coefficient to the stable permeability coefficient of the same rock strata in the simulation area when strain occurs.

5. The method for predicting and evaluating the impact of coal seam mining on groundwater according to claim 4, characterized in that, The groundwater dynamic parameters include: water level distribution, water flow velocity, and water inflow.

6. The method for predicting and evaluating the impact of coal seam mining on groundwater according to claim 5, characterized in that, The method further includes: S5. Based on the groundwater dynamic parameters corresponding to the first and last time steps of the simulation area during the simulation period, the influence of mine water inflow on the groundwater flow field during the simulation period is determined by formula (3). Formula (3) is as follows: ； Where, x i始 It is the i-th groundwater dynamic parameter corresponding to the first time step of the simulation area during the simulation period; x i终 It is the i-th groundwater dynamic parameter corresponding to the last time step of the simulation area during the simulation period; Q represents the impact of mine water inflow on the groundwater flow field during the simulation.

7. An evaluation system for the impact of coal seam mining on groundwater flow field, characterized in that, include: First processor; and a memory that is communicatively connected to the first processor; The memory stores program instructions that can be executed by the processor, and the processor can execute the prediction and evaluation method for the impact of coal seam mining on groundwater as described in any one of claims 1-6 by calling the program instructions.

8. The evaluation system for the impact of coal seam mining on groundwater flow field according to claim 7, characterized in that, The system also includes: water level sensors installed at different water level monitoring points; Each water level sensor is connected to the first processor. The first processor is also used to determine whether the groundwater is in an overflow state based on the water level height information collected by each water level sensor.

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