Coal mine floor water inrush risk assessment method based on multiple factors

Abstract

A coal mine floor water inrush risk assessment method based on multiple factors includes the following steps that firstly, independent coordinates of a mining area serve as a reference, a preset range is delimited to serve as a to-be-measured area, then basic data of the to-be-measured area are collected, data are obtained, meanwhile, fault fractal dimensions are generated, and a contour map of the fault fractal dimensions is generated; the method comprises the following steps of: performing quantification processing on geological structure data, floor water-resisting layer characteristic data, confined water pressure data and mining mine pressure data according to a preset weight to obtain risk scores of the data; according to the sum of the risk scores of the data, the floor water inrush risk is divided according to the total score; the method comprises the following steps: firstly calculating the water inrush critical index of each risk area of a to-be-detected area to obtain a corresponding calculation result, then verifying the calculation result and the floor water inrush risk level, if the results are consistent, carrying out risk management and control, and if the results are not consistent, re-checking data, and carrying out result correction. According to the method, multiple disaster-causing factors are combined and considered, so that the bottom plate water inrush prevention and control are accurate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coal mine safety engineering, in particular to a coal mine floor water inrush risk assessment method based on multiple factors. BACKGROUND

[0002] In the exploitation of coal resources, coalfields are generally threatened by coal seam floor confined water, especially the Ordovician limestone aquifer (referred to as "Ordovician water") has the characteristics of high water pressure (part of the mining area reaches 8~10MPa) and large water volume. Superimposed with geological structures such as faults and karst collapse columns widely developed in the minefield, floor water inrush has become one of the core disasters restricting the safe and efficient mining of coal mines. Floor water inrush is the result of the combined action of mining-induced pressure and water pressure on the floor. Mining-induced pressure causes the water-conducting fracture of the floor aquiclude to a certain depth, which reduces the rock mass strength and weakens the water-resisting performance, causing the redistribution of the floor seepage field. When the confined water further invades along the water-conducting fracture, the rock mass is softened by seepage water, causing the water-conducting fracture to continue to expand, until the minimum principal stress of the floor water-resisting rock mass is less than the water pressure of the confined water, resulting in fracturing and expansion, and water inrush.

[0003] The Chinese patent application with the application number CN202510967856.4 and the application date of July 14, 2025 discloses a rock-soil mass stability analysis method and system based on strain energy density, relating to the technical field of rock-soil mass stability analysis, including obtaining rock-soil mass parameters from field investigation and indoor test; combining the rock-soil mass parameters, the generalized Hooke's law and the Mohr-Coulomb yield criterion to obtain a strain tensor expression, and performing stress tensor calculation to obtain the elastic stress tensor, strain tensor and plastic strain tensor of the rock-soil mass; then performing integral calculation respectively to obtain the total strain energy density increment of the rock-soil mass under different stress states; based on the total strain energy density increment of the rock-soil mass under different stress states, stability analysis is performed to obtain the stability abnormal area of the rock-soil mass. The present application comprehensively considers the elastic and plastic deformation characteristics of the rock-soil mass, improving the accuracy of stability evaluation, but the above-mentioned scheme does not solve the problem that the coal mine floor water inrush risk assessment ignores the synergistic disaster-causing effect of multiple factors, resulting in inaccurate floor water inrush prevention and control. SUMMARY

[0004] The present application aims to provide a coal mine floor water inrush risk assessment method based on multiple factors that considers multiple disaster-causing factors to make floor water inrush prevention and control accurate, in order to solve the problem that the coal mine floor water inrush risk assessment ignores the synergistic disaster-causing effect of multiple factors, resulting in inaccurate floor water inrush prevention and control.

[0005] To achieve the above-mentioned purpose, the technical solution of the present application is as follows: a coal mine floor water inrush risk assessment method based on multiple factors, which comprises the following steps: The first step is to use the independent coordinates of the mining area as a reference to delineate a preset range as the area to be measured. Then, the basic data of the area to be measured are collected to obtain geological structure data, bottom aquitard characteristic data, confined water pressure data and mining pressure data. At the same time, the fault fractal dimension is generated and its contour map is generated. The second step is to quantify the geological structure data, the characteristics of the bottom aquitard layer, the pressure data of confined water, and the mining pressure data according to preset weights to obtain the risk score of each data. The third step is to divide the risk of water inrush into safe zone, transition zone and danger zone based on the total risk score of the above data. The fourth step is to first calculate the critical index of water inrush in each risk zone of the area to be tested, obtain the corresponding calculation results, and then verify the calculation results with the risk level of water inrush in the bottom plate. If the results are consistent, risk control is carried out; if the results are inconsistent, the data is rechecked and the results are corrected.

[0006] In the first step, the basic data includes geological structural data, hydrogeological data, and engineering geological data; The geological structural data includes: obtaining the original distribution map of faults and basic information on collapse columns in the area to be tested; The hydrogeological data include: Ordovician aquifer parameters and water pressure data of the bottom plate aquitard of each borehole. The engineering geological data include: coal seam depth, working face slope length, and mechanical parameters of the bottom strata.

[0007] The geological structural data includes the development characteristics of collapse columns and the distribution characteristics of faults; The distribution characteristics of the fault are processed using image analysis to obtain the fractal dimension data of the fault in the image. Then, the obtained data is processed to obtain the fractal dimension contour map of the fault within the mining area.

[0008] The mining-induced pressure data specifically refers to the depth of damage to the floor caused by mining-induced pressure, which depends on the size of the coal face, the coal seam thickness, the coal seam dip angle, the mining depth, and the lithology and structure of the roof and floor strata of the coal seam. The slope length of the coal face is the main influencing factor on the depth of floor damage, and the calculation formula is as follows:

[0009] In the formula: This refers to the depth of damage to the base plate. The inclination length of the working face; The dip angle of the coal seam; This refers to the depth of the coal seam.

[0010] When determining the depth of floor probing, in mining areas with relatively simple geological structures, the depth of floor probing is calculated based on the thickness of the safety waterproof layer of the floor, using the following formula: ; In the formula: The thickness of the safety waterproof layer is expressed in meters (m). Width of the tunnel floor, in meters; The average density of the waterproof layer of the base slab, in t / m3; The average tensile strength of the waterproof layer of the base slab, in MPa; The maximum head pressure that the waterproof layer of the base slab can withstand, in MPa; During the drilling of the bottom plate, due to the relatively developed geological structure and complex geological conditions of the mine, the bottom plate exploration depth was calculated using the water inrush coefficient formula: ; In the formula: The inrush coefficient is expressed in MPa / m. For the water pressure borne by the waterproof layer of the base slab, the unit is MPa: The thickness of the waterproof layer on the base plate is in meters (m).

[0011] The data on the characteristics of the bottom slab's waterproof layer are as follows: Among the factors affecting the water-conducting failure zone of the bottom slab, the slope length of the working face is the most significant influencing factor. The single correlation coefficient between the water-conducting failure zone of the bottom slab and the slope length of the working face are both above 0.90, indicating a close correlation. The calculation formula is as follows: ; In the formula: The water-conducting failure zone of the bottom plate is measured in meters (m). The inclined length of the working face is expressed in meters (m).

[0012] The critical index for water inrush is used to predict the extent of foundation failure, which is the range of rock strata that meet the conditions for causing water inrush to the foundation. The calculation formula is as follows: ; In the formula: Indicates the critical index for water inrush; This indicates the water pressure borne by the impermeable rock mass at the bottom plate; This represents the minimum principal stress of the water-resistant rock mass at the bottom plate.

[0013] The water inrush at the bottom plate meets two conditions, as follows: First, a water-conducting channel exists. Only when the bottom water-impermeable rock layer is damaged to a certain depth and communicates with or affects the lower aquifer, will a sudden water inrush occur. Secondly, the water pressure of pressurized water. Greater than or equal to the minimum principal stress of the rock strata At this time, confined water seeps into the rock mass along the fissures, and the expansion of the confined water... The cracks gradually expand until they form a water inrush channel, causing water to rush into the bottom plate.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, a multi-factor-based method for assessing the risk of coal mine floor water inrush, a predetermined area is first defined as the test area using independent coordinates of the mining area as a benchmark. Then, basic data of the test area are collected, including geological structure data, floor aquitard characteristic data, confined water pressure data, and mining-induced mine pressure data. Simultaneously, the fault fractal dimension is generated, and its contour map is created. The geological structure data, floor aquitard characteristic data, confined water pressure data, and mining-induced mine pressure data are quantified according to predetermined weights to obtain risk scores for each data point. Based on the sum of the risk scores for each data point, the floor water inrush risk is divided into safe zones, transition zones, and dangerous zones. The critical index for water inrush in each risk zone of the test area is calculated, and the corresponding calculation results are obtained. Then, the calculation results are verified against the floor water inrush risk level. If the results are consistent, risk control is implemented; if the results are inconsistent, the data is re-checked, and the results are corrected. The advantages of this invention are as follows: Firstly, by quantifying and weighting multi-dimensional data such as geological structure, bottom aquitard, confined water pressure, and mining pressure, and combining this with fault fractal dimension contour maps to refine structural risks, we can fully cover the entire disaster chain, including water-conducting channels, water barriers, power sources, and causes of damage. Secondly, by verifying the critical water inrush index in different scenarios, we can check the risk level from a mechanistic perspective, which can reduce the risk misjudgment rate and avoid water inrush accidents caused by single-factor omissions or engineering waste caused by over-evaluation. Secondly, the risk score clearly defines the three-level classification standards of safe zone, transition zone and dangerous zone, and matches them with differentiated control measures: investigate hidden risks in advance, monitor water pressure in real time, block water inrush channels from the source, and the graded control model reduces the incidence of water inrush accidents in high-risk areas, while avoiding project delays caused by excessive control in low-risk areas. Thirdly, in response to the dynamic characteristics of working face advancement and geological condition changes during coal mining, this plan regularly adjusts the risk level by incorporating new data to ensure that the assessment results always match the actual working conditions. This allows for timely adjustments to the mine pressure risk score and simultaneous upgrades to control measures, avoiding risks caused by lagging static assessments. At the same time, accurate risk identification and control can reduce production losses caused by water inrush accidents.

[0015] Therefore, this invention takes into account multiple disaster-causing factors, making the prevention and control of water inrush on the bottom plate more precise.

[0016] 2. In this invention, a multi-factor-based method for assessing the risk of water inrush from the coal mine floor is proposed. A critical water inrush index I is established to determine whether the rock strata possess water-resistant properties. When I > 1, the water-resistant rock strata are considered damaged and no longer water-resistant. The advantages of using this method to determine the depth of floor damage are: it considers the expansion effect of confined water pressure on fissures in the rock strata; and when the floor damage area determined by this method connects to water channels or water sources, such as concealed faults or aquifers, a water inrush accident will inevitably occur, making this method more practical for determining the depth of floor damage. Therefore, this invention is simple to use and yields accurate results.

[0017] 3. In this invention, a multi-factor-based method for assessing the risk of coal mine floor water inrush, the data collection process covers all types of data, including fault / collapse column / aquifer lithology / water pressure / working face parameters, enabling assessment of different geological backgrounds such as Ordovician limestone water threats and collapse column development, dense faults and high water pressure. The water inrush critical index calculation distinguishes between three scenarios: non-structural areas, collapse column areas, and fault areas, setting differentiated thresholds for different scenarios. Furthermore, the mining pressure quantification formula can be dynamically adjusted according to the working face slope length and advance distance, adapting to various mining conditions from thin to thick coal seams and from shallow to deep mining. Therefore, this invention is adaptable and can accommodate more mining scenarios. Attached Figure Description

[0018] Figure 1 This is a distribution diagram of the collapse columns of the present invention.

[0019] Figure 2 This invention provides an average area contour map obtained after analyzing and statistically analyzing the area of ​​collapsed columns.

[0020] Figure 3 This invention is a contour map of the long axis obtained by processing the long axis length data of the collapsed column.

[0021] Figure 4 This invention is a short axis contour map obtained by processing the short axis length data of the collapsed column.

[0022] Figure 5 This is a graph showing the relationship between the minimum principal stress and the pressure of the pressurized water when the working face advances 140m.

[0023] Figure 6 This is a graph showing the relationship between the minimum principal stress and the pressure of the pressurized water when the working face of this invention advances 180m.

[0024] Figure 7 This is a schematic diagram showing the working face advancing a distance of 60m according to the present invention.

[0025] Figure 8 This is a schematic diagram showing the working face advancing 80m in this invention.

[0026] Figure 9 This is a schematic diagram of the working face advancing 180m according to the present invention.

[0027] Figure 10 This is a graph showing the relationship between the minimum principal stress and the pressure of the pressurized water when the working face of this invention advances 60m.

[0028] Figure 11 This is a graph showing the relationship between the minimum principal stress and the pressure of the pressurized water when the working face of this invention advances 110m.

[0029] Figure 12 This is a graph showing the relationship between the minimum principal stress and the pressure of the pressurized water when the working face of this invention advances 160m. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] See Figures 1 to 12 A multi-factor-based method for assessing the risk of coal mine floor water inrush includes the following steps: The first step is to use the independent coordinates of the mining area as a reference to delineate a preset range as the area to be measured. Then, the basic data of the area to be measured are collected to obtain geological structure data, bottom aquitard characteristic data, confined water pressure data and mining pressure data. At the same time, the fault fractal dimension is generated and its contour map is generated. The second step is to quantify the geological structure data, the characteristics of the bottom aquitard layer, the pressure data of confined water, and the mining pressure data according to preset weights to obtain the risk score of each data. The third step is to divide the risk of water inrush into safe zone, transition zone and danger zone based on the total risk score of the above data. The fourth step is to first calculate the critical index of water inrush in each risk zone of the area to be tested, obtain the corresponding calculation results, and then verify the calculation results with the risk level of water inrush in the bottom plate. If the results are consistent, risk control is carried out; if the results are inconsistent, the data is rechecked and the results are corrected.

[0032] In the first step, the basic data includes geological structural data, hydrogeological data, and engineering geological data; The geological structural data includes: obtaining the original distribution map of faults and basic information on collapse columns in the area to be tested; The hydrogeological data include: Ordovician aquifer parameters and water pressure data of the bottom plate aquitard of each borehole. The engineering geological data include: coal seam depth, working face slope length, and mechanical parameters of the bottom strata.

[0033] The geological structural data includes the development characteristics of collapse columns and the distribution characteristics of faults; The distribution characteristics of the fault are processed using image analysis to obtain the fractal dimension data of the fault in the image. Then, the obtained data is processed to obtain the fractal dimension contour map of the fault within the mining area.

[0034] The mining-induced pressure data specifically refers to the depth of damage to the floor caused by mining-induced pressure, which depends on the size of the coal face, the coal seam thickness, the coal seam dip angle, the mining depth, and the lithology and structure of the roof and floor strata of the coal seam. The slope length of the coal face is the main influencing factor on the depth of floor damage, and the calculation formula is as follows:

[0035] In the formula: This refers to the depth of damage to the base plate. The inclination length of the working face; The dip angle of the coal seam; This refers to the depth of the coal seam.

[0036] When determining the depth of floor probing, in mining areas with relatively simple geological structures, the depth of floor probing is calculated based on the thickness of the safety waterproof layer of the floor, using the following formula: ; In the formula: The thickness of the safety waterproof layer is expressed in meters (m). Width of the tunnel floor, in meters; The average density of the waterproof layer of the base slab, in t / m3; The average tensile strength of the waterproof layer of the base slab, in MPa; The maximum head pressure that the waterproof layer of the base slab can withstand, in MPa; During the drilling of the bottom plate, due to the relatively developed geological structure and complex geological conditions of the mine, the bottom plate exploration depth was calculated using the water inrush coefficient formula: ; In the formula: The inrush coefficient is expressed in MPa / m. For the water pressure borne by the waterproof layer of the base slab, the unit is MPa: The thickness of the waterproof layer on the base plate is in meters (m).

[0037] The data on the characteristics of the bottom slab's waterproof layer are as follows: Among the factors affecting the water-conducting failure zone of the bottom slab, the slope length of the working face is the most significant influencing factor. The single correlation coefficient between the water-conducting failure zone of the bottom slab and the slope length of the working face are both above 0.90, indicating a close correlation. The calculation formula is as follows: ; In the formula: The water-conducting failure zone of the bottom plate is measured in meters (m). The inclined length of the working face is expressed in meters (m).

[0038] The critical index for water inrush is used to predict the extent of foundation failure, which is the range of rock strata that meet the conditions for causing water inrush to the foundation. The calculation formula is as follows: ; In the formula: Indicates the critical index for water inrush; This indicates the water pressure borne by the impermeable rock mass at the bottom plate; This represents the minimum principal stress of the water-resistant rock mass at the bottom plate.

[0039] The water inrush at the bottom plate meets two conditions, as follows: First, a water-conducting channel exists. Only when the bottom water-impermeable rock layer is damaged to a certain depth and communicates with or affects the lower aquifer, will a sudden water inrush occur. Secondly, the water pressure of pressurized water. Greater than or equal to the minimum principal stress of the rock strata At this time, the confined water seeps into the rock mass along the fissures. Under the expansion effect of the confined water, the fissures gradually expand until they form a water inrush channel, causing water inrush to the bottom plate.

[0040] The classification of water inrush risk levels is as follows: When the water inrush coefficient is less than 0.06 MPa / m, it is a safe zone for pressurized mining; When the water inrush coefficient is greater than or equal to 0.06 MPa / m and less than 0.10 MPa / m, it is a transition zone for pressurized mining. When the water inrush coefficient is greater than 0.10 MPa / m, it is a water inrush hazard zone during pressurized mining.

[0041] The critical index for water inrush is used to determine whether water inrush has occurred. That is, the relationship between the minimum principal stress of the bottom water-resistant rock mass and the water pressure of the confined water is used to determine whether water inrush has occurred. When the ratio of water pressure to minimum principal stress is greater than 1, it is considered that the water-resistant rock layer has been destroyed and the rock layer no longer has water-resistant properties.

[0042] The supplementary technical features of this invention are as follows: The critical index formula for water inrush based on water pressure and minimum principal stress ratio is: I=P x / σ², where I is the critical index for water inrush, P xFor the water-resistant rock mass to withstand water pressure, σ2 is the minimum principal stress. The judgment criteria are: when I>1, the water-resistant rock layer is damaged, that is, it loses its water-resistant properties; when I≤1, the water-resistant properties are intact. This formula is the first to consider the expansion effect of confined water on the fracture. For example, in the scenario with a collapse column, I=3.33>1, which is judged as a medium risk of water inrush. It is more in line with the water inrush mechanism than the traditional water inrush coefficient method.

[0043] Example 1: A multi-factor-based method for assessing the risk of coal mine floor water inrush, comprising the following steps: The first step is to use the independent coordinates of the mining area as a reference to delineate a preset range as the area to be measured. Then, the basic data of the area to be measured are collected to obtain geological structure data, bottom aquitard characteristic data, confined water pressure data and mining pressure data. At the same time, the fault fractal dimension is generated and its contour map is generated. The second step is to quantify the geological structure data, the characteristics of the bottom aquitard layer, the pressure data of confined water, and the mining pressure data according to preset weights to obtain the risk score of each data. The third step is to divide the risk of water inrush into safe zone, transition zone and danger zone based on the total risk score of the above data. The fourth step is to first calculate the critical index of water inrush in each risk zone of the area to be tested, obtain the corresponding calculation results, and then verify the calculation results with the risk level of water inrush in the bottom plate. If the results are consistent, risk control is carried out; if the results are inconsistent, the data is rechecked and the results are corrected.

[0044] Example 2: Example 2 is basically the same as Example 1, except that: The distribution characteristics of collapse columns were also analyzed using image analysis methods. Specifically, the area, major axis, and minor axis data of the collapse columns in the images were obtained using Image-ProPlus 6.0 software. First, using the independent coordinates of the mining area as the standard, such as... Figure 1 As shown, the distribution map of collapse columns within the range of 92500m≤x≤103500m and 81000m≤y≤93000m was statistically analyzed. The image was divided into equal parts in units of 2000m x 2000m, resulting in 30 images. The remaining part was then divided into units of 1000m x 2000m, resulting in 6 images, for a total of 36 images. The area, major axis, and minor axis data of each of the 36 images were then obtained using software. Finally, the obtained data was processed using software to obtain contour maps of the collapse columns within the mining area. The geological structure scores are as follows: Fault fractal dimension: A fractal dimension < 1.0 is assigned 10 points (low risk), 1.0-1.2 30 points (medium risk), and > 1.2 50 points (high risk). Working face 8419 is located in the central part of the mine field, with a fault fractal dimension of 1.3, earning 50 points. Multiplying this by a weight of 0.18, it receives 9 points. Collapse column development density: The number of collapse columns per unit area is set to < 0.1 / km². 2 10 points, 0.1-0.3 units / km 2 30 points, >0.3 units / km 2 The score is 50 points. The density of collapse columns around the 8419 working face is 0.4 per km. 2 50 points, multiplied by a weight of 0.17, equals 8.5 points; Total score for geological structure: 9 + 8.5 = 17.5 points; The scores for the waterproofing characteristics of the base slab are as follows: Waterproof layer thickness: 10 points are awarded for thicknesses > 50m, 30 points for thicknesses between 45-50m, and 50 points for thicknesses < 45m. The waterproof layer thickness of the bottom plate of working face 8419 is 47.83m, earning 30 points. Multiplying this by a weight of 0.13, the score is 3.9 points. Tensile strength of the impermeable layer: 10 points are set for strength > 8MPa, 30 points for 5-8MPa, and 50 points for < 5MPa. The impermeable layer in this area is mainly composed of sandy mudstone with a tensile strength of 8.94MPa, which is 10 points. Multiplying by the weight of 0.12, it is 1.2 points. Total score for waterproof layer characteristics: 3.9 + 1.2 = 5.1 points; The water pressure score for confined water is as follows: The water pressure is set at 10 points for <0.5MPa, 30 points for 0.5-1.0MPa, and 50 points for >1.0MPa; the water pressure at working face 8419 is 0.909MPa (data from borehole 41 in Table 2-8), which gives 30 points. Multiplying this by a weight of 0.25 gives 7.5 points. The mining pressure score is as follows: The score is set as follows: 10 points for a base plate failure depth <20m, 30 points for 20-25m, and 50 points for >25m; the base plate failure depth of this working face is 24m, so it gets 30 points, which, multiplied by a weight of 0.15, gives it 4.5 points. The total risk score is calculated and divided into zones as follows: Total risk score: 17.5 + 5.1 + 7.5 + 4.5 = 34.6 points; Zoning criteria: A total score of <20 points is designated as a safe zone, 20-40 points as a transition zone, and >40 points as a danger zone. Working face 8419 scored 34.6 points and was classified as a transition zone.

[0045] pass Figure 2It can be seen that the area of ​​collapse columns in the northern, northeastern, eastern, central, and southwestern parts of the current mining area is relatively large, reaching over 5000 m2, indicating that collapse columns are relatively well-developed in these areas; while the area of ​​collapse columns in some areas of the northwest and southeast of the mining area is less than 3000 m2, indicating that collapse column development is relatively weak. Furthermore, through... Figure 3 , Figure 4 The distribution of the major and minor axis contour lines shows that the major and minor axis lengths of the collapse columns are relatively large in the northeastern, eastern, southwestern, and central parts of the well field, with the major axis length exceeding 85m and the minor axis length exceeding 50m, indicating that the collapse columns are relatively well-developed in these areas. In contrast, the major and minor axis lengths of the collapse columns are smaller in the northwestern and southeastern parts of the well field, indicating that the collapse columns are relatively weaker. In summary, the distribution characteristics of the collapse columns shown in the figure are basically consistent.

[0046] Example 3: Example 3 is basically the same as Example 1, except that: Based on the maximum bottom plate failure depth of 24m, and combined with the critical water inrush index, it is determined whether water inrush will occur. That is, when the numerical simulation working face advances from 0m to 200m, the minimum principal stress value and water pressure value at 24m below the bottom boundary of the coal seam are statistically analyzed, and the possibility of water inrush is determined by combining the critical water inrush index.

[0047] Numerical simulation results show that when the working face advances less than 140m, the minimum principal stress at 24m below the bottom boundary of the coal seam is greater than the water pressure, and no water inrush occurs. This will be illustrated using a working face advance distance of 140m as an example. Figure 5 The graph shows the relationship between the minimum principal stress at 24m below the bottom boundary of the coal seam and the pressure of the confined water when the working face advances 140m. The graph shows that from 0m to 140m of the working face, the ratio of the confined water pressure to the minimum principal stress is greater than 1, indicating that no water inrush will occur when the working face advances 140m.

[0048] When the advancing distance is greater than 140m, the minimum principal stress value in a certain range 24m below the bottom boundary of the coal seam is less than the water pressure value. However, the water pressure value in this range is very small (basically maintained between 0.16-0.15MPa), so the probability of large-scale water inrush is low. Moreover, as the advancing distance of the working face increases, the range of water inrush gradually increases. Taking the monitoring point data at 24m below the bottom of the coal seam (maximum failure depth), σ2=2.1MPa, P x =0.15MPa, I=0.15 / 2.1≈0.07<1, indicating no risk of water inrush, consistent with the results of the risk zoning (transition zone).

[0049] This explanation will be based on an example of a working face advancing 180m. Figure 6This is a graph showing the relationship between the minimum principal stress and the pressure of the confined water at a point 24m below the bottom boundary of the coal seam when the working face advances 180m. The graph shows that between 70m and 106m of working face advancement, the pressure of the confined water is less than the minimum principal stress, meaning the ratio is less than 1. This indicates a possibility of water inrush at the 180m advancement point. The monitoring point has σ² = 0.14MPa (local tensile stress of -0.02MPa). x =0.16MPa, I=0.16 / 0.14≈1.14>1, but the water pressure value is only 0.16MPa, which is judged as "potential water seepage risk". Supplementary grouting reinforcement measures for the bottom plate are required, and the risk level is revised to "transition zone - prevention and control required". Taking the compressive stress direction as positive, the figure shows that the minimum principal stress has a negative value, indicating that the previous compressive stress has changed to tensile stress. This is because the mine pressure and confined water below the goaf exert upward pressure, causing the bottom strata to bulge upwards towards the goaf side. The tensile stress generated by the upward bending of the top interface of the strata below the goaf creates tensile cracks, further increasing the possibility of water inrush. However, simulation results show that between 70m and 106m of working face advance, although the minimum principal stress is less than the confined water pressure, the water pressure is only about 0.15MPa within this range, and the distance from the bottom of the coal seam is 24m, so the probability of water inrush is relatively small.

[0050] Example 4: Example 4 is basically the same as Example 1, except that: The pressure of the confined water at the bottom boundary of the model was set to 2 MPa, and the pressure in the concealed fault was set to 0.8 times the pressure at the bottom boundary. As the working face advanced, the initial water pressure distribution on the floor was less affected by the concealed fault. Influenced by the layered distribution of the rock strata, the water pressure distribution also exhibited layered characteristics, decreasing closer to the floor. When the working face advanced beyond a certain distance, the influence of the collapse column on the floor pressure distribution gradually increased. Taking an 80m advance as an example, the water pressure at a depth of 15m below the floor at the mining end of the working face gradually rose to approximately 0.27 MPa. When the working face advanced to 90m, it completely passed through the concealed fault. Afterward, as the working face advanced, the water pressure at the highest point of the collapse column remained at approximately 0.2 MPa. When the working face approached the concealed fault, the water pressure on the coal seam floor increased. When the fracture zone connected with the fault to form a water-conducting channel, a water inrush accident might occur. Subsequently, by changing the confined water pressure value at the bottom boundary of the model (0.3MPa-2MPa), the water pressure distribution characteristics in the formation were consistent with those at 2MPa. The only difference was that the lower the confined water pressure, the lower the water pressure on the bottom plate of the coal seam, and the lower the probability of water inrush accidents. Similarly, based on the calculated maximum floor failure depth of 24m, the occurrence of a water inrush is determined using a critical water inrush index. This index is determined by the relationship between the minimum principal stress of the water-resistant rock mass in the floor and the pressure of the confined water. When the ratio of water pressure to minimum principal stress is greater than 1, the water-resistant rock layer is considered to be damaged and no longer water-resistant. In the numerical simulation, as the working face advances from 0m to 200m, the minimum principal stress and water pressure values ​​at 24m below the bottom boundary of the coal seam are statistically analyzed, and the probability of a water inrush is determined by combining this with the critical water inrush index.

[0051] The pressure of the confined water at the bottom boundary of the model was set to 2 MPa. According to the numerical simulation results, when the working face advance distance is less than 70m, the minimum principal stress 24m below the bottom boundary of the coal seam is greater than the pressure of the confined water, and no water inrush occurs. This will be illustrated using a working face advance distance of 60m as an example. Figure 10 The graph shows the relationship between the minimum principal stress and the pressure of the confined water when the working face advances 60m. The graph indicates that the ratio of the minimum principal stress to the pressure of the confined water is greater than 1, meaning that a sudden water inrush will not occur.

[0052] When the advance distance is between 70-140m, the damaged area of ​​the floor slab is not connected to the concealed fault. However, the pressure of the confined water in a certain area below the goaf is greater than the minimum principal stress, but the pressure value is relatively small, and it is 24m away from the goaf, so the possibility of water inrush is small. When the working face is between 38m-79m, the ratio of the minimum principal stress to the pressure of the confined water is less than 1, indicating that water inrush may occur in this goaf area. However, the water pressure value in this area is between 0.08-0.13MPa, and it is far from the goaf, so the possibility of large-scale water inrush is not high.

[0053] When the advance distance exceeds 140m, the damaged area of ​​the floor slab is connected to the concealed fault, and the pressure of the confined water in a portion of the area below the goaf is greater than the minimum principal stress, increasing the probability of water inrush. However, the confined water pressure is relatively low at this point, and the area is 24m away from the goaf, so the possibility of a large-scale water inrush is low. Between 53m and 102m in the working face, the ratio of the minimum principal stress to the confined water pressure is less than 1, and the fault is connected to the depth of damage in this range. Therefore, the probability of water inrush within this goaf area is relatively high. However, the water pressure in this range is between 0.07 and 0.13 MPa, and the area is far from the goaf, so the possibility of a large-scale water inrush is considered low.

[0054] Example 5: Example 5 is basically the same as Example 1, except that: Assessment Area Background Within the closed area of ​​the No. 15 coal seam at Wulin Well in Yangquan No. 5 Mine (x: 98000-100000m, y: 82000-84000m), there are 22 areas of water accumulation in the goaf (area 588920.6m²).2 The water volume is 326,179.9 m³. 3 The bottom elevation of the goaf is 400-420m, the water level of the lower Ordovician limestone is 410m, the thickness of the aquitard is 46.93-47.96m, the water pressure is 0.657-1.151MPa, and the F5 reverse fault (N65°E, NW44°, drop 9.0m) is developed in the area. With a weight of 0.15, the sub-factors include water head pressure (weight 0.08) and connectivity between the accumulated water and the Ordovician limestone water (weight 0.07). Water head pressure in the goaf: water depth is 5m, water pressure is 0.05MPa, and <0.1MPa is set as 10 points, so 10 points × 0.08 = 0.8 points are obtained; Connectivity: Geophysical exploration shows that the water accumulation area is not directly connected to the Ordovician limestone water (apparent resistivity > 30 Ω·m). Set "no connection" as 10 points, and get 10 points × 0.07 = 0.7 points; Total score for water accumulation in the goaf: 0.8 + 0.7 = 1.5 points.

[0055] Total risk score calculation (original weighting system adjusted to: geological structure 0.3, aquitard 0.25, Ordovician limestone water pressure 0.2, mining-induced ore pressure 0.1, goaf water accumulation 0.15) Geological structure: 17.0 points (fractal dimension of faults 1.2, density of collapse columns 0.2 / km²) 2 ) × 0.3 = 5.1 points; Waterproof layer of the base slab: 5.1 points × 0.25 = 1.275 points; Ordovician limestone water pressure: 30 points (0.8MPa) × 0.2 = 6 points; Mining-induced pressure: 4.0 points (damage depth 20m) × 0.1 = 0.4 points; Water accumulation in the goaf: 1.5 points × 0.15 = 0.225 points; Total risk score: 5.1 + 1.275 + 6 + 0.4 + 0.225 = 13.0 points (safe zone).

[0056] Verification of critical index for water inrush Simulating a scenario where water accumulation in a goaf is "potentially connected" with Ordovician limestone water (assuming activation of the F5 fault): After connection, the total water pressure is 0.05 + 0.8 = 0.85 MPa, σ2 = 0.18 MPa, and I = 0.85 / 0.18 ≈ 4.72 > 1. However, the water replenishment in the mined-out area is limited (326179.9m). 3 Furthermore, the waterproof layer is intact, indicating that "there is no risk of water inrush in the short term, but long-term monitoring of connectivity is required."

[0057] Monthly monitoring of water levels in the goaf (with 3 water level observation wells), and cross-well CT detection every six months to check fault connectivity; Two grouting holes (50m deep) were constructed within a 20m range on both sides of the F5 fault. Cement grout was injected to seal potential cracks. The permeability after grouting should be <1Lu.

[0058] Example 6: Example 6 is basically the same as Example 1, except that: The present invention also includes the construction of a waterproof layer for the base plate, as detailed below: I. Drilling construction, 1. The diameter of the borehole for the water pressure test should be 60mm~150mm. The diameter of the drill bit in this test is 75mm.

[0059] 2. For water pressure test drilling, diamond drilling or cemented carbide drilling should be used. When drilling the test section, clean water drilling should be used, and bentonite, plant glue and other wall protection materials should not be used.

[0060] 3. Drill vertically to the effective water-tight test section below the water-conducting failure zone of the bottom plate, with a test section length of 3-5m.

[0061] II. Drilling Flushing and Hole Wall Observation 1. After drilling, the flushing drill bit should be lowered to the bottom of the hole, and the flow rate should be greater than the drilling water supply. The hole should be flushed until the return water at the hole opening is clean. If there is no return water at the hole opening, the flushing time should not be less than 15 minutes.

[0062] 2. If conditions permit, lower a borehole inspection instrument to observe the integrity of the borehole wall and the development of fractures.

[0063] III. Test Section Isolation 1. Install packers or water-stop plugs. The plugs should be accurately positioned and preferably installed in areas where the rock is relatively intact.

[0064] 2. When using hydraulic or pneumatic plugs, the hydraulic or pneumatic pressure should be 0.5 MPa higher than the maximum test pressure, i.e., the conventional water pressure test is 1.5 MPa. The plug pressure should remain constant during the test.

[0065] For example, when using a hydraulic embolism, water is injected into the packer and pressurized to expand it, preventing water from seeping through the packer and borehole wall during testing. The overflow valve is opened, the water pump is started, the vent valve is opened, and water is then supplied to the test section. After sufficient venting and continuous water flow from the vent valve, it is then closed.

[0066] IV. Water Level Observation 1. Before inserting the plug, the water level in the borehole should be observed once. After the test section is isolated, the water level in the working pipe should be observed again.

[0067] 2. Water level observation in the working pipe should be conducted every 5 minutes. When the water level drop rate is less than 5 cm / min for two consecutive times, the observation work can be completed, and the final observation results should be used to determine the zero line for pressure calculation.

[0068] 3. If pressurized water is found during water level monitoring in the working pipe, the pressurized water level should be monitored. When the pressurized water level exceeds the pipe level, pressure and leakage should be monitored.

[0069] V. Test water pressure 1. The test pressure should be the maximum design pressure of 1.5 MPa, and the duration should be 15 minutes.

[0070] 2. During the experimental water pressure test, check the working condition of the water stop plug, test pipeline, instruments and machinery according to the requirements of the formal water pressure test.

[0071] 3. When embolization is ineffective, measures such as moving the embolization plug, checking the plug, replacing the plug, or filling the plug position with concrete should be taken. If the embolization plug is moved, its movement should not exceed the plug position of the previous test.

[0072] 4. Only after the trial water pressure test is successful can the formal water pressure test of the test section be carried out.

[0073] VI. Pressure and flow rate observation (routine pressure water test to measure permeability and permeability coefficient) 1. Before flow observation, the regulating valve should be adjusted to ensure that the pressure in the test section reaches the predetermined value and remains stable.

[0074] 2. The conventional water pressure test for boreholes shall be conducted using the five-point method, namely, three pressure levels of 0.3MPa-0.6MPa-1.0MPa-0.6MPa-0.3MPa and five stages.

[0075] 3. Flow rate observation should be conducted every 1 minute for five consecutive times. When the flow rate shows no continuous increasing trend, and the difference between the maximum and minimum values ​​among the five flow rate readings is less than 10% of the final value, or the difference between the maximum and minimum values ​​is less than 1 L / min, the seepage flow rate is considered to have stabilized, and the test at this pressure level can be terminated. The final value is taken as the calculated value. If the above conditions are not met, observations must continue until the conditions are met.

[0076] 4. Adjust the pressure of the test section to the next level of pressure value, and repeat the above process until the test section is completed.

[0077] Example 7: A multi-factor-based coal mine floor water inrush risk assessment device, comprising a memory and a processor; The memory is used to store computer program code and transmit the computer program code to the processor; The processor is configured to execute, according to instructions in the computer program code, a multi-factor-based coal mine floor water inrush risk assessment method described in Embodiment 1.

[0078] Example 8: A computer-readable storage medium stores a computer program that, when executed by a processor, implements the multi-factor-based coal mine floor water inrush risk assessment method described in Embodiment 1. The computer-readable storage medium stores computer instructions that cause the computer to implement all or part of the steps of the method described in the embodiments of the present invention. The storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0079] Generally, the computer instructions for implementing the method of the present invention can be carried on any combination of one or more computer-readable storage media. Non-transitory computer-readable storage media can include any computer-readable medium except for the signal itself, which is temporarily propagating.

[0080] Computer-readable storage media can be, for example, but not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatuses, or any combination thereof. A more specific, non-exhaustive list of examples of computer-readable storage media includes: electrical connections having one or more wires; portable computer disks; hard disks; random access memory (RAM); read-only memory (ROM); erasable programmable read-only memory (EKROM or flash memory); optical fibers; portable compact disk read-only memory (CD-ROM); optical storage devices; magnetic storage devices; or any suitable combination thereof. In this invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0081] Computer program code for performing the operations of this invention can be written in one or more programming languages ​​or a combination thereof. These programming languages ​​include object-oriented programming languages—such as Java, Smarttalk, and C++—as well as conventional procedural programming languages—such as the "C" language or similar programming languages. In particular, Python, suitable for neural network computation, and platform frameworks such as TensorFlow and PyTorch can be used. The program code can be executed entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving remote computers, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or connected to an external computer, for example, via the Internet using an Internet service provider.

[0082] The aforementioned equipment and non-transitory computer-readable storage media can be found in the detailed description of a method for intelligent prediction of safety risks of surrounding rock in underground powerhouses of pumped storage power stations and its beneficial effects, which will not be repeated here.

Claims

1. A multi-factor-based method for assessing the risk of water inrush from the coal mine floor, characterized in that: The multi-factor-based coal mine floor water inrush risk assessment method includes the following steps: The first step is to use the independent coordinates of the mining area as a reference to delineate a preset range as the area to be measured. Then, the basic data of the area to be measured are collected to obtain geological structure data, bottom aquitard characteristic data, confined water pressure data and mining pressure data. At the same time, the fault fractal dimension is generated and its contour map is generated. The second step is to quantify the geological structure data, the characteristics of the bottom aquitard layer, the pressure data of confined water, and the mining pressure data according to preset weights to obtain the risk score of each data. The third step is to divide the risk of water inrush into safe zone, transition zone and danger zone based on the total risk score of the above data. The fourth step is to first calculate the critical index of water inrush in each risk zone of the area to be tested, obtain the corresponding calculation results, and then verify the calculation results with the risk level of water inrush in the bottom plate. If the results are consistent, risk control is carried out; if the results are inconsistent, the data is rechecked and the results are corrected.

2. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 1, characterized in that: In the first step, the basic data includes geological structural data, hydrogeological data, and engineering geological data; The geological structural data includes: obtaining the original distribution map of faults and basic information on collapse columns in the area to be tested; The hydrogeological data include: Ordovician aquifer parameters and water pressure data of the bottom plate aquitard of each borehole. The engineering geological data include: coal seam depth, working face slope length, and mechanical parameters of the bottom strata.

3. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 2, characterized in that: The geological structural data includes the development characteristics of collapse columns and the distribution characteristics of faults; The distribution characteristics of the fault are processed using image analysis to obtain the fractal dimension data of the fault in the image. Then, the obtained data is processed to obtain the fractal dimension contour map of the fault within the mining area.

4. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 1, characterized in that: The mining-induced pressure data specifically refers to the depth of damage to the floor caused by mining-induced pressure, which depends on the size of the coal face, the coal seam thickness, the coal seam dip angle, the mining depth, and the lithology and structure of the roof and floor strata of the coal seam. The slope length of the coal face is the main influencing factor on the depth of floor damage, and the calculation formula is as follows: ； In the formula: h is the depth of bottom plate failure; L is the inclined length of the working face; α is the dip angle of the coal seam; H is the burial depth of the coal seam.

5. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 4, characterized in that: When determining the depth of floor probing, in mining areas with relatively simple geological structures, the depth of floor probing is calculated based on the thickness of the safety waterproof layer of the floor, using the following formula: ； In the formula: The thickness of the safety waterproof layer is expressed in meters (m). Width of the tunnel floor, in meters; The average density of the waterproof layer of the base slab, in t / m3; The average tensile strength of the waterproof layer of the base slab, in MPa; The maximum head pressure that the waterproof layer of the base slab can withstand, in MPa; During the drilling of the bottom plate, due to the relatively developed geological structure and complex geological conditions of the mine, the bottom plate exploration depth was calculated using the water inrush coefficient formula: ； In the formula: The inrush coefficient is expressed in MPa / m. For the water pressure borne by the waterproof layer of the base slab, the unit is MPa: The thickness of the waterproof layer on the base plate is in meters (m).

6. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 1, characterized in that: The data on the characteristics of the bottom slab's waterproof layer are as follows: Among the factors affecting the water-conducting failure zone of the bottom slab, the slope length of the working face is the most significant influencing factor. The single correlation coefficient between the water-conducting failure zone of the bottom slab and the slope length of the working face are both above 0.90, indicating a close correlation. The calculation formula is as follows: ； In the formula: The water-conducting failure zone of the bottom plate is measured in meters (m). The inclined length of the working face is expressed in meters (m).

7. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 1, characterized in that: The critical index for water inrush is used to predict the extent of foundation failure, which is the range of rock strata that meet the conditions for causing water inrush to the foundation. The calculation formula is as follows: ； In the formula: Indicates the critical index for water inrush; This indicates the water pressure borne by the impermeable rock mass at the bottom plate; This represents the minimum principal stress of the water-resistant rock mass at the bottom plate.

8. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 7, characterized in that: The water inrush at the bottom plate meets two conditions, as follows: First, a water-conducting channel exists. Only when the bottom water-impermeable rock layer is damaged to a certain depth and communicates with or affects the lower aquifer, will a sudden water inrush occur. Secondly, the water pressure of pressurized water. Greater than or equal to the minimum principal stress of the rock strata At this time, the confined water seeps into the rock mass along the fissures. Under the expansion effect of the confined water, the fissures gradually expand until they form a water inrush channel, causing water inrush to the bottom plate.

9. The method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 1, characterized in that: The classification of water inrush risk levels is as follows: When the water inrush coefficient is less than 0.06 MPa / m, it is a safe zone for pressurized mining; When the water inrush coefficient is greater than or equal to 0.06 MPa / m and less than 0.10 MPa / m, it is a transition zone for pressurized mining. When the water inrush coefficient is greater than 0.10 MPa / m, it is a water inrush hazard zone during pressurized mining.

10. A method for assessing the risk of coal mine floor water inrush based on multiple factors according to claim 9, characterized in that: The critical index for water inrush is used to determine whether water inrush has occurred. That is, the relationship between the minimum principal stress of the bottom water-resistant rock mass and the water pressure of the confined water is used to determine whether water inrush has occurred. When the ratio of water pressure to minimum principal stress is greater than 1, it is considered that the water-resistant rock layer has been destroyed and the rock layer no longer has water-resistant properties.

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