Method for determining mining subsidence area line tower deformation disaster-causing evaluation factor

Abstract

The invention discloses a mining subsidence area line tower deformation disaster-causing evaluation factor determination method. The method comprises the following steps: step 1, preliminarily selecting an influence factor which influences the safety of a power transmission and distribution line tower; step 2, analyzing each primarily selected influence factor, judging whether the influence factor has an influence on the safety of the tower, if so, retaining the influence factor, and if not, deleting the influence factor; step 3, performing multi-collinearity analysis on each factor which affects the safety of the tower, and finally determining an evaluation factor which affects the safety of the tower; the technical problems that in the prior art, determination of the line tower deformation disaster-inducing factors in the mining subsidence area is affected by the mountain microtopography, and a previous goaf deformation research method is not completely applicable are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of transmission tower monitoring, and in particular relates to a method for determining a deformation disaster-causing evaluation factor of a line tower in a goaf collapse area. Background Art

[0002] Almost all mining areas are covered with high-voltage transmission lines. Affected by the ground subsidence in the goaf, their foundations will suffer from settlement, horizontal displacement, tilt, uneven settlement and other damage, causing the height difference between the root opening and the tower legs to change, thus threatening the safe operation of the transmission lines.

[0003] After underground mineral mining, the overburden, the surface and the surface buildings (structures) will be damaged. Taking the common coal longwall mining face as an example, after the rock strata move and stabilize, according to the severity of its damage, it can be roughly divided into collapse zone, crack zone and curved subsidence zone from bottom to top, forming a subsidence basin on the surface. If conventional methods such as leaving protection and rerouting are used to ensure the safe operation of the transmission line, it will cause problems such as increased loss of mineral resources, increased capital demand and longer cycle. In addition, the transmission tower has a small contact area with the ground and a high height. It is sensitive to the surface deformation of the goaf area. Coupled with the influence of mountain micro-topography, the previous research methods of goaf deformation are not completely applicable. Therefore, the study of the disaster-causing factors of line tower deformation in goaf collapse areas has urgent engineering application value and important practical significance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for determining the deformation disaster factors of line towers in a goaf subsidence area, so as to solve the technical problems that the determination of the deformation disaster factors of line towers in a goaf subsidence area in the prior art is affected by the mountain micro-topography, and the previous research methods for goaf area deformation are not fully applicable.

[0005] The technical solution of the present invention is:

[0006] A method for determining a deformation disaster assessment factor of a line tower in a mining-out subsidence area, the method comprising:

[0007] Step 1: Preliminarily select the factors that affect the safety of transmission and distribution line towers;

[0008] Many of the influencing factors are difficult to obtain, such as the time of suspension of mining, groundwater conditions, degree of mining, roof exposure area, exposure time, surrounding rock support measures, rock and soil structural characteristics, collapse laws, etc. These require tracking of the coal mining process at any time, and the factor data are difficult to obtain or difficult to define.

[0009] In view of the above characteristics, the present invention initially selected three types of factors, namely engineering geological factors, mining factors and tower erection factors, to conduct safety evaluation research on transmission and distribution line towers, and selected factors that are relatively easy to obtain. Among them, the engineering geological factors selected the surface slope and the inclination of the coal seam, the mining factors selected the mining depth and thickness ratio, the length of the goaf, the number of mined coal layers, and the spacing between coal seams as possible influencing factors, and the tower erection factors selected the relative position of the tower and the goaf (the horizontal distance between the center points of the goaf) and the tower spacing.

[0010] Step 2: Analyze each of the preliminarily selected influencing factors to determine whether they have an impact on the safety of the tower. If so, retain them; if not, delete them.

[0011] Before conducting a safety evaluation on the transmission and distribution line towers, it is first necessary to conduct a feasibility analysis on the selected influencing factors, mainly using numerical simulation and theoretical analysis to verify whether each factor can affect the safety of the transmission and distribution line towers. When using numerical simulation methods to verify the impact of different factors on the safety of transmission and distribution line towers, a weak rock group + a soft and hard interlayer rock group are selected, and the generalized geological model is divided from bottom to top into bedrock, coal seam, and soft and hard interlayer rock group. The selection of different lithology physical and mechanical parameters is mainly based on the research experience of existing Guizhou mining geological disaster sites and the reference of literature. Specific data are shown in Table 1. The terrain conditions in mountainous areas are complex and micro-topography will have some minor effects on surface deformation. The present invention focuses on the impact of underground mining on surface deformation and tower deformation. For this reason, the terrain of the mining area is simplified into a single straight slope surface in the numerical simulation below. On this basis, the influence of underground mining on the surface, that is, the deformation of the surface tower, under different influencing factors is explored.

[0012] The method for analyzing the various influencing factors preliminarily selected includes: conducting a feasibility analysis on the selected influencing factors, the feasibility analysis is to use numerical simulation and theoretical analysis to verify whether each factor can affect the safety of the transmission and distribution line towers, when using the numerical simulation method to verify the impact of different factors on the safety of the transmission and distribution line towers, select the weak rock group + soft and hard interlayered rock group, and divide the generalized geological model from bottom to top into bedrock, coal seam and soft and hard interlayered rock group.

[0013] Step 3: Conduct multicollinearity analysis on various factors that affect the safety of the tower, and finally determine the evaluation factors that affect the safety of the tower.

[0014] There may be a nonlinear relationship between the various factors. Therefore, in order to ensure the accuracy of the subsequent weight calculation results, it is required that the various influencing factors are independent variables, and there is no collinear relationship between the two factors. The influencing factors with higher multicollinearity are eliminated. The present invention uses multicollinearity results to evaluate the multicollinearity results between factors through variance inflation factor (VIF) and tolerance (TOL).

[0015] The method of multicollinearity analysis of various factors affecting the safety of towers includes: evaluating the multicollinearity results between factors through variance inflation coefficient and tolerance, and the tolerance is the inverse of the variance inflation coefficient. The correlation between factors is calculated using the Pearson correlation coefficient and the Spearman correlation coefficient. The calculation formulas for the variance inflation factor VIF and the Spearman correlation coefficient ρ are as follows:

[0016]

[0017] In the formula, VIF represents the variance inflation factor; A2 represents the variance between sample data; T represents the tolerance;

[0018]

[0019] In the formula, ρ represents the Spearman correlation coefficient; n represents the number of sample data; x i and i Respectively represent different sample data; and Respectively represent x i and i The average value of .

[0020] The method for analyzing various influencing factors of the primary selection includes:

[0021] Surface slope: 6 groups of models were constructed using Midas GTS finite element simulation software. The 6 groups of models maintained the same slope height. The surface slopes were 8°, 15°, 30°, 45°, 60° and 75°, respectively. The coal seam inclination was 5°, the goaf length was 200m, the mining depth-to-thickness ratio was 30, and monitoring points were set up from the bottom of the slope with a spacing of 50m. The total displacement at each surface position after underground coal mining was monitored, and the displacement change was used to determine whether it had any impact on the safety of the transmission and distribution line towers.

[0022] Coal seam inclination: Midas GTS software was used to construct seven groups of models. The coal seam inclinations of each group of models were 0°, 5°, 10°, 15°, 20°, 25° and 30°, respectively. The surface slope was 8°, the goaf length was 200m, and the mining depth-thickness ratio was 30. The underground coal seam mining was simulated. At the same time, a monitoring point was set every 50m on the slope surface starting from the top of the slope to monitor the changes in the total surface displacement of the slope in the seven groups of models. The displacement results of the strata after mining were used to determine whether the safety of the transmission and distribution line towers was affected.

[0023] Goaf length: Midas GTS software was used to construct four groups of models. The goaf lengths of each group of models were 100m, 200m, 300m and 400m, respectively. The surface slope was 8°, the coal seam inclination was 5°, and the mining depth / thickness ratio was 30. The mining conditions of underground coal seams under different goaf lengths were simulated. Starting from the top of the slope, a monitoring point was set every 50m on the slope to obtain the impact of goafs of different lengths on the total surface displacement. Based on the surface displacement results, it was determined whether the safety of the transmission and distribution line towers was affected.

[0024] Number of coal seams mined and the distance between them: Midas GTS software was used to simulate the mining of a single coal seam, two coal seams, and three coal seams. A monitoring point was set every 50 meters from the top of the slope to monitor the displacement changes of the slope when mining different numbers of coal seams. This was used as a basis to verify the feasibility of using the repeated mining of coal seams as a factor affecting the safety of transmission and distribution line towers;

[0025] Mining depth and thickness ratio: Midas GTS software was used to construct four models with mining depth and thickness ratios of 20, 30, 50 and 100. A monitoring point was set up on the slope every 50m from the top of the slope to record the changes in the displacement of the ground under the influence of different coal seam mining depth and thickness ratios, so as to determine the impact of the mining depth and thickness ratio on the safety of transmission towers.

[0026] Beneficial effects of the present invention:

[0027] Aiming at the characteristics of power transmission lines, the present invention initially selects three types of factors, namely engineering geological factors, mining factors and pole tower erection factors, to conduct safety evaluation research on power transmission and distribution line pole towers, and selects factors that are relatively easy to obtain values, wherein the engineering geological factors select the surface slope and the coal seam inclination, the mining factors select the mining depth and thickness ratio, the goaf length, the number of mined coal layers, and the coal seam spacing as possible influencing factors, and the pole tower erection factors select the relative position of the pole tower and the goaf (the horizontal distance between the center points of the goaf) and the pole tower spacing; then, by considering the influence of underground mining on the surface deformation and the pole tower deformation, the influence of underground mining on the deformation of the surface, i.e., the surface pole tower, under different influencing factors is analyzed on this basis, and finally the multicollinearity results between the factors are evaluated through the collinearity results through the variance inflation factor (VIF) and the tolerance (TOL), and the final factors are determined through the results, thereby improving the prediction accuracy of the pole tower deformation.

[0028] The invention solves the technical problems that the existing technology for determining the disaster factors of deformation of line towers in goaf subsidence areas is not completely applicable due to the influence of mountain microtopography, and the previous research methods for deformation of goaf areas are not fully applicable. DETAILED DESCRIPTION

[0029] A method for determining a disaster-causing evaluation factor of a line tower deformation in a mining-out subsidence area comprises:

[0030] Step 1: Preliminarily select the factors that affect the safety of transmission and distribution line towers.

[0031] The terrain conditions in mountainous areas are complex and the micro-topography will have some minor effects on surface deformation. The present invention focuses on the impact of underground mining on surface deformation and tower deformation. For this reason, in the numerical simulations below, the mining area terrain is simplified to a single slope surface. Based on this, the influence of underground mining on the deformation of the surface, i.e., the surface tower, under different influencing factors is explored.

[0032] Many of the influencing factors are difficult to obtain, such as the time of suspension of mining, groundwater conditions, degree of mining, roof exposure area, exposure time, surrounding rock support measures, rock and soil structural characteristics, collapse laws, etc. These require tracking of the coal mining process at any time, and the factor data are difficult to obtain or difficult to define.

[0033] In view of the above characteristics, the present invention initially selected three types of factors, namely engineering geological factors, mining factors and tower erection factors, to conduct safety evaluation research on transmission and distribution line towers, and selected factors that are relatively easy to obtain. Among them, the engineering geological factors selected the surface slope and the inclination of the coal seam, the mining factors selected the mining depth and thickness ratio, the length of the goaf, the number of mined coal layers, and the spacing between coal seams as possible influencing factors, and the tower erection factors selected the relative position of the tower and the goaf (the horizontal distance between the center points of the goaf) and the tower spacing.

[0034] Before conducting a safety evaluation on the transmission and distribution line towers, it is first necessary to conduct a feasibility analysis on the selected influencing factors, mainly using numerical simulation and theoretical analysis to verify whether each factor can affect the safety of the transmission and distribution line towers. When using numerical simulation methods to verify the impact of different factors on the safety of transmission and distribution line towers, a weak rock group + a soft and hard interlayer rock group are selected, and the generalized geological model is divided from bottom to top into bedrock, coal seam, and soft and hard interlayer rock group. The selection of different lithology physical and mechanical parameters is mainly based on the research experience of existing Guizhou mining geological disaster sites and the reference of literature. Specific data are shown in Table 1. The terrain conditions in mountainous areas are complex and micro-topography will have some minor effects on surface deformation. The present invention focuses on the impact of underground mining on surface deformation and tower deformation. For this reason, the terrain of the mining area is simplified into a single straight slope surface in the numerical simulation below. On this basis, the influence of underground mining on the surface, that is, the deformation of the surface tower, under different influencing factors is explored.

[0035] Table 1 Table of physical and mechanical parameters of rock and soil in numerical simulation model

[0036]

[0037]

[0038] Step 2: Analyze the preliminarily selected influencing factors to determine whether they have an impact on the safety of the tower. If not, delete the factors.

[0039] Surface slope:

[0040] When the surface is horizontal, the displacement shape transformation curve of the surface moving basin of the goaf area completely conforms to the standard normal distribution, and the maximum displacement deformation point is located at the center of the goaf. However, when a certain slope is formed on the surface, the initial stress field of the overlying rock strata is asymmetrically distributed, and the goaf is in a biased state. At this time, there will be a certain deviation between the settlement generated at the top of the goaf and the settlement generated under the horizontal surface. Therefore, it is believed that the surface slope is one of the main factors affecting the safety of transmission and distribution line towers. In order to determine the feasibility of surface slope as an influencing factor of transmission tower safety, 6 groups of models were constructed using Midas GTS finite element simulation software. The 6 groups of models keep the same slope height, and all use the common rock strata and slope inversion in Guizhou. The surface slopes are 8°, 15°, 30°, 45°, 60°, and 75° respectively. The other parameters are set as coal seam inclination 5°, goaf length 200m, mining depth and thickness ratio 30, and monitoring points are set from the bottom of the slope with a spacing of 50m to monitor the total displacement at each surface position after underground coal mining.

[0041] According to the displacement changes after underground coal seam mining, it can be seen that with the increase of surface slope, the impact range of mining expands, and the maximum displacement generated also expands. According to the displacement monitoring curve of the slope, it can be seen that when the surface slope is less than 30°, the slope displacement is inversely proportional to the surface slope. At this time, the change degree of the surface of the goaf is small. Since the surface slope is gentle at this time, a large area of ​​the slope will pass over the goaf, so the total displacement of the surface shows a trend of first increasing and then decreasing with the increase of the distance from the bottom of the slope; after the slope exceeds 30°, the relationship between the slope displacement and the surface slope becomes positively correlated. As the slope continues to increase, the stability of the surrounding rock continues to decrease, resulting in a significant increase in the total displacement of the slope surface. In summary, it is more feasible to use the surface slope as an influencing factor for the safety analysis of the transmission and distribution line tower. At the same time, it can be recommended that when erecting the tower, the area with a surface slope below 45° should be selected as much as possible.

[0042] Coal seam inclination:

[0043] During coal seam mining, the collapse and migration direction of the overburden will be affected by the inclination of the coal seam. The overburden will slide and rotate, and stress redistribution will occur inside it, thus presenting different forms of collapse characteristics. Therefore, under the same geological conditions and mining conditions, coal seams with different inclinations will have certain differences in displacement and deformation at the same position on the surface. Therefore, the inclination of the coal seam is determined to be one of the factors that may affect the safety of the tower.

[0044] In order to determine the feasibility of using coal seam inclination as a factor affecting the safety of transmission towers, 7 groups of models were constructed using Midas GTS software. The coal seam inclinations of each group of models were 0°, 5°, 10°, 15°, 20°, 25°, and 30°, respectively. Other factors were set as surface slope 8°, goaf length 200m, and mining depth-thickness ratio 30 to simulate underground coal seam mining. At the same time, starting from the top of the slope, a monitoring point was set every 50m on the slope surface to monitor the changes in the total surface displacement of the slope in the 7 groups of models.

[0045] According to the displacement results of the strata after mining, as the coal seam inclination increases, the impact range of coal seam mining gradually shifts to the direction perpendicular to the coal seam inclination, and the displacement of the surface on the left side of the goaf is also increasing. Overall observation of displacement monitoring shows that the relationship between the total surface displacement on both sides of the goaf and the coal seam inclination is opposite. The total surface displacement on the left side of the goaf (i.e., uphill direction) is positively correlated with the coal seam inclination, while the total surface displacement on the right side of the goaf (i.e., downhill direction) is negatively correlated with the coal seam inclination. The displacement in the uphill direction changes relatively slowly, while the displacement in the downhill direction changes rapidly. When the coal seam inclination is less than 25°, the maximum surface displacement point is located near the center of the goaf. When the coal seam inclination exceeds 25°, the closer to the top of the slope, the greater the surface displacement and gradually decreases with the increase of distance. At this time, the maximum surface displacement will also increase with the increase of the coal seam inclination, and the maximum displacement point is no longer near the center of the goaf. From this, it can be seen that the displacement and relative displacement between two adjacent towers will be different for different coal seam inclinations. Therefore, the coal seam inclination is an influencing factor of the safety of transmission and distribution line towers.

[0046] Length of goaf:

[0047] In order to explore the feasibility of using goaf length as an influencing factor for transmission tower safety, four groups of models were constructed using Midas GTS software. The goaf lengths of each group of models were 100m, 200m, 300m, and 400m, respectively. Other factors were set as surface slope 8°, coal seam inclination 5°, and mining depth and thickness ratio 30. The mining conditions of underground coal seams under different goaf lengths were simulated. Starting from the top of the slope, a monitoring point was set every 50m on the slope to obtain the influence of goafs of different lengths on the total surface displacement.

[0048] According to the displacement monitoring curve and the displacement cloud map of the slope after mining, it can be seen that the length of the goaf has a significant impact on the surface displacement. The surface displacement shows a positive correlation with the length of the goaf. In addition, as the length of the goaf continues to increase, the increase in the surface displacement also increases. Especially after the length of the goaf exceeds 300m, the growth rate of the displacement surges. In addition, since the overburden movement deformation and surface goaf collapse are transmitted from the bottom to the top of the goaf, as the length of the goaf continues to increase, the impact range of coal seam mining is also expanding. Therefore, the relative displacement of two adjacent points on the surface increases. This change is reflected in the transmission and distribution line towers, which may cause the sag offset between adjacent towers to increase. It can be determined that the length of the goaf will have a greater impact on the safety of the tower, so it is used as an influencing factor for the safety analysis of the transmission and distribution line towers.

[0049] Number of coal seams mined, spacing between coal seams (repeated mining):

[0050] Repeated mining means that the overlying rock strata and the surface have experienced a mining disturbance. After a stress redistribution, the rock strata and the surface are further damaged. The types of repeated mining can be divided into thick coal seam layered mining, parallel repeated mining and coal seam group repeated mining according to the relative position relationship of multiple repeated mining intervals. During repeated mining, the new mining will disturb the stress balance of the surrounding rock again, and the bending stiffness, cohesion and internal friction angle of the roof overburden will be reduced, which will cause the overburden to soften and the expansion performance will also be weakened. Therefore, after repeated mining, the movement characteristics of the overlying hard rock strata will change, and the more repeated times, the more obvious the change.

[0051] Midas GTS software was used to simulate the mining of a single coal seam, two coal seams, and three coal seams. A monitoring point was set every 50m from the top of the slope to monitor the displacement changes of the slope when mining different layers of coal seams. This was used as a basis to verify the feasibility of using the repeated mining of coal seams as a factor affecting the safety of transmission and distribution line towers. According to the displacement changes of the strata after mining obtained by simulation, when one coal seam is mined, the scope of mining on the surface is relatively large, but the maximum displacement at this time is the smallest. As the number of repeated mining layers increases, the scope of mining on the surface gradually becomes smaller and there is a gathering phenomenon, and the maximum displacement generated is also increasing. It can be seen from the surface monitoring curve that with the increase in the number of mining layers, the maximum displacement point on the surface gradually shifts to the uphill direction, and the displacement difference between the same distances on the surface is also increasing. It can be preliminarily judged that the sag of the transmission and distribution line may be offset due to the uneven settlement between adjacent towers, and the offset may be positively correlated with the number of coal seams mined. Therefore, it can be considered that the number of mined coal seams and the distance between coal seams (number of repeated mining layers) have a certain impact on the safety of transmission and distribution line towers.

[0052] Mining depth and thickness ratio

[0053] Under the same mining method and roof management method, the main mining factor affecting the surface movement basin is the mining depth-thickness ratio. Mining depth refers to the depth of the coal mining face from the surface, and mining thickness refers to the mining thickness of a single coal seam. Under multi-coal seam mining conditions, if the distance between coal seams is less than the influence range of the lower coal seam, the multi-layer coal seams including the interlayers between them are regarded as one layer.

[0054] 30 meters and 60 meters are often used as the standard for grading the mining depth and thickness ratio, and the mining area is divided into goaf and subsidence zones. Among them, when the mining depth and thickness ratio is less than 30 meters, the surface deformation after coal mining is strong, and sudden non-continuous deformation phenomena such as step-shaped subsidence and large cracks will occur on the surface; when the mining depth and thickness ratio is within the range of 30 to 60 meters, the surface deformation after mining is large, and the surface will generate continuous deformation, and the cracks are only distributed on the edge of the surface movement basin; when the mining depth and thickness ratio is greater than 60 meters, the surface deformation caused by coal seam mining is relatively small. In addition, studies have shown that under the same mining thickness, while the mining depth continues to increase, the surface movement and deformation gradually decrease, but the scope of influence of surface deformation will increase, and the time required for the formation to reach stability after mining will also increase.

[0055] Midas GTS software was used to construct four models with mining depth and thickness ratios of 20, 30, 50, and 100. Other geological conditions and mining conditions in the models were the same. A monitoring point was set up on the slope every 50 meters from the top of the slope to record the changes in the displacement of the ground surface under the influence of different coal seam mining depth and thickness ratios, so as to determine the impact of mining depth and thickness ratio on the safety of transmission towers. Displacement cloud map obtained by simulation.

[0056] From the simulation results, it can be seen that the surface displacement caused by underground mining is significantly negatively correlated with the mining depth and thickness ratio. The relative displacement of two adjacent points decreases with the increase of the mining depth and thickness ratio. That is, the larger the mining depth and thickness ratio, the larger the range of overburden movement, but the deformation of the surface is relatively light. On the contrary, the smaller the mining depth and thickness ratio, the smaller the range of overburden movement, but the deformation of the surface is aggravated, with a gathering phenomenon. Therefore, when analyzing the safety of transmission and distribution line towers in mining-out subsidence areas, the mining depth and thickness ratio is an influencing factor that needs to be considered.

[0057] The relative position between the tower and the goaf is the distance between the tower and the center of the goaf:

[0058] The movement and deformation of the cross-section of the surface moving basin formed after the critical full mining of the horizontal coal seam are basically symmetrically distributed about the center point of the goaf. At this time, the maximum surface subsidence point after underground mining is located at the center of the surface moving basin; the inclination value gradually increases between the boundary of the moving basin to the inflection point, decreases between the inflection point and the maximum subsidence point, and decreases to 0 at the maximum subsidence point. The maximum inclination value is located at the inflection point; the horizontal movement has the same change law as the inclination value.

[0059] The surface of mountainous areas is undulating and the terrain is changeable. Therefore, the surface movement basin formed by mining is different from the surface movement basin in flat land. Specifically, the surface movement basin in mountainous areas is irregular in shape, has a larger impact range, and the settlement at the same point is also greater. According to current research, the horizontal movement curve of the surface in mountainous areas is a curve with a central maximum value biased downhill. When the surface is tilted, the direction of the maximum displacement will shift uphill, and the surface displacement on both sides of the center line of the goaf will no longer be symmetrical, but will show a trend of being relatively gentle on the left side of the center line and relatively steep on the right side of the center line. Therefore, the position relationship of a certain point on the surface of the mountainous area relative to the goaf will have a great impact on the displacement of the point. Considering that the tower is extremely sensitive to the surface tilt deformation due to its own high height, the relative position of the tower and the goaf cannot be ignored when conducting a safety analysis of the transmission line.

[0060] Tower span

[0061] The span of a tower refers to the distance between two adjacent towers in an overhead transmission line. In the design and construction of transmission lines, the size of the span will have a direct impact on the safety of the line, and affect the safety and economy of the entire transmission line. Generally speaking, when the height of the tower is constant, the smaller the span, the smaller the range of sag variation of the conductor and the more stable it is, which makes the transmission line safer. At the same time, the number of towers required for a line will increase, and the construction cost will increase accordingly. In order to ensure the normal operation of the transmission line, the three parameters of span, sag and tower need to be considered comprehensively to ensure safe operation while minimizing costs. The operating experience of my country's transmission line industry shows that for lines with general spans, the distance between the ground conductors in the center of the span is not less than 0.012 times the span plus 1.

[0062] At the same time, the transmission and distribution line towers are generally connected in series, and the displacement changes of the two adjacent towers need to be considered at the same time when passing through the goaf and collapse area. The tower span and the relative position of a single tower from the goaf work together to affect the relative displacement of the two adjacent towers in the transmission and distribution line, thereby causing the conductor sag to shift. Therefore, all of the above factors will affect the safety of the transmission and distribution line towers, and should be considered comprehensively at the same time.

[0063] Step 3: Finalize the evaluation factors based on the preliminary influencing factors.

[0064] The present invention preliminarily determines eight influencing factors, namely, surface slope, coal seam inclination, mining depth and thickness ratio, goaf length, number of mined coal seams, coal seam spacing, relative position of pole tower and goaf (horizontal distance between center points of goaf) and pole tower spacing. There may be nonlinear relationships between the various factors. Therefore, in order to ensure the accuracy of the subsequent weight calculation results, the above eight influencing factors are required to be independent variables, and there will be no collinear relationship between the two, and the influencing factors with high multicollinearity are eliminated. The multicollinearity results are evaluated by variance inflation coefficient (VIF) and tolerance (TOL). The tolerance is the inverse of the variance inflation coefficient. The correlation between the factors can be calculated using the Pearson Correlation Coefficient and the Spearman's Rank Correlation Coefficient. Among them, the Pearson correlation coefficient measures the linear relationship between continuous variables and is applicable to normally distributed data; the Spearman correlation coefficient measures the monotonic relationship between variables, does not depend on the data distribution, is more versatile, and is applicable to nonlinear relationships or non-normally distributed data. The sample data of the internal and external factors of the slope are nonlinear, and their nonlinear correlation degree is calculated by the Spearman correlation coefficient. The calculation formulas of the variance inflation factor (VIF) and the Spearman correlation coefficient (ρ) are as follows:

[0065]

[0066] In the formula, VIF represents the variance inflation factor; A2 represents the variance between sample data; and T represents the tolerance.

[0067]

[0068] In the formula, ρ represents the Spearman correlation coefficient; n represents the number of sample data; xi and yi represent different sample data respectively; and Represent the average values ​​of xi and yi respectively.

[0069] The results of multicollinearity analysis of the above eight factors are shown in Table 2.

[0070] Table 2: Factor multicollinearity analysis results

[0071]

[0072] In all machine learning algorithms, the higher the VIF value, the stronger the collinearity between sample data. When the VIF value of a certain influencing factor exceeds a certain threshold, it means that there is multicollinearity between sample data. The present invention sets this threshold to 10. A VIF value greater than 10 may cause model instability, make it difficult to interpret model coefficients, or make the prediction effect of the model worse. At this time, in machine learning, methods such as removing high VIF influencing factors, merging related influencing factors, increasing the amount of sample data, using regularization methods, and re-evaluating model targets are often used to process sample data with multicollinearity to reduce the VIF value of sample data. The invention uses independent variables with high VIF to process data. It can be seen from the results of multicollinearity analysis between factors that the maximum VIF values ​​of the 8 evaluation factors selected by the present invention are 6.244 (coal seam spacing) and 6.063 (number of mining layers), and the VIF values ​​of the remaining factors are all around 1. Therefore, it can be judged that there is no multicollinearity between the remaining 8 factors, which does not affect the stability of model analysis.

[0073] In the Spearman correlation analysis, the correlation coefficient between variables ranges from [-1, +1], -1 indicates a completely negative correlation, +1 indicates a completely positive correlation, and 0 indicates no linear relationship. Generally, the correlation coefficient is greater than 0.85, which means that the nonlinear correlation is too large. Among the above 8 influencing factors, the correlation coefficient between the number of mining layers and the distance between coal seams is 0.997442479, which means that the positive correlation between the two is very high, with a very strong Spearman correlation, and the nonlinear correlation is too large, which will lead to unstable model analysis and affect the accuracy of the analysis results. Therefore, it is proposed to eliminate the influencing factor of the distance between coal seams to ensure the accuracy of subsequent analysis.

[0074] The final set of evaluation factors includes: surface slope, coal seam inclination, mining depth and thickness ratio, goaf length, number of mining layers, tower spacing, and the horizontal distance between the tower and the center of the goaf.

Claims

1. A method for determining the disaster-causing evaluation factor of line tower deformation in a mining-out subsidence area, characterized by: The method comprises: Step 1: Preliminarily select the factors that affect the safety of transmission and distribution line towers; Step 2: Analyze each of the preliminarily selected influencing factors to determine whether they have an impact on the safety of the tower. If so, retain them; otherwise, delete them. Step 3: Conduct multicollinearity analysis on various factors that affect the safety of the tower, and finally determine the evaluation factors that affect the safety of the tower.

2. The method for determining the disaster-causing evaluation factor of the line tower deformation in the mining-out subsidence area according to claim 1 is characterized by: The influencing factors that are initially selected to affect the safety of transmission and distribution line towers include three types of factors: engineering geological factors, mining factors and tower erection factors. Engineering geological factors include surface slope and coal seam inclination. Mining factors include mining depth and thickness ratio, goaf length, number of mined coal layers and coal seam spacing. Tower erection factors include the relative position of the tower and goaf and the tower spacing.

3. The method for determining the disaster-causing evaluation factor of the line tower deformation in the mining-out subsidence area according to claim 1 is characterized by: The method for analyzing the various influencing factors preliminarily selected includes: conducting a feasibility analysis on the selected influencing factors, the feasibility analysis is to use numerical simulation and theoretical analysis to verify whether each factor can affect the safety of the transmission and distribution line towers, when using the numerical simulation method to verify the impact of different factors on the safety of the transmission and distribution line towers, select the weak rock group + soft and hard interlayered rock group, and divide the generalized geological model from bottom to top into bedrock, coal seam and soft and hard interlayered rock group.

4. The method for determining the disaster-causing evaluation factor of the line tower deformation in the mining-out subsidence area according to claim 2 is characterized by: The method for analyzing various influencing factors of the primary selection includes: Surface slope: Midas GTS finite element simulation software was used to construct 6 groups of models. The 6 groups of models maintained the same slope height. The surface slopes were 8°, 15°, 30°, 45°, 60° and 75°, respectively. The coal seam inclination was 5°, the goaf length was 200m, the mining depth-to-thickness ratio was 30, and monitoring points were set up from the bottom of the slope with a spacing of 50m. The total displacement at each surface position after underground coal mining was monitored, and the displacement change was used to determine whether it had any impact on the safety of the transmission and distribution line towers. Coal seam inclination: Midas GTS software was used to construct 7 groups of models. The coal seam inclinations of each group of models were 0°, 5°, 10°, 15°, 20°, 25° and 30°, respectively. The surface slope was 8°, the goaf length was 200m, and the mining depth-thickness ratio was 30. The underground coal seam mining was simulated. At the same time, starting from the top of the slope, a monitoring point was set every 50m on the slope surface to monitor the changes in the total surface displacement of the slope in the 7 groups of models. The displacement results of the strata after mining were used to determine whether the safety of the transmission and distribution line towers was affected. Goaf length: Midas GTS software was used to construct four groups of models. The goaf lengths of each group of models were 100m, 200m, 300m and 400m, respectively. The surface slope was 8°, the coal seam inclination was 5°, and the mining depth / thickness ratio was 30. The mining conditions of underground coal seams under different goaf lengths were simulated. Starting from the top of the slope, a monitoring point was set every 50m on the slope to obtain the impact of goafs of different lengths on the total surface displacement. Based on the surface displacement results, it was determined whether the safety of the transmission and distribution line towers was affected. Number of coal seams mined and the distance between them: Midas GTS software was used to simulate the mining of a single coal seam, two coal seams, and three coal seams. A monitoring point was set every 50 meters from the top of the slope to monitor the displacement changes of the slope when mining different numbers of coal seams. This was used as a basis to verify the feasibility of using the repeated mining of coal seams as a factor affecting the safety of transmission and distribution line towers; Mining depth and thickness ratio: Midas GTS software was used to construct four models with mining depth and thickness ratios of 20, 30, 50 and 100. A monitoring point was set up on the slope every 50m from the top of the slope to record the changes in the displacement of the ground under the influence of different coal seam mining depth and thickness ratios, so as to determine the impact of the mining depth and thickness ratio on the safety of transmission towers.

5. The method for determining the disaster-causing evaluation factor of line tower deformation in a mining-out subsidence area according to claim 1 is characterized in that: The method of multicollinearity analysis of various factors affecting the safety of towers includes: evaluating the multicollinearity results between factors through variance inflation coefficient and tolerance, and the tolerance is the inverse of the variance inflation coefficient. The correlation between factors is calculated using the Pearson correlation coefficient and the Spearman correlation coefficient. The calculation formulas for the variance inflation factor VIF and the Spearman correlation coefficient ρ are as follows: In the formula, VIF represents the variance inflation factor; A2 represents the variance between sample data; T represents the tolerance; In the formula, ρ represents the Spearman correlation coefficient; n represents the number of sample data; x i and i Respectively represent different sample data; and Respectively represent x i and i The average value of .

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