Method for risk zoning and grading assessment of goaf collapse disasters

Abstract

The present invention provides a method for risk zoning and grading assessment of goaf collapse disasters, which determines the instability probability of each ore pillar in the goaf. Assuming the instability of any ore pillar, the method of repeated iterative instability is used to judge the situation of the instability of the remaining ore pillars caused by the instability of this ore pillar until the instability terminates; then the number of induced ore pillars in the remaining ore pillar group is determined, and the disaster consequence value of the ore pillar is calculated; and the disaster consequence values of all ore pillars are obtained in the above manner, and the instability risk weight value of each ore pillar is calculated; finally, the risk levels of all ore pillars in the goaf are determined, and a risk zoning and grading cloud map of goaf collapse disasters is obtained. Based on the theory of ore pillar group stability and considering the uncertainty of ore pillar strength, the present invention quantifies the potential of goaf collapse, especially the potential of chain collapse of the goaf induced by the instability of a single ore pillar, by introducing induced ore pillars, realizes the risk zoning and grading assessment of goaf chain collapse disasters, and can be used to guide relevant personnel to conduct differential treatment of areas with different risk levels.

Description

Technical Field

[0001] The present invention relates to the technical field of underground mine disaster risk assessment, and particularly relates to a method for zoning and grading assessment of goaf collapse disaster risks. Background Art

[0002] Continuous large-scale exploitation of underground mineral resources often leaves behind a huge number of goafs with complex spatial distributions. Ore pillars are the main supporting units of goafs, bearing the weight of the entire overlying rock stratum of the goafs and playing a crucial role in the stability of goafs. With the deformation and deterioration of the bearing units of goafs, large-scale collapse disasters of goafs are extremely likely to be induced, seriously threatening the safety and sustainable development of mining areas. However, due to the complexity of goaf shapes and geological structures and the uncertainty of ore pillar strengths, there is still a lack of a scientific and reasonable method for assessing the risk of goaf collapse disasters, and it is impossible to carry out refined treatment of different risk areas, making it extremely difficult to prevent and control goaf disasters and frequent large-scale collapse accidents in mines.

[0003] A patent for invention (application number: CN 201910899938.4) discloses a method for identifying dangerous ore pillars in goafs, which calculates the instability risk of ore pillars by combining the instability probability of single ore pillars and the consequences of instability (the loss of the bearing area of the remaining ore pillars in the ore pillar group after the instability of the ore pillar), and realizes the identification of dangerous ore pillars. However, this method does not further conduct a risk assessment on the goaf chain collapse disaster induced by the instability of individual point pillars. In fact, there are not many current risk assessment studies on goaf collapse disasters, especially chain collapse disasters. Two important reasons are summarized as follows: (1) It is difficult to quantify the potential for the occurrence of chain collapse disasters. Taking the loss of the bearing area of the goaf roof exposed by the instability of a single ore pillar as the disaster consequence can intuitively reflect the direct impact of ore pillar instability on the goaf, but it ignores the weakening of the bearing capacity of the remaining stable ore pillar group after local collapse of the goaf caused by the instability of a single ore pillar, and it is impossible to further quantitatively evaluate the potential for chain instability of the ore pillar group to cause goaf chain collapse disasters; (2) It is difficult to determine the specific risk value and risk interval of goaf collapse disasters, especially chain collapse disasters. Different from traditional risk grading assessments that can obtain a large amount of historical data and establish a connection between risk values and disaster consequences, the chain collapse of goafs is a large-scale and relatively rare disaster event, and it is difficult to obtain relevant bases for determining the risk threshold.

[0004] In addition, the stability of the multi-pillar bearing system is closely related to the stability of the pillars, and the stability of the pillars is determined by the relationship between their own strength and the bearing stress. For this reason, many formulas have been proposed by experts and scholars at home and abroad for calculating the strength and bearing stress of the pillars, and these formulas need to consider the problems of pillar size effect and shape effect. At present, no unified determination method has been given for the determination of the equivalent width of the pillars. The commonly used methods for determining the equivalent width of the pillars mainly include: the method based on the hydraulic radius and the inscribed circle method. The former can well determine the equivalent width of the pillars with regular cross-section shapes (such as squares, circles, etc.), but for narrow and long pillars, if the width remains unchanged, as the length of the pillar increases, the calculated equivalent width will be significantly too large. The inscribed circle method takes the diameter of the largest inscribed circle in the cross-section of the pillar as its equivalent width, and this method is only applicable to the pillars with an inscribed circle in the cross-section, but the actual cross-section of the pillar is often an irregular polygon, and the application of this method is significantly limited.

[0005] In view of this, it is necessary to design a method for risk zoning and grading assessment of goaf collapse disasters, especially for risk assessment of the chain collapse disasters in the goaf, fully considering the load transfer and the uncertainty of pillar strength, quantifying the potential of goaf collapse, especially the potential of single-pillar instability inducing chain collapse in the goaf, scientifically and reasonably determining the risk threshold and risk interval, and using an improved and highly universal method for determining the equivalent width of the pillars to calculate the pillar strength and stress, so as to solve the problem of refined assessment of existing goaf collapse risks. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for risk zoning and grading assessment of goaf collapse disasters. For the chain collapse disasters in the goaf, based on the theory of pillar group stability, considering the uncertainty of pillar strength, introducing induced pillars, quantifying the potential of goaf collapse, especially the potential of single-pillar instability inducing chain collapse in the goaf, scientifically and reasonably determining the risk threshold and risk interval, so as to realize the risk zoning and grading assessment of the chain collapse disasters in the goaf.

[0007] To achieve the above invention purpose, the present invention provides a method for risk zoning and grading assessment of goaf collapse disasters, including the following steps:

[0008] S1. Determine the instability probability of each pillar in the goaf;

[0009] S2. Assume that any pillar ω becomes unstable with its instability probability P fω and update the stress σ ω and the factor of safety FOS of all the pillars within the maximum stress diffusion range after the instability of the pillar ω;

[0010] S3. Take the ore pillars within the range where FOS ≤ 1 as new unstable ore pillars, and continue to update the stress σ and FOS of all ore pillars within the maximum stress diffusion range of the unstable ore pillars; repeat the iteration until there are no ore pillars with FOS ≤ 1 among the remaining ore pillars in the goaf, and the remaining ore pillar group is re-stabilized (the stress adjustment between ore pillars ends).

[0011] S4. Judge the number of induced ore pillars in the remaining ore pillar group; the induced ore pillar is: after the ore pillar θ becomes unstable, if it induces the continuous collapse of all other ore pillars in the remaining ore pillar group, then the ore pillar θ is the induced ore pillar.

[0012] S5. Calculate the disaster consequence value C of the ore pillar ω ω ; the disaster consequence value C ω is the ratio of the number of the induced ore pillars exposed after the instability of the ore pillar ω and the subsequent iterative instability to the total number of all ore pillars in the remaining ore pillar group.

[0013] S6. Repeat steps S2 - S5 to obtain the disaster consequence values of all ore pillars in the goaf.

[0014] If, after the instability of the ore pillar ω and through repeated iteration, FOS ≤ 1 for all ore pillars in the goaf, then the ore pillar ω itself is the induced ore pillar, and its disaster consequence value is 1.

[0015] S7. Calculate the instability risk weight values of each ore pillar in the goaf according to the disaster consequence values, and calculate the average risk weight value of all ore pillars.

[0016] S8. Use the average risk weight value in step S7 as the risk threshold to divide the risk intervals, and determine the risk levels of all ore pillars in the goaf according to the risk intervals; mark the risk levels corresponding to all ore pillars on the goaf plan view, and thus obtain the risk zoning and grading cloud map of the goaf collapse disaster.

[0017] As a further improvement of the present invention, in steps S1 - S3, in the calculation of the area, stress, and instability probability within the maximum stress diffusion range, the method for determining the equivalent width of the ore pillar used is based on the centroid of the cross-section.

[0018] As a further improvement of the present invention, the method based on the centroid of the cross-section is as follows:

[0019] (1) Determine the cross-section with the smallest area in the space of the ore pillar to be determined, and judge the shape of the cross-section.

[0020] (2) If the cross-section is a convex polygon, draw the largest circle within the convex polygon with its centroid as the center, and take its diameter as the equivalent width of the ore pillar.

[0021] If the cross-section is a concave polygon, extend one side where the concave angle is located to divide the cross-section into several convex polygons, and determine the centroid of each convex polygon; draw the largest circle within the convex polygon with each centroid as the center, compare the diameters of each circle, and regard the largest diameter as the equivalent width of the ore pillar.

[0022] As a further improvement of the present invention, in step S4, the determination method of the induced ore pillar is as follows:

[0023] SS1. Assume that any ore pillar θ in the remaining ore pillar group becomes unstable;

[0024] SS2. Update the stress σ and FOS of all ore pillars within the maximum stress diffusion range after the ore pillar becomes unstable. θ and FOS;

[0025] SS3. Determine whether there is an ore pillar with a safety factor FOS ≤ 1 within this range;

[0026] If not, the ore pillar θ is not an induced ore pillar;

[0027] If so, regard the ore pillar with a safety factor FOS ≤ 1 as an unstable ore pillar and remove it, and enter step SS4;

[0028] SS4. Determine whether the number of remaining ore pillars is 0;

[0029] If it is 0, it means that all the remaining ore pillars have continuous collapses, and the ore pillar θ is the induced ore pillar;

[0030] If not, continue to perform iterative instability on the remaining ore pillars and return to step SS2.

[0031] As a further improvement of the present invention, the area S of the maximum stress diffusion range v The calculation formula is as follows:

[0032]

[0033] where b is the equivalent width of the ore pillar; L is the maximum distance of ore pillar stress diffusion, and the calculation formula is as follows:

[0034] L = -0.0001H 2 +0.2701H (2)

[0035] where H represents the total thickness of the overlying strata in the goaf.

[0036] As a further improvement of the present invention, in step S1, when calculating the instability probability of the ore pillar, it is assumed that the probability density function of the strength of all individual ore pillars in the ore pillar group follows a lognormal distribution. The lognormal distribution is more suitable for describing non-negative physical parameters (such as ore pillar strength) compared to other normal distributions (such as truncated normal distribution, etc.); the instability probability P of the ore pillar ω fω is calculated by the formula:

[0037]

[0038] where σ pω is the strength of the ore pillar ω, σ ω is the ore pillar stress, Φ is the cumulative probability density distribution function of the ore pillar strength; f(x) is the probability density function of the ore pillar strength.

[0039] As a further improvement of the present invention, for the ore pillar strength σ pω , and the ore pillar stress σ ω , the calculation formulas are respectively:

[0040]

[0041]

[0042] where σ c is the uniaxial compressive strength of the cubic standard ore pillar specimen; b is the equivalent width of the ore pillar; h is the height of the ore pillar; n is the shape factor of the ore pillar, determined according to the width-height ratio of the ore pillar; γ i is the average volume force of the i-th layer of overlying rock above the goaf; H i is the average thickness of the i-th layer of overlying rock above the goaf; S p is the sum of the cross-sectional areas of all ore pillars within the maximum stress diffusion range of the calculated ore pillar stress; S v is the area of the maximum stress diffusion range.

[0043] As a further improvement of the present invention, in step S5, the calculation formula for the disaster consequence value is:

[0044]

[0045] where N tω is the number of induced ore pillars in the remaining ore pillar group formed after the first-round instability of the ore pillar ω; N is the total number of ore pillars in the remaining ore pillar group formed after the first-round instability of the ore pillar ω.

[0046] As a further improvement of the present invention, the calculation method of the safety factor FOS is the ratio of the updated ore pillar strength after stress diffusion to the ore pillar stress.

[0047] As a further improvement of the present invention, in step S8, the average risk weight value is used as a risk threshold for dividing the risk of ore pillars, and several risk intervals are obtained by multiple division according to the risk threshold.

[0048] As a further improvement of the present invention, the multiple selection of the risk threshold and the number of the obtained risk intervals are determined according to the parameters affecting the stability in the actual mined - out area of the mine.

[0049] As a further improvement of the present invention, in step S8, the division of the risk intervals is as follows: less than 1 / 2 of the risk threshold is low risk; between 1 / 2 of the risk threshold and the risk threshold is medium risk; between the risk threshold and 2 times the risk threshold is high risk; greater than 2 times the risk threshold is extremely high risk.

[0050] As a further improvement of the present invention, when marking the risk levels corresponding to all ore pillars on the plan of the mined - out area, different identifiers (such as different colors or symbols) can be used to distinguish ore pillars of different risk levels; when marking the risk level of the same ore pillar, the range of its ore room should be marked corresponding to the same level, that is, to ensure that a continuous and complete risk - zoning and grading cloud map of the mined - out area collapse disaster is finally formed.

[0051] The beneficial effects of the present invention are as follows:

[0052] 1. The present invention provides a method for risk - zoning and grading assessment of mined - out area collapse disasters, which determines the instability probability of each ore pillar in the mined - out area. Assuming the instability of any ore pillar, a method of repeated iterative instability is used to judge the situation of the instability of the remaining ore pillars caused by the instability of this ore pillar until the instability terminates; then the number of induced ore pillars in the remaining ore pillar group is determined, and the disaster consequence value of the ore pillar is calculated; and the disaster consequence values of all ore pillars are obtained in the above - mentioned manner, and the instability risk weight value of each ore pillar is calculated; finally, the risk levels of all ore pillars in the mined - out area are determined, and a risk - zoning and grading cloud map of the mined - out area collapse disaster is obtained. Based on the theory of ore pillar group stability, considering the uncertainty of ore pillar strength, induced ore pillars are introduced, and a judgment process for induced ore pillars is designed. The ratio of the number of induced ore pillars to all ore pillars in the remaining ore pillar group is used as the disaster consequence value of ore pillar instability, realizing the quantification of the potential of mined - out area collapse, especially the chain collapse induced by the instability of a single ore pillar, and further realizing the risk assessment of the mined - out area chain collapse disaster.

[0053] 2. Based on the characteristics that the goaf collapse disaster is different from general disasters, the present invention uses ore pillars as the carrier for risk assessment of goaf collapse disasters, focuses on the risk zoning and grading assessment of a single goaf, and proposes a method for dividing the risk threshold and risk interval for the chain collapse disaster of goafs. The average risk weight value of all calculated ore pillars is used as the risk threshold for dividing the risk of ore pillars, and multiple risk intervals are obtained by multiplying and dividing according to the risk threshold. The meaning of taking the average risk weight value as the risk threshold is as follows: in a stable pillar goaf, the instability risk weight values of each ore pillar are relatively uniform. If the instability risk weight values of all ore pillars fluctuate around the average value, it indicates that there is no local dangerous area in the ore pillar group; if the instability risk weight value of an ore pillar deviates significantly from the average value, it indicates that the deviated ore pillar undertakes more risk values, that is, it is a high-risk ore pillar. Therefore, using the average risk weight value as the risk threshold to divide the risk interval is more reasonable and scientific, and the obtained evaluation results are more accurate.

[0054] 3. In the stability analysis and calculation of ore pillars, the present invention is different from the traditional subordinate area theory, considers the influence of stress diffusion of ore pillars, and makes the calculation results more scientific and reasonable; at the same time, the present invention optimizes the determination method of the equivalent width of ore pillars, proposes to determine the equivalent width of ore pillars based on the centroid method of the cross-section, divides the cross-section with the smallest area in the space of the ore pillar to be calculated into two types: convex polygons and concave polygons, and uses different methods to determine their centroids, and regards the diameter of the centroid circle with the largest area as the equivalent width of the ore pillar. This method for determining the equivalent width of ore pillars has good accuracy and universality, and overcomes the problems of poor adaptability and low accuracy existing in the traditional methods for determining the equivalent width of ore pillars, such as using the hydraulic radius or the inscribed circle method.

[0055] 4. Through the risk zoning and grading assessment method for goaf collapse disasters provided by the present invention, the risk area of the chain collapse disaster of goafs can be scientifically divided, which helps relevant personnel to timely and focus on the treatment of high-risk areas, avoid casualties and property losses, and at the same time helps to supplement and improve the existing goaf risk assessment system. Brief Description of the Drawings

[0056] Figure 1 It is a schematic flow chart of the risk zoning and grading assessment method for goaf collapse disasters of the present invention.

[0057] Figure 2 It is a schematic flow chart of the induced ore pillar judgment method in the present invention.

[0058] Figure 3 It is a schematic diagram for determining the equivalent width of a convex polygon cross-section ore pillar in the present invention.

[0059] Figure 4 It is a schematic diagram for determining the equivalent width of a concave polygon cross-section ore pillar in the present invention.

[0060] Figure 5 This is the plan view of the mined - out area pillars in the embodiment of the present invention.

[0061] Figure 6 This is the plan view of the mined - out area pillars assuming the instability of pillar No. 37 in the embodiment of the present invention.

[0062] Figure 7 This is the plan view of the remaining pillar group after the iterative instability of pillar No. 37 in the embodiment of the present invention.

[0063] Figure 8 This is the plane distribution map of the induced pillars in the remaining pillar group in the embodiment of the present invention.

[0064] Figure 9 This is the schematic diagram of the division of the mined - out area collapse disaster risk interval in the embodiment of the present invention.

[0065] Figure 10 This is the risk - grading cloud map of the mined - out area collapse disaster obtained in the embodiment of the present invention.

[0066] Reference numerals: 1 - mined - out area; 2 - pillar; 3 - maximum stress diffusion range; 4 - induced pillar. Detailed implementation manners

[0067] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the drawings and specific embodiments.

[0068] Here, it should also be noted that in order to avoid obscuring the present invention due to unnecessary details, only the structures and / or processing steps closely related to the solution of the present invention are shown in the drawings, while other details less related to the present invention are omitted.

[0069] In addition, it should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non - exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or further includes elements inherent to such process, method, article or device.

[0070] Please refer to Figure 1 As shown, a method for grading and evaluating the risk of mined - out area collapse disasters includes the following steps:

[0071] S1. Determine the instability probability of each pillar in the mined - out area;

[0072] S2. Assume that any pillar ω becomes unstable with its instability probability P fω becomes unstable, and update the stress σ of all pillars within the maximum stress diffusion range after the instability of pillar ω ωand the factor of safety FOS; the calculation method of the factor of safety FOS is the ratio of the updated pillar strength after stress diffusion to the pillar stress:

[0073] (1) The area S of the maximum stress diffusion range v The calculation formula is as follows:

[0074]

[0075] where b is the equivalent width of the pillar; L is the maximum distance of pillar stress diffusion, and the calculation formula is as follows:

[0076] L = -0.0001H 2 +0.2701H (2)

[0077] where H represents the total thickness of the overlying strata in the goaf;

[0078] (2) The instability probability P of the pillar ω fω The calculation formula is:

[0079]

[0080] where σ pω is the pillar strength of the pillar ω, σ ω is the pillar stress, Φ is the cumulative probability density distribution function of the pillar strength; f(x) is the probability density function of the pillar strength, assuming it follows a lognormal distribution, and the lognormal distribution is more suitable for describing non - negative physical parameters (such as pillar strength) compared to other normal distributions (such as truncated normal distribution, etc.);

[0081] (3) The pillar strength σ pω , the pillar stress σ ω The calculation formulas are respectively:

[0082]

[0083]

[0084] where σ c is the uniaxial compressive strength of the standard cubic pillar specimen; b is the equivalent width of the pillar; h is the height of the pillar; n is the shape factor of the pillar, determined according to the width - height ratio of the pillar; γ i is the average volume force of the i - th overlying strata above the goaf; H i is the average thickness of the i - th overlying strata above the goaf; S p is the sum of the cross - sectional areas of all pillars within the maximum stress diffusion range of the calculated pillar stress; S v 1]is the area of the maximum stress diffusion range;

[0085] S3. Take the pillars within the range where FOS ≤ 1 as new unstable pillars, and continue to update the stress σ and FOS of all pillars within the maximum stress diffusion range of the unstable pillars; repeat the iteration until there are no pillars with FOS ≤ 1 among the remaining pillars in the goaf, and the remaining pillar group is re-stabilized (the stress adjustment between pillars ends);

[0086] S4. Determine the number of induced pillars in the remaining pillar group; an induced pillar is defined as follows: after pillar θ becomes unstable, if it induces the continuous collapse of all other pillars in the remaining pillar group, then pillar θ is the induced pillar;

[0087] S5. Calculate the disaster consequence value C of pillar ω ω ; The disaster consequence value C ω is the ratio of the number of induced pillars exposed after pillar ω becomes unstable and undergoes iterative instability to the total number of all pillars in the remaining pillar group; The formula for calculating the disaster consequence value is:

[0088]

[0089] where N tω is the number of induced pillars in the remaining pillar group formed after the first-round instability of pillar ω; N is the total number of pillars in the remaining pillar group formed after the first-round instability of pillar ω;

[0090] S6. Repeat steps S2 - S5 to obtain the disaster consequence values of all pillars in the goaf;

[0091] If, after pillar ω becomes unstable and through repeated iteration, FOS ≤ 1 for all pillars in the goaf, then pillar ω itself is the induced pillar, and its disaster consequence value is 1;

[0092] S7. Calculate the instability risk weight value of each pillar in the goaf, and calculate the average risk weight value of all pillars;

[0093] The instability risk weight value λ of any pillar ω ω is calculated by the formula:

[0094] S8. Use the average risk weight value in step S7 as the risk threshold to divide the risk interval, and determine the risk level of all pillars in the goaf according to the risk interval; Mark the risk levels corresponding to all pillars on the goaf plan view, and thus obtain the risk zoning and grading cloud map of the goaf collapse disaster.

[0095] In particular, in steps S1 - S3, in the calculation of the area, stress, and instability probability within the maximum stress diffusion range, the method for determining the equivalent width of the pillar used is based on the centroid method of the cross-section. Please refer to Figures 3 to 4 as shown, where Figure 3 is a pillar with a convex polygon cross-section, Figure 4It is a pillar with a concave polygon cross-section. The method for determining the equivalent width of the pillar based on the centroid of the cross-section is specifically as follows:

[0096] (1) Determine the cross-section with the smallest area in the space of the pillar to be determined, and judge the shape of the cross-section;

[0097] (2) If the cross-section is a convex polygon, draw the largest circle inside the convex polygon with its centroid as the center, and regard its diameter b as the equivalent width of the pillar; if the cross-section is a concave polygon, extend one side where the concave angle is located, divide the cross-section into several convex polygons, and determine the centroid of each convex polygon; draw the largest circle inside each convex polygon with its centroid as the center, compare the diameters of each circle (b1 > b3 > b2 > b4), and regard the largest diameter b1 as the equivalent width of the pillar.

[0098] This method can be applied to the determination of the equivalent width of pillars with various shapes, overcoming the problems of poor adaptability and low accuracy existing in the traditional methods such as using the hydraulic radius or the inscribed circle method to determine the equivalent width.

[0099] Please refer to Figure 2 as shown, the judgment method of the induced pillar is as follows:

[0100] SS1. Assume that any pillar θ in the remaining pillar group fails;

[0101] SS2. Update the stress σ θ and FOS of all pillars within the maximum stress diffusion range after the pillar fails;

[0102] SS3. Judge whether there is a pillar with a safety factor FOS ≤ 1 within this range;

[0103] If not, then pillar θ is not an induced pillar;

[0104] If so, remove the pillar with a safety factor FOS ≤ 1 as the failed pillar, and enter step SS4;

[0105] SS4. Judge whether the number of remaining pillars is 0;

[0106] If it is 0, it means that all the remaining pillars have continuous collapses, and pillar θ is the induced pillar;

[0107] If not, continue to perform iterative instability on the remaining pillars and return to step SS2.

[0108] In particular, by introducing the induced pillar, the disaster consequence is defined as the ratio of the number of induced pillars exposed after any pillar fails to the number of all pillars in the remaining stable pillar group formed after the pillar fails, quantifying the potential of goaf collapse, especially the chain collapse of the goaf induced by the instability of a single pillar, and then specifically evaluating the risk of the chain collapse disaster of the goaf.

[0109] Specifically, in step S8, the average risk weight value of all the ore pillars calculated is used as the risk threshold for dividing the ore pillar risks, and several risk intervals are obtained through multiple divisions based on the risk threshold. The multiple selection of the risk threshold and the number of risk intervals obtained are determined according to the parameters affecting the stability in the actual goaf of the mine. Taking the average risk weight value as the risk threshold means that in a stable pillar goaf, the instability risk weight values of each ore pillar are relatively uniform. If the instability risk weight values of all ore pillars fluctuate near the average value, it indicates that there is no local dangerous area in the ore pillar group; if the instability risk weight value of an ore pillar deviates significantly from the average value, it means that the deviated ore pillar bears more risk values, that is, it is a high-risk ore pillar.

[0110] In some specific embodiments, the division of the risk intervals is as follows: less than 1 / 2 of the risk threshold is low risk; between 1 / 2 of the risk threshold and the risk threshold is medium risk; between the risk threshold and 2 times the risk threshold is high risk; greater than 2 times the risk threshold is extremely high risk. When marking the risk levels corresponding to all ore pillars on the goaf plan, different identifications (colors or symbols) can be used to distinguish ore pillars of different risk levels. When marking the risk level of the same ore pillar, the stope range corresponding to the same level should be marked, that is, to ensure that a continuous and complete risk zoning and grading cloud map of the goaf collapse disaster is finally formed.

[0111] Embodiment

[0112] Please refer to Figures 5 to 10 As shown in the figure, this embodiment provides a method for risk zoning and grading assessment of goaf collapse disasters, including the following steps:

[0113] S1. Draw a goaf ore pillar plan according to the actual ore pillar distribution of a certain goaf, as Figure 5 shown in the figure; then label all the ore pillars 2 therein, numbered 1 to 69 respectively;

[0114] S2. Determine the instability probability of each ore pillar 2 in the goaf 1; please refer to Figure 6 shown in the figure. Assume that the 37th ore pillar becomes unstable with its instability probability, and update the stress σ ω and the safety factor FOS of all the ore pillars 2 (i.e., the 29th, 30th, 31st, 36th, 38th, 43rd, 44th, 45th, 51st ore pillars) within the maximum stress diffusion range 3 after instability; the calculation method of the safety factor FOS is the ratio of the ore pillar strength after updated stress diffusion to the ore pillar stress; when calculating the area, stress, and instability probability of the maximum stress diffusion range, the equivalent width of the ore pillar is determined based on the centroid method of the cross-section.

[0115] S3. Take the pillars with FOS ≤ 1 within this range as new unstable pillars, and continue to update the stress σ and FOS of all the pillars within the maximum stress diffusion range of the unstable pillars; repeat the iteration until there are no pillars with FOS ≤ 1 among the remaining pillars in the goaf, and the remaining pillar group is re-stabilized, indicating that the stress adjustment between the pillars is completed; as Figure 7 shown, after analysis, it is obtained that Pillar No. 30, Pillar No. 44, and Pillar No. 37 form a pillar collapse area, and the other pillars 2 form a remaining stable pillar group;

[0116] S4. Judge the number of induced pillars in the remaining pillar group; the induced pillar is: after Pillar θ becomes unstable, it induces all other pillars in the remaining pillar group to collapse continuously, then Pillar θ is the induced pillar; the judgment method of the induced pillar is:

[0117] S41. Assume that any pillar θ in the remaining pillar group becomes unstable;

[0118] S42. Update the stress σ θ and FOS of all the pillars within the maximum stress diffusion range after the pillar becomes unstable;

[0119] S43. Judge whether there are pillars with safety factor FOS ≤ 1 within this range;

[0120] If not, then Pillar θ is not an induced pillar;

[0121] If so, take the pillars with safety factor FOS ≤ 1 as unstable pillars and remove them, and enter step S44;

[0122] S44. Judge whether the number of remaining pillars is 0;

[0123] If it is 0, it means that all the remaining pillars have collapsed continuously, and Pillar θ is the induced pillar;

[0124] If not, continue the iterative instability of the remaining pillars and return to step S42;

[0125] As Figure 8 shown, after judgment and analysis, 14 induced pillars 4 are obtained; the total number of pillars in the remaining pillar group is 66;

[0126] S5. Calculate the disaster consequence value C of Pillar No. 37; the disaster consequence value C is the ratio of the number of induced pillars 4 exposed after Pillar ω becomes unstable to the number of all the pillars 2 in the remaining pillar group; at this time, the disaster consequence value C of Pillar No. 37 = 14 / 66 = 7 / 33;

[0127] S6. Repeat steps S2 to S5 to obtain the disaster consequence values of all the pillars 2 (69 in total) in the goaf;

[0128] S7. Then, calculate the instability risk weight values of each ore pillar 2 in the goaf 1, and calculate the average risk weight value of all ore pillars 2.

[0129] S8. Use the average risk weight value in step S7 as the risk threshold to divide the risk intervals. As Figure 9 shown, the division of the risk intervals is as follows: less than 1 / 2 of the risk threshold is low risk; between 1 / 2 of the risk threshold and the risk threshold is medium risk; between the risk threshold and 2 times the risk threshold is high risk; greater than 2 times the risk threshold is extremely high risk.

[0130] As Figure 10 shown, when marking the risk levels corresponding to all ore pillars on the goaf plan view, different colors are used to distinguish ore pillars with different risk levels. When marking the risk level of the same ore pillar, the range of its ore room is marked according to the corresponding level of the same level, that is, the risk zoning and grading cloud map of the goaf collapse disaster is obtained. Applying the risk zoning and grading cloud map of the goaf collapse disaster obtained by the method of this embodiment to the goaf in the mine, guiding it to focus on supporting the ore pillars in the high-risk area can avoid the occurrence of chain collapse disaster accidents in the goaf.

[0131] In summary, the present invention provides a method for risk zoning and grading assessment of goaf collapse disasters; according to the characteristics of goaf collapse disasters different from general disasters, taking the ore pillar as the carrier for risk assessment of goaf collapse disasters, focusing on the risk zoning and grading assessment of a single goaf, and proposing a method for dividing the risk threshold and risk intervals for goaf chain collapse disasters. In the stability analysis and calculation of ore pillars, different from the traditional subordinate area theory, the influence of ore pillar stress diffusion is considered, making the calculation results more scientific and reasonable. At the same time, the method for determining the equivalent width of ore pillars is also optimized. By introducing induced ore pillars and designing the judgment process of induced ore pillars, taking the ratio of the number of induced ore pillars to all ore pillars in the remaining ore pillar group as the disaster consequence value of ore pillar instability, the quantification of the potential of goaf collapse, especially the chain collapse induced by the instability of a single ore pillar, is realized. Finally, the risk zoning and grading assessment of goaf chain collapse disasters is realized, filling the gap in the risk assessment method of goaf collapse disasters.

[0132] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for risk zoning and grading assessment of goaf collapse disasters, characterized in that, It includes the following steps: S1. Determine the instability probability of each ore pillar in the goaf; S2. Assume that for any ore pillar ω, with its instability probability P fω becomes unstable, update the stress σ ω and the factor of safety FOS of all ore pillars within the maximum range of stress diffusion after the instability of the ore pillar ω. S3. Take the ore pillars with FOS ≤ 1 within the range as new unstable ore pillars, and continue to update the stress σ and FOS of all ore pillars within the maximum stress diffusion range of the unstable ore pillars; repeat the iteration until there are no ore pillars with FOS ≤ 1 among the remaining ore pillars in the goaf, and the remaining ore pillar group is re-stabilized; S4. Judge the number of induced ore pillars in the remaining ore pillar group; the induced ore pillar is: after the ore pillar θ is unstable, it induces the continuous collapse of all other ore pillars in the remaining ore pillar group, then the ore pillar θ is the induced ore pillar; S5. Calculate the disaster consequence value C of the ore pillar ω ω ; The disaster consequence value C ω is the quantity ratio of all the ore pillars of the induced ore pillar and the remaining ore pillar group exposed after the instability of the ore pillar ω and iterative instability; S6. Repeat steps S2 - S5 to obtain the disaster consequence values of all ore pillars in the goaf; If after the ore pillar ω is unstable, after repeated iteration, the FOS of all ore pillars in the goaf ≤ 1, then the ore pillar ω itself is the induced ore pillar, and its disaster consequence value is 1; S7. Calculate the instability risk weight value of each ore pillar in the goaf according to the disaster consequence value, and calculate the average risk weight value of all ore pillars; S8. Use the average risk weight value in step S7 as the risk threshold to divide the risk interval, and determine the risk level of all ore pillars in the goaf according to the risk interval; Mark the risk levels corresponding to all ore pillars on the goaf plan view, and then obtain the risk zoning and grading cloud map of the goaf collapse disaster.

2. The goaf collapse disaster risk zoning and grading assessment method according to claim 1, characterized in that, In steps S1 - S3, in the calculation of the area, stress and instability probability within the maximum stress diffusion range, the method for determining the equivalent width of the ore pillar used is based on the centroid method of the cross-section.

3. The goaf collapse disaster risk zoning and grading assessment method according to claim 2, characterized in that The centroid method based on the cross-section is as follows: (1) Determine the cross-section with the smallest area in the space of the ore pillar to be sought, and judge the shape of the cross-section; (2) If the cross-section is a convex polygon, draw the largest circle within the convex polygon with its centroid as the center, and regard its diameter as the equivalent width of the ore pillar; If the cross-section is a concave polygon, extend one side where the concave angle is located, divide the cross-section into several convex polygons, and determine the centroid of each convex polygon; draw the largest circle within each convex polygon with its centroid as the center, compare the diameters of each circle, and regard the largest diameter as the equivalent width of the ore pillar.

4. The goaf collapse disaster risk zoning and grading assessment method according to claim 1, wherein In step S4, the judgment method of the induced ore pillar is as follows: SS1. Assume that any ore pillar θ in the remaining ore pillar group is unstable; SS2. Update the stress σ of all the ore pillars within the maximum stress diffusion range after the instability of the updated ore pillar θ and FOS; SS3. Judge whether there are ore pillars with safety factor FOS ≤ 1 within this range; If not, the ore pillar θ is not an induced ore pillar; If so, take the ore pillars with safety factor FOS ≤ 1 as unstable ore pillars and remove them, and enter step SS4; SS4. Judge whether the number of remaining ore pillars is 0; If it is 0, it means that all the remaining ore pillars have continuous collapses, and the ore pillar θ is the induced ore pillar; If it is not 0, continue the iterative instability of the remaining ore pillars and return to step SS2.

5. The goaf collapse disaster risk zoning and grading assessment method according to claim 1, wherein In step S5, the formula for calculating the disaster consequence value is: Among them, N tω is the number of induced ore pillars that form the remaining ore pillar group after the first-round instability of ore pillar ω; N is the total number of ore pillars in the remaining ore pillar group formed after the first-round instability of ore pillar ω.

6. The goaf collapse disaster risk zoning and grading assessment method according to claim 1, characterized in that, In step S1, when calculating the instability probability of the ore pillar, it is assumed that the probability density function of the strength of all single ore pillars in the ore pillar group follows a lognormal distribution.

7. The goaf collapse disaster risk zoning and grading assessment method according to claim 1, characterized in that, In step S8, the average risk weight value is used as a risk threshold for dividing the risk of ore pillars, and several risk intervals are obtained by multiple division according to the risk threshold.

8. The goaf collapse disaster risk zoning and grading assessment method according to claim 7, characterized in that The multiple selection of the risk threshold and the number of the obtained risk intervals are determined according to the parameters affecting the stability in the actual goaf of the mine.

9. The goaf collapse disaster risk zoning and grading assessment method according to claim 8, wherein, The division of the risk intervals is as follows: less than 1 / 2 of the risk threshold is low risk; between 1 / 2 of the risk threshold and the risk threshold is medium risk; between the risk threshold and 2 times the risk threshold is high risk; greater than 2 times the risk threshold is extremely high risk.

10. The goaf collapse disaster risk zoning and grading assessment method according to claim 1, characterized in that, When marking the risk levels corresponding to all ore pillars on the goaf plan, different identifications can be used to distinguish ore pillars of different risk levels; when marking the risk level of the same ore pillar, the goaf range corresponding to the same level should be marked accordingly, that is, to ensure that a continuous and complete risk zoning and grading cloud map of goaf collapse disasters is finally formed.

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