A method for evaluating the bearing capacity of fractured rock mass of roadway surrounding rock

Abstract

The application discloses a kind of roadway surrounding rock fissure rock mass bearing capacity evaluation methods, comprising: determining the fissure distribution characteristics of influence roadway surrounding rock rock mass bearing capacity, establish the layered structure model of roadway surrounding rock fissure rock mass bearing capacity;Determine the importance degree index of each fissure distribution characteristics, determine the weight of each influencing factor, determine fissure rock mass strength factor Q interval;Roadway surrounding rock fissure rock mass bearing capacity is classified and evaluated;Quantify the fissure distribution form of roadway surrounding rock rock mass, determine the weight of each influencing factor under the fissure occurrence environment of roadway;The fissure rock mass strength factor Q corresponding to roadway surrounding rock is solved, and the fissure development level evaluation result of roadway surrounding rock is obtained.The application can be according to the fissure distribution characteristics of roadway surrounding rock after roadway excavation detailed, effective, comprehensive analysis and evaluation roadway surrounding rock fissure rock mass bearing capacity, provide evaluation basis for roadway surrounding rock stability control, it has important significance to ensure the safety long-time stability of roadway full life cycle in the process of mine exploitation.

Description

Technical Field

[0001] This invention relates to the field of safety evaluation technology for coal mine tunnel engineering, specifically to a method for assessing the bearing capacity of fractured rock mass surrounding tunnels. Background Technology

[0002] Tunnel excavation is a crucial process in coal mining, with an annual cumulative excavation of up to 12,000 km. The smooth and stable operation of tunnels is essential for ensuring safe and efficient coal production. Rock mass, the object of excavation and support in mines and tunnels, contains numerous joints, fissures, and weak bedding structures due to tectonic movements and mining operations. The bearing capacity of underground rock mass determines the stability of underground engineering projects. The presence of numerous pores, joints, and fissures within the tunnel rock mass can further expand and penetrate during stress redistribution, ultimately leading to instability and failure of the tunnel walls, roof, and floor. The further development of joints and fissures in fractured rock masses is closely related to the deformation and instability of deep rock engineering.

[0003] Therefore, it is particularly important to reasonably examine and accurately evaluate the development of fissures in the surrounding rock of roadways during coal mining. Determining the level of rock fissure development, scientifically assessing the stability of the surrounding rock of roadways, and ensuring safe and efficient mine production are problems that researchers in this field urgently need to solve. Summary of the Invention

[0004] To address the aforementioned technical shortcomings, the purpose of this invention is to provide a method for assessing the bearing capacity of fractured rock masses in roadways. This method precisely quantifies and analyzes the development level of fractures in the roadway's surrounding rock, clarifies the fractured rock mass strength factor Q, and enables the classification of the bearing capacity level of the fractured rock mass, thus providing reliable suggestions for roadway surrounding rock control.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] This invention provides a method for assessing the bearing capacity of fractured rock mass in roadways, comprising the following steps:

[0007] Step 1: Determine the distribution characteristics of fractures that affect the bearing capacity of the surrounding rock mass of the roadway, and establish a layered structural model of the bearing capacity of fractured rock mass of the surrounding rock mass of the roadway.

[0008] Step 2: Determine the importance index of each fracture distribution characteristic, determine the weight of each influencing factor based on the analytic hierarchy process, and determine the range of the fractured rock mass strength factor Q.

[0009] Step 3: Classify and evaluate the bearing capacity of the fractured rock mass surrounding the tunnel according to the Q range of the fractured rock mass strength factor;

[0010] Step 4: Quantify the distribution morphology of fractures in the surrounding rock mass of the tunnel using borehole inspection method, and determine the weight of each influencing factor in the fracture occurrence environment of the tunnel.

[0011] Step 5: Calculate the fractured rock mass strength factor Q corresponding to the surrounding rock of the tunnel to obtain the assessment result of the fracture development level of the surrounding rock of the tunnel;

[0012] Preferably, in step one, the fracture distribution characteristics include: fracture dip angle, fracture length, fracture end distance, fracture vertical distance, number of fractures, and confining pressure of the fractured rock mass;

[0013] Among them, the fracture length refers to the path length of the line connecting the two ends of a single fracture; the fracture dip angle refers to the angle between the direction perpendicular to the surrounding rock wall and the direction of the tunnel in the plane; the distance between the ends of fractures refers to the distance between two adjacent fracture ends when multiple fractures are distributed in a unit area; the vertical distance between fractures refers to the distance between the center points of fractures when multiple fractures are distributed in a unit area; the number of fractures refers to the number of fractures in a unit area; and the confining pressure of fractured rock mass refers to the average pressure formed around the fractured rock mass according to the magnitude of the in-situ stress generated by the tunnel burial depth.

[0014] Preferably, in step one, the layered structural model of bearing capacity of fractured rock mass in the roadway includes three layers: target layer a, criterion layer b, and scheme layer c.

[0015] The target layer a is analyzed for the strength characteristics of fractured rock mass;

[0016] The criterion layer b includes the fracture dip angle b1, fracture length b2, fracture end distance b3, fracture vertical distance b4, number of fractures b5, and confining pressure of the fractured rock mass b6. Each criterion layer contains several sub-criterion layers, wherein:

[0017] The fracture dip angle B1 includes three sub-criteria: less than 30 degrees (b11), 30 to 60 degrees (b12), and greater than 60 degrees (b13).

[0018] The crack length b2 includes two sub-criteria: b21 (less than 20 mm) and b22 (greater than 20 mm).

[0019] The distance b3 from the crack end includes two sub-criteria: b31 (less than 5 mm) and b32 (greater than 5 mm).

[0020] The vertical distance of the crack b4 includes two sub-criteria b42: less than 25 mm b41 and greater than 25 mm.

[0021] The number of fractures, b5, includes sparsely arranged b51 and densely arranged b52.

[0022] The confining pressure b6 of the fractured rock mass includes low confining pressure b61 and high confining pressure b62;

[0023] The scheme layer c is used to evaluate the bearing capacity of fractured rock mass.

[0024] Preferably, in step two, the formula for calculating the importance index of each fracture distribution characteristic is as follows:

[0025]

[0026] In the formula, a ij Let be the relative importance value between the i-th element and the j-th element; a i a represents the importance of the i-th element; j The importance of the j-th element is such that the relative importance value satisfies the requirements of the importance comparison rule of the analytic hierarchy process (AHP). Preferably, in step two, the process of determining the weights of each influencing factor based on the AHP is as follows: Based on the importance comparison values ​​of each factor, establish the following matrixes: fracture rock mass strength analysis judgment matrix A, fracture dip angle judgment matrix B1, fracture length judgment matrix B2, fracture end distance judgment matrix B3, fracture vertical distance judgment matrix B4, fracture number judgment matrix B5, and fracture rock mass confining pressure judgment matrix B6.

[0027] Calculate the maximum eigenvalue and eigenvector of each judgment matrix, and perform a consistency check on the judgment matrix. If the check passes, the importance of each influencing factor is reasonable. If the check fails, the judgment matrix needs to be reconstructed and the consistency check is performed again. The eigenvector value is the basis for the weight of each influencing factor.

[0028] The eigenvectors are obtained by the square root method and normalization, and the largest eigenvalue is obtained by the eigenvector sum-product method, the calculation formula of which is:

[0029]

[0030]

[0031] In the formula, let A be the judgment matrix and W be the eigenvectors of each judgment matrix. i Its largest eigenvalue is λmax. Multiplying each row of matrix A yields the eigenvalue belonging to λ. max The standardized feature vector is W = (W1, W2, ..., W...). n )T;

[0032] The consistency test determines the random consistency ratio by comparing the matrix consistency index CI with the average random consistency index RI of the same order. The formula for this ratio is:

[0033]

[0034]

[0035] In the formula, RI is the random consistency index value, which can be obtained from the table; CI is the consistency index; and n is the order.

[0036] Preferably, in step two, determining the range of fractured rock mass strength factor Q refers to determining the overall range of values ​​for fractured rock mass strength factor Q based on the product of the criterion layer and its corresponding sub-criterion layer.

[0037] Preferably, in step three, the step of classifying and evaluating the bearing capacity of the fractured rock mass surrounding the tunnel according to the fractured rock mass strength factor Q range includes:

[0038] When the strength factor Q of fractured rock mass is between 0.60 and 0.71, the fractures are very well developed, the rock mass has very low bearing capacity, and it is very easy for the fractures to propagate, penetrate, and become unstable, which has a serious impact on underground engineering.

[0039] When the strength factor Q of fractured rock mass is between 0.45 and 0.60, fractures are developed, the rock mass has low bearing capacity, and the rock mass is more prone to penetrating failure, which will have a significant impact on underground engineering.

[0040] When the strength factor Q of fractured rock mass is between 0.30 and 0.45, the fractures are relatively well-developed, the rock mass has a certain bearing capacity, and it requires strong disturbance to further destabilize and fail, which will have a certain impact on some underground engineering projects.

[0041] When the strength factor Q of fractured rock mass is between 0.20 and 0.30, fractures are not easy to develop, the rock mass has high bearing capacity, and it is almost unaffected by the development and penetration of fractures. Underground engineering has high stability in the absence of special environments.

[0042] Preferably, in step four, the process of quantifying the distribution morphology of fractures in the surrounding rock mass of the roadway by borehole inspection involves drilling holes in the top and bottom plates and both sides of the roadway, observing the length, dip angle, and distribution morphology of fractures in the fractured rock mass using a borehole inspection instrument, and exporting digital images of the borehole inspection by computer to analyze the development of fractures in the surrounding rock, thereby obtaining the strength factor Q of the fractured rock mass of the target roadway and the assessment results of the development level of fractures in the surrounding rock of the roadway.

[0043] The beneficial effects of this invention are as follows:

[0044] (1) This method scientifically quantifies the bearing capacity of fractured rock mass based on the occurrence state of fractures in the surrounding rock mass. The borehole inspection method is used to monitor the fractures in the surrounding rock mass as a preliminary means. The hierarchical analysis method is used to conduct weight analysis on the bearing capacity of fractured rock mass under each fracture occurrence state, and the level of bearing capacity of fractured rock mass is comprehensively judged, providing reliable suggestions for the control of surrounding rock in roadways.

[0045] (2) This method closely combines the development status of roadway fractures with the hierarchical analysis method. Through detailed identification of multiple factors of fractures, a layered structural model of the bearing capacity of roadway surrounding rock fracture rock mass is established, realizing a comprehensive assessment of the degree of development of surrounding rock fractures, and then quantitatively analyzing the bearing capacity of rock mass. It has practicality in this technical field.

[0046] (3) This method combines the characteristics and evaluation methods of monitoring surrounding rock fissures during coal mine roadway excavation, and fully considers the principles of scientificity, speed and reliability. It uses borehole observation image results to further statistically analyze the fissure occurrence state, which can effectively provide quantitative evaluation and supplementation of multiple observations such as the loosening zone of the surrounding rock, the expansion of surrounding rock fissures, and the stress of anchor bolt and anchor cable support. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the process for evaluating the bearing capacity of fractured rock mass in roadways according to an embodiment of the present invention;

[0049] Figure 2 This is a layered structural model diagram of the method for assessing the bearing capacity of fractured rock mass surrounding rock in roadways provided in this embodiment of the invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] This embodiment provides a method for assessing the bearing capacity of fractured rock mass in roadways, including the following steps:

[0052] Step 1: Determine the distribution characteristics of fractures that affect the bearing capacity of the surrounding rock mass of the roadway, and establish a layered structural model of the bearing capacity of fractured rock mass of the surrounding rock mass of the roadway.

[0053] The characteristics of the fracture distribution include: fracture dip angle, fracture length, distance between fracture ends, vertical distance between fractures, number of fractures, and confining pressure of the fractured rock mass.

[0054] Crack length refers to the path length of the line connecting the two ends of a single crack;

[0055] The fracture dip angle refers to the angle between the direction perpendicular to the surrounding rock wall and the direction of the tunnel in the plane;

[0056] The distance between the ends of a fracture refers to the distance between two points at the ends of adjacent fractures when multiple fractures are distributed within a unit area.

[0057] The vertical distance between fractures refers to the distance between the center points of multiple fractures distributed within a unit area.

[0058] The number of cracks refers to the number of cracks per unit area;

[0059] Confining pressure in fractured rock mass refers to the average pressure formed around the fractured rock mass based on the magnitude of the in-situ stress generated by the tunnel burial depth.

[0060] The established layered structural model for the bearing capacity of fractured rock mass surrounding the tunnel includes three layers: target layer a, criterion layer b, and scheme layer c.

[0061] Target layer a is for strength characteristic analysis of fractured rock mass; the criterion layer b includes fracture dip angle b1, fracture length b2, fracture end distance b3, fracture vertical distance b4, number of fractures b5, and confining pressure of fractured rock mass b6. Each criterion layer contains several sub-criterion layers, among which...

[0062] The fracture dip angle b1 includes less than 30 degrees. 11 30 degrees to 60 degrees b 12 and greater than 60 degrees b 13 Three sub-criteria,

[0063] Crack length b2 includes less than 20 mm. 21 and greater than 20 mm b 22 Two sub-criteria,

[0064] The distance b3 from the crack end includes less than 5 mm. 31 and greater than 5 mm b 32 Two sub-criteria,

[0065] The vertical distance of the crack b4 includes less than 25 mm. 41 and two sub-criteria b greater than 25 mm 42 ,

[0066] The number of fractures b5 includes sparse arrangement b 51 and dense arrangement b 52 ,

[0067] Confining pressure b6 in fractured rock mass includes low confining pressure b 61 and high confining pressure b 62 Scheme layer c is used to evaluate the bearing capacity of fractured rock mass.

[0068] Step 2: Determine the importance index of each fracture distribution characteristic, determine the weight of each influencing factor based on the analytic hierarchy process, and determine the range of the fractured rock mass strength factor Q.

[0069] The formula for calculating the importance index of each fracture distribution characteristic is as follows:

[0070]

[0071] In the formula, a ij Let be the relative importance value between the i-th element and the j-th element; a i a represents the importance of the i-th element; j Let represent the importance of the j-th element, and let the relative importance value satisfy the requirements of the importance comparison rule of the analytic hierarchy process.

[0072] The process of determining the weights of each influencing factor based on the analytic hierarchy process is as follows: Based on the comparison values ​​of the importance of each factor, establish the following matrixes: fracture rock mass strength analysis judgment matrix A, fracture dip angle judgment matrix B1, fracture length judgment matrix B2, fracture end distance judgment matrix B3, fracture vertical distance judgment matrix B4, fracture number judgment matrix B5, and fracture rock mass confining pressure judgment matrix B6. See Tables 1-7.

[0073] Table 1. Matrix for Judging the Strength of Fractured Rock Mass (A)

[0074]

[0075]

[0076] Table 2 Crack Inclination Angle Judgment Matrix B1

[0077]

[0078] Table 3 Crack Length Judgment Matrix B2

[0079]

[0080] Table 4 Crack tip distance judgment matrix B3

[0081]

[0082] Table 5 Crack Vertical Distance Judgment Matrix B4

[0083]

[0084] Table 6 Crack Quantity Judgment Matrix B

[0085]

[0086]

[0087] Table 7 Crack Quantity Judgment Matrix B6

[0088]

[0089] Calculate the maximum eigenvalue and eigenvector of each judgment matrix, and perform a consistency check on the judgment matrix. If the check passes, the importance of each influencing factor is reasonable. If the check fails, the judgment matrix needs to be reconstructed and the consistency check is performed again. The eigenvector value is the basis for the weight of each influencing factor.

[0090] Given a judgment matrix A, let λ be the largest eigenvalue of A. max Multiply each row of matrix A to obtain the product of the rows belonging to λ. max The standardized feature vector is W = (w1, ..., w n ) T The calculation process is as follows:

[0091] According to the square root method, the elements of the judgment matrix A are multiplied row by row to obtain a new vector A1:

[0092] A1=[630.00000 10.00000 0.00063 0.03333 15.00000 0.50000] T

[0093] Taking the sixth root of the vector of each new element in A1, we get M1:

[0094] M1=[2.9279 1.4678 0.2928 0.5673 1.5704 0.8909] T

[0095] The obtained M1 is normalized to obtain the standardized feature vector W:

[0096] W=[0.3794 0.1902 0.0379 0.0735 0.2035 0.1154] T

[0097] Based on the obtained standardized eigenvector W, calculate the largest eigenvalue λ of the judgment matrix. max Therefore, the maximum eigenvalue λmax of the matrix is:

[0098]

[0099] The consistency index (CI) is used to measure the deviation of a judgment matrix from consistency.

[0100]

[0101] The ratio of the matrix consistency index CI to the average random consistency index RI of the same order is called the random consistency ratio, denoted as:

[0102]

[0103] The random consistency index (RI) value can be obtained by looking up a table, see Table 8.

[0104] Table 8 Random Consistency Index (RI) Values

[0105]

[0106] According to Table 8, the RI value of the 6th order matrix is ​​1.24;

[0107]

[0108] Determining the range of the strength factor Q in fractured rock mass refers to determining the overall value range of the strength factor Q based on the product of the criterion layer and its corresponding sub-criterion layer. The summary of the calculated strength factor of the characteristic vector of fractured rock mass is shown in Table 9.

[0109] Table 9 Summary of Calculation of Eigenvector Intensity Factor of Fractured Rock Mass

[0110]

[0111] Step 3: Classify and evaluate the bearing capacity of the fractured rock mass surrounding the roadway according to the Q range of the fractured rock mass strength factor.

[0112] The specific value of the strength factor Q of fractured rock mass can be represented by the sum of the eigenvectors obtained from the analytic hierarchy process (AHP). Through simple combination and classification, it can be seen that the value range of Q is 0.2075 to 0.7166. By rounding, the bearing capacity of fractured rock mass can be classified within the interval (0.20, 0.71). The classification of the bearing capacity of fractured rock mass is shown in Table 10.

[0113] Table 10 Classification of Bearing Capacity of Fractured Rock Mass

[0114]

[0115] The classification and evaluation of the bearing capacity of the fractured rock mass surrounding the roadway based on the fractured rock mass strength factor Q range includes:

[0116] When the strength factor Q of fractured rock mass is between 0.60 and 0.71, the fractures are very well developed, the rock mass has very low bearing capacity, and it is very easy for the fractures to propagate, penetrate, and become unstable, which has a serious impact on underground engineering.

[0117] When the strength factor Q of fractured rock mass is between 0.45 and 0.60, fractures are developed, the rock mass has low bearing capacity, and the rock mass is more prone to penetrating failure, which will have a significant impact on underground engineering.

[0118] When the strength factor Q of fractured rock mass is between 0.30 and 0.45, the fractures are relatively well-developed, the rock mass has a certain bearing capacity, and it requires strong disturbance to further destabilize and fail, which will have a certain impact on some underground engineering projects.

[0119] When the strength factor Q of fractured rock mass is between 0.20 and 0.30, fractures are not easy to develop, the rock mass has high bearing capacity, and it is almost unaffected by the development and penetration of fractures. Underground engineering has high stability in the absence of special environments.

[0120] Step 4: Quantify the distribution morphology of fractures in the surrounding rock mass of the tunnel using borehole inspection method, and determine the weight of each influencing factor in the fracture occurrence environment of the tunnel.

[0121] The process of quantifying the distribution morphology of fractures in the surrounding rock mass of a roadway using borehole inspection is as follows: boreholes are drilled in the top and bottom plates and both sides of the roadway; the length, dip angle and distribution morphology of fractures in the fractured rock mass are observed using a borehole inspection instrument; the computer exports the digital images of the borehole inspection to analyze the development of fractures in the surrounding rock; and then the strength factor Q of the fractured rock mass of the target roadway and the assessment results of the development level of fractures in the surrounding rock of the roadway are obtained.

[0122] Step 5: Calculate the fractured rock mass strength factor Q corresponding to the surrounding rock of the tunnel to obtain the assessment results of the fracture development level of the surrounding rock of the tunnel.

[0123] Each embodiment can be described and evaluated using the above progressive process. Since each embodiment has differences, different results can be obtained. Regarding the description of the disclosed method for evaluating the bearing capacity of fractured rock mass in roadways, any modifications, equivalent substitutions, improvements, etc., made to the content described in this description without departing from the spirit or principles of this invention are within the scope of protection of the pending claims of this invention.

Claims

1. A method for assessing the bearing capacity of fractured rock mass surrounding a roadway, characterized in that, Includes the following steps: Step 1: Determine the distribution characteristics of fractures that affect the bearing capacity of the surrounding rock mass of the roadway, and establish a layered structural model of the bearing capacity of fractured rock mass of the surrounding rock mass of the roadway. Step 2: Determine the importance index of each fracture distribution characteristic, determine the weight of each influencing factor based on the analytic hierarchy process, and determine the range of the fractured rock mass strength factor Q. Step 3: Classify and evaluate the bearing capacity of the fractured rock mass surrounding the tunnel according to the Q range of the fractured rock mass strength factor; Step 4: Quantify the distribution morphology of fractures in the surrounding rock mass of the tunnel using borehole inspection method, and determine the weight of each influencing factor in the fracture occurrence environment of the tunnel. Step 5: Calculate the fractured rock mass strength factor Q corresponding to the surrounding rock of the tunnel to obtain the assessment result of the fracture development level of the surrounding rock of the tunnel; In step one, the fissure distribution characteristics include: fissure dip angle, fissure length, fissure end distance, fissure vertical distance, number of fissures, and confining pressure of the fissure rock mass; Among them, fracture length refers to the path length of the line connecting the two ends of a single fracture; fracture dip angle refers to the angle between the direction perpendicular to the surrounding rock wall and the direction of the tunnel in the plane; fracture end distance refers to the distance between two adjacent fracture ends when multiple fractures are distributed in a unit area; fracture vertical distance refers to the distance between the center points of multiple fractures when multiple fractures are distributed in a unit area; fracture number refers to the number of fractures in a unit area; and fracture confining pressure refers to the average pressure formed around the fractured rock mass based on the magnitude of the in-situ stress generated by the tunnel burial depth. In step one, the layered structural model of the bearing capacity of the fractured rock mass surrounding the tunnel includes three layers: target layer a, criterion layer b, and scheme layer c. The target layer a is analyzed for the strength characteristics of fractured rock mass; The criterion layer b includes the fracture dip angle b1, fracture length b2, fracture end distance b3, fracture vertical distance b4, number of fractures b5, and confining pressure of the fractured rock mass b6. Each criterion layer contains several sub-criterion layers, wherein: The fracture dip angle B1 includes three sub-criteria: less than 30 degrees (b11), 30 to 60 degrees (b12), and greater than 60 degrees (b13). The crack length b2 includes two sub-criteria: b21 (less than 20 mm) and b22 (greater than 20 mm). The distance b3 from the crack end includes two sub-criteria: b31 (less than 5 mm) and b32 (greater than 5 mm). The vertical distance of the crack b4 includes two sub-criteria b42: less than 25 mm b41 and greater than 25 mm. The number of fractures, b5, includes sparsely arranged b51 and densely arranged b52. The confining pressure b6 of the fractured rock mass includes low confining pressure b61 and high confining pressure b62; The scheme layer c is used to evaluate the bearing capacity of fractured rock mass; In step two, the formula for calculating the importance index of each fracture distribution characteristic is as follows: In the formula, a ij Let be the relative importance value between the i-th element and the j-th element; a i a represents the importance of the i-th element; j Let represent the importance of the j-th element, and let the relative importance value satisfy the requirements of the importance comparison rule of the analytic hierarchy process. In step two, the process of determining the weights of each influencing factor based on the analytic hierarchy process is as follows: establish the following matrix based on the relative importance of each factor: fracture rock mass strength analysis judgment matrix A, fracture dip angle judgment matrix B1, fracture length judgment matrix B2, fracture end distance judgment matrix B3, fracture vertical distance judgment matrix B4, fracture number judgment matrix B5, and fracture rock mass confining pressure judgment matrix B6. Calculate the maximum eigenvalue and eigenvector of each judgment matrix, and perform a consistency check on the judgment matrix. If the check passes, the importance of each influencing factor is reasonable. If the check fails, the judgment matrix needs to be reconstructed and the consistency check is performed again. The eigenvector value is the basis for the weight of each influencing factor. The eigenvectors are obtained by the square root method and normalization, and the largest eigenvalue is obtained by the eigenvector sum-product method, the calculation formula of which is: ; In the formula, let A be the judgment matrix and W be the eigenvectors of each judgment matrix. i Its largest eigenvalue is λmax. Multiplying each row of matrix A and standardizing it yields the eigenvector W = (W1, W2, ..., W...). n ) T ; The consistency test determines the random consistency ratio by comparing the matrix consistency index CI with the average random consistency index RI of the same order. The formula for this ratio is: ; In the formula, RI is the random consistency index value, which can be obtained from the table, and CI is the consistency index.

2. The method for assessing the bearing capacity of fractured rock mass in roadway surrounding rock as described in claim 1, characterized in that, In step two, determining the range of the fractured rock mass strength factor Q refers to determining the overall range of values ​​for the fractured rock mass strength factor Q based on the product of the criterion layer and its corresponding sub-criterion layer.

3. The method for assessing the bearing capacity of fractured rock mass in roadway surrounding rock as described in claim 2, characterized in that, Step three, which involves classifying and evaluating the bearing capacity of the fractured rock mass surrounding the tunnel based on the fractured rock mass strength factor Q range, includes: When the strength factor Q of fractured rock mass is between 0.60 and 0.71, the fractures are very well developed, the rock mass has very low bearing capacity, and it is very easy for the fractures to propagate, penetrate, and become unstable, which has a serious impact on underground engineering. When the strength factor Q of fractured rock mass is between 0.45 and 0.60, fractures are developed, the rock mass has low bearing capacity, and the rock mass is more prone to penetrating failure, which will have a significant impact on underground engineering. When the strength factor Q of fractured rock mass is between 0.30 and 0.45, the fractures are relatively well-developed, the rock mass has a certain bearing capacity, and it requires strong disturbance to further destabilize and fail, which will have a certain impact on some underground engineering projects. When the strength factor Q of fractured rock mass is between 0.20 and 0.30, fractures are not easy to develop, the rock mass has high bearing capacity, and it is almost unaffected by the development and penetration of fractures. Underground engineering has high stability in the absence of special environments.

4. The method for assessing the bearing capacity of fractured rock mass in roadway surrounding rock as described in claim 3, characterized in that, In step four, the process of quantifying the distribution morphology of fractures in the surrounding rock mass of the roadway by borehole inspection is as follows: boreholes are drilled in the top and bottom plates and both sides of the roadway, and the length, dip angle and distribution morphology of fractures in the fractured rock mass are observed by a borehole inspection instrument. The computer exports the digital images of the borehole inspection to analyze the development of fractures in the surrounding rock, and then obtains the strength factor Q of the fractured rock mass of the target roadway and the assessment results of the development level of fractures in the surrounding rock of the roadway.

Images