Comprehensive evaluation method of surrounding rock characteristics

Abstract

The present invention provides a method for comprehensive evaluation of surrounding rock characteristics, including: based on in-situ testing of surrounding rock, obtaining in-situ quality indexes, strength-stress ratio indexes, crack area and rock characteristic indexes of rock mass; based on in-situ quality indexes of rock mass, performing surrounding rock quality evaluation; based on normalization processing of in-situ quality indexes of rock mass, strength-stress ratio indexes and rock characteristic indexes, performing surrounding rock stability evaluation; based on strength-stress ratio indexes and crack area, performing surrounding rock injectability judgment; based on rock characteristic indexes, performing rock compressibility judgment by hierarchical analysis method. The method for comprehensive evaluation of surrounding rock characteristics is a method based on in-situ testing of surrounding rock, rapid testing of multiple parameters of rock mass and accurate multi-dimensional comprehensive evaluation of surrounding rock characteristics, providing a basis for prediction of rock stratum migration and collapse laws, mine pressure manifestation laws and the like in the process of working face mining, and providing a basis for rock stratum control and advanced disaster management.

Description

Technical Field

[0001] The invention relates to the field of mining technology, and in particular to a method for comprehensively evaluating surrounding rock characteristics. Background Art

[0002] The lithology, physics, mechanics and other characteristics of coal and rock and the geomechanical environment in which they are located are the core parameters related to rock strata movement and surrounding rock deformation and destruction during coal mining. They are the basic basis for preventing and controlling disaster threats such as roof collapse, large deformation of surrounding rock, and rock burst. Most parameters are obtained through laboratory tests, which are not only inefficient and costly, but also because the test data obtained out of the original environment has greatly reduced its guiding significance for engineering practice. Rock mass quality evaluation is the basic work related to rock mass classification and its stability control method, and the accuracy of the basic parameters required for such evaluation methods is crucial.

[0003] In-situ testing methods are increasingly widely used due to their high efficiency, low cost, and greater use value of in-situ parameters. However, the traditional comprehensive evaluation of surrounding rock characteristics requires many parameters, too many redundant data collection and testing steps, and the generation of all evaluation results basically depends on the test results in the laboratory. In order to evaluate the surrounding rock of the roadway, it is still necessary to collect in-situ data multiple times to evaluate various surrounding rock characteristics. It can be seen that the traditional comprehensive evaluation of surrounding rock characteristics has the defects of limited adaptability, numerous data, lengthy test process, and low test and evaluation efficiency, so it is not conducive to real-time and accurate guidance of regional mining planning, rock disaster prediction and early warning, and advanced prevention and control. Summary of the invention

[0004] The present invention provides a surrounding rock characteristic comprehensive evaluation method, which is used to solve the defects of the conventional surrounding rock characteristic comprehensive evaluation in the prior art, such as limited adaptability, numerous data, lengthy test process and too low test evaluation efficiency.

[0005] The present invention provides a method for comprehensive evaluation of surrounding rock characteristics, comprising:

[0006] Based on the in-situ test of surrounding rock, obtain the in-situ quality index of rock mass, strength-stress ratio index, fracture area and rock mass characteristic index;

[0007] Perform surrounding rock quality evaluation based on in-situ rock mass quality indicators;

[0008] Based on the normalization of rock mass in-situ quality indicators, strength-stress ratio indicators, and rock mass characteristic indicators, the surrounding rock stability evaluation is performed;

[0009] Based on the strength-stress ratio index and the fracture area, the injectability of the surrounding rock is judged;

[0010] Based on the rock mass characteristic indicators, the compressibility of the rock formation is determined by the hierarchical analysis method.

[0011] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the surrounding rock quality evaluation based on the in-situ quality index of the rock mass includes:

[0012] Obtain basic rock mass quality indicators based on in-situ testing of surrounding rock;

[0013] Based on the basic quality index of rock mass, groundwater influence coefficient, rock layer variation coefficient and layer number influence coefficient, the in-situ quality index of rock mass is obtained;

[0014] Based on the in-situ quality indicators of the rock mass, the rock mass quality classification evaluation results are obtained.

[0015] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the normalization processing based on the in-situ quality index of the rock mass, the strength-stress ratio index, and the rock mass characteristic index to perform surrounding rock stability evaluation includes:

[0016] Based on the in-situ test of surrounding rock, obtain the in-situ quality index of rock mass, strength-stress ratio index, geological structure index, mining index and section index;

[0017] Based on the normalization of the in-situ quality index of the rock mass, the strength-stress ratio index, the geological structure index, the mining index and the cross-section index, the normalized values ​​of the in-situ quality index of the rock mass, the strength-stress ratio index, the geological structure index, the mining index and the cross-section index are obtained;

[0018] Based on the normalized values ​​of the in-situ quality index of the rock mass, the strength-stress ratio index, the geological structure index, the mining index and the cross-section index and the weight mapping relationship, the comprehensive index value is obtained.

[0019] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, a groundwater influence coefficient is obtained based on basic rock mass quality indicators, surrounding rock fissure water pressure and tunnel water output;

[0020] Based on the average in-situ test strength of each rock formation, the mean of the in-situ test strengths of all rock formations and the standard deviation of the in-situ test strengths of all rock formations, the standard score of the strength of each rock formation is obtained; based on the standard score of the strength of each rock formation, the influence coefficient of rock formation variation is obtained;

[0021] Based on the mapping relationship between the measured surrounding rock range and the number of rock layers, the layer number influence coefficient is obtained.

[0022] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the judgment of injectability of surrounding rock based on strength-stress ratio index and fracture area includes:

[0023] Obtain the fracture area per unit drilling length according to the fracture area revealed by drilling;

[0024] The injectability coefficient of the measured surrounding rock is obtained according to the ratio of the fracture area to the strength-stress ratio within the unit borehole length, wherein the strength-stress ratio is a parameter corresponding to the degree of fracture development.

[0025] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, obtaining the fracture area per unit borehole length according to the fracture area exposed by drilling comprises:

[0026] The single fracture area exposed by the drilling hole is obtained according to the product of fracture trace length and fracture width;

[0027] Obtaining the fracture area revealed by the drilling according to the sum of the single fracture areas revealed by the drilling;

[0028] The fracture area per unit borehole length is obtained based on the ratio of the fracture area exposed by the borehole to the borehole length.

[0029] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the compressibility judgment of rock formations based on rock mass characteristic indicators by using a hierarchical analysis method comprises:

[0030] Based on in-situ drilling tests, the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer are obtained;

[0031] Based on the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer, standardized parameters of the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer are obtained;

[0032] Based on the analytic hierarchy process, the weight of each indicator is obtained;

[0033] Based on the standardized parameters of the percentage of brittle mineral components, elastic modulus, fracture pressure, tensile strength of each rock layer and the weight of each index, the compressibility coefficient of each rock layer is obtained.

[0034] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the percentage of brittle mineral components of each rock layer obtained based on in-situ drilling testing includes:

[0035] Based on the natural gamma test, the gamma intensity value of each rock layer is obtained;

[0036] The gamma intensity value of each rock layer was calibrated based on the laboratory rock mineral composition test results to obtain the percentage of mud content in each rock layer;

[0037] Based on the percentage of mud content in each rock layer, the percentage of brittle mineral content in each rock layer is obtained;

[0038] The elastic modulus of each rock layer obtained based on the in-situ test of the borehole includes:

[0039] Based on the borehole penetration method, the rock mass pressure-displacement curve of each rock layer is obtained;

[0040] Based on the rock mass pressure-displacement curve of each rock layer, the elastic modulus of each rock layer is obtained;

[0041] The method of obtaining the fracture pressure and tensile strength of each rock layer based on the in-situ test of the borehole includes:

[0042] Based on hydraulic fracturing, the fracture pressure, maximum horizontal principal stress and minimum principal stress of each rock layer are obtained;

[0043] Based on the fracture pressure, maximum horizontal principal stress and minimum principal stress of each rock layer, the tensile strength of each rock layer is obtained.

[0044] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the basic quality indicators of the rock mass are obtained based on in-situ testing of the surrounding rock, including:

[0045] Based on the borehole penetration method, the average in-situ test strength of each rock layer is obtained;

[0046] Obtaining the weighted strength of the rock formation based on the average in-situ test strength of each rock formation and the thickness of each rock formation;

[0047] Based on the borehole observation, the fracture opening and fracture trace length of each fracture are obtained;

[0048] Based on the fracture aperture and fracture trace length of each fracture, the sum of the fracture cross-sectional areas of the rock formation is obtained;

[0049] Based on the ratio of the sum of the cross-sectional areas of the rock formation fractures to the total area exposed by the rock formation drilling, the fracture area ratio is obtained;

[0050] Based on the proportion of fracture area, the rock integrity index is obtained;

[0051] Based on the weighted strength of rock formations and rock integrity index, basic rock mass quality indicators are obtained.

[0052] According to a method for comprehensive evaluation of surrounding rock characteristics provided by the present invention, the method for obtaining the strength stress ratio index based on in-situ testing of the surrounding rock includes:

[0053] Based on the in-situ test of surrounding rock, the maximum principal stress in the original rock stress and the weighted strength of the uniaxial compressive strength are obtained;

[0054] The strength-stress ratio index is obtained based on the ratio of the weighted strength of the uniaxial compressive strength to the maximum principal stress in the original rock stress.

[0055] The method for comprehensive evaluation of surrounding rock characteristics provided by the present invention includes: obtaining in-situ quality index, strength-stress ratio index, crack area and rock characteristic index of rock mass based on in-situ test of surrounding rock; performing surrounding rock quality evaluation based on in-situ quality index of rock mass; performing surrounding rock stability evaluation based on normalization of in-situ quality index of rock mass, strength-stress ratio index and rock characteristic index; performing surrounding rock injectability judgment based on strength-stress ratio index and crack area; and performing rock compressibility judgment based on rock characteristic index by analytic hierarchy process. The method for comprehensive evaluation of surrounding rock characteristics is a method based on in-situ test of surrounding rock, which can quickly test multiple parameters of rock mass and accurately conduct multi-dimensional comprehensive evaluation of surrounding rock characteristics. It can complete data collection, testing and evaluation in real time in the in-situ of surrounding rock, and has the advantages of high efficiency, speed and accuracy, thereby providing a basis for the prediction of rock stratum migration and collapse law, mine pressure manifestation law and the like in the process of working face mining, and providing a basis for rock stratum control and advanced disaster management. It can be seen that the comprehensive evaluation method of surrounding rock characteristics can obtain one or more in-situ collected data of the surrounding rock mass through drilling, and directly use the in-situ collected data in real time for quality evaluation, stability evaluation, compressibility and injectability judgment, so as to realize the comprehensive evaluation of surrounding rock characteristics and provide accurate, convenient and efficient data support and judgment basis for subsequent on-site support, reinforcement, fracturing and other surrounding rock control.

[0056] The in-situ testing technology of surrounding rock is an important testing technology. It can not only efficiently test a large range of surrounding rock, but also the in-situ test data can better reflect the actual engineering environment than the laboratory test results, and has greater guiding significance for engineering practice. The present invention adopts a large-scale in-situ test to obtain the basic parameters of surrounding rock such as the quality, strength-stress ratio, fracture area, and rock mass characteristics of the surrounding rock, and proposes a comprehensive evaluation method of surrounding rock characteristics based on in-situ testing of rock mass, so as to accurately evaluate the tested surrounding rock from data collection, testing to multi-dimensional evaluation of surrounding rock characteristics. Compared with the traditional judgment method of evaluating the rock mass quality of tunnel surrounding rock in the prior art, which is to send the collected tunnel surrounding rock samples to the laboratory for testing to obtain test data, the test process is inefficient and costly, and the guiding significance of the test data for engineering practice is greatly reduced due to the separation from the in-situ environment. The present invention uses multi-parameter in-situ test data to perform accurate and comprehensive regional comprehensive evaluation of tunnel surrounding rocks, can complete data collection and testing in real time in the surrounding rock in situ, and can quickly and in real time perform multiple types of evaluations of surrounding rock characteristics, which can not only shorten the time from surrounding rock in-situ data collection to surrounding rock characteristic evaluation, and improve evaluation efficiency; but also avoid unnecessary data pollution caused by data transfer to the laboratory, reduce error generation, and improve evaluation accuracy. The surrounding rock characteristic comprehensive evaluation method can realize surrounding rock in-situ data collection, testing and characteristic evaluation, and efficiently and quickly generate accurate evaluation results, providing basic data for the prediction of surrounding rock deformation and damage and the selection of control technologies represented by anchoring, grouting and fracturing weakening, and the design of key parameters, and providing support for the control of disasters such as roof disasters, surrounding rock instability and rock burst, so as to be more conducive to real-time and accurate guidance of regional mining planning, rock disaster prediction and early warning, and advanced prevention and control.

[0057] In addition to the technical problems solved by the present invention, the technical features of the technical solutions constituted, and the advantages brought about by the technical features of these technical solutions described above, other technical features of the present invention and the advantages brought about by these technical features will be further explained in conjunction with the accompanying drawings or will be understood through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0059] Figure 1 is a flow chart of a method for comprehensive evaluation of surrounding rock characteristics provided by an embodiment of the present invention;

[0060] Figure 2is a flow chart for executing surrounding rock quality evaluation in the surrounding rock characteristic comprehensive evaluation method provided by an embodiment of the present invention;

[0061] Figure 3 It is a color map of a comprehensive drilling information map based on in-situ testing of surrounding rock in the method for comprehensive evaluation of surrounding rock characteristics provided by an embodiment of the present invention;

[0062] Figure 4 It is a grayscale image of a comprehensive drilling information image based on an in-situ test of surrounding rock in the method for comprehensive evaluation of surrounding rock characteristics provided by an embodiment of the present invention;

[0063] Figure 5 It is a color map of a single tunnel geological model map in the surrounding rock characteristics comprehensive evaluation method provided by an embodiment of the present invention;

[0064] Figure 6 It is a grayscale image of a single tunnel geological model image in the surrounding rock characteristics comprehensive evaluation method provided by an embodiment of the present invention;

[0065] Figure 7 is a flow chart for performing surrounding rock stability evaluation in the surrounding rock characteristic comprehensive evaluation method provided by an embodiment of the present invention;

[0066] Figure 8 It is a flow chart for executing the judgment of injectability of surrounding rock in the method for comprehensive evaluation of surrounding rock characteristics provided by an embodiment of the present invention;

[0067] Fig. 9 It is a flow chart for executing surrounding rock compressibility judgment in the surrounding rock characteristic comprehensive evaluation method provided by an embodiment of the present invention;

[0068] Fig.10 It is a color map of the rock mass quality drilling assessment of a certain tunnel and the predicted rock mass quality distribution along the tunnel direction provided by a specific embodiment of the present invention;

[0069] Fig.11 It is a grayscale map of drilling assessment of rock mass quality in a certain tunnel and prediction of rock mass distribution along the direction of the tunnel provided by a specific embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0071] like Figure 1 As shown, an embodiment of the present invention provides a method for comprehensive evaluation of surrounding rock characteristics. The method for comprehensive evaluation of surrounding rock characteristics includes:

[0072] Based on the in-situ test of surrounding rock, obtain the in-situ quality index of rock mass, strength-stress ratio index, fracture area and rock mass characteristic index; based on the in-situ quality index of rock mass, perform surrounding rock quality evaluation;

[0073] Based on the normalization of rock mass in-situ quality indicators, strength-stress ratio indicators, and rock mass characteristic indicators, the surrounding rock stability evaluation is performed;

[0074] Based on the strength-stress ratio index and the fracture area, the injectability of the surrounding rock is judged;

[0075] Based on the rock mass characteristic indicators, the compressibility of the rock formation is determined by the hierarchical analysis method.

[0076] This method for comprehensive evaluation of surrounding rock characteristics is a method based on in-situ testing of surrounding rock, rapid testing of multiple parameters of rock mass, and accurate multi-dimensional comprehensive evaluation of surrounding rock characteristics. It can complete data collection, testing and evaluation in real time in the surrounding rock in situ, and has the advantages of high efficiency, speed and accuracy, thus providing a basis for the prediction of rock stratum migration and collapse laws, mine pressure manifestation laws, etc. during the mining process of the working face, and providing a basis for rock stratum control and advanced disaster management. It can be seen that this method for comprehensive evaluation of surrounding rock characteristics can use drilling to obtain one or more in-situ collected data of the surrounding rock mass, and directly use the in-situ collected data in real time for quality evaluation, stability evaluation, compressibility and injectability judgment, to achieve a comprehensive evaluation of surrounding rock characteristics, and provide accurate, convenient and efficient data support and judgment basis for subsequent on-site support, reinforcement, fracturing and other surrounding rock control.

[0077] The in-situ testing technology of surrounding rock is an important testing technology. It can not only efficiently test a large range of surrounding rock, but also the in-situ test data can better reflect the actual engineering environment than the laboratory test results, and has greater guiding significance for engineering practice. The present invention adopts a large-scale in-situ test to obtain the basic parameters of surrounding rock such as the quality, strength-stress ratio, fracture area, and rock mass characteristics of the surrounding rock, and proposes a comprehensive evaluation method of surrounding rock characteristics based on in-situ testing of rock mass, so as to accurately evaluate the tested surrounding rock from data collection, testing to multi-dimensional evaluation of surrounding rock characteristics. Compared with the traditional judgment method of evaluating the rock mass quality of tunnel surrounding rock in the prior art, which is to send the collected tunnel surrounding rock samples to the laboratory for testing to obtain test data, the test process is inefficient and costly, and the guiding significance of the test data for engineering practice is greatly reduced due to the separation from the in-situ environment. The present invention uses multi-parameter in-situ test data to perform accurate and comprehensive regional comprehensive evaluation of tunnel surrounding rocks, can complete data collection and testing in real time in the surrounding rock in situ, and can quickly and in real time perform multiple types of evaluations of surrounding rock characteristics, which can not only shorten the time from surrounding rock in-situ data collection to surrounding rock characteristic evaluation, and improve evaluation efficiency; but also avoid unnecessary data pollution caused by data transfer to the laboratory, reduce error generation, and improve evaluation accuracy. The surrounding rock characteristic comprehensive evaluation method can realize surrounding rock in-situ data collection, testing and characteristic evaluation, and efficiently and quickly generate accurate evaluation results, providing basic data for the prediction of surrounding rock deformation and damage and the selection of control technologies represented by anchoring, grouting and fracturing weakening, and the design of key parameters, and providing support for the control of disasters such as roof disasters, surrounding rock instability and rock burst, so as to be more conducive to real-time and accurate guidance of regional mining planning, rock disaster prediction and early warning, and advanced prevention and control.

[0078] In some embodiments, Figure 2 As shown in the figure, the surrounding rock quality evaluation based on the in-situ rock mass quality indicators mentioned above includes:

[0079] Based on the in-situ test of surrounding rock, the basic rock quality index BQ is obtained;

[0080] Based on the basic rock mass quality index BQ, groundwater influence coefficient K1, rock layer variation coefficient K2 and layer number influence coefficient K3, the rock mass in-situ quality index [BQ] is obtained;

[0081] Based on the rock mass in-situ quality index [BQ], obtain the rock mass quality classification evaluation results;

[0082] Based on the results of in-situ testing of surrounding rock and classification and evaluation of rock mass quality, a two-dimensional rock mass distribution model along the tunnel strike and a three-dimensional rock mass distribution model at the working face were constructed.

[0083] In this implementation, the surrounding rock quality evaluation can determine the rock mass quality classification evaluation results, and then clearly classify the rock mass quality, and predict the deformation and failure of the surrounding rock and select the control form according to the classification results. In addition, based on the completion of the rock mass quality classification evaluation, based on the surrounding rock in-situ test and rock mass quality classification evaluation results, a two-dimensional rock mass quality distribution model along the roadway strike and a three-dimensional rock mass quality distribution model of the working face are constructed to clearly classify and model the quality of the surrounding rock.

[0084] The evaluation of the rock mass quality of the surrounding rock is the basic work related to the rock mass classification and its stability control method. The accuracy of the basic parameters required for the evaluation method is crucial. Compared with the traditional judgment method of the rock mass quality evaluation of the tunnel surrounding rock in the prior art, which is to send the collected tunnel surrounding rock samples to the laboratory for testing to obtain test data, the test process is inefficient and costly, and the guiding significance of the test data for engineering practice is greatly reduced due to the separation from the in-situ environment. The present invention uses multi-parameter in-situ data to evaluate the rock mass quality of the tunnel surrounding rock, which can greatly improve the generation efficiency and accuracy of the quality evaluation results, and can provide a basis for the prediction of the rock layer migration and collapse law, the law of mine pressure manifestation, etc. during the mining process of the working face, and provide a basis for rock layer control and advanced disaster management, so that the subsequent surrounding rock stability analysis and judgment is more accurate and efficient, and provides guidance for the support of the subsequent tunnel or similar conditions. It can also take relevant control measures in time at the early stage of tunnel service according to the judgment results to avoid the instability of the tunnel, and conduct a comprehensive and large-scale early stability pre-evaluation of the tunnel surrounding rock, which is very important for the advanced control of the expected deformation and damage of the tunnel. Moreover, the subsequent stability judgment results can realize the reasonable and differentiated support of the tunnel, take early control measures in a timely and scientific manner, reduce the risk of tunnel disasters, and realize efficient and economical tunnel excavation and maintenance.

[0085] In this embodiment, the above-mentioned surrounding rock in-situ test includes:

[0086] Drill holes at any position of the surrounding rock in the tunnel;

[0087] Based on the borehole peep method, the surrounding rock structure image is obtained, and the crack opening w and crack trace length l of each crack in each rock layer are obtained based on the surrounding rock structure image;

[0088] Obtaining the natural gamma ray intensity of each rock layer in the borehole, and determining the lithology range of each rock layer based on the natural gamma ray intensity of each rock layer;

[0089] Based on the borehole penetration method, the in-situ test strength of each rock layer is obtained;

[0090] Based on the lithology range of each rock layer, the surrounding rock structure image and the in-situ test strength R0, the layered lithology and thickness H of each rock layer are obtained.

[0091] According to an embodiment provided by the present invention, considering the actual engineering operation and the on-site environment, the in-situ test of the surrounding rock implemented on the surrounding rock specifically includes:

[0092] A test location is selected in any tunnel in the coal mine and a borehole of a certain depth is drilled into the surrounding rock;

[0093] The drilling peek method is used to observe the surrounding rock structure and obtain high-definition images of the surrounding rock structure through observation;

[0094] The natural gamma ray tester is used to test the natural gamma ray intensity of different rock layers, and based on the natural gamma ray intensity, the range of lithology of each rock layer in the surrounding rock is preliminarily determined according to the empirical method;

[0095] The borehole penetration method is used to obtain the in-situ strength of each rock layer, so as to subsequently obtain the average in-situ test strength R0 of each rock layer;

[0096] By integrating the borehole structure image, natural gamma ray intensity and the in-situ intensity of each rock layer, more accurate stratified lithology and the thickness H of each rock layer are obtained within the range of lithology values ​​of each rock layer, and a single borehole comprehensive geomechanical model is constructed;

[0097] The single borehole comprehensive geomechanical model described in this embodiment includes the following: Figure 3 and Figure 4 The comprehensive borehole information diagram based on in-situ measurements shown in the figure contains geological and mechanical parameter information such as the stratified lithology of the surrounding rock layers, the thickness H of each rock layer, the natural gamma intensity, the structural image, and the in-situ strength of each rock layer, as well as geometric information such as three-dimensional coordinates.

[0098] In this embodiment, the basic rock mass quality index BQ can be obtained through the in-situ test of the surrounding rock, and the in-situ rock mass quality index [BQ] is calculated using the basic rock mass quality index BQ, the groundwater influence coefficient K1, the rock layer variation coefficient K2 and the layer number influence coefficient K3. The in-situ rock mass quality index is [BQ], then [BQ] = BQ-100 (K1+K2+K3).

[0099] According to an embodiment provided by the present invention, based on the in-situ test of the surrounding rock, obtaining the basic rock quality index BQ includes:

[0100] Based on the in-situ test of surrounding rock, the weighted strength R of rock formation and the rock integrity index Kv are obtained;

[0101] Based on the weighted strength R of the rock formation and the rock integrity index Kv, the basic rock quality index BQ is obtained.

[0102] According to a specific embodiment provided by the present invention, based on the in-situ test of the surrounding rock, obtaining the basic rock quality index BQ further includes:

[0103] Based on the in-situ test of the surrounding rock, the average in-situ test strength R0 of each rock layer, as well as the crack opening w and crack trace length l of each crack are obtained;

[0104] Based on the average in-situ test strength R0 of each rock layer and the thickness H of each rock layer, the weighted strength R of the rock layer is obtained;

[0105] Based on the crack opening w and crack trace length l of each crack, the sum of the cross-sectional areas S of the rock formation cracks is obtained;

[0106] Based on the ratio of the sum of the cross-sectional areas of the rock formation fractures S to the total area of ​​the rock formation exposed by drilling S0, the fracture area ratio k is obtained. l ;

[0107] Based on the crack area ratio k l , and obtain the rock integrity index K v ;

[0108] Based on the rock formation weighted strength R and rock integrity index K v , obtain the basic rock quality index BQ.

[0109] In this embodiment, the borehole penetration method is used for in-situ strength testing, and the surrounding rock structure is observed in combination with the borehole penetration method. Through the observation, a high-definition surrounding rock structure image is obtained to determine the thickness H of each rock layer and the average in-situ test strength R0 of each rock layer. Then the weighted strength of the rock layer is Wherein, m is the number of rock layers in the surrounding rock being measured revealed by drilling.

[0110] The surrounding rock structure image is processed by drilling peek to obtain the number of cracks in each rock layer n and the crack opening w and crack trace length l of each crack. The product of the crack opening w and the crack trace length l is the cross-sectional area of ​​the crack, so the sum of the cross-sectional areas of the cracks in the rock layer is Fracture area ratio k l k l =S / S0, S0 is the total area exposed by drilling in the rock formation.

[0111] Definition of rock integrity index K v The crack area ratio k l The corresponding relationship with the rock integrity is shown in Table 1. l Correspondingly selected rock integrity index K v .

[0112] Table 1

[0113] <![CDATA[k l ]]> 0～0.1％ 0.1％～0.4％ 0.4％～0.7％ 0.7％～1.0％ ≥1.0％ <![CDATA[K v ]]> 1～0.95 0.95～0.65 0.65～0.35 0.35～0.05 0.05 Completeness whole More complete More broken broken Extremely Broken

[0114] The calculation method of Kv for the first 4 columns is:

[0115] The reference standard is GB / T50218-2014 "Engineering Rock Mass Classification Standard" (issued on August 27, 2014, and implemented on May 1, 2015), then the basic rock mass quality index BQ = 100 + 3R + 250K v .

[0116] According to an embodiment provided by the present invention, the groundwater influence coefficient K1 is obtained based on the basic rock mass quality index BQ, the surrounding rock fissure water pressure p and the tunnel water output Q.

[0117] In this embodiment, the tunnel surrounding rock fissure water pressure p (MPa) and tunnel water output Q (L / min·10m) are obtained by detecting the tunnel surrounding rock. Referring to Table 2 below, the groundwater influence coefficient K1 is determined in combination with the basic rock mass quality index BQ.

[0118] Table 2

[0119]

[0120] According to an embodiment provided by the present invention, based on the average in-situ test strength R0 of each rock formation, the mean μ of the in-situ test strengths of all rock formations, and the standard deviation σ of the in-situ test strengths of all rock formations, the standard score z of the strength of each rock formation is obtained;

[0121] Based on the standard score z of each rock formation strength, the rock formation variation influence coefficient K2 is obtained.

[0122] In this embodiment, the quotient of the difference between the average in-situ test strength R0 of each rock formation and the mean μ of the in-situ test strengths of all rock formations and the standard deviation σ of the in-situ test strengths of all rock formations is used as the standard score z of the strength of each rock formation, that is, the standard score z of the strength of each rock formation = (R0-μ) / σ. Among the standard scores of the strength of each rock formation, the minimum standard score of the strength of each rock formation is selected, and the rock formation variation influence coefficient K2 can be determined through the following Table 3. When the minimum rock formation strength is greater than 40MPa, it is not applicable and the value is 0.

[0123] Table 3

[0124]

[0125] According to an embodiment provided by the present invention, based on the mapping relationship between the measured surrounding rock range and the number of rock layers, the layer number influence coefficient K3 is obtained.

[0126] In this embodiment, the number of rock layers is the number of rock layers within 10m of the measured surrounding rock, and the number of rock layers is obtained based on the in-situ test of the surrounding rock, and the layer number influence coefficient K3 is correspondingly determined according to the following Table 4. In other embodiments, when the measured surrounding rock exceeds the range of 10m, the number of layers in the first row of the table below increases by 1 for every 5m increase in depth, and the value of K3 in the second row remains unchanged.

[0127] Table 4

[0128] Number of rock layers within 10m 1 2 3 4 5 ≥6 <![CDATA[K3]]> 0 0.2 0.4 0.6 0.8 1

[0129] In this embodiment, after obtaining the basic rock mass quality index BQ, groundwater influence coefficient K1, rock layer variation coefficient K2 and layer number influence coefficient K3, the rock mass in-situ quality index [BQ] is calculated [BQ] = BQ-100 (K1+K2+K3).

[0130] According to the calculation results, the rock mass quality is classified with reference to Table 5 below, and the deformation and failure prediction of the surrounding rock and the selection of the control form are carried out according to the classification results.

[0131] Table 5

[0132]

[0133] According to an embodiment provided by the present invention, the construction of a two-dimensional rock mass distribution model along the tunnel strike and a three-dimensional rock mass distribution model on the working face based on the surrounding rock in-situ test and rock mass quality evaluation results includes:

[0134] In-situ testing of surrounding rock was performed based on multiple drilling positions in the same tunnel to obtain a single tunnel geological model and a two-dimensional rock mass distribution model along the tunnel strike.

[0135] Based on the geological model of a single tunnel of multiple tunnels, a three-dimensional geological model of the working face is obtained;

[0136] Based on the three-dimensional geological model of the working face and the rock mass quality classification and evaluation results, a three-dimensional rock mass quality distribution model of the working face is constructed.

[0137] According to an embodiment provided by the present invention, performing in-situ testing of surrounding rocks at multiple drilling positions in the same tunnel to obtain a geological model of a single tunnel includes:

[0138] Based on the in-situ testing of surrounding rock at multiple drilling positions along the axial direction of the same roadway, a single roadway geological model is obtained;

[0139] Based on the geological model of a single tunnel, the interpolation method and thermal cloud map characterization method are used to obtain the rock mass distribution cloud map along the axial direction of the tunnel.

[0140] According to an embodiment provided by the present invention, an interpolation method and a thermal cloud image characterization method are used to construct a two-dimensional rock mass distribution model along the direction of the tunnel and a three-dimensional rock mass distribution model of the working face.

[0141] In this embodiment, the above-mentioned surrounding rock in-situ test is used for any test borehole in the same tunnel to obtain a single borehole comprehensive geomechanical model, and the single borehole comprehensive geomechanical models obtained from multiple test boreholes in the same tunnel are combined to establish a single tunnel geological model obtained from multiple test boreholes along the tunnel axis, and then obtain the distribution characteristics of the roof rock layer along the tunnel axis. In addition, combined with the above-mentioned rock mass quality evaluation results, the interpolation method and thermal cloud map characterization method are used to obtain the rock mass quality distribution cloud map along the tunnel axis, providing a basis for tunnel stability assessment, prediction, monitoring, etc.

[0142] In this embodiment, the drilling data obtained by in-situ testing of multiple surrounding rocks in two or more lanes of the working face are combined with the following Figure 5 and Figure 6 The geological models of the single tunnels of the multiple tunnels shown in the figure are combined to establish a three-dimensional geological model of the working face. In addition, based on the rock mass quality evaluation results, the interpolation method and the thermal cloud image representation method are used to construct a two-dimensional rock mass quality distribution model along the tunnel direction and a three-dimensional rock mass quality distribution model of the working face, which provides a basis for the prediction of the rock stratum migration and collapse laws and the law of mine pressure manifestation during the mining process of the working face, and provides a basis for rock stratum control and advanced disaster management.

[0143] The surrounding rock quality evaluation method described in this embodiment can establish a transparent geological model based on the in-situ measured data of the borehole, and can perform accurate numerical calculations based on the model to simulate the rock movement and surrounding rock deformation caused by tunnel excavation, working face mining, etc., and can predict the law of mine pressure manifestation based on the measured data of similar conditions to guide engineering design and production practice; moreover, the geological model and rock mass distribution model constructed by the surrounding rock quality evaluation method can accurately show the geological and geometric characteristics of the surrounding rock, and can provide accurate basic parameters for intelligent mining.

[0144] In some embodiments, Figure 7 As shown, the above-mentioned normalization processing based on the in-situ quality index of the rock mass, the strength-stress ratio index, and the rock mass characteristic index is performed to perform the surrounding rock stability evaluation, including:

[0145] Based on the in-situ test of surrounding rock, the in-situ quality index [BQ] of rock mass, the strength-stress ratio index k1, the geological structure index k2, the mining index k3 and the cross-section index k4 are obtained;

[0146] Based on the normalization of the rock mass in-situ quality index [BQ], strength-stress ratio index k1, geological structure index k2, mining index k3 and cross-section index k4, the normalized values ​​of the rock mass in-situ quality index [BQ], strength-stress ratio index k1, geological structure index k2, mining index k3 and cross-section index k4 are obtained. k ;

[0147] Based on the normalized values ​​of the rock mass in-situ quality index [BQ], strength-stress ratio index k1, geological structure index k2, mining index k3 and cross-section index k4, the k And the weight mapping relationship, obtain the comprehensive index value T.

[0148] It should be noted that, consistent with the above-mentioned surrounding rock quality evaluation, drilling is performed on the surrounding rock to be tested, and various tests are performed on the drilling holes and the surrounding rock to be tested to obtain corresponding data parameters, which is the in-situ test of the surrounding rock.

[0149] The present invention performs an in-situ test on the surrounding rock before the actual project begins, obtains the in-situ quality index [BQ] of the rock mass, the strength-stress ratio index k1, the geological structure index k2, the mining index k3 and the cross-section index k4 through the test results, and then performs normalization processing on the in-situ quality index [BQ] of the rock mass, the strength-stress ratio index k1, the geological structure index k2, the mining index k3 and the cross-section index k4 respectively, to obtain the normalized value d1 of the in-situ quality index of the rock mass, the normalized value d2 of the strength-stress ratio index, the normalized value d3 of the geological structure index, the normalized value d4 of the mining index and the normalized value d5 of the cross-section index, and finally the normalized value d1 of the in-situ quality index of the rock mass, the normalized value d2 of the strength-stress ratio index, the normalized value d3 of the geological structure index, the normalized value d4 of the mining index and the normalized value d5 of the cross-section index in combination with the weight values ​​W corresponding to all the indicators in the weight mapping relationship. i , and obtain the comprehensive index value T. The comprehensive index value T can be used to classify the measured surrounding rock and determine the degree of stability of the surrounding rock. Based on the experience of mine support engineering, the support and control forms and key parameter solutions for surrounding rocks of different stability are given to control the surrounding rock more accurately.

[0150] Compared with the traditional judgment method of tunnel surrounding rock stability in the prior art, which indirectly evaluates the deformation and damage of the surrounding rock, the response characteristics of the support body, etc. through monitoring means, it has little effect on the advance evaluation of the stability of the tunnel during the entire service cycle, and the monitoring is mostly local monitoring. The present invention uses multi-parameter in-situ data to judge the stability of the tunnel surrounding rock, which can provide guidance for the support of subsequent tunnels or tunnels with similar conditions. It can also take relevant control measures in time at the early stage of tunnel service according to the judgment results to avoid instability of the tunnel. It is very important to conduct a comprehensive and large-scale early stability pre-assessment of the tunnel surrounding rock for the advance control of expected tunnel deformation and damage. The stability judgment result can realize the reasonable and differentiated support of the tunnel, take early control measures in a timely and scientific manner, reduce the risk of tunnel disasters, and realize efficient and economical tunnel excavation and maintenance.

[0151] In this embodiment, the process of obtaining the in-situ quality index [BQ] of the rock mass has been described in detail in the part of performing the surrounding rock quality evaluation, and the repeated parts will not be repeated here.

[0152] The rock mass in-situ quality index [BQ] is a decreasing index. The normalization of the rock mass in-situ quality index [BQ] needs to be performed according to the following formula (1) to obtain the normalized value d1 of the rock mass in-situ quality index:

[0153]

[0154] Determine the maximum value of the possible range of rock mass in-situ quality index [BQ] is D kmax After determining the rock mass in-situ quality index [BQ], the rock mass in-situ quality index [BQ] is used as D k , put it into formula (1) for calculation, and finally get d k That is, the normalized value d1 of the rock mass in-situ quality index. The in-situ rock mass quality index [BQ] and d k The relationship is shown in Table 6 below.

[0155] Table 6

[0156]

[0157] According to an embodiment provided by the present invention, based on the in-situ test of the surrounding rock, obtaining the strength stress ratio index k1 includes:

[0158] Based on the in-situ test of surrounding rock, the maximum principal stress σ1 in the original rock stress and the weighted strength r of the uniaxial compressive strength are obtained;

[0159] Based on the ratio of the weighted strength r of the uniaxial compressive strength to the maximum principal stress σ1 in the original rock stress, the strength-stress ratio index k1 is obtained.

[0160] In this embodiment, an in-situ test method of the surrounding rock is adopted to obtain the maximum principal stress σ1 in the original rock stress; the weighted strength r of the uniaxial compressive strength is obtained according to the in-situ test of the surrounding rock, and the ratio of the weighted strength r of the uniaxial compressive strength to the maximum principal stress σ1 in the original rock stress is the strength-stress ratio index k1=r / σ1.

[0161] According to the statistical data of the distribution range of the in-situ stress of the sedimentary rock strata in coal mines and the strength of the surrounding rocks, the strength-stress ratio is classified into 4, 3, and 2.

[0162] The strength-stress ratio index k1 is a decreasing index. The normalization of the strength-stress ratio index k1 needs to be performed according to the following formula (2), and then the normalized value d2 of the rock mass in-situ quality index is obtained:

[0163]

[0164] Determine the maximum value of the possible value range of the strength stress ratio index k1 is D kmax After determining the strength-stress ratio index k1, the strength-stress ratio index k1 is used as Dk , put it into formula (2) for calculation, and finally get d k That is the normalized value d2 of the strength-stress ratio index, summarizing the strength-stress ratio index k1 and d k The relationship is shown in Table 7 below.

[0165] Table 7

[0166] <![CDATA[Strength stress ratio index k1]]> ≥4 4～3 3～2 ≤2 <![CDATA[Score 100*d k > 100 100～75 75～50 50～0

[0167] According to an embodiment provided by the present invention, based on the in-situ test of the surrounding rock, obtaining the cross-section index k4 includes:

[0168] Based on the area s of the tunnel cross section, the cross section index k4 is obtained.

[0169] In this embodiment, the cross-section impact is scored according to the size of the designed tunnel cross-section to obtain the cross-section index k4.

[0170] The area s of the cross section is an increasing index. The normalization processing of the cross section index k4 needs to be performed according to the following formula (3), and then the normalized value d5 of the cross section index is obtained:

[0171]

[0172] Determine the maximum value of the possible range of the cross-sectional area s as D kmax After determining the area s of the cross section, use the area s of the cross section as D k , put it into formula (3) for calculation, and finally get d k That is the normalized value d5 of the cross-section index, summarizing the cross-section index k4 and d k The relationship is shown in Table 8 below.

[0173] Table 8

[0174] <![CDATA[The cross-sectional area s (m 2 )]]> ≤12 12～18 18-24 ≥24 <![CDATA[Score 100*d k > 100-50 50-25 25-0 0

[0175] According to an embodiment provided by the present invention, based on the in-situ test of the surrounding rock, obtaining the geological structure index k2 includes:

[0176] Based on the distance between the tunnel and the geological structure, the minimum distance between the tunnel and the geological structure is obtained as the geological structure index k2.

[0177] In this embodiment, the distance between the tunnel and the geological structure is obtained by integrating the mine geological data and related test results, and the minimum distance between the tunnel and the geological structure is obtained. The degree to which the tunnel is affected by the geological structure is analyzed based on the minimum distance between the tunnel and the geological structure, and the geological structure index k2 is given.

[0178] According to an embodiment provided by the present invention, based on normalizing the geological structure indicator k2, obtaining the normalized value d3 of the geological structure indicator includes:

[0179] Based on the geological structure type of the tunnel excavation and the surrounding area, the geological structure type score A was obtained;

[0180] The geological structure index k2 is normalized based on the geological structure type score A to obtain the normalized value d3 of the geological structure index.

[0181] In this embodiment, the structural type of the tunnel excavation and the surrounding area can be determined in accordance with the "Coal Mine Geological Work Rules" and DZ / T 0215-2020 "Mineral Geological Exploration Specifications Coal" to determine the geological structure type of the tunnel excavation and the surrounding area, and then score it according to the minimum distance between the tunnel and the geological structure.

[0182] The minimum distance between the tunnel and the geological structure is a decreasing index. The normalization of the geological structure index k2 needs to be performed according to the following formula (4) to obtain the normalized value d3 of the geological structure index:

[0183]

[0184] According to the geological structure type of the tunnel excavation and the surrounding area, the maximum and minimum values ​​of the corresponding geological structure type score A are determined as A max and A min , determine that the maximum possible value of the minimum distance between the roadway and the geological structure under the geological structure type score A is D kmax After determining the minimum distance between the roadway and the geological structure, the minimum distance between the roadway and the geological structure is taken as D k , put it into formula (4) for calculation, and finally get d k That is the normalized value of geological structure index d3. The normalized value of geological structure index d3 and d k The relationship is shown in Table 9 below.

[0185] Table 9

[0186]

[0187]

[0188] According to an embodiment provided by the present invention, the mining index k3 is obtained based on similar conditions in the mine or monitoring of adjacent tunnels, and the mining impact is scored.

[0189] The mining index k3 is an interval increasing index. The normalization processing of the mining index k3 needs to be performed according to the following formula (5) to obtain the normalized value d4 of the mining index:

[0190]

[0191] Determine the maximum and minimum values ​​of the possible value range of mining index k3 as D kmax and D kmin After determining the mining index k3, the mining index k3 is used as D k , put it into formula (5) for calculation, and finally get d k That is the normalized value d4 of the mining index, summarizing the cross-section index k3 and d k The relationship is shown in Table 10 below.

[0192] Table 10

[0193] <![CDATA[Mining-induced index k3]]> 1～1.2 1.2～1.5 1.5～1.8 ≥1.8 <![CDATA[Score 100*d k > 100-75 75-37.5 37.5-0 0

[0194] In this embodiment, the weight value W corresponding to each indicator is determined based on actual engineering experience. i The weight mapping relationship of the components is shown in Table 11 below.

[0195] Table 11

[0196] index Weight value Rock mass quality index 0.2 Strength stress ratio index 0.25 Geological structural indicators 0.25 Mining indicators 0.2 Tunnel section index 0.1

[0197] According to the weight values ​​of each indicator listed in Table 11, the score of each indicator is calculated as the normalized value d i And the corresponding weight value W i The sum of the scores of all indicators is the comprehensive indicator value.

[0198] By comparing the comprehensive index value T with the type score range in Table 12 below, the surrounding rock stability type identification result can be determined.

[0199] Table 12

[0200] type I II III IV Comprehensive index value T 100～75 75～50 50～25 <25 Surrounding rock stability Stablize Basic stability Unstable Very unstable

[0201] In some embodiments, Figure 8 As shown in the figure, based on the strength-stress ratio index and the fracture area, the injection feasibility judgment of the surrounding rock includes:

[0202] According to the crack area S revealed by the drilling, the crack area per unit drilling length is obtained;

[0203] The injectability coefficient k of the measured surrounding rock is obtained according to the ratio of the fracture area within the unit borehole length to the strength-stress ratio λ, where the strength-stress ratio λ is a parameter corresponding to the degree of fracture development.

[0204] The execution of the surrounding rock injectability judgment in the embodiment of the present invention is a method for judging the feasibility of grouting of surrounding rock. Drilling is performed on the surrounding rock to be tested, and the crack area per unit drilling length can be obtained based on the crack area S exposed by the drilling. The injectability coefficient k of the surrounding rock to be tested can be obtained based on the ratio of the crack area per unit drilling length to the strength stress ratio λ.

[0205] The strength-stress ratio λ is a parameter corresponding to the degree of crack development. The degree of crack development in the surrounding rock is an important parameter that can characterize the grouting volume and is also the most direct method to judge the injectability of the surrounding rock. Therefore, the degree of crack development per unit borehole length is used to quantitatively evaluate the injectability. In the prior art, the calculation method of the degree of crack development needs to be based on the void volume formed by the cracks. However, the cracks are irregularly distributed in space, and it is difficult to obtain the void volume through direct observation, that is, the extension length and expansion area of ​​the cracks in the surrounding rock cannot be accurately obtained through detection, so the obtained degree of crack development is difficult to more truly and accurately reflect the actual situation of the cracks.

[0206] However, the development degree of the surrounding rock is closely related to the stress environment in which the surrounding rock is located and the strength of the surrounding rock itself. The greater the stress and the lower the strength, the higher the degree of crack development, that is, the greater the crack extension coefficient. Therefore, the crack extension coefficient can be estimated by the strength-stress ratio λ, and the crack extension coefficient is inversely proportional to the strength-stress ratio λ. The present invention uses the method of multiplying the crack area S exposed by the borehole by the crack extension coefficient for calculation and judgment, that is, the injectability coefficient k is the ratio of the crack area per unit borehole length to the strength-stress ratio λ, which can avoid the means of obtaining the crack development degree through the void volume formed by the crack, and can more accurately judge the injectability of the measured surrounding rock.

[0207] Moreover, by judging the feasibility of grouting of the surrounding rock, a quantitative evaluation of the injectability of the surrounding rock can be achieved, which can intuitively reflect the feasibility of grouting reinforcement of the surrounding rock, increase the scientific nature of grouting engineering decision-making, and provide data support for grouting volume estimation, material selection, equipment selection, parameter design, etc., laying the foundation for achieving good engineering results.

[0208] According to one embodiment of the present invention, obtaining the fracture area per unit drilling length according to the fracture area S revealed by drilling includes:

[0209] The single fracture area exposed by the drilling hole is obtained according to the product of fracture trace length l and fracture width w;

[0210] The crack area S revealed by the drilling is obtained according to the sum of the single crack areas revealed by the drilling;

[0211] The fracture area per unit length of the borehole is obtained according to the ratio of the fracture area S revealed by the borehole to the length of the borehole L.

[0212] In this embodiment, after drilling a hole on the surrounding rock to be tested, multiple cracks may be generated within a certain range from the borehole to the interior of the surrounding rock. Each crack has a crack trace length l and a crack width w. The area of ​​a single crack exposed by the drilling is the product of the crack trace length l and the crack width w of the crack. The crack area S exposed by the drilling is the total area of ​​all cracks generated by the drilling, that is, the sum of the single crack areas exposed by the drilling, that is, Where n is the number of cracks produced by drilling.

[0213] The fracture area per unit borehole length is the ratio of the fracture area S exposed by the borehole to the length of the borehole L.

[0214] According to an embodiment provided by the present invention, the strength-stress ratio λ is obtained according to the ratio of the weighted average strength R of the rock formation within the drilling exposure range to the maximum principal stress σ1 in the original rock stress.

[0215] In this embodiment, the strength-stress ratio λ, a commonly used index in rock mass mechanics, is used to characterize the degree of fracture development. The strength-stress ratio λ is the ratio of the weighted average strength R of the rock formation within the drilling exposure range to the maximum principal stress σ1 in the original rock stress, that is, So the injectability coefficient

[0216]

[0217] According to an embodiment provided by the present invention, the weighted average strength R of the rock formations within the drilling exposure range is obtained according to the in-situ strength R0 of the rock mass of each rock formation and the layer thickness H of each rock formation.

[0218] In this embodiment, the weighted average strength of the rock formations in the drilling exposure range can be calculated by combining the in-situ strength R0 of each rock formation with the layer thickness H of each rock formation. Where m is the number of layers in the rock formation.

[0219] According to an embodiment provided by the present invention, hydraulic fracturing or stress relief method is used to test the original rock stress, and the maximum principal stress σ1 in the original rock stress is obtained. In this embodiment, the original rock stress is tested by hydraulic fracturing or stress relief method to obtain the maximum principal stress σ1 in the original rock stress. The maximum principal stress σ1 in the original rock stress can reflect the actual ground compressive stress level of the surrounding rock being tested.

[0220] According to an embodiment provided by the present invention, a borehole peep method is used to test the surrounding rock structure to obtain the number of cracks, crack width, crack trace length and borehole length. In this embodiment, the surrounding rock structure is tested by the borehole peep method, and the number of cracks n, crack opening w, crack trace length l, borehole length L and other indicators are obtained.

[0221] According to an embodiment provided by the present invention, the in-situ strength R0 of the rock mass of each rock layer is obtained by using the drilling penetration method. In this embodiment, the in-situ strength R0 of the rock mass of each rock layer is obtained by using the drilling penetration method.

[0222] According to an embodiment provided by the present invention, the layer thickness H of each rock layer is obtained by using the natural gamma test and the borehole peeping results. In this embodiment, while the in-situ strength R0 of the rock mass of each rock layer is obtained by the borehole probing method, the thickness H of each layer is obtained by combining the natural gamma test and the borehole peeping results, and the weighted average strength R of the rock layer within the borehole exposure range is calculated.

[0223] In the above embodiment, the method for judging the injectability of surrounding rock in the embodiment of the present invention is a method for judging the injectability of surrounding rock based on in-situ testing of rock mass, which can make a relatively accurate preliminary evaluation of the injectability of surrounding rock according to the in-situ test data, so as to make a quick decision, and scientifically and rationally select grouting materials, processes and equipment, so as to economically and efficiently perform grouting reinforcement of surrounding rock. The injectability of surrounding rock is evaluated by using the on-site in-situ test data. First, the in-situ test data can better reflect the actual state of the project than theoretical estimation or simulation calculation, and the data is more reliable.

[0224] According to an embodiment provided by the present invention, the depth of the borehole is greater than 2 times the width of the tunnel. In this embodiment, a borehole of a certain depth is drilled in the surrounding rock to be grouting, and the depth of the borehole is greater than 2 times the width of the tunnel.

[0225] According to an embodiment provided by the present invention, the grouting feasibility of the surrounding rock is judged based on the injectability coefficient k and the feasibility reference range.

[0226] In this embodiment, based on engineering experience, grouting tests or water pressure tests, the statistical relationship between the injectability coefficient k of the rock formation and the grouting volume under different mining stages or working conditions in a single coal mine or mining area is obtained, and this statistical relationship is summarized as a reference range for grouting credibility, thereby obtaining an empirical classification standard for the injectability coefficient k, as shown in Table 13.

[0227] Table 13

[0228] k ≤a a<k≤b b<k<c ≥c Injectability Difference medium better good

[0229] The injectability coefficient k obtained according to the above method is judged according to the classification standard to determine the degree of grouting feasibility of the surrounding rock, and the injectability evaluation result of the tested surrounding rock is obtained. The grouting feasibility decision, grouting method, material and equipment selection are made according to the evaluation result.

[0230] In some embodiments, Fig. 9 As shown, the above-mentioned rock mass characteristic index-based, rock formation compressibility judgment by the hierarchical analysis method includes:

[0231] Based on the in-situ drilling test, the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer are obtained. b and tensile strength σ t ;

[0232] Based on the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer b and tensile strength σ t , obtain the percentage b of brittle mineral components, elastic modulus E, and fracture pressure P of each rock layer b and tensile strength σ t The standardized parameter S i ;

[0233] Based on the analytic hierarchy process, the weight of each indicator is obtained;

[0234] Based on the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer b , tensile strength σ t The standardized parameter S i And the weights of each indicator are used to obtain the compressibility coefficient FI of each rock formation.

[0235] Relevant studies at home and abroad have shown that the brittleness of rocks is an important essential characteristic that characterizes the initiation and expansion of rock cracks. Brittleness can be characterized by parameters such as brittle mineral components, elastic modulus and Poisson's ratio. The greater the brittleness, the stronger the compressibility, that is, the greater the proportion of brittle mineral components, the greater the elastic modulus, and the smaller the Poisson's ratio, the stronger the compressibility. The initiation pressure represents the difficulty of the rock formation to produce cracks in the formation stress environment where it is located. The greater the initiation pressure, the more difficult the crack initiation is and the worse the compressibility is. Fracture toughness is a parameter that characterizes the difficulty of the crack extending forward, but fracture toughness needs to be obtained by laboratory testing. A large number of studies have shown that fracture toughness, especially type I fracture toughness, has a strong correlation with tensile strength. Tensile strength can be used instead of fracture toughness to characterize the difficulty of crack extension and expansion. The greater the tensile strength, the more difficult the crack extension is and the worse the compressibility is.

[0236] Through the above summary of relevant research results on rock compressibility at home and abroad, combined with many years of experience in coal mine roof rock fracturing design and construction, four parameters, namely brittle mineral component content, elastic modulus, fracture pressure and tensile strength, which can be obtained through in-situ testing, are selected for compressibility evaluation.

[0237] In the method for comprehensive evaluation of surrounding rock characteristics of the embodiment of the present invention, in the judgment of the compressibility of the rock formation, the surrounding rock is drilled and the corresponding test is performed in combination with the influence of the drilling on the surrounding rock, so as to obtain the percentage b of brittle mineral components, the elastic modulus E, and the fracture pressure P. b and tensile strength σ tAs the basis for judging the compressibility of each rock layer, the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer were obtained. b and tensile strength σ t The parameters were standardized and the brittle mineral component percentage b, elastic modulus E, and fracture pressure P, which were the factors affecting the compressibility of the rock formation, were analyzed using the hierarchical analysis method. b and tensile strength σ t Perform weight analysis to obtain the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P b and tensile strength σ t The weight value U i , forming the weights of each indicator, and finally combining the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer. b and tensile strength σ t The standardized parameter S i And the weights of each indicator are used to obtain the compressibility coefficient FI of each rock formation.

[0238] The method for judging the compressibility of coal-bearing sedimentary strata provided in the embodiment of the present invention can make quantitative judgments on the compressibility of each stratum. By testing multiple in-situ data in the borehole and adopting a comprehensive evaluation method to judge the compressibility of rock strata in different layers, the testing and evaluation efficiency is greatly improved. At the same time, the description of the rock strata and distribution characteristics by the test results of the borehole is more accurate than the comprehensive bar chart of the prior art, and it is possible to more reasonably select the fracturing layer, perform parameter design, process optimization and equipment selection, and achieve a better fracturing effect.

[0239] In this embodiment, the weight value U of the above-mentioned influencing factors is i The analytic hierarchy process is used to obtain the brittle mineral content b, elastic modulus E, fracture pressure P b and tensile strength σ t Four indicators are used as judgment indicators for comprehensive evaluation. It is difficult to complete the compressibility decision by comparing the evaluation indicators of a single compressibility influencing factor. There are mutual influences between the factors. The reliability and independence of the comprehensive data are finally selected as the brittle mineral content b, elastic modulus E, and fracture pressure P. b , tensile strength σ t The four indicators are used as evaluation indices to establish a hierarchical model for comprehensive judgment of the compressibility of rock formations.

[0240] According to the hierarchical analysis method, a hierarchical structure is established, a pairwise comparison judgment matrix is ​​constructed, characteristic roots and characteristic vectors are calculated, and any two judgment indicators are compared item by item, and values ​​are assigned according to the importance of the judgment indicators. The compressibility judgment indicators are compared pairwise to obtain a judgment matrix. The judgment matrix scale and its meaning are shown in Table 14.

[0241] Table 14

[0242]

[0243]

[0244] For example, when the elastic modulus E and the rupture pressure P b After calculating the characteristic roots and characteristic vectors, we get A ij is 5, which proves that the elastic modulus E is greater than the rupture pressure P b Strong and important

[0245] Use the sum-product method or square root method to solve the eigenvector corresponding to the maximum eigenvalue of the judgment matrix, and perform a consistency check on the judgment matrix based on the maximum eigenvalue. When the consistency is unsatisfactory, the judgment matrix needs to be readjusted to meet the required accuracy of the consistency test (generally 0.1, and when the test standard is less than 0.1, the judgment matrix is ​​considered acceptable). The eigenvector is normalized to become the weight vector.

[0246] According to an embodiment provided by the present invention, based on the in-situ test of the borehole, obtaining the percentage b of the brittle mineral components of each rock layer includes:

[0247] Based on the natural gamma test, the gamma intensity value of each rock layer is obtained;

[0248] The gamma intensity value of each rock layer is calibrated based on the laboratory rock mineral composition test results to obtain the shale content percentage a of each rock layer;

[0249] Based on the mud content percentage a of each rock layer, the brittle mineral content percentage b of each rock layer is obtained.

[0250] In this embodiment, the gamma intensity value of each rock layer is obtained by natural gamma test, and is calibrated according to the laboratory rock mineral composition test results to obtain the mud content percentage a of the rocks in different rock layers, and the brittle mineral content percentage b of each rock layer is b=1-a.

[0251] According to an embodiment provided by the present invention, based on the in-situ test of the borehole, obtaining the elastic modulus E of each rock formation includes:

[0252] Based on the borehole penetration method, the rock mass pressure-displacement curve of each rock layer is obtained;

[0253] Based on the rock mass pressure-displacement curve of each rock layer, the elastic modulus E of each rock layer is obtained.

[0254] In this embodiment, the rock mass pressure-displacement curves of different rock layers are obtained by using the borehole penetration method, and then the rock mass pressure-displacement curves are fitted to obtain the elastic modulus E of the different rock layers.

[0255] According to an embodiment provided by the present invention, based on the in-situ test of the borehole, the fracture pressure P of each rock layer is obtained. b and tensile strength σ t include:

[0256] Based on the hydraulic fracturing method, the fracture pressure P of each rock layer is obtained. b , maximum horizontal principal stress σ H and the minimum principal stress σ h ;

[0257] Based on the fracture pressure P of each rock layer b , maximum horizontal principal stress σ H and the minimum principal stress σ h , and obtain the tensile strength σ of each rock layer t .

[0258] In this embodiment, the hydraulic fracturing method can be used to obtain the fracture pressure P of the rock formation. b , the maximum horizontal principal stress σ H and the minimum principal stress σ h According to the formula, the burst pressure P b =3σ h -σ H +σ t , the tensile strength σ can be further calculated t .

[0259] According to an embodiment provided by the present invention, based on the percentage b of brittle mineral components, elastic modulus E, and fracture pressure P of each rock layer, b and tensile strength σ t , obtain the percentage b of brittle mineral components, elastic modulus E, and fracture pressure P of each rock layer b and tensile strength σ t The standardized parameter S i include:

[0260] The percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer based on the range change b and tensile strength σ t Unify the parameters and obtain the percentage b of brittle mineral components, elastic modulus E, and fracture pressure P of each rock layer. b and tensile strength σ t The standardized parameter S i .

[0261] In this embodiment, the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P b and tensile strength σ tAs judgment indicators, they all have their own units and dimensions, and need to be standardized before participating in the calculation. Since the judgment indicators are divided into positive and negative indicators, the positive indicator means the larger the indicator value, the better, and the negative indicator means the smaller the indicator value, the better, so the percentage of brittle mineral components b and elastic modulus E in the judgment indicators are positive indicators, and the fracture pressure P b and tensile strength σ t It is a reverse indicator. For the convenience of calculation, the extreme change is used to compare the percentage of brittle mineral components b and the elastic modulus E is a positive indicator, and the fracture pressure P b and tensile strength σ t Unify parameters.

[0262] After the elastic modulus E is subjected to the range variation parameter unification, the standardized parameter B1 of the elastic modulus E is obtained: (EE min ) / (E max -E min ), E max is the maximum elastic modulus of the rock layer revealed by this borehole, E min is the minimum value. You can also select the maximum and minimum values ​​of the elastic modulus of this mine or this mining area or even a larger area according to the scope of evaluation; the rupture pressure P b After unifying the range variation parameters, the rupture pressure P is obtained. b The standardized parameter C1=(P bmax -P b ) / (P bmax -P bmin ), P bmax and P bmin are the maximum and minimum values ​​of fracture fracturing respectively; the tensile strength σ t After unifying the range variation parameters, the tensile strength σ is obtained t The standardized parameter D1=(σ tmax -σ t ) / (σ tmax -σ tmin );σ tmax and σ tmin are the maximum and minimum values ​​of tensile strength, respectively.

[0263] According to an embodiment provided by the present invention, the standardized parameter A1 of the percentage b of the brittle mineral component of each rock layer is a decimal value of the percentage b of the brittle mineral component of each rock layer. In this embodiment, the parameter of the percentage b of the brittle mineral component of each rock layer can be unified and directly expressed as a decimal value A1. For example, when the percentage b of the brittle mineral component is 50%, the standardized parameter A1 of the percentage b of the brittle mineral component is 0.5 after the parameter is unified. When the percentage b of the brittle mineral component is 89%, the standardized parameter A1 of the percentage b of the brittle mineral component is 0.89 after the parameter is unified.

[0264] According to an embodiment provided by the present invention, based on the percentage b of brittle mineral components, elastic modulus E, and fracture pressure P of each rock layer, b , tensile strength σ t The standardized parameter S i And the weight of each index, the compressibility coefficient FI of each rock layer is obtained, including:

[0265] The standardized parameter A1 based on the percentage b of brittle mineral components in each rock layer, the standardized parameter B1 of elastic modulus E, and the fracture pressure P b Standardized parameters C1, tensile strength σ t The standardized parameter D1 and its weight value U in each indicator weight i The product of the brittle mineral composition percentage b, elastic modulus E, and fracture pressure P of each rock layer is obtained. b and tensile strength σ t Comprehensive indicators of

[0266] Based on the percentage of brittle mineral components b, elastic modulus E, and fracture pressure P of each rock layer b and tensile strength σ t The sum of the comprehensive indicators is used to obtain the compressibility coefficient FI of each rock layer.

[0267] In this embodiment, the standardized parameter S i With weight value U i The weighted value is the compressibility coefficient FI of the rock formation, that is, FI is the compressibility coefficient, dimension 1; S i is the standardized value of the judgment index of each rock layer; U i is the weight value of the rock formation judgment index; n is the number of parameters.

[0268] According to an embodiment provided by the present invention, the feasibility of fracturing each rock formation is determined based on the compressibility coefficient FI of each rock formation and the feasibility reference range.

[0269] According to the implementation process, monitoring data, implementation effect of hydraulic fracturing projects, the statistical relationship between the compressibility coefficient FI of rock strata at different levels of the same coal seam roof in a coal mine or mining area and the fracturing implementation effect is obtained, thereby obtaining the empirical classification standard of the compressibility coefficient FI of the rock strata as shown in Table 15.

[0270] Table 15

[0271] FI ≤a a<FI≤b b<FI<c ≥c Compressibility Difference medium better good

[0272] The compressibility coefficient FI model can quantitatively calculate the fracturing coefficient of the roof rock formation, and can also use the compressibility coefficient FI to select the fracturing layer according to the distribution characteristics of different parameters at depth in the test borehole.

[0273] Corresponding to the execution of surrounding rock quality evaluation in the comprehensive evaluation method of surrounding rock characteristics described in this embodiment, the following first specific test example is given.

[0274] like Fig.10 and Fig.11 As shown in the figure, a coal mine is mining a new working face in a new mining area. The rock mass characteristics are unknown. In order to provide a basic reference for the subsequent working face and mining area, a series of in-situ drilling tests are carried out in the tunneling tunnel to evaluate the quality of the surrounding rock and its changes. A typical drilling test and quality assessment process is as follows.

[0275] 1. Drilling in-situ parameter test

[0276] Drill holes with a diameter of 56 mm and a depth of 20 m.

[0277] The borehole was peeped and the rock mass image was obtained and digitized, revealing 20 fractures in the borehole, as well as the opening degree and trace length of each fracture, as shown in Table 16 below.

[0278] Table 16 Crack parameters

[0279]

[0280]

[0281] The hydraulic fracturing method was used to measure the ground stress in the intact rock section deep in the borehole, and the maximum principal stress was found to be 19.6MPa.

[0282] The in-situ strength test of rock mass was carried out by using the borehole penetration method. Combined with the peep image, the number of rock layers revealed was 6. The thickness and in-situ strength of each rock layer were obtained, as shown in Table 17.

[0283] Table 17 Drilling exposure rock formation parameters

[0284] Layer number Rock layer thickness (m) Average strength (MPa) 1 2.5 18.1 2 4 23.2 3 3.2 13.7 4 5.6 28.6 5 2.8 32 6 1.9 24.3

[0285] 2. Calculation of basic rock mass quality and in-situ quality indicators

[0286] According to the calculation of the fracture data, the cross-sectional area of ​​the fracture exposed by the drilling is 0.024m 2 , crack area ratio k l It is 0.68%, and the rock integrity index Kv is 0.37.

[0287] After weighting, the weighted strength R of the borehole rock mass is 23.9MPa. After the strength of each layer is converted to standard points, the minimum standard value is -1.57, so the value of K2 is 0.6; the number of rock layers exposed in the shallow part of the borehole at 10m is 4, so the value of K3 is 0.6.

[0288] The basic rock mass quality index BQ is

[0289] BQ = 100 + 3R + 250Kv = 264.2

[0290] The water outflow from the tunnel roof in the test area was monitored and counted. The tunnel was dripping, and the flow rate Q was 8L / min·10m, so the value of K1 was 0.2.

[0291] Then the rock mass in-situ quality index [BQ] is

[0292] [BQ]=BQ-100(K1+K2+K3)=264.2-100×(0.2+0.6+0.6)=124.2

[0293] According to the classification standards, the surrounding rock of this borehole and the surrounding area it represents is classified as poor, and surrounding rock control and stability monitoring should be strengthened.

[0294] Corresponding to the execution of surrounding rock stability evaluation in the comprehensive evaluation method of surrounding rock characteristics described in this embodiment, the following second specific test example is given.

[0295] As the burial depth of a coal mine increases, the stability of the surrounding rock becomes worse. To ensure safety, a stability evaluation is planned to be carried out in a certain tunnel. The tunnel has been opened and relevant tests are carried out at the opening.

[0296] 1. In-situ drilling test and rock mass quality impact scoring

[0297] Drill holes with a diameter of 56 mm and a depth of 20 m;

[0298] The drilling hole was used to observe the rock mass and obtain the rock mass image, which was then digitized. The drilling hole revealed 15 cracks, as well as the opening w and length l of each crack. The cross-sectional area S of the crack was calculated to be 0.054m 2 , accounting for k l is 1.54%, and Kv is 0.696;

[0299] In the complete rock section deep in the borehole, the hydraulic fracturing method was used to measure the ground stress, and the maximum principal stress σ1 was 19.6MPa;

[0300] The in-situ strength test of rock mass was carried out by drilling penetration method. Combined with the peep image, the number of exposed rock layers was 6, so the value of K3 was 0.6. The thickness and in-situ strength of each rock layer were obtained, and the weighted strength R of the rock layer was 21.8MPa after weighting. After the strength of each layer was converted to standard score, the minimum value of the standard score was -1.5, so the value of K2 was 0.6.

[0301] BQ = 100 + 3R + 250Kv = 339.4

[0302] The water discharge from the tunnel roof in the test area was monitored and counted. The tunnel was dripping and the water discharge Q was 8L / min·10m, so the value of K1 was 0.2.

[0303] [BQ]=BQ-100(K1+K2+K3)=339.4-100*(0.2+0.6+0.6)=199.4

[0304] Calculation shows that the rock mass quality impact score d1 = 39.88.

[0305] 2. Strength-stress ratio affects the score

[0306] The strength-stress ratio index k1 calculated from the above data is 0.855, and the strength-stress ratio impact score d2 = 27.81 is obtained.

[0307] 3. Geological structure impact score

[0308] According to the existing geological data of the mine, the mine's geological structure complexity is medium, and it is also known that the tunnel is expected to intersect with two faults, that is, the minimum distance from the geological structure is 0. Therefore, the geological structure impact score d3 = 50.

[0309] 4. Mining impact score

[0310] Based on the monitoring of the adjacent working faces and tunnels in the mine, the mining coefficient k3=1.48 is obtained, and the mining impact score d4=40 is calculated.

[0311] 5. Tunnel section impact assessment

[0312] The length and width of the tunnel are 5m and 3.5m respectively, and the cross-sectional area s is 17.5m 2 , the calculated cross-sectional area impact score is d5=27.

[0313] 6. Comprehensive calculation and evaluation

[0314] By multiplying the scores of each influencing factor by the weight and taking the sum, we can get the comprehensive score T=38.13.

[0315] According to the classification range, the surrounding rock of this tunnel belongs to Class III unstable surrounding rock. It is recommended to take measures such as strengthening support and reinforcing special sections to ensure the stability of the surrounding rock.

[0316] Corresponding to the execution of surrounding rock injectability judgment in the surrounding rock characteristics comprehensive evaluation method described in this embodiment, the following third specific test example is given.

[0317] Under the influence of high stress environment and mining, the tunnel of a coal mine is severely damaged and has developed internal cracks. Grouting is required to reinforce it to ensure the normal use of the tunnel. Therefore, this method is used to evaluate the injectability of surrounding rock. Main results and process:

[0318] Drilling (drilling diameter 56mm, depth 20m);

[0319] By using the peek method and digital processing, 15 cracks were exposed in the borehole, as well as the opening and trace length of each crack. The cross-sectional area of ​​the crack was calculated to be 0.054m 2 ;

[0320] In the complete rock section deep in the borehole, the hydraulic fracturing method was used to measure the ground stress, and the maximum principal stress was 25.5MPa;

[0321] The in-situ strength test of rock mass was carried out by using the borehole penetration method. Combined with the peep image, the thickness and in-situ strength of each rock layer were obtained. After weighting, the borehole rock mass strength was 21.8Mpa.

[0322] Comprehensive calculation shows that the injectability coefficient of the surrounding rock in the test area is 0.003158.

[0323] By conducting test evaluations and grouting tests in different areas of the mine, and based on the statistical results of the grouting volume of a single borehole, the classification range of the mine's injectability coefficient is roughly as shown in Table 18 below.

[0324] Table 18

[0325] k ≤0.001 0.001＜k≤0.003 0.003＜k＜0.005 ≥0.005 Injectability Difference medium better good

[0326] Corresponding to the execution of surrounding rock compressibility judgment in the surrounding rock characteristics comprehensive evaluation method described in this embodiment, the following fourth specific test example is given.

[0327] In order to solve the problems of high mine pressure, a mine planned to implement hydraulic fracturing and weakening of the roof rock layer. Before the construction, the in-situ test method was used to evaluate the compressibility. The main process is as follows:

[0328] (1) Drill holes with a depth of 40 m (the length of the holes must be equal to or greater than the height of the rock strata that is difficult to collapse estimated based on relevant geological data); a total of 7 rock strata were exposed.

[0329] (2) The gamma intensity value of the rock formation is obtained by natural gamma test, and calibrated according to the laboratory rock mineral composition test results. The inversion results show that the percentage of mud content in different rock formations is a, and the percentage of brittle mineral content is b = 1-a. The results are shown in Table 19 below.

[0330] Table 19

[0331]

[0332]

[0333] (3) The borehole probing method was used to obtain the pressure-displacement curves of the rock masses at different levels, and the in-situ strength and elastic modulus E of the rock masses at different levels were obtained as shown in Table 20 below.

[0334] Table 20

[0335] Layer number Compressive strength(MPa) Elastic modulus(GPa) 1 65.1 13.20 2 73.8 22.17 3 42.9 6.46 4 55.4 8.29 5 85.3 17.85 6 34.2 10.04 7 116.8 32.58

[0336] (4) Using hydraulic fracturing method to obtain the fracture pressure P of the rock layer b , the maximum horizontal principal stress σ H , minimum horizontal principal stress σ h According to the formula P b =3σ h -σ H +σ t , and the tensile strength σ is obtained t ; As shown in Table 21 below.

[0337] Table 21

[0338]

[0339] (5) Using the hierarchical analysis method, the brittle mineral content b, elastic modulus E, and fracture pressure P b , tensile strength σ t Four indicators are used as evaluation indicators for comprehensive evaluation.

[0340] The parameters were standardized according to the above method to obtain the normalized values ​​of each parameter.

[0341] As shown in Table 22 below.

[0342] Table 22

[0343]

[0344] By comprehensively drawing on existing research results and combining engineering experience, the judgment matrix shown in the table is determined, that is, the brittle mineral content is the most important, slightly more important than the elastic modulus and the fracture pressure, and the elastic modulus and the fracture pressure are equally important. Considering that the tensile strength mainly affects the extent of crack extension, it can be improved by increasing the fracturing flow and pressure, optimizing the fracturing fluid and other technical means, so it is defined that the brittle mineral content is more important than the tensile strength. As shown in Table 23 below.

[0345] Table 23 Evaluation index judgment matrix A

[0346] Influencing factors Brittle mineral content Elastic modulus Burst pressure tensile strength Brittle mineral content 1 3 3 5 Elastic modulus 1 / 3 1 1 3 Burst pressure 1 / 3 1 1 3 tensile strength 1 / 5 1 / 3 1 / 3 1

[0347] The eigenvector corresponding to the maximum eigenvalue of the judgment matrix is ​​solved by the sum-product method or the square root method, and the judgment matrix is ​​checked for consistency based on the maximum eigenvalue. If the consistency is not satisfactory, the judgment matrix needs to be readjusted to meet the required accuracy of the consistency test (generally 0.1, and the judgment matrix is ​​considered acceptable when the test standard is less than 0.1). The eigenvector is normalized to become the weight vector. The calculation results are shown in Table 24.

[0348] Table 24 Evaluation index calculation weights

[0349]

[0350]

[0351] In the above table, M i is the continuous product of each row of elements in the judgment matrix; U' i M i The rth root, in this case r = 4; U i is the weight coefficient of each rock formation evaluation parameter; AU is the matrix A and U i The product of max is the maximum eigenvalue of the judgment matrix; CI is the deviation consistency index of the judgment matrix; RI is the average random consistency index of the same order; CR is the random consistency ratio, which is the ratio of CI to RI.

[0352] The square root method was used to calculate the weights of the four indicators of brittle mineral content, elastic modulus, fracture pressure, and tensile strength, which were 0.520490138, 0.200959887, 0.200959887, and 0.077590089, respectively. The consistency index CR value was 0.016 < 0.1, indicating that the judgment matrix met the consistency test and was acceptable.

[0353] The rock formation compressibility coefficient is obtained by adding the standardized value to the weight coefficient. The calculation formula is:

[0354]

[0355] Where FI is the compressibility coefficient; S i is the standardized value of each rock formation evaluation parameter; U i is the weight coefficient of each rock formation evaluation parameter; n is the number of parameters, here n is 4.

[0356] The evaluation indicators of each rock formation revealed by the borehole are weighted and summed, and the results are shown in Table 25 below.

[0357] Table 25 Evaluation results of rock formation compressibility index

[0358] Layer number Compressibility Index 1 0.543024 2 0.488855 3 0.517912 4 0.517156 5 0.618368 6 0.57118 7 0.90423

[0359] Based on the microseismic monitoring of fracturing events during the fracturing construction process, a comprehensive judgment based on the number of events, event energy and fracturing radius can be made to obtain a rough classification of the compressibility indicators of different rock formations as shown in Table 26 below.

[0360] Table 26

[0361] FI ≤0.3 0.3<FI≤0.5 0.5<FI<0.7 ≥0.7 Compressibility Difference medium better good

[0362] Subsequent fracturing projects in mines and similar conditions can be evaluated based on the compressibility evaluation and combined with this empirical value, and carry out engineering parameter design, equipment and process selection and matching, etc.

[0363] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for comprehensive evaluation of surrounding rock characteristics, characterized in that: include: Based on the in-situ test of surrounding rock, obtain the in-situ quality index of rock mass, strength-stress ratio index, fracture area and rock mass characteristic index; Based on the basic quality index of rock mass, groundwater influence coefficient, rock layer variation coefficient and layer number influence coefficient, the in-situ quality index of rock mass is obtained; Perform surrounding rock quality evaluation based on in-situ rock mass quality indicators; Based on the normalization of rock mass in-situ quality indicators, strength-stress ratio indicators, and rock mass characteristic indicators, the surrounding rock stability evaluation is performed; Based on the strength-stress ratio index and the fracture area, the injectability of the surrounding rock is judged; Based on the rock mass characteristic indicators, the compressibility of the rock formation is determined by the hierarchical analysis method; The rock mass characteristic indicators include the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer.

2. The method for comprehensive evaluation of surrounding rock characteristics according to claim 1, characterized in that: The performing of surrounding rock quality evaluation based on the rock mass in-situ quality index comprises: Obtain basic rock mass quality indicators based on in-situ testing of surrounding rock; Based on the basic quality index of rock mass, groundwater influence coefficient, rock layer variation coefficient and layer number influence coefficient, the in-situ quality index of rock mass is obtained; Based on the in-situ quality indicators of the rock mass, obtain the rock mass quality classification evaluation results; Based on the results of in-situ testing of surrounding rock and classification and evaluation of rock mass quality, a two-dimensional rock mass distribution model along the tunnel strike and a three-dimensional rock mass distribution model at the working face were constructed.

3. The method for comprehensive evaluation of surrounding rock characteristics according to claim 2, characterized in that: The normalization process based on the rock mass in-situ quality index, the strength-stress ratio index, and the rock mass characteristic index to perform surrounding rock stability evaluation includes: Based on the in-situ test of surrounding rock, obtain the in-situ quality index of rock mass, strength-stress ratio index, geological structure index, mining index and section index; Based on the normalization of the in-situ quality index of the rock mass, the strength-stress ratio index, the geological structure index, the mining index and the cross-section index, the normalized values ​​of the in-situ quality index of the rock mass, the strength-stress ratio index, the geological structure index, the mining index and the cross-section index are obtained; Based on the normalized values ​​of the in-situ quality index of the rock mass, the strength-stress ratio index, the geological structure index, the mining index and the cross-section index and the weight mapping relationship, the comprehensive index value is obtained.

4. The method for comprehensive evaluation of surrounding rock characteristics according to claim 3 is characterized in that: Based on the basic quality indicators of rock mass, the water pressure in surrounding rock fissures and the water output of the roadway, the groundwater influence coefficient is obtained; Based on the average in-situ test strength of each rock formation, the mean of the in-situ test strengths of all rock formations and the standard deviation of the in-situ test strengths of all rock formations, the standard score of the strength of each rock formation is obtained; Based on the standard score of each rock layer strength, the rock layer variation influence coefficient is obtained; Based on the mapping relationship between the measured surrounding rock range and the number of rock layers, the layer number influence coefficient is obtained.

5. The method for comprehensive evaluation of surrounding rock characteristics according to claim 1, characterized in that: The injectability determination of surrounding rock based on the strength-stress ratio index and the fracture area includes: Obtain the fracture area per unit drilling length according to the fracture area revealed by drilling; The injectability coefficient of the measured surrounding rock is obtained according to the ratio of the fracture area to the strength-stress ratio within the unit borehole length, wherein the strength-stress ratio is a parameter corresponding to the degree of fracture development.

6. The method for comprehensive evaluation of surrounding rock characteristics according to claim 5, characterized in that: The method of obtaining the fracture area per unit drilling length according to the fracture area revealed by drilling comprises: The single fracture area exposed by the drilling hole is obtained according to the product of fracture trace length and fracture width; Obtaining the fracture area revealed by the drilling according to the sum of the single fracture areas revealed by the drilling; The fracture area per unit borehole length is obtained based on the ratio of the fracture area exposed by the borehole to the borehole length.

7. The method for comprehensive evaluation of surrounding rock characteristics according to claim 1, characterized in that: The method of judging the compressibility of rock formations by using the hierarchical analysis method based on rock mass characteristic indicators includes: Based on in-situ drilling tests, the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer are obtained; Based on the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer, standardized parameters of the percentage of brittle mineral components, elastic modulus, fracture pressure and tensile strength of each rock layer are obtained; Based on the analytic hierarchy process, the weight of each indicator is obtained; Based on the standardized parameters of the percentage of brittle mineral components, elastic modulus, fracture pressure, tensile strength of each rock layer and the weight of each index, the compressibility coefficient of each rock layer is obtained.

8. The method for comprehensive evaluation of surrounding rock characteristics according to claim 7, characterized in that: The brittle mineral composition percentages of each rock layer obtained based on the in-situ drilling test include: Based on the natural gamma test, the gamma intensity value of each rock layer is obtained; The gamma intensity value of each rock layer was calibrated based on the laboratory rock mineral composition test results to obtain the percentage of mud content in each rock layer; Based on the percentage of mud content in each rock layer, the percentage of brittle mineral content in each rock layer is obtained; The elastic modulus of each rock layer obtained based on the in-situ test of the borehole includes: Based on the borehole penetration method, the rock mass pressure-displacement curve of each rock layer is obtained; Based on the rock mass pressure-displacement curve of each rock layer, the elastic modulus of each rock layer is obtained; The method of obtaining the fracture pressure and tensile strength of each rock layer based on the in-situ test of the borehole includes: Based on hydraulic fracturing, the fracture pressure, maximum horizontal principal stress and minimum principal stress of each rock layer are obtained; Based on the fracture pressure, maximum horizontal principal stress and minimum principal stress of each rock layer, the tensile strength of each rock layer is obtained.

9. The method for comprehensive evaluation of surrounding rock characteristics according to any one of claims 1 to 8, characterized in that: The basic rock mass quality indicators obtained based on the in-situ test of the surrounding rock include: Based on the borehole penetration method, the average in-situ test strength of each rock layer is obtained; Obtaining the weighted strength of the rock formation based on the average in-situ test strength of each rock formation and the thickness of each rock formation; Based on the borehole observation, the fracture opening and fracture trace length of each fracture are obtained; Based on the fracture aperture and fracture trace length of each fracture, the sum of the fracture cross-sectional areas of the rock formation is obtained; Based on the ratio of the sum of the cross-sectional areas of the rock formation fractures to the total area exposed by the rock formation drilling, the fracture area ratio is obtained; Based on the proportion of fracture area, the rock integrity index is obtained; Based on the weighted strength of rock formations and rock integrity index, basic rock mass quality indicators are obtained.

10. The method for comprehensive evaluation of surrounding rock characteristics according to any one of claims 1 to 8, characterized in that: The strength stress ratio index obtained based on the in-situ test of the surrounding rock includes: Based on the in-situ test of surrounding rock, the maximum principal stress in the original rock stress and the weighted strength of the uniaxial compressive strength are obtained; The strength-stress ratio index is obtained based on the ratio of the weighted strength of the uniaxial compressive strength to the maximum principal stress in the original rock stress.

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