Methods for judging the stability of surrounding rock

Abstract

The present invention relates to the field of mining technology, and in particular to a method for judging the stability of surrounding rock, including: obtaining in-situ quality indicators, strength-stress ratio indicators, geological structure indicators, mining indicators and cross-section indicators of rock mass based on in-situ testing of surrounding rock; obtaining normalized values ​​of in-situ quality indicators, strength-stress ratio indicators, geological structure indicators, mining indicators and cross-section indicators of rock mass based on normalization processing of in-situ quality indicators, strength-stress ratio indicators, geological structure indicators, mining indicators and cross-section indicators of rock mass; obtaining comprehensive index values ​​based on normalized values ​​of in-situ quality indicators, strength-stress ratio indicators, geological structure indicators, mining indicators and cross-section indicators of rock mass and weight mapping relationship. The stability of tunnel surrounding rock is judged by multi-parameter in-situ data, and relevant control measures are taken in time in the early stage of tunnel service according to the judgment results to avoid instability of the tunnel, and a comprehensive and large-scale early stability pre-evaluation of tunnel surrounding rock is carried out.

Description

Technical Field

[0001] The invention relates to the technical field of mining, and in particular to a method for judging the stability of surrounding rocks. Background Art

[0002] The traditional evaluation method for tunnel surrounding rock stability is to indirectly evaluate the deformation and damage of the surrounding rock, the response characteristics of the support body, etc. through monitoring means. This method has a relatively positive significance for the determination and early warning of the risk of surrounding rock instability, but it has little effect on the advanced evaluation of the stability of the tunnel during the entire service cycle, and the monitoring is mostly local. Summary of the invention

[0003] The present invention provides a method for judging the stability of surrounding rock to solve one of the defects in the prior art. The stability of tunnel surrounding rock is judged by multi-parameter in-situ data, which can provide guidance for the support of subsequent tunnel excavation or tunnels with similar conditions. Relevant control measures can also be taken in time at the early stage of tunnel service according to the judgment result to avoid instability of the tunnel. A comprehensive and large-scale early stability pre-evaluation of the tunnel surrounding rock is very important for the advance control of expected tunnel deformation and damage.

[0004] The present invention provides a method for determining the stability of surrounding rock, comprising:

[0005] 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;

[0006] 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;

[0007] 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.

[0008] According to a method for determining the stability of surrounding rock provided by the present invention, the method of obtaining the in-situ quality index of the rock mass based on the in-situ test of the surrounding rock comprises:

[0009] Obtain basic rock mass quality indicators based on in-situ testing of surrounding rock;

[0010] Based on the basic quality indicators of the rock mass, the groundwater influence coefficient, the rock layer variation coefficient and the layer number influence coefficient, the in-situ quality indicators of the rock mass are obtained.

[0011] According to a method for determining the stability of surrounding rock provided by the present invention, the basic quality index of the rock mass is obtained based on in-situ testing of the surrounding rock, which includes:

[0012] Based on the borehole penetration method, the average in-situ test strength of each rock layer is obtained;

[0013] 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;

[0014] Based on the borehole observation, the fracture opening and fracture trace length of each fracture are obtained;

[0015] 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;

[0016] 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;

[0017] Based on the proportion of fracture area, the rock integrity index is obtained;

[0018] Based on the weighted strength of rock formations and rock integrity index, basic rock mass quality indicators are obtained.

[0019] According to a method for judging the stability of surrounding rock 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] According to a method for judging the stability of surrounding rock provided by the present invention, based on the average in-situ test strength of each rock layer, the mean of the in-situ test strengths of all rock layers and the standard deviation of the in-situ test strengths of all rock layers, the standard score of the strength of each rock layer is obtained;

[0021] Based on the standard score of each rock formation strength, the rock formation variation influence coefficient is obtained.

[0022] According to a method for determining the stability of surrounding rock provided by the present invention, a layer number influence coefficient is obtained based on a mapping relationship between a measured surrounding rock range and the number of rock layers.

[0023] According to a method for determining the stability of surrounding rock provided by the present invention, the method of obtaining the strength stress ratio index based on in-situ testing of the surrounding rock includes:

[0024] 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;

[0025] 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.

[0026] According to a method for determining the stability of surrounding rock provided by the present invention, based on in-situ testing of surrounding rock, obtaining cross-section indicators includes:

[0027] Based on the area of ​​the tunnel section, the section index is obtained.

[0028] According to a method for determining the stability of surrounding rock provided by the present invention, the method for obtaining geological structure indicators based on in-situ testing of surrounding rock includes:

[0029] Based on the distance between the roadway and the geological structure, the minimum distance between the roadway and the geological structure is obtained as a geological structure indicator.

[0030] According to a method for determining the stability of surrounding rock provided by the present invention, the step of obtaining a normalized value of a geological structure indicator based on normalizing the geological structure indicator includes:

[0031] Based on the geological structure type of the tunnel excavation and the surrounding area, a geological structure type score is obtained;

[0032] The geological structure indicators are normalized based on the geological structure type score to obtain the normalized values ​​of the geological structure indicators.

[0033] The method for determining the stability of surrounding rock provided by the present invention is to drill holes on the surrounding rock to be tested, and to obtain corresponding data parameters based on various tests of the drilling holes and the surrounding rock to be tested, which is an in-situ test of the surrounding rock. 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.

[0034] 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 testing data can better reflect the actual engineering environment than the laboratory test results, and has greater guiding significance for engineering practice. The present invention provides a method for judging the stability of tunnel surrounding rock based on in-situ testing of rock mass. It adopts multiple geological, mechanical and structural parameters obtained by large-scale in-situ testing, considers the influence of geological structure, mining impact, cross-section characteristics, etc., establishes a comprehensive evaluation model for the stability of tunnel surrounding rock, and evaluates the stability of tunnel surrounding rock.

[0035] 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.

[0036] 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

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only 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.

[0038] Figure 1 It is a flow chart of a method for determining the stability of surrounding rock provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following embodiments of the present invention are described in further detail in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0040] In the description of the embodiments of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limitations on the embodiments of the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0041] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0042] In the embodiments of the present invention, unless otherwise clearly specified and limited, the first feature being "above" or "below" the second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0043] In addition, in the description of the embodiments of the present invention, unless otherwise specified, "multiple", "multiple roots", and "multiple groups" mean two or more, and "several", "several roots", and "several groups" mean one or more.

[0044] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0045] like Figure 1 As shown, the method for determining the stability of surrounding rock provided by the embodiment of the present invention includes:

[0046] 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;

[0047] 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 ;

[0048] 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.

[0049] The method for determining the stability of surrounding rock in the embodiment of the present invention is to drill holes on the surrounding rock to be tested, and to perform various tests based on the drilling holes and the surrounding rock to be tested to obtain corresponding data parameters, which is an in-situ test of the surrounding rock. 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 the degree of stability of the surrounding rock can be determined. Based on the experience of mine support engineering, the support and control forms and key parameter solutions for surrounding rocks of different stability levels are given to control the surrounding rock more accurately.

[0050] 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 testing data can better reflect the actual engineering environment than the laboratory test results, and has greater guiding significance for engineering practice. The present invention provides a method for judging the stability of tunnel surrounding rock based on in-situ testing of rock mass. It adopts multiple geological, mechanical and structural parameters obtained by large-scale in-situ testing, considers the influence of geological structure, mining impact, cross-section characteristics, etc., establishes a comprehensive evaluation model for the stability of tunnel surrounding rock, and evaluates the stability of tunnel surrounding rock.

[0051] 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.

[0052] 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 1 below.

[0053] Table 1

[0054] index Weight value Rock mass quality index 0.2 Strength stress ratio index 0.25 Geological structural indicators 0.25 <![CDATA[ Mining indicators ]]> 0.2 Tunnel section index 0.1

[0055] According to the weight values ​​of each indicator listed in Table 1, 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.

[0056] By comparing the comprehensive index value T with the type score interval in Table 2 below, the surrounding rock stability type identification result can be determined.

[0057] Table 2

[0058] 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

[0059] According to an embodiment provided by the present invention, based on the in-situ test of the surrounding rock, obtaining the in-situ quality index [BQ] of the rock mass includes:

[0060] Based on the in-situ test of surrounding rock, the basic rock quality index BQ is obtained;

[0061] Based on the basic rock quality index BQ, groundwater influence coefficient K1, rock layer variation coefficient K2 and layer number influence coefficient K3, the in-situ rock mass quality index [BQ] is obtained.

[0062] 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 [BQ] = BQ-100 (K1+K2+K3).

[0063] 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:

[0064] Based on the borehole penetration method, the average in-situ test strength R0 of each rock layer was obtained;

[0065] 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;

[0066] Based on the borehole observation, the fracture opening w and fracture trace length l of each fracture are obtained;

[0067] 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;

[0068] 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 ;

[0069] Based on the crack area ratio k l , obtain the rock integrity index Kv;

[0070] Based on the weighted strength R of the rock formation and the rock integrity index Kv, the basic rock quality index BQ is obtained.

[0071] In this embodiment, the in-situ strength test is carried out by using the borehole penetration method, and combined with the borehole peep test, the thickness H of each rock layer and the average in-situ test strength R0 of each rock layer are obtained, and the weighted strength of the rock layer is Wherein, m is the number of rock layers in the measured surrounding rock.

[0072] By drilling and peering, the surrounding rock structure image is processed to obtain the number of cracks n in each rock layer 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. Therefore, the sum of the cross-sectional areas of the cracks in the rock layer and the crack area ratio k are l k l =S / S0, S0 is the total area exposed by drilling in the rock formation.

[0073] Definition of rock integrity index Kv and crack area ratio k l The corresponding relationship with the rock integrity is shown in Table 3. l The corresponding rock integrity index Kv is selected.

[0074] Table 3

[0075] k 0-0.1％ 0.1％-0.4％ 0.4％-0.7％ 0.7％-1.0％ ≥1.0％ Kv 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

[0076] in, k lmin is k in Table 3 above l The minimum value of the interval in the range, k lmax is k in Table 3 above l The maximum value of the range, Kv min is k in Table 3 above l The minimum value of the interval corresponding to the Kv range, Kv max is k in Table 3 above l The maximum value of the interval corresponding to the Kv range.

[0077] According to the "Engineering Rock Mass Classification Standard", the basic rock mass quality index BQ=100+3R+250Kv.

[0078] 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.

[0079] In this embodiment, the surrounding rock fissure water pressure p (MPa) and the tunnel water output Q (L / min·10m) are obtained by detecting the tunnel surrounding rock. Referring to Table 4 below, the groundwater influence coefficient K1 is determined in combination with the basic rock mass quality index BQ.

[0080] Table 4

[0081]

[0082] 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;

[0083] Based on the standard score z of each rock layer strength, the rock layer variation influence coefficient K2 is obtained.

[0084] 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 5. When the minimum rock formation strength is greater than 40MPa, it is not applicable and the value is 0.

[0085] Table 5

[0086] Minimum standard score for each rock layer ≤-1.8 -1.8～-1.6 -1.6～-1.4 -1.4～-1.2 -1.2～-1 ≥-1 <![CDATA[K2]]> 1 0.8 0.6 0.4 0.2 0

[0087] 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.

[0088] 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 6. 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.

[0089] Table 6

[0090] Number of rock layers within 10m range. 1 2 3 4 5 ≥6 <![CDATA[K3。]]> 0 0.2 0.4 0.6 0.8 1

[0091] 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)

[0092] 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:

[0093]

[0094] 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 7 below.

[0095] Table 7

[0096]

[0097] 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:

[0098] 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;

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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:

[0103]

[0104] 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 D k , 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 8 below.

[0105] Table 8

[0106] <![CDATA[Strength stress ratio index k1]]> ≥4 4～3 3～2 ≤2 <![CDATA[Score 100*d k > 100 100～75 75～50 50～0

[0107] 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:

[0108] Based on the area s of the tunnel cross section, the cross section index k4 is obtained.

[0109] 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.

[0110] 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:

[0111]

[0112] 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 9 below.

[0113] Table 9

[0114] <![CDATA[The area s (m 2 )]]> ≤12 12～18 18-24 ≥24 <![CDATA[Score 100*d k > 100-50 50-25 25-0 0

[0115] 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:

[0116] 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.

[0117] 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.

[0118] 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:

[0119] Based on the geological structure type of the tunnel excavation and the surrounding area, the geological structure type score A was obtained;

[0120] 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.

[0121] 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.

[0122] 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:

[0123]

[0124] 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 10 below.

[0125] Table 10

[0126]

[0127] 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.

[0128] 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:

[0129]

[0130] 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 11 below.

[0131] Table 11

[0132] <![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

[0133] 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.

[0134] 1. In-situ drilling test and rock mass quality impact scoring

[0135] Drill holes with a diameter of 56 mm and a depth of 20 m;

[0136] The drilling hole was used to observe the rock mass and the rock mass image was obtained and digitized. The drilling hole revealed 15 cracks, as well as the opening w and the 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;

[0137] 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;

[0138] 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.

[0139] BQ = 100 + 3R + 250Kv = 339.4

[0140] 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.

[0141] [BQ]=BQ-100(K1+K2+K3)=339.4-100*(0.2+0.6+0.6)=199.4

[0142] Calculation shows that the rock mass quality impact score d1 = 39.88.

[0143] 2. Strength-stress ratio affects the score

[0144] 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.

[0145] 3. Geological structure impact score

[0146] 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.

[0147] 4. Mining impact score

[0148] 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.

[0149] 5. Tunnel section impact assessment

[0150] 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.

[0151] 6. Comprehensive calculation and evaluation

[0152] By multiplying the scores of each influencing factor by the weight and taking the sum, we can get the comprehensive score T=38.13.

[0153] 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.

[0154] 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 determining the stability of surrounding rock, 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, 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 rock mass in-situ quality index, strength-stress ratio index, geological structure index, mining index and cross-section index and the weight mapping relationship, the comprehensive index value is obtained; The in-situ quality indicators of the rock mass obtained based on the in-situ test of the surrounding rock include: 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 influence coefficient and layer number influence coefficient, the in-situ quality index of rock mass 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; Obtain mining indicators based on similar conditions in the mine or monitoring of adjacent tunnels; The geological structure indicators obtained based on the in-situ test of the surrounding rock include: Based on the distance between the roadway and the geological structure, the minimum distance between the roadway and the geological structure is obtained as a geological structure indicator; Based on the in-situ test of surrounding rock, the cross-section indicators obtained include: Based on the area of ​​the tunnel section, the section index is obtained; The groundwater influence coefficient is obtained based on the basic quality indicators of the rock mass, the water pressure in the surrounding rock fissures and the water output of the tunnel.

2. The method for determining the stability of surrounding rock according to claim 1, 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.

3. The method for determining the stability of surrounding rock according to claim 1, 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.

4. The method for determining the stability of surrounding rock according to claim 1, characterized in that: The step of obtaining the normalized value of the geological structure indicator based on the normalized processing of the geological structure indicator includes: Based on the geological structure type of the tunnel excavation and the surrounding area, a geological structure type score is obtained; The geological structure indicators are normalized based on the geological structure type score to obtain the normalized values ​​of the geological structure indicators.

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