A method and system for classifying and determining surrounding rock of hard rock in high ground stress areas

Abstract

The present invention relates to the field of geotechnical and water conservancy and hydropower engineering, and discloses a surrounding rock classification and determination method for hard rock in high ground stress areas, comprising the following steps: (1) obtaining judgment data of target underground engineering rock mass quality, wherein the judgment data includes rock strength score data A, rock mass integrity score data B, structural surface state score data C, groundwater state score data D, and main structural surface attitude score data E; (2) calculating a total engineering rock mass quality score HC, where HC = A + B + C + D + E; (3) obtaining ground stress influencing factor data; (4) performing score correction based on the HC value according to the surrounding rock ground stress influencing factors to obtain a final rock mass score T'; and (5) obtaining a surrounding rock classification result based on the rock mass score T'. The present invention can improve the accuracy of surrounding rock classification and determination of hard rock in high and extremely high ground stress areas.

Description

Technical Field

[0001] The present invention relates to the fields of geotechnical engineering, water conservancy and hydropower engineering, and in particular to a surrounding rock classification and determination method for hard rock in high ground stress areas. Background Art

[0002] Surrounding rock classification is an evaluation of surrounding rock quality from an engineering geological perspective. Its final results play a key role in qualitatively studying the deformation magnitude and stability analysis of surrounding rock, and are the main basis for scientifically formulating excavation construction procedures and support measures.

[0003] Internationally, research on surrounding rock classification (rock quality grading) has broadly evolved through two phases. The first phase, before the 1970s, primarily focused on qualitative or single-index evaluation of surrounding rock quality. Representative examples include the Proctor Rock Solidity Index classification (1906), Terzaghi's (1946) rock load classification, and Deere's (1963) rock quality index (RQD) classification. The second phase, after the 1970s, saw the continuous expansion of human engineering activities and the increasing complexity of engineering geological conditions. Single-index surrounding rock classification methods were no longer adequate for engineering needs, leading to the development of numerous classification methods based on quantitative, multi-index comprehensive evaluations. Among them, the representative ones are: the rock structure evaluation system (RSR method) proposed by GE Wickham et al. (1972, 1974), the geomechanical classification system (RMR method) proposed by Bieniawski (1974), the rock quality index Q classification system proposed by Barton et al. (1974), the geological strength index system (GSI method) proposed by Hoek et al. (1974), the RCT method proposed by John et al. (1980), the QTS method proposed by Otakar (1985), and the (1996) proposed the RMi method. Domestically, since the 1980s, Chinese scholars have conducted extensive research on surrounding rock classification for specific projects, gradually developing these research into national standards and industry regulations. Representative examples include the National Standard BQ Rock Mass Classification Method (1994) and the HC Method for the Engineering Geological Classification of Hydropower Surrounding Rocks recommended in the "Code for Geological Investigation of Hydropower Engineering" (GB50287-2017). Currently, the main methods used for classifying surrounding rock for large underground caverns in hydropower projects in my country include the HC method, the Q method, the RMR method, and the BQ method. Each method considers the influence of in-situ stress in different ways: the HC method uses the surrounding rock strength-stress ratio as a limiting criterion to account for the influence of in-situ stress; the Q method considers the influence of in-situ stress through the stress reduction factor (SRF); the RMR method does not directly consider in-situ stress; and the BQ method considers the influence of in-situ stress through the in-situ stress correction factor. The HC method refers to the method in which the total score HC value of the sum of the five factors that control the stability of surrounding rock, namely rock strength, rock integrity, structural surface state, groundwater and main structural surface attitude, as specified in Appendix L of the "Code for Geological Investigation of Hydropower Engineering" GB50287-2016, is used as the basic criterion.

[0004] High geostress areas refer to areas with initial geostress between 20 and 30 MPa. The current international and domestic rock mass classification methods mentioned above are not applicable to high geostress areas. These methods are too simple and have poor applicability for the classification of high geostress areas. In recent years, domestic scholars have carried out a revision of the rock mass classification method that takes high geostress conditions into account in combination with specific projects to address the shortcomings of the commonly used classification methods in that they are too simple and have poor applicability, and have achieved a series of research results. The revision ideas can be summarized into two types: 1) Directly modify the original classification indicators to reflect the influence of high geostress; 2) Add new indicators that can reflect high geostress on the basis of the existing classification.

[0005] Although a lot of engineering experience and research results have been achieved in the classification of surrounding rock under high ground stress environment, the existing surrounding rock classification method is not adaptable and targeted enough for caverns in high ground stress areas. In addition, the main problems in the surrounding rock quality classification of domestic water conservancy and hydropower underground caverns are as follows: the surrounding rock classification method under medium and low ground stress is relatively mature. In the past, surrounding rock classification was mostly carried out under such conditions, and the results obtained were relatively satisfactory. However, the surrounding rock classification method under high ground stress conditions is still immature and is not suitable for surrounding rock classification under high ground stress conditions.

[0006] In addition, although the existing surrounding rock classification takes into account the structural surface conditions that are most unfavorable to stability, factors such as the number of new structural surfaces after excavation also have a certain impact on the stability of the surrounding rock. Therefore, the classification results obtained by applying the existing classification method to high ground stress conditions are not accurate. Summary of the Invention

[0007] The present invention aims to provide a method for classifying and determining surrounding rocks of hard rocks in high-in-situ stress areas, so as to more accurately classify surrounding rocks in high-in-situ stress areas.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for classifying and determining surrounding rock of hard rock in high ground stress areas comprises the following steps:

[0010] (1) Obtaining judgment data on the quality of the target underground engineering rock mass, wherein the judgment data includes rock strength scoring data A, rock mass integrity scoring data B, structural surface status scoring data C, groundwater status scoring data D, and main structural surface occurrence scoring data E;

[0011] (2) Calculate the total engineering rock mass quality score HC, HC = A + B + C + D + E;

[0012] (3) Obtain data on factors affecting ground stress;

[0013] (4) According to the factors affecting the ground stress of the surrounding rock, the score is corrected with the HC value as the basic score to obtain the final rock mass score T';

[0014] (5) Obtain the surrounding rock classification results based on the rock mass score T'.

[0015] Preferably, as an improvement, the factors affecting ground stress include: new cracks F, residual porosity G one week after blasting pre-cracking, rock burst damage depth H, and rock burst characteristics I.

[0016] Preferably, as an improvement,

[0017] The rock mass score T' is calculated as follows: T' = HC + F + G + H + I;

[0018] in:

[0019] When the number of new cracks is 0 to 1 / m, the value of F ranges from 0 to -1 points;

[0020] When the number of new cracks is 2 to 4 per meter, the value of F is -2 to -4 points; when the number of new cracks is greater than 5 per meter, the value of F is -5 points.

[0021] When the residual hole rate is greater than 80% after one week of blasting pre-splitting, the value range of G is 0 to -1 points;

[0022] When the residual hole rate is greater than 30-80% one week after blasting pre-splitting, the value range of G is -2 to -4 points;

[0023] When the residual hole rate is less than 30% one week after blasting pre-splitting, the value of G is -5 points;

[0024] When the rockburst damage depth is less than 0.1m, the value range of H is 0 to -1 points;

[0025] When the rockburst damage depth is 0.1 to 0.5 m, the value range of H is -2 to -4 points;

[0026] When the rock burst damage depth is greater than 0.5m, the value of H is -5 points;

[0027] When the intensity level of the rockburst characteristic is a minor rockburst, the value range of I is 0 to -1 points;

[0028] When the intensity level of the rockburst characteristic is moderate rockburst, the value range of I is -2 to -4 points;

[0029] When the intensity level of the rockburst characteristic is severe rockburst or extremely severe rockburst, the value of I is -5 points.

[0030] Preferably, as an improvement,

[0031] The steps for obtaining the surrounding rock classification results according to the rock mass score T' in step (5) are as follows:

[0032] The surrounding rock type is determined based on the following criteria:

[0033] When T'>85, the surrounding rock category is type I;

[0034] When 75<T'≤85, the surrounding rock category is type II and the surrounding rock category subclass is type II1;

[0035] When 65<T'≤75, the surrounding rock category is type II and the surrounding rock category subclass is type II2;

[0036] When 55<T'≤65, the surrounding rock category is type III and the surrounding rock category subclass is type III1;

[0037] When 45<T'≤55, the surrounding rock category is type III and the surrounding rock category subclass is type III2;

[0038] When 35<T'≤45, the surrounding rock type is IV and the surrounding rock type subtype is IV1;

[0039] When 25<T'≤35, the surrounding rock type is IV and the surrounding rock type subtype is IV2;

[0040] When T'≤25, the surrounding rock category is type V.

[0041] Preferably, as an improvement,

[0042] The steps to obtain the judgment data of the target underground engineering rock mass quality are as follows:

[0043] Drill holes in the target underground engineering rock mass area and extract cores. Test the cores and the surrounding rocks around the holes to obtain judgment data on the quality of the target underground engineering rock mass.

[0044] A classification and determination method for surrounding rock of hard rock in high ground stress area, applicable to the uniaxial compressive strength σ of rock mass c The ratio of the maximum principal stress σ1 is greater than 4, and the uniaxial compressive strength of the rock mass σ c Under working conditions above 60MPa.

[0045] Preferably, as an improvement, corresponding support measures are taken for different types of surrounding rocks, and the support measures include one or more of shotcrete, prestressed anchor rods, steel mesh, short advance and multiple cycles, advanced stress relief, anchor cables, and advanced support.

[0046] The invention discloses a surrounding rock classification determination method for hard rocks in high ground stress areas, which is applicable to the surrounding rock classification determination of hard rocks in high ground stress areas.

[0047] Preferably, as an improvement, it is applicable to the determination of the surrounding rock type of delayed rock burst.

[0048] A surrounding rock classification and determination system for hard rock in high ground stress areas, including:

[0049] A judgment data acquisition unit is used to obtain rock strength score data A, rock mass integrity score data B, structural surface status score data C, groundwater status score data D, and main structural surface occurrence score data E;

[0050] Engineering rock mass quality calculation unit, used to calculate the total engineering rock mass quality score HC, HC = A + B + C + D + E;

[0051] A ground stress influencing factor data acquisition unit, used to acquire ground stress influencing factor data;

[0052] The surrounding rock stress correction unit is used to correct the score based on the HC value according to the factors affecting the surrounding rock stress and obtain the final rock mass score T';

[0053] The surrounding rock classification unit is used to obtain the surrounding rock classification results based on the rock mass score T'.

[0054] The principles and advantages of this solution are:

[0055] In the process of studying the classification and determination of surrounding rock, the inventors found that the existing research ideas have the following deficiencies:

[0056] The HC method (GB50287-2016), which is the closest to the present invention, is widely used in the water conservancy and hydropower industry as a national standard. However, it still has certain shortcomings:

[0057] (1) The HC method is not applicable to underground caverns with a depth less than 2 times the cave diameter or span, and is not applicable to special rocks (expansive rocks, salt rocks), karst caves, and soil caverns;

[0058] (2) The HC method has certain limitations in classifying rock masses in extremely high stress areas;

[0059] (3) When the HC method is used to classify the surrounding rock of large-span caverns, internationally accepted surrounding rock classifications (such as the Q system classification) can also be used for comparison.

[0060] Ground stress classification is an important indicator for identifying and evaluating the degree of impact of ground stress on engineering projects. Based on the ground stress data and deformation characteristics of more than 20 projects, it is shown that the current national standard "Specifications for Geological Investigation of Hydropower Engineering" uses the maximum principal stress value and the rock strength stress ratio S (Rb / σm) as the classification index to determine the results inconsistently. There is a certain deviation between the current rock strength stress ratio classification standard and the actual situation of the project, and there is a problem that the impact of high ground stress on the project is underestimated. The present invention provides a surrounding rock classification and determination method for high ground stress and extremely high ground stress areas. Through the surrounding rock classification ground stress impact correction factor scoring table and the surrounding rock classification determination considering ground stress correction, the above-mentioned problems existing in the existing methods are solved to a certain extent.

[0061] Furthermore, while existing surrounding rock classifications consider the least stable structural planes, factors such as the number of newly formed structural planes after excavation also have a certain impact on surrounding rock stability. This invention, by introducing newly formed fractures, improves the reliability of surrounding rock classification and is a future development direction.

[0062] Issues such as rockburst and its impact on surrounding rock classification are still unclear and require further research. However, the classification method in this invention uses factors such as new cracks, residual porosity one week after blasting pre-cracking, rockburst damage depth, and rockburst characteristics as correction criteria, which can more accurately classify surrounding rock.

[0063] The present invention macroscopically introduces residual porosity, cross-section formation, and rockburst phenomenon, and through a scoring table of surrounding rock classification ground stress influence correction factors and surrounding rock classification judgment considering ground stress correction, can improve the accuracy of surrounding rock classification judgment of hard rocks in highland and extremely high ground stress areas.

[0064] In practical application, the present invention is suitable for excavation of rock masses with great burial depth or high ground stress. c The ratio of the maximum principal stress σ1 is greater than 4, and the uniaxial compressive strength of the rock mass σ c Above 60MPa.

[0065] The present invention addresses the underestimation of the impact of high geostress on engineering projects and provides a reference for rock mass classification in high and extremely high geostress areas. In high and extremely high geostress areas, determining rock mass classification levels using this method can be used to guide construction, save costs, and improve efficiency. Furthermore, this method is also applicable to the classification of surrounding rock for large-span caverns in brittle rock in high and extremely high stress areas, as well as for determining the surrounding rock type for delayed rockbursts, thus having a wide range of applications.

[0066] The present invention proposes corresponding support measures for different grades of surrounding rock, including shotcrete, prestressed anchor rods, steel mesh, short advance and multiple cycles, advanced stress relief, anchor cables, advanced support and other "rigid and flexible" comprehensive support methods, and the treatment effect is basically controllable. DETAILED DESCRIPTION

[0067] The following is further described in detail through specific implementation methods:

[0068] Example

[0069] A method for classifying and determining surrounding rock of hard rock in high ground stress areas comprises the following steps:

[0070] (1) According to the HC method, the judgment data of the target underground engineering rock mass quality is obtained. The steps for obtaining the judgment data of the target underground engineering rock mass quality are as follows: drilling a hole in the target underground engineering rock mass area and taking out a core, testing the core and the surrounding rock around the hole, and obtaining the judgment data of the target underground engineering rock mass quality.

[0071] The judgment data include rock strength score data A; rock integrity score data B; structural surface status score data C; groundwater status score data D; main structural surface occurrence score data E;

[0072] (2) Calculate the total engineering rock mass quality score HC, HC = A + B + C + D + E;

[0073] The HC method is used as the basic criterion to judge the rock mass quality. According to Appendix L of the "Code for Geological Investigation of Hydropower Engineering" GB50287-2016, the total score HC value of the sum of the five factors that control the stability of the surrounding rock, namely rock strength, rock mass integrity, structural surface state, groundwater and main structural surface occurrence is the basic criterion. The scoring details are as follows:

[0074] 1) Surrounding rock engineering geological classification can be divided into preliminary surrounding rock classification and detailed surrounding rock classification. Based on the classification results, the stability of the surrounding rock is evaluated and can serve as the basis for determining the support type. The surrounding rock classification should comply with the requirements of Table 1.

[0075] Table 1 Classification of surrounding rock engineering geology

[0076]

[0077] 2) The preliminary classification of surrounding rock is mainly based on rock type and rock structure type or rock integrity, which is applicable to the planning and pre-feasibility study stages and should comply with the provisions of Table 2.

[0078] Table 2 Preliminary classification of surrounding rock

[0079]

[0080]

[0081] 3) The determination of rock type shall comply with the provisions of Table 3.

[0082] Table 3 Classification of rock types

[0083]

[0084] 4) The classification of rock mass integrity shall comply with the provisions of Table 4.

[0085] Table 4 Classification of rock mass integrity

[0086]

[0087] Note: Structural surface spacing refers to the average spacing between main structural surfaces.

[0088] 5) The detailed classification of surrounding rock should be based on the total score of the sum of five factors that control the stability of surrounding rock, namely, rock strength, rock integrity, structural surface state, groundwater and main structural surface attitude. The surrounding rock strength stress ratio is the limiting criterion. It is mainly used in the feasibility study, bidding and construction detailed design stages, and should comply with the provisions of Table 5.

[0089] Table 5 Detailed classification of surrounding rock of underground caverns

[0090] Surrounding rock type Total score of surrounding rock (T) Surrounding rock strength stress ratio (s) I T>85 >4 II 85≥T>65 >4 Ⅲ 65≥T>45 >2 IV 45≥T>25 >2 Ⅴ T≤25

[0091] Note: For Class I, II, III, IV, and V surrounding rock, when its strength-stress ratio is less than that specified in this table, the surrounding rock category should be reduced by one level accordingly.

[0092] 6) The surrounding rock strength stress ratio S can be calculated according to formula (Formula 1):

[0093]

[0094] Where: Rb—saturated uniaxial compressive strength of rock (MPa);

[0095] KV—rock mass integrity coefficient, which is the square of the ratio of the longitudinal wave velocity of the rock mass to the longitudinal wave velocity of the corresponding rock;

[0096] σm—maximum principal stress of surrounding rock (MPa), which can be replaced by self-weight stress when there is no measured data.

[0097] 7) The scoring of the five factors in the detailed classification of underground cavern surrounding rock should comply with the following regulations:

[0098] 1. The rock strength rating shall comply with the requirements of Table 7-1.

[0099] Table 7-1 Rock strength rating

[0100]

[0101] Note: 1. When the saturated uniaxial compressive strength of rock is greater than 100 MPa, the rock strength score is 30.

[0102] 2. When the sum of the rock integrity and structural surface status scores is less than 5, if the rock strength score is greater than 20, it shall be scored as 20.

[0103] 2. The scoring of rock mass integrity shall comply with the provisions of Table 7-2.

[0104] Table 7-2 Rock mass integrity rating

[0105]

[0106] Note: 1. When 60MPa≥Rb>30MPa, and the sum of the rock mass integrity and structural surface status scores is >65, a score of 65 shall be applied.

[0107] 2. When 30MPa≥Rb>15MPa, and the sum of the rock integrity score and the structural surface status score is >55, a score of 55 shall be applied.

[0108] 3. When 15MPa≥Rb>5MPa, and the sum of the rock integrity score and the structural surface status score is >40, a score of 40 shall be applied.

[0109] 4. When Rb≤5MPa, it is an extremely soft rock, and the rock integrity and structural surface status are not included in the scoring.

[0110] 3. The scoring of structural surface status shall comply with the provisions of Table 7-3.

[0111] Table 7-3 Structural surface status rating

[0112]

[0113]

[0114] Note: 1. When the extension length of the structural surface is less than 3m, the structural surface status score of hard rock and relatively soft rock will be increased by 3 points; soft rock will be increased by 2 points; when the extension length of the structural surface is greater than 10m, the structural surface status score of hard rock and relatively soft rock will be reduced by 3 points, and soft rock will be reduced by 2 points.

[0115] 2. When the structural surface opening is greater than 10 mm and there is no filling, the structural surface status score is zero.

[0116] 4. The scoring of groundwater status shall comply with the provisions of Table 7-4.

[0117] Table 7-4 Groundwater Status Rating

[0118]

[0119] Note: The basic factor score T' is the sum of the aforementioned rock strength score A, rock mass integrity score B and structural surface status score C.

[0120] 5. The scoring of the attitude of the main structural surface shall comply with the provisions of Table 7-5.

[0121] Table 7-5 Occurrence scores of main structural surfaces

[0122]

[0123] Note: For surrounding rocks classified as poor integrity, relatively broken and broken according to the degree of rock integrity, no correction is made to the main structural surface attitude score.

[0124] (3) Obtain data on factors affecting ground stress; factors affecting ground stress include: new cracks F, residual porosity G after one week of blasting pre-cracking, rockburst damage depth H, and rockburst characteristics I;

[0125] In this embodiment, the newly formed cracks F are obtained by actual statistics during on-site geological logging and drilling television; the residual hole rate G is obtained one week after blasting pre-cracking: after the complete rock mass is blasted and excavated, blasthole residual holes will remain in the excavation section. The occurrence of rock burst (slabbing, spalling) will reduce the number, length and rate of residual holes. The residual hole rate can be calculated by on-site statistics of the number and length of residual holes in the blastholes; the rock burst damage depth H is obtained by measuring the cross-sectional diagram; the intensity level of the rock burst feature I is a macro-qualitative comprehensive analysis, combined with microseismic monitoring methods to assist in judgment and determination.

[0126] (4) Based on the factors affecting the in-situ stress of the surrounding rock, the score is corrected with the HC value as the basic score to obtain the final rock mass score T'; in this embodiment, based on the newly formed cracks, the residual porosity after one week of blasting pre-cracking, the rock burst damage depth, and the rock burst characteristics, the HC value is used as the basic value to correct the in-situ stress factors. The rock mass score T' is calculated as follows: T' = HC + F + G + H + I;

[0127] in:

[0128] The score correction method for the correction factor of the surrounding rock classification ground stress is shown in Table 8.

[0129] Table 8 Scoring table of correction factors affecting ground stress according to surrounding rock classification

[0130]

[0131] Specifically: In this embodiment, when the number of new cracks F is 0, the value range of F is 0 points; when the number of new cracks F is 1, the value range of F is -1 points;

[0132] When there are 2 new cracks F, the value range of F is -2 points; when there are 4 new cracks F, the value range of F is -4 points;

[0133] In this embodiment, when the number of newly formed cracks is a different intermediate value, a value can be obtained using a linear interpolation method.

[0134] When the residual hole rate is of different intermediate values ​​after one week of blasting pre-cracking, the value can be obtained according to the linear interpolation method.

[0135] When the rock burst damage depth is 0.1m, the value of H is -2 points; when the rock burst damage depth is 0.5m, the value of H is -4 points. When the rock burst damage depth is different in between, the value can be obtained according to the linear interpolation method.

[0136] (5) The surrounding rock classification result is obtained based on the rock mass score T'. The surrounding rock classification is determined based on the in-situ stress correction. Based on the HC method in Appendix L of GB50287-2016 for surrounding rock engineering geological classification, the in-situ stress correction factor score is considered. The HC value is corrected by the in-situ stress influencing factor score to obtain the final rock mass quality score T', which is substituted into Table 9 for surrounding rock classification.

[0137] Table 9 Surrounding rock classification determination table considering ground stress correction

[0138]

[0139] In Table 9, Class V surrounding rock has the lowest grade, with poor to extremely poor integrity. It is difficult to accumulate large ground stress energy. The high ground stress has no significant effect on hard rock and can be treated without reduction.

[0140] Based on the characteristics of hydropower projects, to better implement support design and control project costs, the surrounding rock types can be divided into two sub-classes, each with a score of 10. For example, the corresponding score for III1 is: 55 < T' ≤ 65, and the corresponding score for III2 is: 45 < T' ≤ 55. The surrounding rock quality of III1 is better than that of III2.

[0141] Subclassification of surrounding rock mass provides a more accurate classification of surrounding rock quality. Type I rock mass has no developed fractures, a complete, monolithic rock mass, and generally no rockbursts. The cavern is stable and generally requires no support, so no classification is made. Type V rock mass has poor surrounding rock conditions, developed joints and fractures, and a fragmented rock mass. However, no rockbursts are likely to occur, so no classification is made.

[0142] The present invention also provides a surrounding rock classification and determination system for hard rock in high ground stress areas, comprising:

[0143] A judgment data acquisition unit is used to obtain rock strength score data A, rock mass integrity score data B, structural surface status score data C, groundwater status score data D, and main structural surface occurrence score data E;

[0144] Engineering rock mass quality calculation unit, used to calculate the total engineering rock mass quality score HC, HC = A + B + C + D + E;

[0145] A ground stress influencing factor data acquisition unit, used to acquire ground stress influencing factor data;

[0146] The surrounding rock stress correction unit is used to correct the score based on the HC value according to the factors affecting the surrounding rock stress and obtain the final rock mass score T';

[0147] The surrounding rock classification unit is used to obtain the surrounding rock classification results based on the rock mass score T'.

[0148] In practical application, the present invention is suitable for excavation of rock masses with great burial depth or high ground stress, such as underground powerhouses and diversion tunnels of large hydropower projects such as Shuangjiangkou and Jinping, and deep cavern excavation of railway and highway projects. c The ratio of the maximum principal stress σ1 is greater than 4, and the uniaxial compressive strength of the rock mass σ c The method is applicable to the working conditions above 60 MPa and is suitable for rock excavation and surrounding rock classification determination of hard rocks in high geostress areas. In addition, the determination method in this embodiment is also applicable to the surrounding rock classification determination of large-span caverns of brittle rocks in high geostress areas and extremely high geostress areas, as well as the surrounding rock classification determination of delayed rock bursts.

[0149] The three major caverns of the Shuangjiangkou Hydropower Station's underground powerhouse, currently under construction, are being classified using this method. Excavation revealed that the surrounding rock of these three caverns is primarily Class III, with Class IV indicating the presence of lamprophyre veins and affected zones, compressional fracture zones, and minor faults. Due to the prolonged stress release from the central pilot tunnel and first-layer excavation, some Class II surrounding rock has developed in the second layers of the tailgate and main transformer chambers.

[0150] This invention proposes corresponding support measures for different grades of surrounding rock, including shotcrete, prestressed anchors, steel mesh, short-footage, multiple cycles, advanced stress relief, anchor cables, and advanced support, combining a combination of rigidity and flexibility. The treatment effect is generally controllable. Furthermore, the method of this invention requires only minor modifications to the HC method, resulting in high reliability and simplicity.

[0151] The present invention provides a surrounding rock classification and determination method for hard rock in high and extremely high geostress areas. The method macroscopically introduces residual porosity, cross-section formation, and rockburst phenomena. By using a surrounding rock classification geostress influence correction factor scoring table and surrounding rock classification determination considering geostress correction, the accuracy of surrounding rock classification and determination of hard rock in high and extremely high geostress areas is improved. The method is used to guide construction, save costs, and improve efficiency. Corresponding support measures are proposed for different grades of surrounding rock. The method is highly practical and suitable for wide promotion and use.

[0152] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A method for classifying and determining surrounding rock mass of hard rock in high geostress areas, characterized by: The following steps are included: (1) Obtain judgment data on the quality of the target underground engineering rock mass, including rock strength scoring data A, rock mass integrity scoring data B, structural surface status scoring data C, groundwater status scoring data D, and main structural surface occurrence scoring data E; (2) Calculate the total engineering rock mass quality score HC, HC = A + B + C + D + E; (3) Obtain data on factors affecting ground stress, including: new cracks F, residual porosity G one week after blasting pre-cracking, rockburst damage depth H, and rockburst characteristics I; (4) According to the factors affecting the in-situ stress of the surrounding rock, the score is corrected based on the HC value to obtain the final rock mass score T'. The calculation method of the rock mass score T' is as follows: T'=HC+F+G+H+I; in: When the number of new cracks is 0 to 1 / m, the value of F ranges from 0 to -1 points; When the number of new cracks is 2 to 4 per meter, the value of F is -2 to -4 points; when the number of new cracks is greater than 5 per meter, the value of F is -5 points. When the residual hole rate is greater than 80% one week after blasting pre-splitting, the value range of G is 0 to -1 points; When the residual hole rate is greater than 30% to 80% one week after blasting pre-splitting, the value range of G is -2 to -4 points; When the residual hole rate is less than 30% one week after blasting pre-splitting, the value of G is -5 points; When the rockburst damage depth is less than 0.1m, the value range of H is 0 to -1 points; When the rockburst damage depth is 0.1 to 0.5 m, the value range of H is -2 to -4 points; When the rock burst damage depth is greater than 0.5m, the value of H is -5 points; When the intensity level of the rockburst characteristic is a minor rockburst, the value range of I is 0 to -1 points; When the intensity level of the rockburst characteristic is moderate rockburst, the value range of I is -2 to -4 points; When the intensity level of the rockburst characteristic is severe rockburst or extremely severe rockburst, the value of I is -5 points; (5) Obtain the surrounding rock classification results based on the rock mass score T'.

2. The method for classifying and determining surrounding rock of hard rock in high geostress areas according to claim 1, characterized in that: The steps for obtaining the surrounding rock classification results based on the rock mass score T' in step (5) are as follows: The surrounding rock type is determined based on the following criteria: When T'>85, the surrounding rock category is type I; When 75<T'≤85, the surrounding rock category is type II and the surrounding rock category subclass is type II1; When 65<T'≤75, the surrounding rock category is type II and the surrounding rock category subclass is type II2; When 55<T'≤65, the surrounding rock category is type III and the surrounding rock category subclass is type III1; When 45<T'≤55, the surrounding rock category is type III and the surrounding rock category subclass is type III2; When 35<T'≤45, the surrounding rock category is type IV and the surrounding rock category subclass is type IV1; When 25<T'≤35, the surrounding rock category is type IV and the surrounding rock category subclass is type IV2; When T'≤25, the surrounding rock category is type V.

3. The method for classifying and determining surrounding rock of hard rock in high geostress areas according to claim 1, characterized in that: The steps to obtain the judgment data of the target underground engineering rock mass quality are as follows: Drill holes in the target underground engineering rock mass area and extract cores. Test the cores and the surrounding rocks around the holes to obtain judgment data on the quality of the target underground engineering rock mass.

4. The method for classifying and determining surrounding rock of hard rock in high geostress areas according to claim 1, characterized in that: Applicable to the uniaxial compressive strength of rock mass σ c The ratio of the maximum principal stress σ1 is greater than 4, and the uniaxial compressive strength of the rock mass σ c Under working conditions above 60MPa.

5. The method for classifying and determining surrounding rock of hard rock in high geostress areas according to claim 2, characterized in that: Corresponding support measures are taken for different types of surrounding rock, including one or more of shotcrete, prestressed anchor rods, steel mesh, short advance and multiple cycles, advanced stress relief, anchor cables, and advanced support.

6. The method for classifying and determining surrounding rock of hard rock in high geostress areas according to claim 1, characterized in that: Applicable to the determination of surrounding rock types of hard rocks in high ground stress areas.

7. The method for classifying and determining surrounding rock of hard rock in high geostress areas according to claim 1, characterized in that: Applicable to the determination of surrounding rock types for delayed rockbursts.

8. A system for classifying and determining surrounding rock masses of hard rock in high geostress areas, characterized by: include, A judgment data acquisition unit is used to obtain rock strength score data A, rock mass integrity score data B, structural surface status score data C, groundwater status score data D, and main structural surface occurrence score data E; Engineering rock mass quality calculation unit, used to calculate the total engineering rock mass quality score HC, HC = A + B + C + D + E; A ground stress influencing factor data acquisition unit is used to acquire ground stress influencing factor data, where the ground stress influencing factors include: newly formed cracks F, residual porosity G after one week of blasting pre-cracking, rock burst damage depth H, and rock burst characteristics I; The surrounding rock stress correction unit is used to correct the score based on the HC value according to the factors affecting the surrounding rock stress, and obtain the final rock mass score T'. The calculation method of the rock mass score T' is as follows: T'=HC+F+G+H+I; in: When the number of new cracks is 0 to 1 / m, the value of F ranges from 0 to -1 points; When the number of new cracks is 2 to 4 per meter, the value of F is -2 to -4 points; when the number of new cracks is greater than 5 per meter, the value of F is -5 points. When the residual hole rate is greater than 80% one week after blasting pre-splitting, the value range of G is 0 to -1 points; When the residual hole rate is greater than 30% to 80% one week after blasting pre-splitting, the value range of G is -2 to -4 points; When the residual hole rate is less than 30% one week after blasting pre-splitting, the value of G is -5 points; When the rockburst damage depth is less than 0.1m, the value range of H is 0 to -1 points; When the rockburst damage depth is 0.1 to 0.5 m, the value range of H is -2 to -4 points; When the rock burst damage depth is greater than 0.5m, the value of H is -5 points; When the intensity level of the rockburst characteristic is a minor rockburst, the value range of I is 0 to -1 points; When the intensity level of the rockburst characteristic is moderate rockburst, the value range of I is -2 to -4 points; When the intensity level of the rockburst characteristic is severe rockburst or extremely severe rockburst, the value of I is -5 points; The surrounding rock classification unit is used to obtain the surrounding rock classification results based on the rock mass score T'.

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