A method for quantitatively estimating potential rockburst pit depth considering structural plane and excavation disturbance effect

Abstract

The present application relates to a kind of potential rock burst pit depth quantitative estimation method considering structural plane and excavation disturbance effect, obtain the initial maximum principal stress and rock uniaxial compressive strength of the region to be estimated, preliminary evaluation whether it has the potential to occur rock burst;Surrounding rock is estimated to estimate the scope of excavation damage zone by sound wave test;According to the sound wave test data, the disturbance factor at different depths is estimated;According to the change characteristics of disturbance factor, the height damage zone and weak damage zone range of surrounding rock in excavation damage zone are estimated;Estimate the potential rock burst pit depth of surrounding rock.The present application not only considers rock strength and stress condition, but also considers the influence of structural plane and excavation disturbance on potential rock burst pit depth, uses high-precision, low-cost and convenient sound wave test technology and a small amount of rock indoor strength test can be realized, with greater innovation, practicality, economy and feasibility.

Description

Technical Field

[0001] This invention relates to a method for quantitatively estimating the depth of potential rockburst craters that takes into account structural planes and excavation disturbance effects, belonging to the field of rockburst disaster prediction and prevention in deep hard rock engineering. Background Technology

[0002] Rockburst is a common geological hazard during the excavation of deep hard rock engineering projects. It often causes damage to the support system, damage to machinery and equipment, casualties, and over-excavation of the surrounding rock. These serious consequences are all attributed to the detachment of rock fragments (pieces) from the parent rock in the form of peeling, ejection, and throwing from potential rockburst pits. Therefore, the estimation of potential rockburst pits is of great significance for the prediction and prevention of rockburst disasters, and can also provide a reference for the formulation of support schemes.

[0003] Currently, rock burst intensity and potential rockburst crater depth are mostly predicted using rock strength-stress ratio indices (including the ratio of uniaxial compressive strength to initial maximum principal stress and the ratio of maximum tangential stress to uniaxial compressive strength). Engineering practice shows that existing methods are mostly applicable to the exploration and design stage and projects with relatively good surrounding rock quality. Since rockbursts occur during excavation, the dynamic loads induced by excavation and disturbances such as static stress adjustments are closely related to the timing and intensity of rockbursts. In addition, the rock mass, the bearing medium of a rockburst, is a natural material that often contains joints, fissures, and other structural planes due to historical geological activities. The properties of these structural planes affect the strength and energy storage characteristics of the rock mass, thus playing a crucial role in the potential and extent of rockbursts.

[0004] Traditional methods clearly cannot account for the impact of excavation disturbance and structural planes on potential rockburst craters. The rock mass strength parameters in the Hoek-Brown strength criterion are jointly determined by three indicators: uniaxial compressive strength of rock, disturbance factor D, and geological strength index GSI. Using the rock mass strength-stress ratio (rock mass strength to maximum principal stress index) as an indicator not only considers rock strength and stress factors but also includes the effects of excavation disturbance and structural planes. Therefore, it is necessary to establish a quantitative estimation method for the depth of potential rockburst craters that considers the effects of structural planes and excavation disturbance based on this method, so as to provide a reference for predicting the damage range of rockburst disasters and formulating targeted excavation, prevention, and support schemes. Summary of the Invention

[0005] This invention provides a method for quantitatively estimating the depth of potential rockburst craters that takes into account structural planes and excavation disturbance effects, aiming to solve the problem that traditional evaluation methods cannot be applied to the real-time assessment of rockburst craters during the construction phase.

[0006] The technical solution adopted by this invention to solve its technical problem is:

[0007] A method for quantitatively estimating the depth of potential rockburst craters, taking into account structural planes and excavation disturbance effects, specifically includes the following steps:

[0008] Step S1: Define the area to be estimated and conduct a preliminary evaluation of whether the area has the potential for rockburst. The criteria for this judgment include the initial maximum principal stress σ1 and the uniaxial compressive strength of the rock σ. c If the area to be estimated does not have the potential for rockburst, the step terminates; if the area to be estimated has the potential for rockburst, continue to step S2.

[0009] Step S2: Conduct acoustic wave testing on the surrounding rock within the area to be estimated. Determine the extent of the excavation damage zone based on the P-wave velocity of the acoustic wave. The depth of the excavation damage zone is defined as h. EDZ ;

[0010] Step S3: After determining the extent of the excavation damage zone, the quality of the structural surface is quantitatively characterized by the geological strength index GSI, and the excavation disturbance effect is characterized by the disturbance factor D. The geological strength index GSI and the disturbance factor D are estimated based on the acoustic test data.

[0011] Step S4: Estimate the extent of the high-damage zone and weak-damage zone of the surrounding rock in the excavation damage zone based on the variation characteristics of the obtained disturbance factor D, and define the distribution depth h of the excavation damage zone. EDZ The depth of the highly damaged area within is h. HDZ The depth of the weak damage zone is h. WDZ ;

[0012] Step S5: Based on the depth h of the highly damaged area defined in step S4 HDZ The depth of the weak damage zone is h WDZ and the depth h of the excavation damage zone EDZ By combining the variation law of the disturbance factor D inside the surrounding rock, the potential rockburst crater depth of the surrounding rock is estimated.

[0013] As a further preferred embodiment of the present invention, in step S1, the step of evaluating whether the area to be estimated has the potential to experience a rockburst is as follows:

[0014] Step S11: Obtain the initial maximum principal stress σ1 and the uniaxial compressive strength σ of the rock in the area to be estimated based on geological survey data and laboratory test results. c ;

[0015] Step S12: The prerequisite for rockburst is the presence of high ground stress. The criteria for determining high ground stress are:

[0016]

[0017] When the initial maximum principal stress σ1 and the uniaxial compressive strength of the rock σ cIf formula (1) is satisfied, it can be determined that the area has the potential to cause a rockburst, and step S2 continues; if it is not satisfied, the area does not have the potential to cause a rockburst, and the quantitative estimation of the rockburst crater depth terminates.

[0018] As a further preferred embodiment of the present invention, in step S2, the step of determining the extent of the excavation damage zone is as follows:

[0019] Step S21: Measure the P-wave velocity of acoustic waves at different depths from the excavation profile within the area to be estimated;

[0020] Step S22: The region with more stable P-wave velocity changes at greater depths is considered the undamaged zone UZ, and the low-velocity zone closer to the excavation profile is designated as the excavation damage zone. The depth of the excavation damage zone is defined as h. EDZ ;

[0021] As a further preferred embodiment of the present invention, in step S3, the step of estimating the geological strength index GSI is as follows:

[0022] Step S311: Obtain the GSI characterized by seismic P-wave velocity based on the conversion relationship between the Geological Strength Index (GSI) and the Rock Mass Geological Classification System (RMR); wherein, the conversion relationship between GSI and RMR is as follows:

[0023] GSI = RMR 76 (2)

[0024] In formula (2), RMR 76 For the 1976 version of the RMR rating system, when RMR 76 When the value is >18, equation (2) holds true; RMR 76 The following empirical relationship exists between P-wave velocity and seismic wave velocity:

[0025] RMR 76 =(40V) s-p +10) / 3 (3)

[0026] In formula (3), V s-p The velocity of the P-wave in seismic waves;

[0027] Substituting formula (2) into formula (3), we obtain the GSI characterized by the P-wave velocity of seismic waves:

[0028] GSI = (40V) s-p +10) / 3 (4);

[0029] Step S312: By linearly fitting a large amount of seismic wave and acoustic P-wave velocity data of engineering rock masses, a linear relationship was found between the seismic wave P-wave velocity and the acoustic P-wave velocity. The fitting equation is:

[0030] V s-p=0.893v a-p +0.151 (5)

[0031] In formula (5), v a-p The velocity of sound wave P is in km / s;

[0032] Step S313, substitute formula (5) into formula (4) to obtain:

[0033] GSI = 11.907v a-p +5.347 (6);

[0034] Step S314: The average wave velocity in the undamaged zone UZ from step S22 is taken as the P-wave velocity v of the rock mass in the undamaged zone UZ. a-p0 , will v a-p0 Substituting into formula (6) yields the geological strength index GSI of the surrounding rock;

[0035] As a further preferred embodiment of the present invention, in step S3, the step of estimating the disturbance factor D is as follows:

[0036] Step S321: Obtain the relationship between the deformation modulus of the rock mass and the deformation modulus of the undamaged rock mass based on the empirical formula for the deformation modulus of the rock mass. The empirical formula is:

[0037] E rm =E i exp((RMR 89 -100) / 36) (7)

[0038] In formula (7), E i The elastic modulus of rock is expressed in GPa; RMR. 89 For the 1989 version of the RMR rating system, when RMR 89 >23, equation (7) holds true; where RMR 89 The empirical relationship with GSI is RMR 89 =0.827GSI+15.394, then formula (7) can be expressed as:

[0039] E rm =E i exp((0.827GSI-84.606) / 36) (8);

[0040] Substituting formula (6) into formula (8) yields:

[0041] E rm =E i exp(0.274v a-p -2.227) (9);

[0042] According to formula (9), the relationship between the rock mass deformation modulus and the deformation modulus of the undamaged rock mass is obtained, that is, the rock mass deformation modulus E rm (The ratio with the deformation modulus E of the undamaged rock mass rm0 is:

[0043]

[0044] Step S322,

[0045] Hoek et al. proposed that the rock mass deformation modulus E rm and the deformation modulus E of the undamaged rock mass rm0 The ratio can be expressed as:

[0046] E rm / E rm0 = 1 - 0.5D (11)

[0047] Combining formulas (10) and (11), the expression of the disturbance factor D estimated by the acoustic wave P-wave velocity can be obtained as:

[0048]

[0049] As a further preference of the present invention, in step S4, the area within the excavation damage zone distribution depth h EDZ where D = 1 is regarded as the highly damaged zone, and the distribution depth of the highly damaged zone is expressed as h HDZ , m; the area where 1 < D < 0 is classified as the weakly damaged zone, and the distribution depth of the weakly damaged zone is expressed as h WDZ , m;

[0050] As a further preference of the present invention, in step S5, the steps for estimating the potential rockburst pit depth of the surrounding rock are:

[0051] Step S51, according to the change law of the disturbance factor D inside the surrounding rock, it is divided into the following two categories:

[0052] The first category: When h HDZ > 0, the variation function of the disturbance factor D with the depth d is:

[0053]

[0054] In formula (13), d is the distance from the excavation contour surface, m; h EDZ is the excavation damage zone distribution depth; h WDZ is the distribution depth of the weakly damaged zone in the excavation damage zone, h WDZ = h EDZ - h HDZ ;

[0055] The second category: When h HDZWhen d = 0, the perturbation factor D varies with depth d as follows:

[0056]

[0057] In formula (14), D s The disturbance factor at the excavation outline surface;

[0058] Step S52, assuming the disturbance level that causes a rockburst is considered the critical disturbance factor D. rb Let h in formula (13) HDZ <h<h EDZ The corresponding function is equal to D. rb Determine the potential rockburst crater depth h. rb :

[0059] h rb =(1-D rb )h WDZ +h HDZ (15);

[0060] Let h in formula (14) <h EDZ The corresponding function is equal to D. rb Determine the potential rockburst crater depth h. rb :

[0061]

[0062] As a further preferred embodiment of the present invention, in step S52, if the rockburst crater depths corresponding to formulas (15) and (16) are to be obtained, the critical damage factor D corresponding to the rockburst needs to be determined. rb The specific steps are as follows:

[0063] Step S521, based on the 2002 version of the generalized Hoek-Brown strength criterion:

[0064]

[0065] In formula (17), σ1 is the first principal stress at failure, σ2 is the second principal stress at failure, and σ3 is the third principal stress at failure.

[0066]

[0067]

[0068]

[0069] In formula (18), m i These are material constants related to the hardness of the rock;

[0070] Let σ3 = 0 MPa in formula (17), then the uniaxial compressive strength of the rock mass is:

[0071] σ cm =σ c ·s a (twenty one);

[0072] Step S522, substitute formulas (19) and (20) into formula (21) to obtain

[0073]

[0074] Then the rock mass strength stress ratio σ cm / σ1 is:

[0075]

[0076] Step S523, assuming the critical strength stress ratio of the rock mass at the time of the rock burst is T rb Then we have:

[0077]

[0078] Step S524: Solve equation (24) to obtain the critical disturbance factor D corresponding to rockburst. rb :

[0079]

[0080] Step S525: Substitute formula (25) into formula (15) to obtain the potential rockburst crater depth h in the first case of the variation of the disturbance factor D within the surrounding rock. rb for:

[0081]

[0082] Substituting formula (25) into formula (16), we obtain the potential rockburst crater depth h in the second case of the variation of the disturbance factor D within the surrounding rock. rb for:

[0083]

[0084] In formulas (26) and (27), T rb =0.2.

[0085] By employing the above technical solutions, the present invention has the following beneficial effects compared to the prior art:

[0086] 1. The method for quantitatively estimating the depth of potential rockburst craters that considers structural planes and excavation disturbance effects provided by this invention not only considers rock strength and geostress factors, but also structural planes and excavation disturbance effects, overcoming the shortcomings of traditional methods that are only suitable for preliminary assessments in the exploration stage and are difficult to adapt to complex construction conditions.

[0087] 2. The method for quantitatively estimating the depth of potential rockburst craters, which takes into account structural planes and excavation disturbance effects, provided by this invention, can achieve quantitative estimation of the depth of potential rockburst craters by combining a small number of indoor rock strength tests with acoustic wave testing of the surrounding rock, and has strong practicality.

[0088] 3. The quantitative estimation method for potential rockburst crater depth considering structural planes and excavation disturbance effects provided by this invention is convenient to measure and operate, can effectively estimate the depth of potential rockburst craters, and has great reference value for optimizing excavation and support schemes. At the same time, the estimation method has low cost and high accuracy, and has strong economic efficiency and feasibility. Attached Figure Description

[0089] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0090] Figure 1 This is a flowchart of the method for quantitatively estimating the depth of potential rockburst craters, taking into account structural planes and excavation disturbance effects, provided by the present invention.

[0091] Figure 2 This is a schematic diagram showing the distribution depth of the excavation damage zone, strong damage zone, weak damage zone, and potential rockburst crater in the quantitative estimation method for potential rockburst crater depth considering structural planes and excavation disturbance effects provided by the present invention.

[0092] Figure 3 This is a schematic diagram of the P-wave velocity of sound at different depths in a preferred embodiment of the present invention;

[0093] Figure 4 This is a schematic diagram of the disturbance factor D of the surrounding rock at different depths in a preferred embodiment of the present invention. Detailed Implementation

[0094] The present invention will now be described in further detail with reference to the accompanying drawings. The specific dimensions used in this embodiment are merely illustrative and do not limit the scope of protection of the present invention.

[0095] As described in the background section, traditional methods often use the rock strength-to-stress ratio as an indicator to predict the intensity of rockbursts and the depth of potential rockburst craters. However, in actual excavation, many factors can induce rockbursts, such as excavation-induced dynamic loads, disturbances caused by static stress adjustments, or the properties of structural surfaces. These factors cannot be reflected in traditional methods. Therefore, this application attempts to establish a new quantitative estimation method for the depth of potential rockburst craters, which not only considers rock strength and stress factors but also includes the effects of excavation disturbances and structural surfaces, providing a reference for predicting the damage range of rockburst disasters and developing targeted excavation, prevention, and support plans.

[0096] Figure 1 The diagram shows a flowchart of the method for quantitatively estimating the depth of potential rockburst craters, considering structural planes and excavation disturbance effects, provided in this application. The method specifically includes the following steps:

[0097] Step S1: Define the area to be estimated and conduct a preliminary evaluation of whether the area has the potential for rockburst. The criteria for this judgment include the initial maximum principal stress σ1 and the uniaxial compressive strength of the rock σ. c If the area to be estimated does not have the potential for rockburst, the step terminates; if the area to be estimated has the potential for rockburst, continue to step S2.

[0098] Step S2: Conduct acoustic wave testing on the surrounding rock within the area to be estimated. Determine the extent of the excavation damage zone based on the P-wave velocity of the acoustic wave. The depth of the excavation damage zone is defined as h. EDZ ;

[0099] Step S3: After determining the extent of the excavation damage zone, the quality of the structural surface is quantitatively characterized by the geological strength index GSI, and the excavation disturbance effect is characterized by the disturbance factor D. The geological strength index GSI and the disturbance factor D are estimated based on the acoustic test data.

[0100] Step S4: Estimate the extent of the high-damage zone and weak-damage zone of the surrounding rock in the excavation damage zone based on the variation characteristics of the obtained disturbance factor D, and define the distribution depth h of the excavation damage zone. EDZ The depth of the highly damaged area within is h. HDZ The depth of the weak damage zone is h. WDZ ;

[0101] Step S5: Based on the depth h of the highly damaged area defined in step S4 HDZ The depth of the weak damage zone is h. WDZ and the depth h of the excavation damage zone EDZ By combining the variation law of the disturbance factor D inside the surrounding rock, the potential rockburst crater depth of the surrounding rock is estimated.

[0102] In step S1, the specific steps for evaluating whether the area to be estimated has the potential for rockburst are as follows:

[0103] Step S11: Obtain the initial maximum principal stress σ1 and the uniaxial compressive strength σ of the rock in the area to be estimated based on geological survey data and laboratory test results. c ;

[0104] Step S12: According to the research of Gong Fengqiang et al., rockburst is a typical geological hazard in high-stress areas. Therefore, the prerequisite for the occurrence of rockburst is the presence of high-stress conditions. The criteria for identifying high-stress conditions are as follows:

[0105]

[0106] When the initial maximum principal stress σ1 and the uniaxial compressive strength of the rock σ c If formula (1) is satisfied, it can be determined that the area has the potential to cause a rockburst, and step S2 continues; if it is not satisfied, the area does not have the potential to cause a rockburst, and the quantitative estimation of the rockburst crater depth terminates.

[0107] In step S2, the specific steps for determining the extent of the excavation damage zone are as follows:

[0108] Step S21: Drill acoustic test holes into the surrounding rock in the area to be estimated according to national or industry standards to conduct acoustic tests. The hole depth is determined based on experience (it must exceed the excavation damage area). If there is no similar experience, a depth of 8-10m is generally used to measure the P-wave velocity of acoustic waves at different depths from the excavation profile in the area to be estimated.

[0109] Step S22: The surrounding rock near the excavation outline is subjected to strong excavation disturbance, resulting in deterioration of its mechanical properties and lower P-wave velocity, while the rock wave velocity in the undamaged zone is higher. Therefore, the area with more stable P-wave velocity at greater depths is considered the undamaged zone UZ, and the low-velocity area closer to the excavation outline is designated as the excavation damage zone. The depth of the excavation damage zone is defined as h. EDZ (m).

[0110] The method for obtaining the Geological Strength Index (GSI) involved in step S3 is the core of this application. This is because the GSI is an important indicator in the Hoek-Brown criterion that characterizes the influence of the quality of rock mass structural planes on the mechanical parameters of the surrounding rock (GSI values ​​range from 5 to 100; the higher the value, the less developed the rock mass structural planes are, and the better the condition of the structural planes). The traditional basis for determining GSI values ​​is shown in Table 1.

[0111] Table 1

[0112]

[0113] As shown in Table 1, the scoring is based entirely on the qualitative characteristics of the structural surfaces, and is therefore easily affected by the user's experience level, leading to inconsistent results. This application provides a method for estimating the Geological Strength Index (GSI), which can achieve accurate calculation. The specific steps are as follows:

[0114] Step S311: Obtain the GSI characterized by seismic P-wave velocity based on the conversion relationship between the Geological Strength Index (GSI) and the Rock Mass Geological Classification System (RMR). This is because the GSI and another commonly used rock mass geological analysis system, RMR, have a good conversion relationship. The aforementioned conversion relationship between GSI and RMR is as follows:

[0115] GSI = RMR 76 (2)

[0116] In formula (2), RMR 76 For the 1976 version of the RMR rating system, when RMR 76 >18, equation (2) holds true; Li Shuo-biao and Xue Ya-dong, combining the research of Serafim and Pereira and Barton, proposed RMR 76 The following empirical relationship exists between P-wave velocity and seismic wave velocity:

[0117] RMR 76 =(40V) s-p +10) / 3 (3)

[0118] In formula (3), V s-p The velocity of the seismic P-wave is expressed in km / s.

[0119] Substituting formula (2) into formula (3), we obtain the GSI characterized by seismic P-wave velocity:

[0120] GSI = (40V) s-p +10) / 3 (4);

[0121] Step S312: Seismic P-wave velocity and acoustic P-wave velocity generally have a good linear relationship. By summarizing multiple dam foundation rock engineering and deep rock auxiliary tunnel exploration data, a good linear relationship was found between the two (correlation coefficient can reach 0.97). The specific fitting curve equation is expressed as follows:

[0122] V s-p =0.893v a-p +0.151 (5)

[0123] In formula (5), v a-p The velocity of sound wave P is in km / s;

[0124] Step S313, substitute formula (5) into formula (4) to obtain:

[0125] GSI = 11.907v a-p +5.347 (6);

[0126] Step S314: The average wave velocity in the undamaged zone UZ from step S22 is taken as the P-wave velocity v of the rock mass in the undamaged zone UZ. a-p0 , will v a-p0 Substituting into formula (6) will yield the geological strength index GSI of the surrounding rock.

[0127] The specific steps for estimating the disturbance factor D, which characterizes the excavation disturbance effect, in step S3 are as follows:

[0128] Step S321: Through fitting analysis of a large amount of data, Galera et al. proposed the rock mass deformation modulus E. rm The empirical formula for the relationship between the deformation modulus of rock mass and the deformation modulus of undamaged rock mass is derived from the empirical formula for the deformation modulus of rock mass. The empirical formula is as follows:

[0129] E rm =E i exp((RMR 89 -100) / 36) (7)

[0130] In formula (7), E i The elastic modulus of rock is expressed in GPa; RMR. 89 For the 1989 version of the RMR rating system, when RMR 89 Equation (7) holds true at >23; among which, Zhang et al. gave RMR 89 The empirical relationship with GSI is RMR 89 =0.827GSI+15.394, then formula (7) can be expressed as:

[0131] E rm =E i exp((0.827GSI-84.606) / 36) (8);

[0132] Substituting formula (6) into formula (8) yields:

[0133] E rm =E i exp(0.274v a-p -2.227) (9);

[0134] According to formula (9), the relationship between the deformation modulus of rock mass and the deformation modulus of undamaged rock mass is obtained, that is, the deformation modulus E of rock mass. rm (corresponding wave speed is v) a-p ) and the deformation modulus E of undamaged rock mass rm0(corresponding to the wave velocity of v a-p0 ) the ratio is as follows:

[0135]

[0136] Step S322, Hoek et al. proposed the deformation modulus E of rock mass rm and the deformation modulus E of the undamaged rock mass rm0 The ratio can be expressed as:

[0137] E rm / E rm0 = 1 - 0.5D (11)

[0138] Combining formulas (10) and (11), the expression of the disturbance factor D estimated by the acoustic wave P-wave velocity can be obtained as:

[0139]

[0140] In formula (12), D represents the disturbance factor, which can be used to characterize the excavation disturbance effect (the influence of blasting or unloading relaxation). The value range of D is 0-1. D = 0 means that the rock mass is not damaged by the disturbance effect, and D = 1 means that the rock mass is highly damaged. Substituting the wave velocities measured at different depths d (m) into formula (12), the corresponding disturbance factor D can be obtained.

[0141] In step S4, according to the disturbance factor D at different depths obtained in step S3, generally, the area near the excavation contour is more strongly disturbed and the disturbance factor D is larger. Figure 2 As shown, the area where D = 1 within the distribution depth h EDZ of the excavation damage zone is regarded as the highly damaged zone, and the distribution depth of the highly damaged zone is expressed as h HDZ (m); the area where 1 < D < 0 is classified as the weakly damaged zone, and the distribution depth of the weakly damaged zone is expressed as h WDZ (m).

[0142] In step S5, the steps to estimate the potential rockburst pit depth of the surrounding rock are as follows:

[0143] Step S51, according to the variation law of the disturbance factor D inside the surrounding rock, it is divided into the following two categories:

[0144] The first category: When h HDZ > 0, the variation function of the disturbance factor D with the depth d is:

[0145]

[0146] In formula (13), d is the distance from the excavation contour, m; h EDZ is the distribution depth of the excavation damage zone; h WDZh represents the depth of the weakly damaged zone within the excavated damaged area. WDZ =h EDZ -h HDZ ;

[0147] Category 2: When h HDZ When d = 0, the perturbation factor D varies with depth d as follows:

[0148]

[0149] In formula (14), D s The disturbance factor at the excavation outline surface;

[0150] Step S52: Since rockburst is also a sudden destruction that occurs after the surrounding rock is disturbed and the damage evolves to a certain extent, it can be assumed that the disturbance level that causes rockburst is considered as the critical disturbance factor D. rb For the case of formula (13), the disturbance factor of the highly damaged zone is relatively large (D=1). Once the surrounding rock has the potential to cause a rockburst, the range of the highly damaged zone must be within the depth range of the potential rockburst crater, while the bottom of the potential rockburst crater should be within the weakly damaged zone, i.e., the critical disturbance factor D. rb Since it is located in the weak damage zone, we can let h in formula (13) be... HDZ <h<h EDZ The corresponding function is equal to D. rb Determine the potential rockburst crater depth h. rb :

[0151] h rb =(1-D rb )h WDZ +h HDZ (15);

[0152] Let h in formula (14) <h EDZ The corresponding function is equal to D. rb Determine the potential rockburst crater depth h. rb :

[0153]

[0154] As can be seen from step S52, to obtain the rockburst crater depths corresponding to formulas (15) and (16), it is necessary to determine the critical damage factor D corresponding to the rockburst. rb The critical damage factor D is also given here. rb Specific steps:

[0155] Step S521, based on the 2002 version of the generalized Hoek-Brown strength criterion:

[0156]

[0157] In formula (17), σ1 is the first principal stress at failure, σ2 is the second principal stress at failure, and σ3 is the third principal stress at failure, where m b , s, and a are all material constants, determined by the following formulas:

[0158]

[0159]

[0160]

[0161] In formula (18), m i For material constants related to rock hardness, the suggestion of Hoek et al. can be followed to determine them by laboratory rock tests;

[0162] Let σ3 = 0 MPa in formula (17), then the uniaxial compressive strength of the rock mass is:

[0163] σ cm =σ c ·s a (twenty one);

[0164] Step S522, substitute formulas (19) and (20) into formula (21) to obtain

[0165]

[0166] Then the rock mass strength stress ratio σ cm / σ1 is:

[0167]

[0168] Step S523, assuming the critical strength stress ratio of the rock mass at the time of the rock burst is T rb Then we have:

[0169]

[0170] Step S524: Solve equation (24) to obtain the critical disturbance factor D corresponding to rockburst. rb :

[0171]

[0172] Step S525: Substitute formula (25) into formula (15) to obtain the potential rockburst crater depth h in the first case of the variation of the disturbance factor D within the surrounding rock. rb for:

[0173]

[0174] Substituting formula (25) into formula (16), we obtain the potential rockburst crater depth h in the second case of the variation of the disturbance factor D within the surrounding rock. rb for:

[0175]

[0176] In formulas (26) and (27), it should be noted that the critical rock mass strength stress ratio T rb The rockburst situation in similar projects can be used as an analogy. If no relevant experience is available, this application presents the results summarized from three underground engineering rockburst case studies, which show that the rock mass strength stress ratio σ in the rockburst occurrence area is... cm / σ1≤0.2, therefore T rb Based on experience, T can be chosen. rb =0.2. Therefore, based on the aforementioned steps, the initial maximum principal stress σ1 and the uniaxial compressive strength σ of the rock are... c Geological strength index (GSI), excavation damage depth, height damage depth, weak damage zone depth, and disturbance factor D at the excavation profile surface. s By combining formulas (26) and (27), the potential rockburst crater in the surrounding rock can be quantitatively estimated.

[0177] To illustrate in more detail the quantitative estimation method for potential rockburst crater depth provided in this application, preferred embodiments are provided for the convenience of those skilled in the art. The following description uses a water diversion tunnel with a burial depth of 1500-2525m as an example.

[0178] First, in this embodiment, the initial maximum principal stress σ1 in the region to be estimated is approximately 60 MPa, and the uniaxial compressive strength of the rock is σ c The rock strength and stress in this area are 90 MPa. According to formula (1), the rock strength and stress in this area meet the four conditions in formula (1). Therefore, this area has the potential to cause rockbursts, and the depth of potential rockburst craters can be estimated.

[0179] The second step involved drilling a 10m deep acoustic test borehole into the surrounding rock of the area to be estimated. Using single-hole acoustic testing technology, a transducer probe capable of transmitting and receiving acoustic waves was moved from the bottom of the borehole to the opening every 0.25m, and the P-wave velocity of the adjacent rock mass was measured. The test results are as follows: Figure 3 As shown in the figure, the distribution pattern of sound wave velocity shows that the wave velocity change is relatively stable in the range of more than 2.2m from the excavation outline. Therefore, the area beyond 2.2m is considered as the undamaged area, while the area within 2.2m is obviously in the low wave velocity area and is considered as the excavation damage area.

[0180] The third step is to take the average value v of the wave velocity measured in the second step for the undamaged area. a-p0= 6.02 km / s. Substituting the average wave velocity into Equation (6), the GSI of this area can be obtained as 77; substituting the wave velocities at different depths measured in the second step and v a-p0 = 6.02 km / s into Equation (12), the disturbance factor D at different depths can be obtained as shown Figure 4 .

[0181] Step 4: From the distribution law of the disturbance factor D in Figure 4 , it can be seen that the disturbance factor D = 1 in the range of d ≤ 1.0 m from the excavation profile surface. Therefore, the distribution depth of the highly damaged area is h HDZ = 1.0 m; in the range of 1.0 m < d < 2.2 m from the excavation profile surface, the disturbance factor 0 < D < 1. Therefore, this area is regarded as a weakly damaged area, and the distribution depth of the weakly damaged area it involves is h WDZ = 1.2 m.

[0182] Step 5: According to Step 4, it can be known that there is a highly damaged area in the surrounding rock of the area to be estimated in this embodiment, that is, h HDZ = 1.0 m > 0. Therefore, Equation (26) should be used to estimate the depth of the potential rockburst pit. The critical rock mass strength stress ratio T corresponding to rockburst rb According to the summary of engineering experience, take T rb = 0.2. Substitute the obtained σ1 = 60 MPa, σ c = 90 MPa, GSI = 77, h HDZ = 1.0 m, h WDZ = 1.2 m and T rb = 0.2 into Equation (26), then the depth of the potential rockburst pit h of this area can be obtained rb = 1.11 m.

[0183] So far, the quantitative estimation of the potential rockburst pit in the area to be estimated of a diversion tunnel with a buried depth of 1500 - 2525 m in this embodiment has been realized. The estimation result is that the potential rockburst depth h rb = 1.11 m. Similarly, if the result obtained in the third step is that there is no highly damaged area (that is, h HDZ = 0 m), then σ1, σ c , GSI, h EDZ , D s and T rb of the area to be estimated should be substituted into Equation (27) to solve the depth of the potential rockburst pit h rb .

[0184] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0185] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0186] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0187] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for quantitatively estimating the depth of potential rockburst craters, considering structural planes and excavation disturbance effects, characterized in that: Specifically, the following steps are included: Step S1: Define the area to be estimated and conduct a preliminary evaluation of whether the area has the potential for rockburst. The criteria for this judgment include the initial maximum principal stress. σ 1 and uniaxial compressive strength of rock σ c If the area to be estimated does not have the potential for rockburst, the step terminates; if the area to be estimated has the potential for rockburst, continue to step S2. Step S2: Conduct acoustic wave testing on the surrounding rock within the area to be estimated. Determine the extent of the excavation damage zone based on the P-wave velocity. The depth of the excavation damage zone is defined as... h EDZ ; Step S3: After determining the extent of the excavation damage zone, the quality of the structural surface is quantitatively characterized using the Geological Strength Index (GSI) and the disturbance factor is used. D Characterizing the excavation disturbance effect, the geological strength index (GSI) and disturbance factor are estimated based on acoustic test data. D ; The steps for estimating the Geological Strength Index (GSI) are as follows: Step S311, based on the Geological Strength Index (GSI) and the Rock Mass Geological Classification System RMR The conversion relationship is used to obtain the GSI characterized by seismic P-wave velocity; where GSI is related to... RMR The conversion relationship is as follows: (2) In formula (2), RMR 76 For the 1976 version of the RMR rating system, when RMR 76 When the value is greater than 18, equation (2) holds true; RMR 76 The following empirical relationship exists between P-wave velocity and seismic wave velocity: (3) In formula (3), The velocity of the P-wave in seismic waves; Substituting formula (2) into formula (3), we obtain the GSI characterized by the P-wave velocity of seismic waves: (4)； Step S312: By linearly fitting a large amount of seismic wave and acoustic P-wave velocity data of engineering rock masses, a linear relationship was found between the seismic wave P-wave velocity and the acoustic P-wave velocity. The fitting equation is: (5) In formula (5), v a-p The velocity of sound wave P is in km / s; Step S313, substitute formula (5) into formula (4) to obtain: (6)； Step S314: The average wave velocity in the undamaged zone UZ from step S22 is taken as the P-wave velocity of the rock mass in the undamaged zone UZ. v a-p0 ,Will v a-p0 Substituting into formula (6) yields the geological strength index GSI of the surrounding rock; Estimating the disturbance factor D The steps are as follows: Step S321: Obtain the relationship between the deformation modulus of the rock mass and the deformation modulus of the undamaged rock mass based on the empirical formula for the deformation modulus of the rock mass. The empirical formula is: (7) In formula (7), E i Let be the elastic modulus of the rock, in GPa; RMR 89 For the 1989 version of the RMR rating system, when RMR 89 >23, equation (7) holds true; where, RMR 89 and GSI The empirical relationship between them is RMR 89 =0.827GSI+15.394, then formula (7) can be expressed as: (8)； Substituting formula (6) into formula (8) yields: (9)； The relationship between the deformation modulus of rock mass and the deformation modulus of undamaged rock mass is obtained according to formula (9), that is, the deformation modulus of rock mass. E rm Deformation modulus of undamaged rock mass E rm0 The ratio is: (10)； In step S322, Hoek et al. proposed the rock mass deformation modulus. E rm Deformation modulus of undamaged rock mass E rm0 The ratio can be expressed as: (11) Combining formulas (10) and (11), the expression for the disturbance factor D estimated using the P-wave velocity of sound can be obtained as follows: (12) Step S4: Based on the obtained disturbance factor D The variation characteristics are used to estimate the height of the damaged zone and the extent of the weakly damaged zone of the surrounding rock in the excavation damage zone, defined at the distribution depth of the excavation damage zone. h EDZ The depth of the highly damaged area within is h HDZ The depth of the weak damage zone is h WDZ ; Step S5: Depth of the highly damaged area as defined in step S4 h HDZ Depth of weak damage zone distribution h WDZ and the depth of the excavation damage zone h EDZ Combined with disturbance factor D Based on the variation patterns within the surrounding rock, the potential depth of rockburst craters can be estimated.

2. The method for quantitatively estimating the depth of potential rockburst craters considering structural planes and excavation disturbance effects according to claim 1, characterized in that: In step S1, the step of evaluating whether the area to be estimated has the potential for rockburst is as follows: Step S11: Obtain the initial maximum principal stress of the area to be estimated based on geological survey data and indoor test results. σ 1 and uniaxial compressive strength of rock σ c ; Step S12: The prerequisite for rockburst is the presence of high ground stress. The criteria for determining high ground stress are: (1) When the initial maximum principal stress σ 1 and uniaxial compressive strength of rock σ c If formula (1) is satisfied, it can be determined that the area has the potential to cause a rockburst, and step S2 continues; if it is not satisfied, the area does not have the potential to cause a rockburst, and the quantitative estimation of the rockburst crater depth terminates.

3. The method for quantitatively estimating the depth of potential rockburst craters considering structural planes and excavation disturbance effects according to claim 2, characterized in that: In step S2, the step of determining the extent of the excavation damage zone is as follows: Step S21: Measure the P-wave velocity of acoustic waves at different depths from the excavation profile within the area to be estimated; Step S22: The region with more stable P-wave velocity changes at greater depths is considered the undamaged zone UZ, and the low-velocity zone closer to the excavation profile is designated as the excavation damage zone. The depth of the excavation damage zone distribution is defined as... h EDZ .

4. The method for quantitatively estimating the depth of potential rockburst craters considering structural planes and excavation disturbance effects as described in claim 3, characterized in that: In step S4, the depth of the excavation damage zone is determined. h EDZ Internal manifestations D The area with a value of 1 is considered a highly damaged area, and the depth of the highly damaged area is represented as... h HDZ m; for expressions of 1 < D The region with a value less than 0 is designated as a weak damage zone, and the depth of the weak damage zone is represented as... h WDZ , m.

5. The method for quantitatively estimating the depth of potential rockburst craters considering structural planes and excavation disturbance effects according to claim 4, characterized in that: In step S5, the step of estimating the potential rockburst crater depth of the surrounding rock is as follows: Step S51, based on the disturbance factor D The variation patterns within the surrounding rock can be divided into the following two categories: Category 1: When h HDZ When >0, the disturbance factor D With depth d The function of change is: (13) In formula (13), d The distance from the excavation outline is in meters (m). h EDZ This represents the depth of the excavation damage zone. h WDZ The depth of the weakly damaged zone within the excavated damaged area. h WDZ = h EDZ - h HDZ ; Category Two: When h HDZ When =0, the disturbance factor D With depth d The function of change is: (14) In formula (14), D s The disturbance factor at the excavation outline surface; Step S52, assuming the disturbance level that causes a rockburst is considered the critical disturbance factor. D rb Let formula (13) h HDZ < h < h EDZ The corresponding function is equal to D rb Determine the potential rockburst crater depth h rb : (15)； Let formula (14) h < h EDZ The corresponding function is equal to D rb Determine the potential rockburst crater depth h rb : (16)。 6. The method for quantitatively estimating the depth of potential rockburst craters considering structural planes and excavation disturbance effects according to claim 5, characterized in that: In step S52, if the rockburst crater depths corresponding to formulas (15) and (16) are to be obtained, the critical damage factor corresponding to the rockburst needs to be determined. D rb The specific steps are as follows: Step S521, based on the 2002 version of the generalized Hoek-Brown strength criterion: (17) In formula (17), σ 1 represents the first principal stress at failure. σ 2 represents the second principal stress at failure. σ 3 represents the third principal stress at failure, where, (18) (19) (20) In formula (18), m i These are material constants related to the hardness of the rock. Let formula (17) σ If 3 = 0 MPa, then the uniaxial compressive strength of the rock mass is: (21)； Step S522, substitute formulas (19) and (20) into formula (21) to obtain (22) Then the rock mass strength stress ratio σ cm / σ 1 is: (23)； Step S523, assuming the critical strength stress ratio of the rock mass at the time of the rock burst is... T rb Then we have: (24)； Step S524, Solve by taking the equality sign of formula (24). D This is the critical disturbance factor corresponding to rockburst. D rb : (25)； Step S525: Substitute formula (25) into formula (15) to obtain the disturbance factor. D In the first scenario of changes within the surrounding rock, the potential depth of the rockburst crater... h rb for: (26)； Substituting formula (25) into formula (16), we obtain the disturbance factor. D In the second scenario involving variations within the surrounding rock, the potential depth of the rockburst crater... h rb for: (27) In formulas (26) and (27), T rb =0.2.

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