A method and system for analyzing stability of surrounding rock based on H-B criterion empirical parameter quantitative determination

Abstract

The application discloses a kind of based on H-B criterion experience parameter quantitative determination surrounding rock stability analysis method, including the following steps: obtaining rock material constant m i , rock uniaxial compressive strength σ ci And carry out acoustic wave test to obtain the rock mass acoustic wave velocity at different depths perpendicular to the surrounding rock surface, calculate the average acoustic wave velocity of original rock area, according to the average acoustic wave velocity combined with the quantitative calculation of wave velocity method the geological strength index GSI m0 And damage factor D, according to the change rule of damage factor D, the quantitative change relationship of damage factor D at different depths d from the surrounding rock surface is summarized, the quantitative change relationship of three experience parameters (m b , s and a) at different depths d from the surrounding rock is obtained, the equivalent continuity of three experience parameters is valued using micro-element method and numerical analysis method, and the stability of surrounding rock is evaluated.The present application lays an important foundation for subsequent surrounding rock stability analysis, disaster prevention and control and other problems.

Description

Technical Field

[0001] This invention belongs to the field of deep surrounding rock stability evaluation, and specifically relates to a method and system for analyzing surrounding rock stability based on empirical parameters determined by the HB criterion. Background Technology

[0002] With the depletion of shallow resources and the increasing saturation of space utilization, deep rock engineering, with its abundant resource reserves and great potential for space development, has gradually become the norm. However, the complex geological environment presents significant challenges to the construction of deep rock engineering projects. High ground stress is the most prominent environmental characteristic of deep rock engineering. Tunnel boring machines (TBMs) and drill and blast (D&B) are currently the two most commonly used excavation methods for deep rock masses. Excavation disrupts the initial equilibrium state of the rock mass, and under the combined action of stress redistribution and dynamic loads, an excavation damage zone is formed at a certain depth from the surrounding rock surface. The mechanical properties of the rock mass in the damage zone deteriorate, significantly impacting the stability of the surrounding rock and often serving as a catalyst for various geological disasters in underground rock engineering (such as sudden large deformations, collapses, and rock bursts). Determining rock mass mechanical parameters is fundamental to evaluating surrounding rock stability, predicting geological disasters, and designing support schemes. Currently, the commonly used methods for determining rock mass mechanical parameters are in-situ testing and empirical methods.

[0003] In the 2002 and 2018 versions of the HB guidelines, Hoek and Brown provided recommended values ​​for the damage factor D after excavation of underground rock engineering rock masses, as shown in Table 1.

[0004] Table 1. Recommended values ​​for damage factor D in the HB criterion.

[0005]

[0006]

[0007] Analysis of the description in Table 1 reveals some issues with the recommended values ​​for D in the HB criterion:

[0008] (1) Table 1 only shows three rock mass appearance pictures, and the description of the degree of damage on site is mostly qualitative. This makes it difficult to evaluate the degree of damage after excavation of surrounding rock of different quality, and the evaluation results will also rely heavily on human subjective experience.

[0009] (2) Since only the mechanical properties of the surrounding rock damage zone will be affected after the rock mass is excavated, while the original rock zone is basically unaffected (D=0), it is crucial to determine the extent of the damage zone, but Table 1 does not provide a clear delineation standard.

[0010] (3) Although the range of D is 0 to 1, Table 1 only gives four cases: D = 0, D = 0.8, D = 0.5, and D changes linearly from 1 to 0. It does not involve how to determine other values ​​of D in the range of 0 to 1.

[0011] (4) The working condition in Table 1, number 4, mentions that D decreases linearly from 1 to 0 within 2m from the surface of the surrounding rock. However, no guidance is given on how to apply this linear decrease to numerical analysis (such as stability evaluation, disaster prediction, etc.), which causes great confusion for users.

[0012] The above analysis shows that GSI and the disturbance factor D are significantly influenced by the level of human experience. Therefore, the three empirical parameters m in the generalized HB criterion are... b Determining , s, and a presents significant challenges. Furthermore, these three empirical parameters are generally the basic material parameters used in numerical analysis of surrounding rock stability using the HB criterion. Therefore, m b The difficulty in determining s and a further hinders the accurate evaluation of surrounding rock stability. Therefore, it is essential to find a quantitative method for determining the empirical parameters of the HB criterion and a system for evaluating surrounding rock stability. Summary of the Invention

[0013] To address the aforementioned technical problems, the present invention aims to provide a method for quantitatively determining the empirical parameters of the HB criterion and a system for evaluating the stability of surrounding rock. It not only provides a quantitative method for the three empirical parameters of the HB criterion using the wave velocity method, but also establishes an application system for the estimation results of these empirical parameters in surrounding rock stability analysis using the infinitesimal element method. This aims to solve the problem of determining the three empirical parameters (m...) in the HB criterion. b The problems of relying heavily on qualitative descriptions from the field, having results that are greatly influenced by the richness of human experience, and being difficult to apply in the process of surrounding rock stability analysis are as follows:

[0014] To achieve the above results, the technical solution adopted by the present invention is as follows:

[0015] A method for analyzing the stability of surrounding rock based on the quantitative determination of empirical parameters according to the HB criterion includes the following steps:

[0016] Step 1: Obtain the material constant m of the rock i Uniaxial compressive strength σ of rock ci And acoustic wave tests were conducted to obtain the acoustic wave velocity of the rock mass at different depths perpendicular to the surface of the surrounding rock;

[0017] Step 2: Based on the acoustic velocities of the rock mass at different depths obtained in Step 1, delineate the extent of the surrounding rock damage zone and the original rock zone, and quantitatively calculate the geological strength index (GSI) of the surrounding rock using the wave velocity method. m0 Damage factor D at different depths from the surrounding rock;

[0018] Step 3: Based on the variation law of damage factor D, summarize the quantitative variation relationship of damage factor D at different depths d from the surface of the surrounding rock;

[0019] Step 4: For the original rock mass, obtain the three empirical parameters (m) in the HB criterion based on the initial values ​​of the damage factor D and the geological strength GSI. b The initial values ​​of s and a) are used to obtain three empirical parameters (m) for the rock mass in the damaged area. b Quantitative expressions for s and a) are obtained, and then three empirical parameters (m) at different depths d from the surrounding rock are obtained. b The quantitative relationship between s and a);

[0020] Step 5: Use the infinitesimal element method and numerical analysis to assign equivalent continuity values ​​to the three empirical parameters as they change with depth;

[0021] Step 6: Calculate the cumulative maximum displacement of the surrounding rock surface using the three empirical parameters that were continuously assigned values ​​in Step 5, and evaluate the stability of the surrounding rock based on the cumulative maximum displacement value.

[0022] Furthermore, the depth of the test hole for the acoustic wave test in step 1 is at least 8 meters.

[0023] Furthermore, the method for delineating the extent of the surrounding rock damage zone and the original rock zone in step 2 is as follows:

[0024] Based on the acoustic velocities of the rock mass at different depths obtained in step 1, and considering that the acoustic velocities of the damaged rock mass are generally lower than those of the original rock mass, the area with relatively low wave velocity within a certain depth from the surface of the surrounding rock is identified as the damaged zone. The area outside the damaged zone, i.e., the area with relatively high wave velocity, is considered the original rock mass. Further, in step 2, the geological strength index (GSI) is calculated. m0 The method is as follows:

[0025] Seismic wave P-wave velocity S p Rock mass geomechanical classification index RMR 76 With rock mass deformation modulus E m The relationships are as follows:

[0026]

[0027]

[0028] Meanwhile, GSI and RMR 76 Conditions met:

[0029] GSI = RMR 76 (3)

[0030] According to formulas (1) to (3), the GSI and the P-wave velocity S of the rock mass seismic wave are obtained.p The relationship between them is:

[0031]

[0032] Rock mass seismic wave P-wave velocity S p With the sound wave velocity V of the rock mass p It has the following linear relationship:

[0033] S p =kV p +b (5)

[0034] Wherein, GSI is the geological strength index, V p denoted as P-wave velocity of rock mass, in km / s; k and b are fitting constants between seismic waves and rock mass acoustic velocities, obtained from geological survey data.

[0035] By combining formulas (4) and (5), the relationship between GSI and the acoustic velocity V of the rock mass can be established. p Quantitative expressions between them:

[0036]

[0037] The average sound wave velocity V of the original rock mass p0 Substituting into formula (6), the GSI in the HB criterion is quantitatively determined. m0 The value is calculated using the following formula:

[0038]

[0039] Furthermore, in step 2, the wave velocity method is used to quantitatively obtain the surrounding rock damage factor D as follows:

[0040] Deformation modulus E of rock mass m The relationship with damage factor D is as follows:

[0041]

[0042] Where E0 is the deformation modulus of the original rock mass;

[0043] Rock mass deformation modulus E m The relationship between the velocity of sound waves in rock mass and the velocity of sound waves is expressed as follows:

[0044] E m =aexp(cV p (9)

[0045] Where a and c are fitting constants, which are obtained by fitting the rock mass deformation modulus and acoustic velocity data from the geological survey data in the early stage of the project.

[0046] The deformation modulus of the original rock mass is obtained as follows:

[0047] E0 = aexp(cV) p0 (10)

[0048] Based on the relationship between the rock mass deformation modulus and the sound wave velocity, and the deformation modulus of the original rock mass, the following relationship is obtained:

[0049]

[0050] Based on the above formula, the quantitative value of the rock mass damage factor D is obtained as follows:

[0051] D = 2{1-exp[c(V p -V p0 (12)

[0052] The damage factor D ranges from 0 to 1. When D > 1, it is considered that D = 1, and when D < 0, it is considered that D = 0.

[0053] Furthermore, the method for calculating the quantitative variation relationship of the damage factor D at different depths d from the surrounding rock surface in step 3 is as follows:

[0054] First, the variation of damage factor D with depth d is classified into three types: constant type, linear decreasing type, and constant-linear decreasing composite type.

[0055] 1) Constant type: The damage factor D of the entire surrounding rock damage zone is constant. In this case, the variation law of the damage factor D of the rock mass in the damage zone is described as follows:

[0056] D(d)=D f (13)

[0057] Where D(d) is the functional expression of the damage factor at different depths d from the surrounding rock; D f The damage factor at the surface of the surrounding rock;

[0058] 2) Linear decreasing type: The damage factor of the entire surrounding rock damage zone shows a linear decreasing trend with increasing depth d from the surrounding rock surface. The change law of D in this case can be described as follows:

[0059]

[0060] Among them, H EDZ The depth of the damaged area;

[0061] 3) Constant-linear decreasing composite type: The damage factor D remains constant within a certain depth h from the surrounding rock surface, i.e., D = D f Within the damage zone outside the h range, the damage factor increases with depth (dh) from D f The linear decrease in D can be described as follows:

[0062]

[0063] After observing the distribution characteristics of the damage factor D at different depths from the surrounding rock in the damaged area, the quantitative expression of the continuity of the damage factor D with depth d is obtained according to formulas (13) to (15).

[0064] Furthermore, in step 4, three empirical parameters (m) are calculated at different depths d from the surrounding rock. b The method for quantitatively determining the relationship between s and a) is as follows:

[0065] (1) For the original rock mass, the damage factor D = 0 and GSI = GSI are set. m0 Substituting into formulas (2) to (4), we obtain the three empirical parameters m. b0 s0 and a0;

[0066] (2) For the rock mass in the damaged area, as can be seen from the results of steps 2 and 3, by substituting formulas (1) and (13) to (15) into formulas (3) to (4), we can obtain the quantitative expressions for the three empirical parameters m. b (d), s(d), and a(d), that is:

[0067]

[0068]

[0069]

[0070] According to the quantitative relationship of the continuity function of the three empirical parameters in the HB criterion as a function of the distance from the surrounding rock depth d, the parameter a is only related to GSI. Therefore, the parameter a(d) in the damaged area is actually equal to a0 in the original rock area, that is, a(d) = a0.

[0071] Furthermore, the method for assigning equivalent continuity values ​​to the three empirical parameters as a function of depth in step 5 is as follows:

[0072] (1) The m of the original rock mass b s and a are respectively assigned the value of m obtained in step 4. b0 s0 and a0;

[0073] (2) Parameter a is only related to GSI m0 Regarding this, the parameter 'a' of the damaged area is assigned the value a(d) = a0 obtained in step 4, because parameter m b And s not only depend on GSI m0 Moreover, it is related to the damage factor D; for different damage factors D, the corresponding m b The method for assigning values ​​to the s-parameter in numerical software:

[0074] 1) When the damage factor D obtained from step 3 has a constant segment, i.e., D(d) = D f At this time, the m of the rock mass in the damaged area b Assigning values ​​to GSI and s respectively m0 With D(d)=D f The solution obtained by substituting the empirical parameters into the quantitative expression is m. b (d) and s(d);

[0075] 2) When the damage factor D obtained in step 2 has a linear decreasing segment, the method of infinitesimal elements is used to solve for m. b And s, the specific steps are as follows:

[0076] ① Divide the linearly decreasing segment of D within the damaged area into n equally spaced sub-regions, where n is a natural number;

[0077] ② Divide the damage factor D in the n sub-regions according to the depth from the surrounding rock surface, from shallow to deep, following an arithmetic progression. f / n decreases sequentially;

[0078] ③ Solve for the corresponding m based on the damage factor D of each sub-region. b And s, together with other parameters required for the simulation, are used to assign values ​​to the rock mass of each sub-region of the surrounding rock;

[0079] ④ Monitor the final displacement of a monitoring point on the surface of the surrounding rock after excavation until the final displacement no longer changes significantly with the increase of the number of divisions n. At this point, it is considered that the n sub-regions are equivalent to the continuous assignment of three empirical parameters in the linearly decreasing segment of the damage zone D.

[0080] Furthermore, step 6 specifically determines the stability of the surrounding rock based on the magnitude of the displacement change. Based on steps 1 to 5, two monitoring points are set on the surface of the surrounding rock. The ratio of the maximum cumulative displacement value of the two monitoring points to the distance between the two monitoring points is taken as the relative displacement value of the surrounding rock. If the obtained relative displacement value of the monitoring point is close to the allowable relative displacement value of the surrounding rock of the project, then the surrounding rock is determined to be unstable; otherwise, it is in a stable state.

[0081] A system for analyzing the stability of surrounding rock based on empirical parameters determined by the HB criterion includes:

[0082] Velocity acquisition module: It is configured to perform the following action: acquire the material constant m of the rock. i Uniaxial compressive strength σ of rock ci And acoustic wave tests were conducted to obtain the acoustic wave velocity of the rock mass at different depths perpendicular to the surface of the surrounding rock;

[0083] The parameter calculation module is configured to perform the following actions: delineate the extent of the surrounding rock damage zone and the original rock zone, and quantitatively calculate the geological strength index (GSI) of the surrounding rock using the wave velocity method. m0 Damage factor D at different depths from the surrounding rock;

[0084] Based on the variation law of damage factor D, the quantitative variation relationship of damage factor D at different depths d from the surrounding rock surface was summarized; and three empirical parameters (m) at different depths d from the surrounding rock were obtained. b The quantitative relationship between s and a);

[0085] The assignment module is configured to perform the following actions: using the infinitesimal method and numerical analysis to assign equivalent continuity values ​​for the three empirical parameters as they change with depth;

[0086] The stability analysis module is configured to perform the following actions: calculate the cumulative maximum displacement of the surrounding rock surface obtained by using the three empirical parameters that are continuously assigned values ​​in step 5, and evaluate the stability of the surrounding rock based on the cumulative maximum displacement value.

[0087] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0088] (1) This invention proposes three empirical parameters (m) in the HB criterion based on the wave velocity method. b The quantitative method for determining s and a) avoids the strong reliance on human experience in determining these three parameters in existing criteria.

[0089] (2) This invention provides for the first time the variation trends of three types of damage factors D in deep surrounding rock damage zones (i.e., constant type, linear decreasing type and constant-linear decreasing composite type), which not only enriches the suggestions for the value of D in the HB criterion, but also provides users with a reference idea when analyzing the variation law of surrounding rock damage factors.

[0090] (3) This invention solves the problem of m in the HB criterion by using the concept of infinitesimal element method. b The challenge of continuously assigning values ​​to s and a in numerical analysis software lays an important foundation for subsequent problems such as surrounding rock stability analysis and disaster prevention and control. Attached Figure Description

[0091] Figure 1 This is a flowchart of the method of the present invention;

[0092] Figure 2 The data provided are the acoustic P-wave velocity data of the surrounding rock at station K15+100 in this embodiment of the invention.

[0093] Figure 3 The data provided are the acoustic P-wave velocity data of the surrounding rock at station K15+500 in this embodiment of the invention.

[0094] Figure 4 The data provided are the acoustic P-wave velocity data of the surrounding rock at station K16+100 in this embodiment of the invention.

[0095] Figure 5 This illustrates the variation law of damage factor D in the surrounding rock damage zone at station K15+100 in this embodiment of the invention.

[0096] Figure 6 This illustrates the variation law of damage factor D in the surrounding rock damage zone at station K15+500 in this embodiment of the invention.

[0097] Figure 7 This illustrates the variation law of damage factor D in the surrounding rock damage zone at station K16+100 in this embodiment of the invention.

[0098] Figure 8 This is a schematic diagram illustrating the assignment of three empirical parameters to the surrounding rock mass at station K15+100 in an embodiment of the present invention.

[0099] Figure 9 This is a schematic diagram illustrating the division of the surrounding rock damage zone at station K15+500 into two sub-regions in an embodiment of the present invention.

[0100] Figure 10 This is a schematic diagram showing the division of the surrounding rock damage zone at station K15+500 into 5 sub-regions in an embodiment of the present invention;

[0101] Figure 11 In this embodiment of the invention, the final horizontal displacement of monitoring point A is given by dividing the surrounding rock damage zone at station K15+500 into n different sub-regions;

[0102] Figure 12 This is a schematic diagram of dividing the surrounding rock damage zone at station K16+100 into 10 sub-regions in an embodiment of the present invention. Detailed Implementation

[0103] The following example illustrates the specific implementation of this invention using the stability evaluation of the surrounding rock of a water diversion tunnel with a burial depth of approximately 1500m in a hydropower project in Southwest my country as an example.

[0104] like Figure 1 As shown, the present invention discloses a method for quantitatively determining empirical parameters of the HB criterion and a system for evaluating the stability of surrounding rock, comprising the following steps:

[0105] Step 1: Obtain the material constant m of the rock i Uniaxial compressive strength σ of rock ci And acoustic wave tests were conducted to obtain the acoustic wave velocity of the rock mass at different depths perpendicular to the surface of the surrounding rock;

[0106] Specifically, based on geological survey data and indoor rock test data from the pre-construction period, the surrounding rock lithology of the water diversion tunnel in this example is mainly marble, with a m i =25.

[0107] According to the recommendations in Part 10 of the "Code for Testing Rocks in Water Conservancy and Hydropower Engineering" (SLT 264-2020) – "Sonic Testing of Rock Mass", the P-wave velocity of the rock mass at different depths perpendicular to the surface of the surrounding rock should be obtained. It should be noted that in order to ensure that the test results can simultaneously include the acoustic velocities of the damaged area and the original rock area, the depth of the acoustic test hole should be at least 8m.

[0108] Specifically, following the recommendations in Part 10—"Sonic Testing of Rock Mass" of the "Code for Rock Testing of Water Conservancy and Hydropower Projects" (SLT 264-2020), after the excavation of the surrounding rock of the water diversion tunnel in this embodiment, acoustic tests were conducted on the surrounding rock at chainages K15+100, K15+500, and K16+100. Two parallel boreholes, each 8m deep, were drilled perpendicular to the surface of the surrounding rock sidewall for acoustic penetration testing. The acoustic transceiver was moved from the bottom of the borehole to the opening at intervals of 0.2m. The P-wave velocities of the surrounding rock at different depths at chainages K15+100, K15+500, and K16+100 were obtained as follows: Figure 2 , Figure 3 as well as Figure 4 As shown.

[0109] Step 2: Calculate the average acoustic velocity in the original rock area, and quantitatively calculate the geological strength index (GSI) of the surrounding rock based on the average acoustic velocity and the wave velocity method. m0 and damage factor D;

[0110] Specifically, firstly, the magnitude of the P-wave velocity is closely related to the mechanical properties of the rock mass. Generally speaking, rock masses with poor mechanical properties have lower P-wave velocities, indicating that the mechanical properties of the rock mass in the damaged zone have deteriorated compared to the original rock mass. Based on the test results obtained in step 2, the depth involved in the low-wave velocity zone is determined to be the depth H of the damaged zone. EDZ (m), the average value of all wave velocities in the original rock area is the average P-wave velocity V of the original rock mass. p0 In this embodiment, the depth H of the damaged zone of the surrounding rock at chainages K15+100, K15+500, and K16+100 of the water diversion tunnel is... EDZ (m) and average P-wave velocity V p0 Marked separately Figure 2 , Figure 3 and Figure 4 middle.

[0111] Secondly, during the early stages of construction, seismic and acoustic wave tests were conducted on the geology of the project site. The linear fitting relationship between the P-wave velocity and the seismic wave velocity was S. p =kV p+b, where k = 0.89 and b = 0.27. Substitute this into formula (7) and combine it with... Figures 2-4 The average P-wave velocity V obtained in the calculation p0 The geological strength index (GSI) of the surrounding rock at K15+100 can then be obtained. m0 =78, Geological strength index (GSI) of surrounding rock at K15+500 m0 =76; Geological strength index (GSI) of K16+100 surrounding rock m0 =80.

[0112] Finally, by applying the rock mass deformation modulus and acoustic velocity data from the preliminary geological survey data of the project to the functional model E0=aexp(cV p0 After fitting, the fitting constants between the two are a = 0.1856 and c = 0.8492. Therefore, according to formula (12), the quantitative expression of the damage factor D of the surrounding rock in this embodiment can be obtained as D = 2{1-exp[0.8492(V p -V p0 )]}.

[0113] Step 3: Based on the data from the acoustic wave test and the variation law of the damage factor D, the quantitative variation relationship of the damage factor D at different depths d from the surface of the surrounding rock is obtained;

[0114] Specifically, since the original rock mass is assumed to be undamaged, the damage factor D = 0 for the original rock mass after excavation in this embodiment. For the damaged rock mass, according to the quantification formula of the damage factor D obtained in step 3, D = 2{1-exp[0.8492(V p -V p0 )]}, combined Figures 2-4 Based on the acoustic wave test data, the variation patterns of the damage factor D at different depths from the surrounding rock within the damage zone at K15+100, K15+500, and K16+100 can be obtained as follows: Figure 5 , Figure 6 and Figure 7 As shown. From Figures 5-7 It can be seen that the variation law of the damage factor D of the rock mass in the damaged area conforms to formulas (13) to (15). Therefore, for the station K15+100, according to formula (13), the damage factor D(d) K15+100 =D f D f =0.87, then D(d) K15+100 for:

[0115] D(d) K15+100 =1.0 (19)

[0116] For station K15+500, combined with Figure 3The damage factor D(d) can be obtained from formula (14). K15+500 for:

[0117]

[0118] For station K16+100, combined with Figure 4 and Figure 7 The damage factor D(d) can be obtained from formula (15). K16+100 for:

[0119]

[0120] Therefore, formulas (19) to (21) are the fitting function relationship between the damage factor D of the surrounding rock and the depth d in this embodiment.

[0121] Step 4: Obtain three empirical parameters (m) at different depths d from the surrounding rock. b The quantitative relationship between s and a);

[0122] Specifically, firstly, for the original rock mass, the damage factor D=0 and the GSI obtained in step 3 are... m0 Substituting these values ​​into formulas (2) to (4), the corresponding m values ​​of the original rock mass at K15+100, K15+500, and K16+100 can be obtained. b0 The calculation results for s0 and a0 are shown in Table 2.

[0123] Table 2 shows the calculated values ​​of three empirical parameters for rock masses in the original rock areas at different station numbers in the embodiments.

[0124]

[0125] Secondly, since parameter a is only related to GSI, the empirical parameter a of the rock mass in the damaged zone is the same as that of the original rock zone, i.e., a(d) = a0. For the surrounding rock damaged zone at station K15+100, the empirical parameter m... b Solving for s and a can yield GSI m0 Substituting 78 and formula (19) into formulas (16) to (18), we can obtain the quantitative expressions for the continuity of the three empirical parameters as follows:

[0126]

[0127]

[0128] a K15+100 (d)=a0=0.500707 (24)

[0129] For the surrounding rock damage zone at station K15+500, GSI can be used. m0Substituting 76 and formula (20) into formulas (16) to (18), we can obtain the quantitative expressions for the continuity of the three empirical parameters as follows:

[0130]

[0131]

[0132] a K15+500 (d)=a0=0.500838 (27)

[0133] For the surrounding rock damage zone at station K16+100, GSI can be used. m0 Substituting 80 and formula (21) into formulas (16) to (18), we can obtain the quantitative expressions for the continuity of these two empirical parameters as follows:

[0134]

[0135]

[0136] a K16+100 (d)=a0=0.500593 (30)

[0137] Step 5: Use the infinitesimal element method and numerical analysis to assign equivalent continuity values ​​to the three empirical parameters as they change with depth;

[0138] Specifically, firstly, according to Figure 5 As shown in formula (19), the surrounding rock damage factor D at station K15+100 is a constant. Therefore, in the numerical simulation, the m value in Table 2 of the original rock mass is assigned to the rock mass. b0 =11.39485, s0=0.08677, a0=0.500707. The three parameters of the damaged area are assigned the results of formulas (22) to (23), and the schematic diagram of the surrounding rock parameters after assignment is shown below. Figure 8 As shown.

[0139] Secondly, for station K15+500, the m value in Table 2 of the original rock area... b0 =10.609321, s0=0.069483, a0=0.500838. For the damaged area, according to Figure 6 As shown in formula (20), the disturbance factor D decreases linearly within the damaged area. According to steps 3 and 4, the depth H of the damaged area... EDZ =1.6m, damage factor D of the surrounding rock surface f =0.87. Using the concept of the infinitesimal element method, the damage area is first divided into two equally spaced sub-regions. The damage factor D in each sub-region of the linear variation segment is then arranged in an arithmetic progression from shallow to deep. f / n = 0.87 / 2 = 0.435, decreasing sequentially. The damage factors D of the two sub-regions are 0.87 and 0.435 respectively (e.g., Figure 9 As shown), the three empirical parameters (m) corresponding to the damage factors of the two sub-regions are solved according to formulas (2) to (3). b Then, numerical calculations were performed, and the horizontal displacement at monitoring point A on the surrounding rock surface after stress equilibrium was 1.1 cm; secondly, the damaged area was divided into 4 sub-regions at equal intervals, and the damage factor D in each sub-region of the linear variation segment was arranged in an arithmetic progression from shallow to deep according to the arithmetic progression D. f / 4=0.87 / 4=0.2175 decreasing, the damage factors D of the two sub-regions are 0.87, 0.6525, 0.435, and 0.2175 respectively (e.g., Figure 10 As shown in the figure, the three empirical parameters corresponding to the damage factors of each region are assigned and numerical calculations are performed again. After stress equilibrium, the horizontal radial displacement at monitoring point A is 0.6 cm. Repeating the above steps, this embodiment also divides the damage area into 5, 8, 10, and 20 equal parts, respectively. The trend of the horizontal displacement of monitoring point A with the increase of the number of divisions n is shown in the figure. Figure 11 As shown in the figure, when n≥10, the horizontal displacement of monitoring point A is basically stable at 0.35cm, and no longer changes significantly with the increase of n. At this time, it can be considered that when the damaged area is divided into 10 equal parts, the linear change of the damage factor D can be achieved. According to the HB criterion, different empirical parameters corresponding to D are assigned to each sub-region (the empirical parameters corresponding to n=10 are shown in Table 3), so that the equivalent continuity of the empirical parameters with depth can be achieved.

[0140] Table 3. Calculated values ​​of three empirical parameters for different sub-regions when the damage zone at station K15+500 is divided into 10 sub-regions (n=10).

[0141]

[0142] Finally, for station K16+100, the m value in Table 2 of the original rock area assignment table... b0 =12.238541, s0=0.108368, a0=0.500593; For the damaged zone, parameter a is equal to a0=0.500593 in the original rock zone, so a is also assigned the value 0.500593 to the rock mass in the damaged zone. According to Figure 7 As shown in formula (21), the disturbance factor D remains constant within the damage zone h = 1.4 m, and then decreases linearly. For the rock mass in the damage zone with constant values, D = 0 and GSI = 80 are substituted into formulas (2) to (4) to obtain three empirical parameters and assigned to the rock mass. For the linearly decreasing segment, the rock mass in the linear segment is divided into n sub-regions using the method of infinitesimal elements. The damage factor D in the n sub-regions is then divided according to the depth from the surrounding rock surface from shallow to deep according to the arithmetic progression D.f / n(D f =1.0) decreasing sequentially. The corresponding m is calculated based on the damage factor D of each sub-region. b And s, together with other parameters required for simulation, are assigned values ​​to the rock mass of each sub-region of the surrounding rock. The final displacement of monitoring point A on the surface of the surrounding rock after excavation is monitored. After trial calculation, it was found that when n = 10 sub-regions, the final displacement of A no longer changes significantly with the increase of the number of sub-regions n. At this time, the n = 10 sub-regions can be considered as equivalent to the equivalent continuity assignment of the three empirical parameters in the damage zone. The damage factor D values ​​corresponding to each sub-region after division and the corresponding calculated values ​​of the three empirical parameters are shown in the figure. Figure 12 As shown in Table 4.

[0143] Table 4. Calculated values ​​of three empirical parameters for different sub-regions when the damage zone at station K16+100 is divided into 10 sub-regions (n=10).

[0144]

[0145] Step 6: Evaluate the stability of the surrounding rock based on steps 1-5.

[0146] Specifically, in this embodiment, two monitoring points, namely monitoring points A and B, are set on the surface at the maximum diameter of the tunnel. Figures 8-10 and Figure 12As shown, the distance between the two monitoring points is 12.4m. In this project, referring to the "Technical Specification for Safety Monitoring of Hydropower and Water Conservancy Project Construction" (DLT5308-2013), the allowable relative displacement value of the surrounding rock at a burial depth of 1500m is specified as follows (lower limit for brittle surrounding rock, upper limit for plastic surrounding rock): 0.1%–0.5% for Class II surrounding rock; 0.4%–1.2% for Class III surrounding rock; and 0.8%–2.0% for Class IV surrounding rock. According to geological survey data, the surrounding rock at chainages K15+100, K15+500, and K16+100 in this embodiment is Class II surrounding rock, exhibiting brittleness; therefore, the allowable relative displacement value of the tunnel surrounding rock is 0.1%. For chainage K15+100, according to the numerical analysis results in step 6, the maximum cumulative displacement of the two monitoring points is 0.9cm, and the relative displacement value is 0.9cm / 12.4m = 0.073%, which is close to 0.1%. The stability of the surrounding rock here is close to the critical value, and excavation activities need to be temporarily stopped. The surrounding rock support needs to be strengthened first. For chainage K15+500, according to the numerical analysis results in step 6, the maximum cumulative displacement of the two monitoring points is 0.7cm, and the relative displacement value is 0.7cm / 12.4m = 0.056%. This value is still significantly lower than the allowable value of 0.1%, indicating that the surrounding rock stability is relatively high, and excavation can continue. For chainage K16+100, according to the numerical analysis results in step 6, the maximum cumulative displacement of the two monitoring points is 1.15cm, and the relative displacement value is 0.7cm / 12.4m = 0.093%, which is very close to the allowable value of 0.1%. This indicates that the surrounding rock has a high possibility of instability, and construction needs to be stopped immediately, with the surrounding rock support strengthened.

[0147] Thus, the quantitative determination of empirical parameters in the HB criterion and the evaluation of surrounding rock stability in this embodiment of the invention have been achieved.

[0148] It should be noted that the above examples are only used to illustrate the method of the present invention in detail, and are not intended to limit its scope of application. Those skilled in the art can make modifications and substitutions to the method of the present invention, but this does not mean that it departs from the scope defined by the claims of the present invention.

Claims

1. A method for analyzing the stability of surrounding rock based on the quantitative determination of empirical parameters according to the HB criterion, characterized in that, Includes the following steps: Step 1: Obtain the material constant m of the rock i Uniaxial compressive strength σ of rock ci And acoustic wave tests were conducted to obtain the acoustic wave velocity of the rock mass at different depths perpendicular to the surface of the surrounding rock; Step 2: Based on the acoustic velocities of the rock mass at different depths obtained in Step 1, delineate the extent of the surrounding rock damage zone and the original rock zone, and quantitatively calculate the geological strength index (GSI) of the surrounding rock using the wave velocity method. m0 Damage factor D at different depths from the surrounding rock; Step 3: Based on the variation law of damage factor D, summarize the quantitative variation relationship of damage factor D at different depths d from the surface of the surrounding rock; Step 4: For the original rock mass, obtain the three empirical parameters (m) in the HB criterion based on the initial values ​​of the damage factor D and the geological strength GSI. b The initial values ​​of s and a) are used to obtain three empirical parameters (m) for the rock mass in the damaged area. b Quantitative expressions for s and a) are obtained, and then three empirical parameters (m) at different depths d from the surrounding rock are obtained. b The quantitative relationship between s and a); Step 5: Use the infinitesimal element method and numerical analysis to assign equivalent continuity values ​​to the three empirical parameters as they change with depth; Step 6: Calculate the cumulative maximum displacement of the surrounding rock surface using the three empirical parameters that were continuously assigned values ​​in Step 5, and evaluate the stability of the surrounding rock based on the cumulative maximum displacement value.

2. The method for analyzing surrounding rock stability based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 1, characterized in that, The depth of the test hole for the acoustic wave test in step 1 is at least 8 meters.

3. The method for analyzing the stability of surrounding rock based on the quantitative determination method of empirical parameters according to claim 1, characterized in that, The method for delineating the extent of the surrounding rock damage zone and the original rock zone in step 2 is as follows: Based on the rock mass acoustic velocity obtained at different depths in step 1, and considering that the acoustic velocity of the damaged rock mass is generally lower than that of the original rock mass, the area with relatively low wave velocity within a certain depth from the surface of the surrounding rock is identified as the damaged area, and the area outside the damaged area, i.e., the area with relatively high wave velocity, is the original rock mass.

4. The method for analyzing surrounding rock stability based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 1, characterized in that, Step 2 calculates the geological strength index (GSI) m0 The method is as follows: Seismic wave P-wave velocity S p Rock mass geomechanical classification index RMR 76 With rock mass deformation modulus E m The relationships are as follows: Meanwhile, GSI and RMR 76 Conditions met: GSI=RMR 76 (3) According to formulas (1) to (3), the GSI and the P-wave velocity S of the rock mass seismic wave are obtained. p The relationship between them is: Rock mass seismic wave P-wave velocity S p With the sound wave velocity V of the rock mass p It has the following linear relationship: S p =kV p +b (5) Wherein, GSI is the geological strength index, V p is the P-wave velocity of the rock mass, in km / s, and k and b are the fitting constants between the seismic wave velocity and the rock mass acoustic velocity, obtained from geological exploration data. By combining formulas (4) and (5), the relationship between GSI and the acoustic velocity V of the rock mass can be established. p Quantitative expressions between them: The average sound wave velocity V of the original rock mass p0 Substituting into formula (6), the GSI in the HB criterion is quantitatively determined. m0 The value is calculated using the following formula:

5. The method for analyzing the stability of surrounding rock based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 4, characterized in that, In step 2, the wave velocity method is used to quantitatively obtain the surrounding rock damage factor D as follows: Deformation modulus E of rock mass m The relationship with damage factor D is as follows: Where E0 is the deformation modulus of the original rock mass; Rock mass deformation modulus E m The relationship between the velocity of sound waves in rock mass and the velocity of sound waves is expressed as follows: AND m =aexp(cV p ) (9) Where a and c are fitting constants, which are obtained by fitting the rock mass deformation modulus and acoustic velocity data from the geological survey data in the early stage of the project. The deformation modulus of the original rock mass is obtained as follows: E0=aexp(cV p0 ) (10) Based on the relationship between the rock mass deformation modulus and the sound wave velocity, and the deformation modulus of the original rock mass, the following relationship is obtained: Based on the above formula, the quantitative value of the rock mass damage factor D is obtained as follows: D=2{1-exp[c(V p -V p0 )]} (12) The damage factor D ranges from 0 to 1. When D > 1, it is considered that D = 1, and when D < 0, it is considered that D = 0.

6. The method for analyzing surrounding rock stability based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 1, characterized in that, The method for calculating the quantitative variation of damage factor D at different depths d from the surrounding rock surface in step 3 is as follows: First, the variation law of damage factor D with depth d is divided into three categories: constant type, linear decreasing type, and constant-linear decreasing composite type. 1) Constant type: The damage factor D of the entire surrounding rock damage zone is constant. In this case, the variation law of the damage factor D of the rock mass in the damage zone is described as follows: D(d)=D f (13) Where D(d) is the functional expression of the damage factor at different depths d from the surrounding rock; D f The damage factor at the surface of the surrounding rock; 2) Linear decreasing type: The damage factor of the entire surrounding rock damage zone shows a linear decreasing trend with increasing depth d from the surrounding rock surface. The change law of D in this case can be described as follows: Among them, H EDZ The depth of the damaged area; 3) Constant-linear decreasing composite type: The damage factor D remains constant within a certain depth h from the surrounding rock surface, i.e., D = D f Within the damage zone outside the h range, the damage factor increases with depth (dh) from D f The linear decrease in D can be described as follows: After observing the distribution characteristics of the damage factor D at different depths from the surrounding rock in the damaged area, the quantitative expression of the continuity of the damage factor D with depth d is obtained according to formulas (13) to (15).

7. The method for analyzing surrounding rock stability based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 1, characterized in that, In step 4, three empirical parameters (m) are calculated at different depths d from the surrounding rock. b The method for quantitatively determining the relationship between s and a) is as follows: (1) For the original rock mass, the damage factor D = 0 and GSI = GSI are set. m0 Substituting into formulas (2) to (4), we obtain the three empirical parameters m. b0 s0 and a0; (2) For the rock mass in the damaged area, as can be seen from the results of steps 2 and 3, by substituting formulas (1) and (13) to (15) into formulas (3) to (4), we can obtain the quantitative expressions for the three empirical parameters m. b (d), s(d), and a(d), that is: According to the quantitative relationship of the continuity function of the three empirical parameters in the HB criterion as a function of the distance from the surrounding rock depth d, the parameter a is only related to GSI. Therefore, the parameter a(d) in the damaged area is actually equal to a0 in the original rock area, that is, a(d) = a0.

8. The method for analyzing surrounding rock stability based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 1, characterized in that, The method for assigning equivalent continuity values ​​to the three empirical parameters as a function of depth in step 5 is as follows: (1) The m of the original rock mass b , s, and a are respectively assigned the value of m obtained in step 4. b0 s0 and a0; (2) Parameter a is only related to GSI m0 Regarding this, the parameter 'a' of the damaged area is assigned the value a(d) = a0 obtained in step 4, because parameter m b And s not only depend on GSI m0 Moreover, it is related to the damage factor D, and for different damage factors D, m b The method for assigning values ​​to the s-parameter in numerical software: 1) When the damage factor D obtained from step 3 has a constant segment, i.e., D(d) = D f At this time, the m of the rock mass in the damaged area b Assigning values ​​to GSI and s respectively m0 With D(d)=D f The solution obtained by substituting the empirical parameters into the quantitative expression is m. b (d) and s(d); 2) When the damage factor D obtained in step 2 has a linear decreasing segment, the method of infinitesimal elements is used to solve for m. b And s, the specific steps are as follows: ① Divide the linearly decreasing segment of D within the damaged area into n equally spaced sub-regions, where n is a natural number; ② Divide the damage factor D in the n sub-regions according to the depth from the surrounding rock surface, from shallow to deep, following an arithmetic progression. f / n decreases sequentially; ③ Solve for the corresponding m based on the damage factor D of each sub-region. b And s, together with other parameters required for the simulation, are used to assign values ​​to the rock mass of each sub-region of the surrounding rock; ④ Monitor the final displacement of a monitoring point on the surface of the surrounding rock after excavation until the final displacement no longer changes significantly with the increase of the number of divisions n. At this point, it is considered that the n sub-regions are equivalent to the continuous assignment of three empirical parameters in the linearly decreasing segment of the damage zone D.

9. The method for analyzing surrounding rock stability based on the quantitative determination method of empirical parameters according to the HB criterion as described in claim 1, characterized in that, Step 6 specifically determines the stability of the surrounding rock based on the magnitude of the displacement change. Based on steps 1 to 5, two monitoring points are set on the surface of the surrounding rock. The ratio of the maximum cumulative displacement value of the two monitoring points to the distance between the two monitoring points is taken as the relative displacement value of the surrounding rock. If the obtained relative displacement value of the monitoring point is close to the allowable relative displacement value of the surrounding rock of the project, it is determined that the surrounding rock is unstable; otherwise, it is in a stable state.

10. A system for quantitatively determining surrounding rock stability based on empirical parameters of the HB criterion, characterized in that, include: Velocity acquisition module: It is configured to perform the following action: acquire the material constant m of the rock. i Uniaxial compressive strength σ of rock ci And acoustic wave tests were conducted to obtain the acoustic wave velocity of the rock mass at different depths perpendicular to the surface of the surrounding rock; The parameter calculation module is configured to perform the following actions: delineate the extent of the surrounding rock damage zone and the original rock zone, and quantitatively calculate the geological strength index (GSI) of the surrounding rock using the wave velocity method. m0 Damage factor D at different depths from the surrounding rock; Based on the variation law of damage factor D, the quantitative variation relationship of damage factor D at different depths d from the surrounding rock surface was summarized; and three empirical parameters (m) at different depths d from the surrounding rock were obtained. b The quantitative relationship between s and a); The assignment module is configured to perform the following actions: using the infinitesimal method and numerical analysis to assign equivalent continuity values ​​for the three empirical parameters as they change with depth; The stability analysis module is configured to perform the following actions: calculate the cumulative maximum displacement of the surrounding rock surface obtained by using the three empirical parameters that are continuously assigned values ​​in step 5, and evaluate the stability of the surrounding rock based on the cumulative maximum displacement value.

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