Surrounding rock grading correction method considering heat, water and force coupling effect

Abstract

The invention discloses a surrounding rock grading correction method considering a heat, water and force coupling effect, which comprises the following steps: drilling a rock body at a to-be-researched engineering part to prepare a plurality of standard samples, carrying out vacuum water saturation on all the standard samples, and wiping the surface moisture of the standard samples after vacuum water saturation; carrying out a saturated granite uniaxial test and a heat-water-force coupling orthogonal test on the plurality of saturated standard samples to obtain rock saturated uniaxial strength and multi-field coupling rock theoretical uniaxial strength; the quotient of the theoretical uniaxial strength of the multi-field coupling rock and the saturated uniaxial strength of the rock is adopted as a surrounding rock grading correction coefficient; and according to the surrounding rock grading correction coefficient, multi-field coupling environment surrounding rock grading based on BQ grading, a Q system and / or RMi rock mass quality is corrected.

Description

Technical Field

[0001] The invention belongs to the technical field of surrounding rock classification of tunnels and underground engineering, and in particular relates to a surrounding rock classification correction method taking into account the coupling effects of heat, water and force. Background Art

[0002] The energy and space demands brought about by economic and social development have forced more and more national key projects to move to deep areas, such as the Sichuan-Tibet Railway, the Yarlung Zangbo River downstream hydropower project and other national strategic projects. The engineering rock mass in the deep environment is deeply affected by the high geothermal-high geostress-high osmotic pressure coupling environment. The mechanical response of the engineering rock mass is complex and changeable, which greatly affects the fine classification of the deep rock mass quality during the construction stage. It is urgent to solve the problem of identifying the degradation of the relevant mechanical parameters of the engineering rock mass under the multi-field coupling environment.

[0003] Generally speaking, thermal expansion of rock minerals and thermal cracking between minerals caused by high temperature will lead to significant changes in the mechanical properties of rocks. At the same time, coupled with the continuous influence of underground seepage field pore pressure and water-rock physicochemical effects, the initiation, expansion and penetration of microcracks inside the surrounding rock mass under the conditions of thermal-hydraulic-mechanical multi-field coupling are strengthened, resulting in reduced rock strength and weakened stability, causing surrounding rock failure and instability. Existing rock mass classification, such as the modified BQ rock mass classification, Q system, RMi, etc., the commonly used surrounding rock classification methods have recognized the influence of factors such as groundwater, geological structure and geostress on the surrounding rock quality evaluation results, and further evaluated the classification results considering geostress and groundwater, but did not fully consider the influence of temperature and coupled environment on the mechanical properties of rock mass, resulting in low classification accuracy, which in turn caused the construction method or support method of the rock mass determined by the classification to be improper, posing certain safety hazards.

[0004] Therefore, it is urgent to propose a surrounding rock classification correction method that considers the effects of high ground temperature and multi-field coupling environment on the deterioration of the mechanical properties of engineering rock mass. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the surrounding rock classification correction method taking into account the coupling effects of heat, water and force provided by the present invention solves the problem that the existing rock mass quality classification method does not take into account the deterioration effect of high geothermal and multi-field coupling environment on the mechanical properties of engineering rock mass, resulting in inaccurate rock mass quality classification.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] A surrounding rock classification correction method considering the coupling effects of heat, water and force is provided, which comprises the following steps:

[0008] S1. Drill the rock mass of the project to be studied to prepare multiple standard samples, and saturate all the standard samples with water under vacuum, and then wipe off the surface moisture of the standard samples after saturation with water under vacuum;

[0009] S2. Carry out saturated granite uniaxial test and thermal-hydraulic-mechanical coupling orthogonal test on multiple water-saturated standard specimens to obtain the saturated uniaxial strength of rock and the multi-field coupled theoretical uniaxial strength of rock;

[0010] S3. The quotient of the multi-field coupled rock theoretical uniaxial strength and the rock saturated uniaxial strength is used as the surrounding rock classification correction coefficient;

[0011] S4. According to the surrounding rock classification correction factor, the multi-field coupled environment surrounding rock classification based on BQ classification, Q system and / or RMi rock mass quality is corrected:

[0012] [BQ] THM =100+3αR c +250K v -100(K1+K2+K3)

[0013]

[0014] Among them, [BQ] THM , Q THM and RMi THM are the basic rock mass quality indicators BQ, Q and RMi respectively; α is the surrounding rock classification correction coefficient; R c is the saturated uniaxial strength of rock; K1 is the correction factor for the influence of groundwater on underground projects; K2 is the correction factor for the influence of the main structural surface of underground projects; K3 is the correction factor for the influence of the initial stress state; K v is the quantitative index of classification factors; RQD is the rock quality index; J n is the level of the number of joint groups; J r J is the grade of joint surface roughness; a is the degree of alteration or the grade of clay-filled joint sets; J w is the level of groundwater inflow and pressure impact; SRF is the stress reduction factor; J c is the structural surface condition coefficient; V b is the volume of the block cut by the structural surface; D is the transition parameter, D = 0.37J c -0.2 .

[0015] Furthermore, the method of conducting a saturated granite uniaxial test to obtain the saturated uniaxial strength of the rock includes:

[0016] S21. Place the standard sample on the loading table of the test machine of the GCTS system, and install the axial displacement sensor, the circumferential displacement sensor and the acoustic emission probe on the heat shrink film surface of the standard sample respectively;

[0017] S22, testing the specimen at a preset axial deformation rate, and recording basic mechanical parameters of the rock mass during the test;

[0018] S23. After all standard specimens have completed step S21 and step S22, the stress of the standard specimens under each load is calculated according to the cross-sectional area of ​​the standard specimens:

[0019]

[0020] Where, σ is stress; P is load; A is the cross-sectional area of ​​the standard specimen;

[0021] S24. According to the stress under each load, the stress evolution curve of the standard specimen during the loading process is obtained, and the maximum value in the stress evolution curve is selected as the saturated uniaxial strength of the rock.

[0022] Furthermore, the method of conducting thermal-hydraulic-mechanical coupling orthogonal test to obtain the multi-field coupled rock theoretical uniaxial strength includes:

[0023] A1. Apply confining pressure to the saturated standard sample, apply osmotic pressure when the set confining pressure is reached, then heat to the target temperature and maintain it for a preset time, and perform a loading test until the standard sample is destroyed;

[0024] A2. When multiple saturated standard specimens have completed step A1, the confining pressure recorded during the test in step A1 and the rock compressive strength under the corresponding confining pressure are used to calculate the effective confining pressure and effective peak strength:

[0025]

[0026] Where, variable i = 1 and 3, σ3 is the recorded confining pressure; σ1 is the rock compressive strength corresponding to σ3; and are effective peak strength and effective confining pressure respectively; P w is the interstitial water pressure;

[0027] A3. Fit the effective confining pressure and effective peak strength of multiple standard samples to obtain the fitting formula:

[0028]

[0029] A4. Calculate the internal friction angle of the rock based on the slope and intercept of the fitted straight line. and cohesion c:

[0030]

[0031] Where m and b are the slope and intercept of the line respectively;

[0032] A5. According to the internal friction angle of rock and cohesion c, calculate the theoretical uniaxial strength of multi-field coupled rock:

[0033]

[0034] in, is the theoretical uniaxial strength of multi-field coupled rock.

[0035] Furthermore, the method of conducting thermal-hydraulic-mechanical coupling orthogonal test to obtain the multi-field coupled rock theoretical uniaxial strength includes:

[0036] B1. Apply confining pressure to the saturated standard sample, apply osmotic pressure when the set confining pressure is reached, then heat to the target temperature and maintain it for a preset time, and perform a loading test until the standard sample is destroyed;

[0037] B2. Use the temperature increment and rock elastic modulus obtained in the multi-field coupling test phase to calculate the multi-field coupling rock theoretical uniaxial strength:

[0038]

[0039] in, is the theoretical uniaxial strength of multi-field coupled rock; C v is the constant volume specific heat of rock material; ΔT and E are the temperature increment and rock elastic modulus in the multi-field coupling test phase, respectively; R c is the saturated uniaxial strength of rock; k is the first fitting parameter; E0 is the elastic modulus of rock under uniaxial conditions.

[0040] Furthermore, the method for constructing the expression of the multi-field coupled rock theoretical uniaxial strength in step B2 includes:

[0041] B21. Construct a model of releasable elastic energy under thermal and hydrothermal coupling conditions:

[0042]

[0043] Among them, U e The rock can release elastic energy; and are effective peak strength, effective principal stress and effective confining pressure respectively; μ is Poisson's ratio;

[0044] B22. According to the saturated uniaxial strength of rock, construct the critical value G of the maximum energy release rate c :

[0045]

[0046] Among them, K3 is the material constant;

[0047] B23. Determine the strength criterion for overall rock failure under thermal-hydraulic coupling conditions:

[0048]

[0049] B24. Substituting the releasable elastic energy model into the strength criterion of rock overall failure, the expression can be obtained:

[0050]

[0051] B25. Use the strain energy dispersion coefficient to correct the expression in step B24 to obtain the rock energy strength criterion under the condition of thermal water-hydraulic coupling:

[0052]

[0053] Where N is the strain energy dispersion coefficient, n is the second fitting parameter;

[0054] B26, let the rock energy strength criterion make The uniaxial strength expression of multi-field coupled rock theory is obtained:

[0055]

[0056] Furthermore, when the BQ classification is corrected, the saturated uniaxial strength of rock R c and the quantitative index K of the grading factor v The conditions are as follows: when R c >90K v +30, R c =90K v +30; when K v >0.04R c hour,

[0057] K v =0.04R c +0.4.

[0058] Furthermore, the standard sample is a granite sample.

[0059] Furthermore, after the basic rock mass quality indicators BQ, Q and RMi are obtained, the rock mass quality grade of the rock mass at the engineering site to be studied is obtained according to the grading standards of the basic rock mass quality indicators BQ, Q and RMi and their corresponding rock mass quality grades.

[0060] The beneficial effects of the present invention are as follows: Starting from the multi-field coupling environment commonly faced in deep engineering and the groundwater description in the surrounding rock classification method, this scheme obtains the mechanical parameters of the rock through uniaxial tests and multi-field coupling tests, and then obtains the multi-field coupling rock theoretical uniaxial strength and rock saturated uniaxial strength based on the mechanical parameters, and then determines the surrounding rock classification correction coefficient. Compared with the existing surrounding rock classification method, this scheme combines the indoor test results to obtain the multi-field coupling theoretical uniaxial strength, takes into account the degradation effect of thermal-hydraulic-mechanical multi-field coupling on the mechanical properties of the surrounding rock mass, and makes the surrounding rock classification results more accurate, providing more reliable guarantees for the reasonable design and safe construction of tunnels and underground projects, and can reduce the existing safety hazards to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 Flow chart of the surrounding rock classification correction method considering the coupling effects of heat, water and force.

[0062] Figure 2 : is the compressive strength of granite under multi-field coupling conditions according to an embodiment of the present invention.

[0063] Figure 3 : is the linear relationship between the effective confining pressure and the effective peak stress of granite under multi-field coupling conditions according to an embodiment of the present invention. DETAILED DESCRIPTION

[0064] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0065] This scheme mainly modifies the mainstream surrounding rock classification methods at home and abroad (BQ classification, RMR classification, Q system three methods). To this end, this embodiment first describes the groundwater status involved in the mainstream surrounding rock classification methods at home and abroad, as shown in Tables 1 to 3.

[0066] Table 1 Groundwater discharge status of BQ classification

[0067]

[0068] Table 2 Description of indicators for RMR grading

[0069]

[0070]

[0071] Table 3 Parameter description of Q system

[0072]

[0073] In Table 1, p is the water pressure in the surrounding rock fissures of the underground project (MPa), and Q is the water output per 10m of hole length (L / min·10m). In the Q system, the values ​​of items C to F are all rough estimates, 10kg / cm 2 =1MPa water pressure in the surrounding rock fissures of underground projects.

[0074] It can be seen from Table 1 that the water pressure p of groundwater surrounding rock fissures is usually divided into 0.1MPa, 0.5MPa and 1MPa, and the corresponding water output Q per 10m of hole length is 25L / min·10m, 125L / min·10m and 250L / min·10m respectively.

[0075] At the same time, in Table 4, the consideration of groundwater in surrounding rock classification standard methods such as "Railway Tunnel Design Code" TB10003-2016, "Hydraulic Tunnel Design Code" SL279, "Geophysical Survey Code for Water Conservancy and Hydropower Engineering" GB50487, and Rock Structure Evaluation Classification Method (RSR) is fully investigated.

[0076] Table 4

[0077]

[0078] It can be seen from Table 4 that the maximum groundwater surrounding rock fissure water pressure p threshold considered in the existing surrounding rock classification specifications and methods is 1 MPa, and the maximum water yield Q is 125 L / min·10 m. Therefore, the maximum seepage pressure condition in the multi-field coupled complete rock test can be limited to 1 MPa, and the simulated seepage pressure conditions can be set to 0.1 MPa, 0.5 MPa, and 1 MPa respectively, referring to the classification of groundwater surrounding rock fissure water pressure p in the specifications.

[0079] At the same time, the test temperature conditions were set with reference to the high geothermal environment faced in the construction of existing deep tunnel projects. Existing studies predict that the maximum tunnel temperature of the Layue Tunnel can exceed 60°C, and the maximum geothermal temperature in the completed Sangzhuling Tunnel reached nearly 90°C.

[0080] Therefore, combined with the high temperature environment actually faced by deep engineering, the room temperature of 25°C is used as the benchmark, and the simulation temperature is set to 60°C and 100°C with equal gradients. At the same time, considering that the subsequent surrounding rock classification correction needs to be combined with the Mohr-Coulomb criterion to obtain the theoretical uniaxial strength, the confining pressure can be set at a lower level, such as 2, 5, and 10 MPa, and the multi-field coupled complete rock test conditions are obtained as shown in Table 5.

[0081] Table 5

[0082] Confining pressure setting (MPa): 2 5 10 Osmotic pressure setting (MPa): 0.1 0.5 1 Temperature setting (℃): 25 60 100

[0083] The following is a combination of the selected parameters analyzed in Tables 1 to 5, and a saturated granite uniaxial test and a thermal-hydraulic-mechanical coupling orthogonal test are carried out to correct the surrounding rock classification:

[0084] refer to Figure 1 , Figure 1 A surrounding rock classification correction method considering the coupling effects of heat, water and force is shown; the method S includes steps S1 to S4.

[0085] In step S1, a rock mass of the project to be studied is drilled to prepare a plurality of standard samples, and all the standard samples are vacuum saturated with water, and then the surface moisture of the vacuum saturated standard samples is wiped dry; in this scheme, the preferred standard sample is a granite sample.

[0086] The detailed implementation process of step S1 is:

[0087] The granite blocks were drilled from a tunnel excavation. According to the national standard "Methods for Determining Physical and Mechanical Properties of Coal and Rock", the granite was processed into standard specimens with a diameter of 50mm and a height of 100mm. The non-parallelism of the two ends of the specimen was no more than 0.05mm; the diameter deviation of the upper and lower ends of the specimen should not be greater than 0.3mm, and the surface of the specimen should be smooth to avoid stress concentration caused by irregular surfaces. Subsequently, the granite was vacuum saturated with water for 48 hours using a vacuum saturation device to ensure that the specimen was in a saturated state.

[0088] In step S2, saturated granite uniaxial test and thermal-hydraulic-mechanical coupling orthogonal test are carried out on multiple saturated standard specimens to obtain the saturated uniaxial strength of rock and the multi-field coupled theoretical uniaxial strength of rock; this scheme relies on the GCTS high-temperature rock mechanics test system to carry out saturated granite uniaxial test and thermal-hydraulic-mechanical coupling orthogonal test.

[0089] The GCTS high-temperature rock mechanics test system is equipped with a confining pressure and axial loading system, a permeable water pressure loading and temperature control system. It can apply a maximum confining pressure of 140MPa, a maximum pore water pressure of 140MPa and a maximum axial load of 4600kN, and heat the standard sample to a maximum temperature of 150℃. During the test, temperature control, loading rate, load and deformation measurement are all controlled by computer programs and measured by high-precision sensors, and data collection and recording are automatically performed. An axial displacement sensor with a range of ±2.5mm and a circumferential displacement sensor with a range of ±2.5mm are used to measure the axial strain and circumferential strain of the loaded sample. The axial displacement sensor, circumferential displacement sensor and acoustic emission probe are installed on the surface of the sample heat shrink film, and vaseline is applied between the probe and the heat shrink film. The stroke of the axial and circumferential displacement sensors is adjusted to ensure that the displacement sensors are always within the effective range during the test.

[0090] During implementation, the method for conducting saturated granite uniaxial test to obtain the saturated uniaxial strength of rock preferably includes:

[0091] S21. Place the standard sample on the loading table of the test machine of the GCTS system, and install the axial displacement sensor, the circumferential displacement sensor and the acoustic emission probe on the heat shrink film surface of the standard sample respectively;

[0092] S22, testing the sample at a preset axial deformation rate, and recording the basic mechanical parameters of the rock mass during the test; the preset axial deformation rate is 0.04 mm / min;

[0093] S23. After all standard specimens have completed step S21 and step S22, the stress of the standard specimens under each load is calculated according to the cross-sectional area of ​​the standard specimens:

[0094]

[0095] Where, σ is stress; P is load; A is the cross-sectional area of ​​the standard specimen;

[0096] S24, according to the stress under each load, obtain the stress evolution curve of the standard sample during the loading process, and select the maximum value in the stress evolution curve as the saturated uniaxial strength of the rock;

[0097] The mechanical parameters of multiple standard specimens obtained using the test parameters given above can be found in Table 6.

[0098] Table 6

[0099]

[0100] In step S3, the quotient of the multi-field coupled rock theoretical uniaxial strength and the rock saturated uniaxial strength is used as the surrounding rock classification correction coefficient:

[0101]

[0102] In step S4, the surrounding rock classification based on the multi-field coupled environment of BQ classification, Q system and / or RMi rock mass quality is corrected according to the surrounding rock classification correction coefficient:

[0103] [BQ] THM =100+3αR c +250K v -100(K1+K2+K3)

[0104]

[0105] Among them, [BQ] THM , Q THM and RMi THMare the basic rock mass quality indicators BQ, Q and RMi respectively; α is the surrounding rock classification correction coefficient; R c is the saturated uniaxial strength of rock; K1 is the correction factor for the influence of groundwater on underground projects; K2 is the correction factor for the influence of the main structural surface of underground projects; K3 is the correction factor for the influence of the initial stress state; K v is the quantitative index of classification factors; RQD is the rock quality index; J n is the level of the number of joint groups; J r J is the grade of joint surface roughness; a is the degree of alteration or the grade of clay-filled joint sets; J w is the level of groundwater inflow and pressure impact; SRF is the stress reduction factor; J c is the structural surface condition coefficient; V b is the volume of the block cut by the structural surface; D is the transition parameter, D = 0.37J c -0.2 .

[0106] In step S4, when the BQ classification is corrected, the rock saturated uniaxial strength R c and the quantitative index K of the grading factor v The conditions are as follows: when R c >90K v +30, R c =90K v +30; when K v >0.04R c When K v =0.04R c +0.4.

[0107] This scheme provides two methods for conducting thermal-hydraulic-mechanical coupling orthogonal tests to obtain the theoretical uniaxial strength of multi-field coupled rocks. The first method is:

[0108] A1. Apply confining pressure to the saturated standard sample, apply osmotic pressure when the set confining pressure is reached, then heat to the target temperature and maintain it for a preset time, and perform a loading test until the standard sample is destroyed;

[0109] The detailed implementation process of step A1 is as follows:

[0110] (1) Apply confining pressure: Increase the confining pressure to the target confining pressure value (2MPa, 5MPa, 10MPa) at 3MPa / min

[0111] (2) Applying osmotic pressure: The osmotic pressure of this test was set to 0.1, 0.5, and 1 MPa. After reaching the set confining pressure, the water pressure at the inlet of the granite sample was increased to the set value, and the water pressure at the outlet was set to 0.

[0112] (3) Loading test: After heating to the target temperature (60°C, 100°C) and maintaining for 30 minutes, the granite is subjected to a loading test at a loading rate of 0.04 mm / min until the sample is destroyed, and the mechanical parameters of the granite under different conditions are recorded. For example, Figure 2 The strength degradation characteristics of granite under different temperatures and osmotic pressures under a confining pressure of 2 MPa.

[0113] A2. When multiple saturated standard specimens have completed step A1, the confining pressure recorded during the test in step A1 and the rock compressive strength under the corresponding confining pressure are used to calculate the effective confining pressure and effective peak strength:

[0114]

[0115] Among them, variable i = 1 and 3, σ3 is the recorded confining pressure; σ1 is the rock compressive strength corresponding to σ3; σ1 e and are effective peak strength and effective confining pressure respectively; P w is the interstitial water pressure;

[0116] A3. Fit the effective confining pressure and effective peak strength of multiple standard samples to obtain the fitting formula:

[0117]

[0118] The fitting formula can be referred to Figure 3 In this embodiment, the preferred values ​​of m and b are 13.32 and 156.78.

[0119] A4. Calculate the internal friction angle of the rock based on the slope and intercept of the fitted straight line. and cohesion c:

[0120]

[0121] Where m and b are the slope and intercept of the line respectively;

[0122] A5. According to the internal friction angle of rock and cohesion c, calculate the theoretical uniaxial strength of multi-field coupled rock:

[0123]

[0124] in, is the theoretical uniaxial strength of multi-field coupled rock.

[0125] The second method provided in this scheme to carry out thermal-hydraulic-mechanical coupling orthogonal test to obtain the multi-field coupled rock theoretical uniaxial strength includes:

[0126] B1. Apply confining pressure to the saturated standard sample, apply osmotic pressure when the set confining pressure is reached, then heat to the target temperature and maintain it for a preset time, and perform a loading test until the standard sample is destroyed;

[0127] B2. Use the temperature increment and rock elastic modulus obtained in the multi-field coupling test phase to calculate the multi-field coupling rock theoretical uniaxial strength:

[0128]

[0129] in, is the theoretical uniaxial strength of multi-field coupled rock; C v is the constant volume specific heat of rock material; ΔT and E are the temperature increment and rock elastic modulus in the multi-field coupling test phase, respectively; R c is the saturated uniaxial strength of rock; k is the first fitting parameter; E0 is the elastic modulus of rock under uniaxial conditions.

[0130] In one embodiment of the present invention, the method for constructing the expression of the multi-field coupled rock theoretical uniaxial strength in step B2 includes:

[0131] B21. Construct a model of releasable elastic energy under thermal and hydrothermal coupling conditions:

[0132]

[0133] Among them, U e The rock can release elastic energy; and are effective peak strength, effective principal stress and effective confining pressure respectively; μ is Poisson's ratio;

[0134] B22. According to the saturated uniaxial strength of rock, construct the critical value G of the maximum energy release rate c :

[0135]

[0136] Among them, K3 is the material constant;

[0137] B23. Determine the strength criterion for overall rock failure under thermal-hydraulic coupling conditions:

[0138]

[0139] B24. Substituting the releasable elastic energy model into the strength criterion of rock overall failure, the expression can be obtained:

[0140]

[0141] B25. Use the strain energy dispersion coefficient to correct the expression in step B24 to obtain the rock energy strength criterion under the condition of thermal water-hydraulic coupling:

[0142]

[0143] Where N is the strain energy dispersion coefficient, n is the first fitting parameter;

[0144] B26, let the rock energy strength criterion make The uniaxial strength expression of multi-field coupled rock theory is obtained:

[0145]

[0146] After the basic rock mass quality indicators BQ, Q and RMi are obtained, the rock mass quality grade of the rock mass at the engineering site to be studied is obtained according to the grading standards of the basic rock mass quality indicators BQ, Q and RMi and their corresponding rock mass quality grades.

[0147] Based on the detailed test parameters given in this embodiment when conducting uniaxial tests and multi-field coupled orthogonal tests, some multi-field coupled surrounding rock classification correction coefficients that can be obtained in combination with the surrounding rock classification correction method of this scheme are shown in Table 7.

[0148] Table 7

[0149]

[0150] In the present embodiment, when the uniaxial test and the multi-field coupling test are carried out, the granite used is a representative of igneous rock, and the multi-field coupling environment can cause a maximum strength degradation effect of 12% on it. This result can provide a reference for the correction of surrounding rock classification under the multi-field coupling environment.

Claims

1. A surrounding rock classification correction method considering the coupling effects of heat, water and force, characterized in that: Includes steps: S1. Drill the rock mass of the project to be studied to prepare multiple standard samples, and saturate all the standard samples with water under vacuum, and then wipe off the surface moisture of the standard samples after saturation with water under vacuum; S2. Carry out saturated granite uniaxial test and thermal-hydraulic-mechanical coupling orthogonal test on multiple water-saturated standard specimens to obtain the saturated uniaxial strength of rock and the multi-field coupled theoretical uniaxial strength of rock; S3. The quotient of the multi-field coupled rock theoretical uniaxial strength and the rock saturated uniaxial strength is used as the surrounding rock classification correction coefficient; S4. According to the surrounding rock classification correction factor, the multi-field coupled environment surrounding rock classification based on BQ classification, Q system and / or RMi rock mass quality is corrected: [BQ] THM =100+3αR c +250K v -100(K1+K2+K3) Among them, [BQ] THM , Q THM and RMi THM are the basic rock mass quality indicators BQ, Q and RMi respectively; α is the surrounding rock classification correction coefficient; R c is the saturated uniaxial strength of rock; K1 is the correction factor for the influence of groundwater on underground projects; K2 is the correction factor for the influence of the main structural surface of underground projects; K3 is the correction factor for the influence of the initial stress state; K v is the quantitative index of classification factors; RQD is the rock quality index; J n is the level of the number of joint groups; J r J is the grade of joint surface roughness; a is the degree of alteration or the grade of clay-filled joint sets; J w The level of groundwater inflow and pressure impact; SRF is the stress reduction factor; J c is the structural surface condition coefficient; V b is the volume of the block cut by the structural surface; D is the transition parameter, D = 0.37J c -0.2 .

2. The surrounding rock classification correction method considering the coupling effects of heat, water and force according to claim 1 is characterized in that: The methods for conducting uniaxial tests on saturated granite to obtain the saturated uniaxial strength of rock include: S21. Place the standard sample on the loading table of the test machine of the GCTS system, and install the axial displacement sensor, the circumferential displacement sensor and the acoustic emission probe on the heat shrink film surface of the standard sample respectively; S22, testing the specimen at a preset axial deformation rate, and recording basic mechanical parameters of the rock mass during the test; S23. After all standard specimens have completed step S21 and step S22, the stress of the standard specimens under each load is calculated according to the cross-sectional area of ​​the standard specimens: Where, σ is stress; P is load; A is the cross-sectional area of ​​the standard specimen; S24. According to the stress under each load, the stress evolution curve of the standard specimen during the loading process is obtained, and the maximum value in the stress evolution curve is selected as the saturated uniaxial strength of the rock.

3. The surrounding rock classification correction method considering the coupling effects of heat, water and force according to claim 1 is characterized in that: The method of conducting thermal-hydraulic-mechanical coupling orthogonal test to obtain the theoretical uniaxial strength of multi-field coupled rock includes: A1. Apply confining pressure to the saturated standard sample, apply osmotic pressure when the set confining pressure is reached, then heat to the target temperature and maintain it for a preset time, and perform a loading test until the standard sample is destroyed; A2. When multiple saturated standard specimens have completed step A1, the confining pressure recorded during the test in step A1 and the rock compressive strength under the corresponding confining pressure are used to calculate the effective confining pressure and effective peak strength: Where, variable i = 1 and 3, σ3 is the recorded confining pressure; σ1 is the rock compressive strength corresponding to σ3; and are effective peak strength and effective confining pressure respectively; P w is the interstitial water pressure; A3. Fit the effective confining pressure and effective peak strength of multiple standard samples to obtain the fitting formula: A4. Calculate the internal friction angle of the rock based on the slope and intercept of the fitted straight line. and cohesion c: Among them, m and b are the slope and intercept of the straight line respectively; A5. According to the internal friction angle of rock and cohesion c, calculate the theoretical uniaxial strength of multi-field coupled rock: in, is the theoretical uniaxial strength of multi-field coupled rock.

4. The surrounding rock classification correction method considering the thermal, water and mechanical coupling effects according to claim 1 is characterized in that: The method of conducting thermal-hydraulic-mechanical coupling orthogonal test to obtain the theoretical uniaxial strength of multi-field coupled rock includes: B1. Apply confining pressure to the saturated standard sample, apply osmotic pressure when the set confining pressure is reached, then heat to the target temperature and maintain it for a preset time, and perform a loading test until the standard sample is destroyed; B2. Use the temperature increment and rock elastic modulus obtained in the multi-field coupling test phase to calculate the multi-field coupling rock theoretical uniaxial strength: in, is the theoretical uniaxial strength of multi-field coupled rock; C v is the constant volume specific heat of rock material; ΔT and E are the temperature increment and rock elastic modulus in the multi-field coupling test phase, respectively; R c is the saturated uniaxial strength of rock; k is the first fitting parameter; E0 is the elastic modulus of rock under uniaxial conditions.

5. The surrounding rock classification correction method considering the thermal, water and mechanical coupling effects according to claim 4 is characterized in that: The method for constructing the expression of the multi-field coupled rock theoretical uniaxial strength in step B2 includes: B21. Construct a model of releasable elastic energy under thermal and hydrothermal coupling conditions: Among them, U e The rock can release elastic energy; and are effective peak strength, effective principal stress and effective confining pressure respectively; μ is Poisson's ratio; B22. According to the saturated uniaxial strength of rock, construct the critical value G of the maximum energy release rate c : Among them, K3 is the material constant; B23. Determine the strength criterion for overall rock failure under thermal-hydraulic coupling conditions: B24. Substituting the releasable elastic energy model into the strength criterion of rock overall failure, the expression can be obtained: B25. Use the strain energy dispersion coefficient to correct the expression in step B24 to obtain the rock energy strength criterion under the condition of thermal water-hydraulic coupling: Where N is the strain energy dispersion coefficient, n is the second fitting parameter; B26, let the rock energy strength criterion make The uniaxial strength expression of multi-field coupled rock theory is obtained:

6. The surrounding rock classification correction method considering the coupling effects of heat, water and force according to any one of claims 1 to 5, characterized in that: When correcting the BQ classification, the saturated uniaxial strength of rock R c and the quantitative index K of the grading factor v The conditions are as follows: when R c >90K v +30, R c =90K v +30; when K v >0.04R c When K v =0.04R c +0.

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7. The surrounding rock classification correction method considering the thermal, water and mechanical coupling effects according to any one of claims 1 to 5, characterized in that: The standard sample is a granite sample.

8. The surrounding rock classification correction method considering the thermal, water and mechanical coupling effects according to any one of claims 1 to 5, characterized in that: After obtaining the basic rock mass quality indicators BQ, Q and RMi, it also includes: According to the classification standards of the basic rock mass quality indicators BQ, Q and RMi and their corresponding rock mass quality grades, the rock mass quality grade of the project to be studied is obtained.

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