A method for determining peak strength and residual strength of surrounding rock of a cavern based on drilling data

Abstract

This invention provides a method for determining the peak strength and residual strength of surrounding rock in underground caverns based on borehole data. The method includes arranging geological boreholes at one sidewall, the arch, and the face of the underground cavern; testing the longitudinal wave velocity of the rock mass at different depths within the boreholes; determining the thickness of the loosened and fractured rock mass to be excavated based on the wave velocity; calculating the volume and joint condition coefficient of intact and loosened / fractured rock mass blocks; and calculating the GSI value of the intact rock mass and the residual GSI of the loosened / fractured rock mass. r The peak strength of intact rock mass and the residual strength parameters of relaxed fractured rock mass are estimated using the generalized Hoek-Brown failure criterion. This invention can accurately and quickly estimate the peak strength of intact rock mass and the residual strength parameters of relaxed fractured rock mass, and has the advantages of good economy and convenient on-site operation. It can provide a reliable basis for the stability evaluation and support design of surrounding rock in underground engineering, optimize design schemes, and save engineering costs.

Description

Technical Field

[0001] This invention relates to a method for determining the peak strength and residual strength of the surrounding rock of a cavern, belonging to the field of underground engineering technology. Background Technology

[0002] In engineering projects such as tunnels, underground caverns, and roadways, a better understanding of the strength characteristics of rock masses, including peak and residual strength, will help save costs and improve safety. However, obtaining rock mass mechanical parameters quickly and accurately is a challenging task.

[0003] In-situ tests of rock masses, such as uniaxial compression, triaxial compression, and shear tests, are the most direct methods for studying rock mass strength. Although in-situ tests can obtain the peak strength and residual strength parameters of jointed rock masses, most tests are time-consuming, expensive, and technically challenging.

[0004] Rock mass classification is an important indicator for evaluating rock mass quality. Establishing a link between rock mass classification and rock mass mechanical parameters is a relatively convenient and objective method for determining these parameters. However, among current rock mass classification systems, only the GSI classification system is directly linked to rock mass parameters. When using GSI classification, the characteristics of rock mass structure and structural planes are mainly described qualitatively. This method relies on the engineer's extensive experience and reasonable judgment, and thus carries a certain degree of subjectivity.

[0005] Drilling is a primary method in engineering exploration, capable of revealing various information such as underground faults, joints, and groundwater. It is also economical and highly practical. A key question is how to utilize drilling data to accurately quantify the GSI values ​​of rock masses in different locations, particularly the residual GSI of excavated, loosened, and fractured rock masses. r This allows for the accurate and rapid acquisition of peak and residual strength parameters of the rock mass, which is particularly important for engineers to conduct stability analysis and evaluation of the surrounding rock of underground caverns. It can also reduce the influence of personal subjective factors. Summary of the Invention

[0006] The purpose of this invention is to provide a method for determining the peak strength and residual strength of the surrounding rock in a cavern based on borehole data. This method can accurately quantify the GSI values ​​of the rock mass in both intact and excavated loose and fractured zones, and then accurately and quickly determine the peak strength and residual strength characteristics of the surrounding rock in the field based on the Hoek-Brown criterion.

[0007] Therefore, the technical solution adopted by the present invention is as follows:

[0008] A method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data, characterized by the following steps:

[0009] (1) A geological borehole is arranged on one side wall, the arch, and the front face of the underground cavern;

[0010] (2) Test the longitudinal wave velocity of the rock mass at different depths in the geological borehole, and determine the thickness of the loosened and fractured rock mass to be excavated based on the wave velocity;

[0011] (3) Based on the borehole video data and core sample information, the volume V of the intact rock mass was calculated. b and the volume V of the loosened and fractured rock mass br and the joint condition coefficient J of intact rock mass c and joint condition coefficient J of relaxed fractured rock mass cr ;

[0012] (4) According to The GSI values ​​of intact rock masses and residual GSI values ​​of relaxed fractured rock masses were calculated respectively. r value;

[0013] (5) The peak strength of intact rock mass and the participating strength parameters of relaxed fractured rock mass are estimated by using the generalized Hoek-Brown failure criterion, including the deformation modulus, internal friction angle, cohesion, compressive strength and tensile strength of rock mass.

[0014] Preferably, for drilling, the drilling depth is 2 to 3 times the hole diameter, while ensuring that the three holes are spatially perpendicular to each other.

[0015] Furthermore, core data was obtained from the borehole, and cores with good integrity were collected for indoor uniaxial compression tests to obtain the uniaxial saturated compressive strength σ of the rock block. c ;

[0016] Furthermore, regarding the determination of the thickness of the excavated loose and fractured rock mass, the average longitudinal wave velocity v0 of the deep intact rock mass is first determined. Based on the principle that the longitudinal wave velocity of the excavated loose and fractured rock mass is lower than that of the intact rock mass, the thickness of the excavated loose and fractured rock mass in each borehole is determined.

[0017] Furthermore, a borehole panoramic camera was used to digitally image the borehole wall, obtaining planar unfolded images of the top arch, sidewalls, and the front face of the borehole. The planar unfolded images of the borehole were analyzed to obtain the spatial orientation of the dominant structural planes. Based on the determined excavated loosening fracture zone and intact rock mass zone, a set of dominant structural planes with the smallest spacing corresponding to the intact rock mass zone in each of the three boreholes was statistically obtained, with corresponding spacings of s1, s2, and s3, respectively. Similarly, a set of dominant structural planes with the smallest spacing corresponding to the excavated loosening fracture zone in each of the three boreholes was statistically obtained, with corresponding spacings of s1, s2, and s3, respectively. 1r s 2r s 3r ;

[0018] According to V b = s1s2s3 calculates the initial volume V of the rock block in the intact rock mass region b According to V br = s 1r s 2r s 3r The residual rock volume V of the excavated relaxed fractured zone was calculated. br .

[0019] Furthermore, the deformation modulus E of the intact rock mass m Deformation modulus E of relaxed fractured rock mass mr The calculation method is as follows:

[0020] When σ c When ≤100MPa:

[0021]

[0022] When σ c When >100 MPa:

[0023]

[0024] In the formula, D is the excavation disturbance parameter, due to GSI and GSI r The impact of excavation damage has been taken into account during the value selection process, so D = 0 is used when calculating parameters using this method.

[0025] Peak compressive strength σ of intact rock mass cm Residual compressive strength of relaxed fractured rock mass The calculation method is as follows:

[0026]

[0027] Peak internal friction angle φ of intact rock mass, residual internal friction angle φ of relaxed fractured rock mass r The calculation method is as follows:

[0028]

[0029] Peak cohesion c of intact rock mass, residual cohesion c of relaxed fractured rock mass r The calculation method is as follows:

[0030]

[0031] In the formula: ,

[0032] For tunnel engineering:

[0033]

[0034] Peak tensile strength σ of intact rock mass t Residual tensile strength of relaxed fractured rock mass The calculation method is as follows:

[0035]

[0036] in,

[0037]

[0038]

[0039]

[0040] m i These are constants related to lithology.

[0041] The beneficial effects of this invention are as follows: This invention provides a rapid method for determining the peak strength and residual strength of the surrounding rock of a cavern based on borehole data. It uses borehole acoustic testing results to obtain the thickness of the excavated, relaxed, and fractured rock mass. Combined with core samples and borehole photographs, the GSI values ​​of the intact rock mass and the relaxed, fractured rock mass are calculated respectively. Furthermore, the peak strength of the intact rock mass and the residual strength parameters of the relaxed, fractured rock mass can be accurately and quickly estimated using the generalized Hoek-Brown failure criterion. This method has advantages such as good economy and convenient on-site operation, and can provide a reliable basis for the stability evaluation and support design of surrounding rock in underground engineering, optimizing design schemes and saving engineering costs. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in this embodiment or the prior art, the accompanying drawings used in the embodiment will be briefly introduced below.

[0043] Figure 1 This is a flowchart illustrating the method for determining the peak and residual strength parameters of the surrounding rock in the cavern according to the present invention.

[0044] Figure 2 This is a schematic diagram of the geological borehole layout in an embodiment of the present invention;

[0045] Figure 3 This is a schematic diagram of the borehole acoustic test results in an embodiment of the present invention.

[0046] Figure 4 This is a schematic diagram illustrating the optimal spacing values ​​for the advantageous structural surfaces based on borehole imaging in an embodiment of the present invention. Detailed Implementation

[0047] Referring to the accompanying drawings, the present invention provides a method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data. The specific implementation steps are as follows:

[0048] Step 1: Drill one geological borehole each on one side wall, the arch, and the front face of the underground cavern, labeled 2, 1, and 3 respectively. The borehole depth should be 2-3 times the cavern diameter. Ensure the three boreholes are perpendicular to each other. Core samples are taken from these boreholes to obtain core data. Collect cores with good integrity and conduct uniaxial compression tests to determine the uniaxial saturated compressive strength σ of the rock blocks. c ;

[0049] Step 2: Clean the geological borehole and test the longitudinal wave velocity of the rock mass at different depths inside the borehole;

[0050] Step 3: Analyze the P-wave velocity data of the rock mass. Based on the P-wave velocity, determine the excavation of the loosened fractured zone and the intact rock mass zone. First, determine the average P-wave velocity v0 of the deep intact rock mass. Based on the principle that the P-wave velocity of the excavated loosened fractured rock mass is lower than that of the intact rock mass, determine the thickness of the loosened fractured rock mass excavated in each borehole. Typical acoustic wave test results and the method for determining the thickness of the loosened fractured rock mass are as follows: Figure 3 As shown;

[0051] Step 4: Use a borehole panoramic camera to digitally image the borehole wall and obtain planar unfolded images of the top arch, sidewalls and the front face of the borehole.

[0052] Step 5: Analyze the planar unfolded image of the borehole to obtain the spatial orientation of the dominant structural surfaces in the image. Based on the excavated relaxed fracture zone and intact rock mass zone determined in Step 3, statistically analyze the dominant structural surfaces with the smallest spacing corresponding to the intact rock mass zone in each of the three boreholes. Here, these are numbered as the first joint (top arch borehole), the second joint (sidewall borehole), and the third joint (face borehole), with corresponding spacings of s1, s2, and s3, respectively. Similarly, statistically analyze the dominant structural surfaces with the smallest spacing corresponding to the excavated relaxed fracture zone in each of the three boreholes. Here, these are numbered as the fourth joint (top arch borehole), the fifth joint (sidewall borehole), and the sixth joint (face borehole), with corresponding spacings of s1, s2, and s3, respectively. 1r s 2r s 3r The minimum spacing of a certain borehole dominant structural plane is defined as follows: Figure 4 As shown;

[0053] Step 6: According to V b = s1s2s3 calculates the initial volume V of the rock block in the intact rock mass region b , and according to V br =s 1r s2r s 3r The residual rock volume V of the excavated relaxed fractured zone was calculated. br ;

[0054] Step 7: Based on the planar unfolded image of the borehole described in Step 4, obtain the macroscopic joint fluctuation score J for the intact rock mass zone and the excavated loose fractured zone according to Table 1. w J wr .

[0055] Table 1 Jointed macroscopic volatility J w score

[0056]

[0057] Step 8: Based on the dominant structural planes revealed by the borehole core as described in Step 1, obtain the joint micro-smoothness scores J for the intact rock mass area and the excavated loose and fractured area, respectively, according to Table 2. s J sr .

[0058] Table 2 Joint microsmoothness J s score

[0059]

[0060] Step 9: Based on the filling state of the dominant structural planes revealed by the borehole core as described in Step 1, obtain the structural plane alteration influence coefficient score J for the intact rock mass area and the excavated loose and fractured area, respectively, according to Table 3. A J Ar .

[0061] Table 3. Structural surface alteration influence coefficient J A score

[0062]

[0063] Step 10: According to J c =J w J s / J A The joint condition coefficient J of the intact rock mass zone was calculated. c According to J cr =J wr J sr / J Ar The residual joint condition coefficient J of the excavated relaxed fractured zone was calculated. cr .

[0064] Step 11: According to The initial volume V of the rock blocks in the intact rock mass area b and joint condition coefficient J cSubstituting the values, the GSI of the intact rock mass is calculated; the residual rock block volume V in the relaxed fractured zone is calculated. br and residual joint condition coefficient J cr Substituting the values, the residual GSI of the relaxed fractured rock mass can be calculated. r ;

[0065] Step 12: Utilize the intact rock mass GSI and the residual GSI of the relaxed fractured rock mass obtained in Step 11 r The peak strength and residual strength of the surrounding rock were calculated separately, including the deformation modulus, internal friction angle, cohesion, compressive strength, and tensile strength of the rock mass:

[0066] In step 12, the deformation modulus E of the intact rock mass m Deformation modulus E of relaxed fractured rock mass mr The calculation method is as follows:

[0067] When σ c When ≤100MPa:

[0068]

[0069] When σ c When >100 MPa:

[0070]

[0071] In the formula, D is the excavation disturbance parameter, due to GSI and GSI r The impact of excavation damage has been taken into account during the value selection process, so D = 0 is used when calculating parameters using this method.

[0072] The peak compressive strength σ of the intact rock mass in step 12 cm Residual compressive strength of relaxed fractured rock mass The calculation method is as follows:

[0073]

[0074] In step 12, the peak internal friction angle φ of the intact rock mass and the residual internal friction angle φ of the relaxed fractured rock mass are... r The calculation method is as follows:

[0075]

[0076] In step 12, the peak cohesion c of the intact rock mass and the residual cohesion c of the relaxed fractured rock mass are... r The calculation method is as follows:

[0077]

[0078] In the formula: ,

[0079] For tunnel engineering:

[0080]

[0081] Peak tensile strength σ of intact rock mass in step 12 t Residual tensile strength of relaxed fractured rock mass The calculation method is as follows:

[0082]

[0083] in,

[0084]

[0085]

[0086]

[0087] m i These are constants related to lithology.

[0088] This invention has used specific examples to illustrate the principles and implementation methods of the invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the invention; this part should not be construed as a limitation of the invention. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the invention, and these all fall within the protection scope of the invention.

Claims

1. A method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data, characterized in that... Includes the following steps: (1) A geological borehole is arranged on one side wall, the arch, and the front face of the underground cavern, and the three boreholes are perpendicular to each other in space; (2) Test the longitudinal wave velocity of the rock mass at different depths in the geological borehole, and determine the thickness of the loosened and fractured rock mass to be excavated based on the wave velocity; (3) According to the drilling camera data and the core situation, the complete rock mass rock volume V b and the loose broken rock mass rock volume V br are calculated, and the joint condition coefficient J c of the complete rock mass and the joint condition coefficient J cr of the loose broken rock mass are calculated; (4) According to The GSI values ​​of intact rock masses and residual GSI values ​​of relaxed fractured rock masses were calculated respectively. r value; (5) The peak strength of intact rock mass and the participating strength parameters of relaxed fractured rock mass are estimated by using the generalized Hoek-Brown failure criterion, including the deformation modulus, internal friction angle, cohesion, compressive strength and tensile strength of rock mass; In step (3), a borehole panoramic camera is used to digitally image the borehole wall, obtaining planar unfolded images of the top arch, sidewalls, and front face of the borehole. The planar unfolded images of the borehole are analyzed to obtain the spatial orientation of the dominant structural planes in the images. Based on the determined excavation relaxation fracture zone and intact rock mass zone, a set of dominant structural planes with the smallest spacing corresponding to the intact rock mass zone in the three boreholes are statistically obtained, with the corresponding spacings being s1, s2, and s3, respectively. A set of dominant structural planes with the smallest spacing corresponding to the excavation relaxation fracture zone in the three boreholes are statistically obtained, with the corresponding spacings being s1, s2, and s3, respectively. 1r s 2r s 3r According to V b = s1s2s3 calculates the initial volume V of the rock block in the intact rock mass region b According to V br = s 1r s 2r s 3r The residual rock volume V of the excavated relaxed fractured zone was calculated. br .

2. The method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data as described in claim 1, characterized in that... For drilling, the drilling depth is 2 to 3 times the hole diameter, while ensuring that the three holes are spatially perpendicular to each other.

3. The method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data as described in claim 1, characterized in that... Through the core data of the borehole, a core with good integrity is collected, a uniaxial compression test is conducted in a laboratory, and a uniaxial saturated compressive strength σ c of the rock mass is obtained.

4. The method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data as described in claim 1, characterized in that... To determine the thickness of the excavated loose and fractured rock mass, the average longitudinal wave velocity v0 of the deep intact rock mass is first determined. Based on the principle that the longitudinal wave velocity of the excavated loose and fractured rock mass is lower than that of the intact rock mass, the thickness of the excavated loose and fractured rock mass in each borehole is determined.

5. The method for determining the peak strength and residual strength of cavern surrounding rock based on borehole data as described in claim 1, characterized in that... Deformation modulus E of intact rock mass m Deformation modulus E of relaxed fractured rock mass mr The calculation method is as follows: When σ c When ≤100MPa: When σ c When >100 MPa: In the formula, D is the excavation disturbance parameter, due to GSI and GSI r The impact of excavation damage has been taken into account during the value selection process, so D = 0 is used when calculating parameters using this method; Peak compressive strength σ of intact rock mass cm Residual compressive strength of relaxed fractured rock mass The calculation method is as follows: Peak internal friction angle φ of intact rock mass, residual internal friction angle φ of relaxed fractured rock mass r The calculation method is as follows: Peak cohesion c of intact rock mass, residual cohesion c of relaxed fractured rock mass r The calculation method is as follows: In the formula: , For tunnel engineering: Peak tensile strength σ of intact rock mass t Residual tensile strength of relaxed fractured rock mass The calculation method is as follows: in, m i These are constants related to lithology.

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