Valuing method of underground cavern group surrounding rock support design parameters

Abstract

The invention discloses a valuing method of underground cavern surrounding rock support design parameters, relates to the field of testing or analyzing materials by means of measuring chemical or physical properties of the materials, and aims to improve pertinence and accuracy of the underground cavern surrounding rock support design parameters. According to the technical scheme, the value taking method for the surrounding rock support design parameters of the underground cavern group comprises the steps that firstly, a plurality of representative rock masses are obtained from the underground cavern group to be subjected to support design, then the uniaxial compressive strength of each rock mass is tested, rock mass quality grading is carried out, the support design parameters are preliminarily planned, and the support design parameters of the underground cavern group are calculated; then rock mechanics tests are carried out on rock masses in different occurrence environments, different rock mass types and different construction scenes respectively, rock mechanics test data are obtained, corresponding uniaxial compressive strength is calculated, and then support design parameters of the rock masses are determined; the blindness and limitation of the surrounding rock support design mainly according to the uniaxial compressive strength of the rock mass in the existing specification are avoided. The method is used for underground cavern surrounding rock support design.

Description

Technical Field

[0001] The present invention relates to the field of testing or analyzing materials by measuring the chemical or physical properties of materials, and in particular to the field of rock engineering mechanics. Specifically, it is a method for determining the support design parameters of the surrounding rock of an underground cavern group. Background Art

[0002] The development and utilization of deep underground space face problems such as complex geological occurrence environments and variable rock mass properties, posing huge challenges to the support design of large underground cavern groups and seriously threatening the construction and operation safety of deep underground space. At present, the support design of large underground cavern groups first considers the uniaxial compressive strength of the rock mass, divides the rock mass grade, and then conducts the support design accordingly, which has great blindness and limitations and is significantly empirical. The stress state of the surrounding rock is significantly correlated with the occurrence location of the surrounding rock, the construction process, the natural quality of the rock mass, the groundwater state, etc., and the uniaxial compressive strength is the mechanical parameter of the rock under ideal conditions. Therefore, it is necessary to systematically carry out rock mechanics tests for different environments, different rock occurrence states, and whether the rock mass is intact, etc., to make the support design of the surrounding rock of large underground cavern groups more targeted. Summary of the Invention

[0003] The present invention provides a method for determining the support design parameters of the surrounding rock of an underground cavern group, aiming to improve the pertinence and accuracy of the support design parameters of the surrounding rock of the underground cavern group.

[0004] The technical solution adopted by the present invention is: a method for determining the support design parameters of the surrounding rock of an underground cavern group, including the following steps:

[0005] S1. Obtain a plurality of representative rock masses from the underground cavern group where the support design is to be carried out.

[0006] S2. Test the uniaxial compressive strength of each rock mass, conduct rock mass quality classification, and preliminarily determine the support design parameters.

[0007] Specifically: the rock mass quality is divided into Class I, Class II, Class III, Class IV, and Class V surrounding rocks.

[0008] S3. Conduct tests respectively according to the characteristics of each rock mass.

[0009] S3-1. For the rock mass without surrounding pressure and repeatedly disturbed by construction, conduct a uniaxial cyclic loading and unloading test to obtain the uniaxial cyclic compressive strength of the rock mass, and then calculate the uniaxial compressive strength. The uniaxial compressive strength = uniaxial cyclic compressive strength / index value C, and then determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength; where the index value C is the ratio of the measured uniaxial cyclic compressive strength to the measured uniaxial compressive strength of the rock mass.

[0010] S3-2. For the rock mass with confining pressure around and free from construction disturbance, conduct a conventional triaxial loading test to obtain the triaxial compressive strength of the rock mass, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass based on the calculated uniaxial compressive strength. Among them, the strengthening coefficient A is the ratio of the measured triaxial compressive strength to the measured uniaxial compressive strength of the rock mass.

[0011] S3-3. For the rock mass with confining pressure around and subjected to repeated construction disturbance, conduct a triaxial cyclic loading and unloading test to obtain the triaxial cyclic compressive strength of the rock mass, then calculate the triaxial compressive strength. The triaxial compressive strength = triaxial cyclic compressive strength / index value B. Then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass based on the calculated uniaxial compressive strength. Among them, the index value B is the ratio of the measured triaxial cyclic compressive strength to the measured triaxial compressive strength of the rock mass.

[0012] To better simulate the repeated construction disturbance, furthermore: in steps S3-1 and S3-3, the frequency and intensity of cyclic loading and unloading are consistent with the repeated construction disturbance.

[0013] S3-4. For the rock mass with only one side facing free space, first conduct a free-space loading test to obtain the inflection point strength, then calculate the triaxial compressive strength according to the corresponding relationship F(N) between the triaxial compressive strength and the inflection point strength, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass based on the calculated uniaxial compressive strength. Among them, the inflection point strength refers to the strength corresponding to the inflection point of the strain in the stress-strain curve of the rock mass. The corresponding relationship F(N) is obtained by fitting the measured triaxial compressive strength and the measured inflection point strength of multiple groups of this rock mass under the same confining pressure conditions.

[0014] To make the free-space loading test closer to the actual stress condition of the rock mass at the tunnel face, furthermore: in step S3-4, the instrument used for the free-space loading test is a true triaxial instrument, and the confining pressure condition of the test is consistent with the in-situ measured ground stress.

[0015] S3-5. For the rock mass with groundwater, conduct a loading test under the combined action of water pressure and axial pressure to measure the long-term creep strength. Then calculate the triaxial compressive strength according to the corresponding relationship G(N) between the triaxial compressive strength and the creep strength, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass based on the calculated uniaxial compressive strength. Among them, the corresponding relationship G(N) is obtained by fitting the measured triaxial compressive strength and the measured creep strength of multiple groups of this rock mass under the same confining pressure conditions.

[0016] In order to make the loading test under the combined action of water pressure and axial pressure closer to the actual situation, further: in step S3-5, when conducting the loading test under the combined action of water pressure and axial pressure, first immerse the specimen in water, then apply water confining pressure to the specimen to a predetermined value and maintain the water confining pressure, where the water confining pressure is consistent with the water pressure actually borne by the rock mass, and finally apply axial load to the specimen until the specimen fails or the axial load reaches the preset value.

[0017] S3-6. For a rock mass with initial damage, prefabricate damage to the rock mass according to the initial damage, then conduct a uniaxial loading test to obtain the damaged compressive strength, and then calculate the triaxial compressive strength according to the corresponding relationship H(N) between the triaxial compressive strength and the damaged compressive strength. Then calculate the uniaxial compressive strength, where the uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength. Among them, the corresponding relationship H(N) is obtained by fitting the triaxial compressive strength and the damaged compressive strength of multiple groups of this rock mass under the same initial damage conditions.

[0018] In order to make the uniaxial loading test closer to the actual situation, further: in step S3-6, the initial damage of the rock mass includes joints, fissures, and faults. The prefabricated damage to the rock mass is prefabricated fissures, and the number, angle, length, and width of the fissures are determined according to the in-situ rock mass behavior.

[0019] In order to make the support design parameters of the rock mass more accurate, further: in steps S3-4, S3-5, and S3-6, the support method and parameters are also corrected according to the deformation and failure characteristics of the rock mass. Among them, the deformation and failure characteristics include tensile failure, shear failure, and ejection failure. The correction method is: use rapid closed shotcrete to suppress ejection failure, use prestressed anchor bolts to suppress shear failure, and use ordinary mortar anchor bolts to suppress tensile failure.

[0020] The beneficial effects of the present invention are as follows: The present invention conducts rock mechanics tests on rock masses in different occurrence environments, different rock types, and different construction scenarios respectively, obtains rock mechanics test data, calculates the corresponding uniaxial compressive strength, and then determines the support design parameters of the rock mass according to the calculated uniaxial compressive strength, avoiding the blindness and limitations of the existing specifications that mainly design the surrounding rock support only according to the uniaxial compressive strength of the rock mass, and is a beneficial improvement to the surrounding rock support design of large underground cavern groups. The present invention conducts tests and analyzes the mechanical properties of rock masses in complex occurrence environments, reflects the damage mechanisms of rock masses in various scenarios, determines the support design parameters of rock masses more targeted and accurately, is more refined than the existing support design methods, and has positive significance for ensuring the stability of the surrounding rock and optimizing the use of materials, and is a breakthrough in the traditional surrounding rock support design of large underground cavern groups. Specific embodiments

[0021] The present invention will be further described below.

[0022] The method for determining the support design parameters of the surrounding rock of the underground cavern group of the present invention conducts different rock mechanics tests corresponding to the possible states that the surrounding rock of the large underground cavern group may face, obtains rock mechanics test data, and avoids the blindness and limitations of the existing specifications in determining the support design of the surrounding rock only mainly based on the uniaxial compressive strength. The method for determining the support design parameters of the surrounding rock of the underground cavern group includes the following steps.

[0023] S1. Obtain a plurality of representative rock masses from the underground cavern group for which the support design is to be carried out.

[0024] S2. Test the uniaxial compressive strength of each rock mass, conduct rock mass quality classification, and preliminarily determine the support design parameters. For example, after testing the uniaxial compressive strength of each rock mass, classify the rock mass quality into Class I, Class II, Class III, Class IV, and Class V surrounding rocks according to the existing specifications. When preliminarily determining the support design parameters, the current specifications such as the "Design Code for Underground Powerhouses of Hydropower Stations" and the "Design Code for Hydraulic Tunnels" can be used as the basis.

[0025] S3. Conduct tests respectively according to the characteristics of each rock mass. Different tests are conducted respectively according to the position, stress, properties, and construction disturbance conditions of each rock mass.

[0026] S3-1. For the rock mass without surrounding pressure and repeatedly disturbed by construction, this rock mass is mostly free face, basically without surrounding pressure. Conduct a uniaxial cyclic loading and unloading test on the rock mass to simulate the repeated disturbance of construction, obtain the uniaxial cyclic compressive strength of the rock mass, and then calculate the uniaxial compressive strength. Uniaxial compressive strength = uniaxial cyclic compressive strength / index value C. Then determine the support design parameters of this rock mass according to the calculated uniaxial compressive strength. Among them, the index value C is the ratio of the measured uniaxial cyclic compressive strength to the measured uniaxial compressive strength of this rock mass.

[0027] S3-2. For the rock mass with surrounding pressure and not disturbed by construction, this rock mass is a deep unloaded rock mass. Conduct a conventional triaxial loading test on the rock mass to obtain the triaxial compressive strength of the rock mass, and then calculate the uniaxial compressive strength. Uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of this rock mass according to the calculated uniaxial compressive strength. When determining the support design parameters, the existing industry specifications can be consulted. Among them, the strengthening coefficient A is the ratio of the measured triaxial compressive strength to the measured uniaxial compressive strength of this rock mass.

[0028] S3-3. For a rock mass with confining pressure around it and subjected to repeated construction disturbances, this rock mass is a deep rock mass, but due to repeated construction disturbances, a triaxial cyclic loading and unloading test is carried out on the rock mass to simulate the repeated construction disturbances, and the triaxial cyclic compressive strength of the rock mass is obtained. Then, the triaxial compressive strength is calculated, where the triaxial compressive strength = triaxial cyclic compressive strength / index value B. Next, the uniaxial compressive strength is calculated, where the uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, the support design parameters of this rock mass are determined based on the calculated uniaxial compressive strength. Among them, the meaning of the strengthening coefficient A is referred to in step S3-2; the index value B is the ratio of the measured triaxial cyclic compressive strength to the measured triaxial compressive strength of this rock mass.

[0029] In steps S3-1 and S3-3, cyclic loading and unloading are used to determine the support design of surrounding rocks under cyclic loading and unloading conditions, such as conditions like compressed air energy storage and stress wave rock breaking caused by blasting excavation. To better simulate the repeated construction disturbances, in steps S3-1 and S3-3, the frequency and intensity of cyclic loading and unloading are consistent with the repeated construction disturbances, that is, the frequency and intensity of cyclic loading and unloading are determined according to the construction disturbances.

[0030] S3-4. For a rock mass with only one side facing the open air, this rock mass is generally a rock mass located at the tunnel face. First, an open-air loading test is carried out on this rock mass to obtain the inflection point strength. Then, according to the corresponding relationship F(N) between the triaxial compressive strength and the inflection point strength, the triaxial compressive strength is calculated. Next, the uniaxial compressive strength is calculated based on the calculated triaxial compressive strength, where the uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, the support design parameters of this rock mass are determined based on the calculated uniaxial compressive strength.

[0031] The air-free surface loading test mainly focuses on the mechanical property mechanism of rock mass with one side being air-free, and is used to determine the support design of rock when no closing measures are taken after the surrounding rock is excavated. The air-free surface loading test focuses on obtaining the deformation and failure mutation characteristics of the rock mass when it is approaching failure under the condition of extremely high in-situ stress, obtaining the stress-strain curve of the rock mass under specific confining pressure conditions, and extracting the strength corresponding to the inflection point of the strain, that is, obtaining the inflection point strength. The air-free surface loading test refers to that after the rock specimen is prepared, for example, the rock is made into a cubic specimen, the specimen has no confining pressure in one horizontal direction, has confining pressure in another horizontal direction, and the two horizontal directions are perpendicular to each other. Then, an axial load is applied to the specimen, and the direction of the axial load is vertically downward, so that the air-free surface loading test is close to the actual stress condition of the rock mass at the tunnel face. The instrument used for the air-free surface loading test is a true triaxial instrument, and the confining pressure condition of the test is consistent with the in-situ stress measured on site. The inflection point strength refers to the strength corresponding to the inflection point of the strain in the stress-strain curve of the rock mass during the air-free surface loading test. The corresponding relationship F(N) is a functional relationship obtained by fitting the measured triaxial compressive strength and the measured inflection point strength of multiple groups of this rock mass under the same confining pressure condition, and software such as origin and excel can be used for fitting. Measure the inflection point strength of the specimen under a certain confining pressure condition, measure the triaxial compressive strength of the specimen under the same confining pressure condition, and form a set of data corresponding relationship; adjust the confining pressure condition to form N sets of data corresponding relationships, where N is a positive integer greater than 2, and the corresponding relationship F(N) can be obtained by fitting through software.

[0032] S3-5. For a rock mass with groundwater, regardless of its confining pressure condition and whether it is disturbed by construction, conduct a loading test under the combined action of water pressure and axial pressure on the rock mass to measure the long-term creep strength; then, according to the corresponding relationship G(N) between the triaxial compressive strength and the creep strength, calculate the triaxial compressive strength; then calculate the uniaxial compressive strength according to the calculated triaxial compressive strength, uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A; finally, determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength.

[0033] The loading test under the combined action of water pressure and axial pressure aims at the mechanical properties of rock mass when groundwater is abundant and the rock mass is under the combined action of high in-situ stress and high groundwater. According to the long-term water-rock coupling characteristics, the surrounding rock support technology under the combined action of high in-situ stress and high groundwater can be proposed pertinently. For the loading test under the combined action of water pressure and axial pressure, first immerse the specimen directly in water, then apply water confining pressure to the specimen to a predetermined value and keep the water confining pressure, where the water confining pressure is consistent with the actual water pressure borne by the rock mass, making the loading test under the combined action of water pressure and axial pressure closer to the actual situation. Finally, apply axial load to the specimen until the specimen fails or the axial load reaches the preset value. The long-term strength of creep is the strength corresponding to the failure of the specimen under the preset water confining pressure condition. The corresponding relationship G(N) is the functional relationship obtained by fitting the measured triaxial compressive strength and the measured creep strength of multiple groups of this rock mass under the same confining pressure condition, and software such as origin and excel can be used for fitting.

[0034] For the loading test under the combined action of water pressure and axial pressure, the pressure water for applying water confining pressure to the specimen is pressed into micro-pores and micro-fractures in the form of a medium. Therefore, it is necessary to study the support and expansion effect of the water medium on pores and fractures, obtain the creep test curve, and focus on comparing and analyzing the long-term mechanical properties of the rock mass under the direct action of traditional MTS triaxial creep and water confining pressure. By analyzing the differences in creep time curves and using microscopic scanning (CT, electron microscope scanning) to obtain the promotion mechanism of water on internal damage of the rock mass, and using the fractal dimension to quantitatively describe the relationship between microscopic damage and strength, a support technology for weakening the deterioration influence mechanism of water confining pressure can be proposed from the perspective of quantitatively controlling microscopic damage.

[0035] S3-6. For a rock mass with initial damage, that is, for an incomplete rock mass with joints, fractures, faults, etc., prefabricate damage to the rock mass according to the initial damage. For example, prefabricate fractures in the specimen by wire cutting to simulate the initial damage. The number, angle, length, and width of the fractures are determined according to the in-situ rock mass state, making the specimen with fractures as close as possible to the rock mass with initial damage. Then, conduct a uniaxial loading test. Generally, use a press to conduct uniaxial loading on the specimen to obtain the damage compressive strength. Then, according to the corresponding relationship H(N) between the triaxial compressive strength and the damage compressive strength, calculate the triaxial compressive strength, and then calculate the uniaxial compressive strength according to the calculated triaxial compressive strength. Uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength.

[0036] The damage compressive strength is the peak strength at which the specimen with prefabricated damage fails under uniaxial loading, that is, the strength corresponding to the highest point of the stress-strain curve. The corresponding relationship H(N) is a functional relationship obtained by fitting the triaxial compressive strength and the damage compressive strength of multiple groups of this rock mass under the same initial damage conditions, and software such as origin and excel can be used for fitting.

[0037] Prefabricate damage to the rock mass and conduct uniaxial loading tests. Focus on analyzing the mechanical properties of the rock mass with initial damage such as natural fissures or faults in the rock mass. According to the damage development characteristics of the prefabricated damage (fractures, faults, weak structural planes), obtain the stress-strain curve, and use it to specifically propose support methods for stopping cracks in the surrounding rock and controlling damage development.

[0038] Finally, in steps S3-1 to S3-6, the support design parameters corresponding to the rock mass are determined according to the calculated uniaxial compressive strength, which is actually a correction of the initially proposed support design parameters in step S2. In order to make the support design parameters of the rock mass more accurate, in steps S3-4, S3-5, and S3-6, the support method and parameters are also corrected according to the deformation and failure characteristics of the rock mass; among them, the deformation and failure characteristics include tensile failure, shear failure, and ejection failure; the correction method is carried out according to the rock mass damage mechanism. For example, the correction method is: use rapid sealing shotcrete to inhibit ejection failure, use prestressed anchor bolts to inhibit shear failure, and use ordinary mortar anchor bolts to inhibit tensile failure.

Claims

1. A method for determining the design parameters of surrounding rock support for underground cavern groups, characterized in that, It includes the following steps: S1. Obtain multiple representative rock masses from the underground cavern group where the support design is to be carried out; S2. Test the uniaxial compressive strength of each rock mass, conduct rock mass quality classification, and preliminarily determine the support design parameters; S3. Conduct tests respectively according to the characteristics of each rock mass; S3-1. For the rock mass without surrounding pressure and repeatedly disturbed by construction, conduct uniaxial cyclic loading and unloading tests to obtain the uniaxial cyclic compressive strength of the rock mass, then calculate the uniaxial compressive strength. The uniaxial compressive strength = uniaxial cyclic compressive strength / index value C, and then determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength. Among them, the index value C is the ratio of the measured uniaxial cyclic compressive strength to the measured uniaxial compressive strength of the rock mass; S3-2. For the rock mass with surrounding pressure and not disturbed by construction, conduct conventional triaxial loading tests to obtain the triaxial compressive strength of the rock mass, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A, and finally determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength. Among them, the strengthening coefficient A is the ratio of the measured triaxial compressive strength to the measured uniaxial compressive strength of the rock mass; S3-3. For the rock mass with surrounding pressure and repeatedly disturbed by construction, conduct triaxial cyclic loading and unloading tests to obtain the triaxial cyclic compressive strength of the rock mass, then calculate the triaxial compressive strength. The triaxial compressive strength = triaxial cyclic compressive strength / index value B, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A, and finally determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength. Among them, the index value B is the ratio of the measured triaxial cyclic compressive strength to the measured triaxial compressive strength of the rock mass; S3-4. For the rock mass with only one side facing the open space, first conduct open space loading tests to obtain the inflection point strength, then calculate the triaxial compressive strength according to the corresponding relationship F(N) between the triaxial compressive strength and the inflection point strength, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A, and finally determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength. Among them, the inflection point strength refers to the strength corresponding to the inflection point of the strain in the stress-strain curve of the rock mass; the corresponding relationship F(N) is obtained by fitting the measured triaxial compressive strength and the measured inflection point strength of multiple groups of this rock mass under the same surrounding pressure conditions; S3-5. For the rock mass with groundwater, conduct loading tests under the combined action of water pressure and axial pressure to measure the creep long-term strength; then calculate the triaxial compressive strength according to the corresponding relationship G(N) between the triaxial compressive strength and the creep strength, then calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A, and finally determine the support design parameters of the rock mass according to the calculated uniaxial compressive strength. Among them, the corresponding relationship G(N) is obtained by fitting the measured triaxial compressive strength and the measured creep strength of multiple groups of this rock mass under the same surrounding pressure conditions; S3-6. For a rock mass with initial damage, prefabricate damage to the rock mass according to the initial damage, then conduct a uniaxial loading test to obtain the damaged compressive strength, and then calculate the triaxial compressive strength according to the corresponding relationship H(N) between the triaxial compressive strength and the damaged compressive strength. Next, calculate the uniaxial compressive strength. The uniaxial compressive strength = triaxial compressive strength / strengthening coefficient A. Finally, determine the support design parameters of the rock mass based on the calculated uniaxial compressive strength. Among them, the corresponding relationship H(N) is obtained by fitting the triaxial compressive strength and the damaged compressive strength of multiple groups of this rock mass under the same initial damage conditions.

2. The method for determining the design parameters of surrounding rock support for underground cavern groups according to claim 1, characterized in that: In step S2, the rock mass quality is divided into five categories: Class I, Class II, Class III, Class IV, and Class V surrounding rocks.

3. The method for determining the design parameters of the surrounding rock support of the underground cavern group according to claim 1, characterized in that: In steps S3-1 and S3-3, the frequency and intensity of cyclic loading and unloading are consistent with the repeated construction disturbances.

4. The method for determining the design parameters of surrounding rock support for underground cavern groups according to claim 1, characterized in that: In step S3-4, the instrument used for the free-face loading test is a true triaxial instrument, and the confining pressure condition of the test is consistent with the in-situ measured ground stress.

5. The method for determining the design parameters of surrounding rock support for underground cavern groups according to claim 1, characterized in that: In step S3-5, when conducting a loading test under the combined action of water pressure and axial pressure, first immerse the specimen in water, then apply a water confining pressure to the specimen to a predetermined value and maintain the water confining pressure, which is consistent with the water pressure actually borne by the rock mass. Finally, apply an axial load to the specimen until the specimen fails or the axial load reaches the preset value.

6. The method for determining the design parameters of the surrounding rock support of the underground cavern group according to claim 1, characterized in that: In step S3-6, the initial damage of the rock mass includes joints, fissures, and faults. The prefabricated damage to the rock mass is prefabricated fissures, and the number, angle, length, and width of the fissures are determined according to the in-situ rock mass behavior.

7. The method for determining the design parameters of surrounding rock support for underground cavern groups according to any one of claims 1 to 6, characterized in that: In steps S3-4, S3-5, and S3-6, the support method and parameters are also corrected according to the deformation and failure characteristics of the rock mass. Among them, the deformation and failure characteristics include tensile failure, shear failure, and ejection failure. The correction methods are as follows: use rapid closed shotcrete to inhibit ejection failure, use prestressed anchor bolts to inhibit shear failure, and use ordinary mortar anchor bolts to inhibit tensile failure.