A method for determining stress migration support of underground engineering

Abstract

This invention belongs to the field of geotechnical engineering technology, and in particular relates to a method for determining stress migration support in underground engineering. The method includes: establishing an in-situ monitoring system for surrounding rock fracture based on the correlation between the fracture depth and support strength of the surrounding rock in underground engineering and the rock brittle-ductile transformation index within the confining pressure range of the project, and the correlation between the gradual nature of surrounding rock fracture and staged support. The method for determining stress migration support in underground engineering provided by this invention can dynamically optimize the timing, method, and strength of support to mobilize the self-bearing potential of deep surrounding rock, thereby achieving active control and safe and stable stress migration in underground engineering.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, and in particular relates to a method for determining stress migration support in underground engineering. Background Technology

[0002] The increasing depletion of shallow resources and space is driving geotechnical engineering to gradually extend into deeper underground layers. Underground engineering projects face complex geological environments, significant nonlinear mechanical properties of surrounding rock, and diverse failure modes, posing severe challenges to the design of underground engineering support systems. Current underground engineering support designs largely rely on empirical methods based on engineering analogies, lacking quantitative and reasonable theoretical guidance. Therefore, a deep understanding of the rock fracture-support coupling system is crucial. By designing phased support measures and proactively adjusting stress concentration areas in the surrounding rock, the bearing capacity of deep surrounding rock can be fully mobilized, achieving optimal overall safety of the surrounding rock in underground engineering projects. Summary of the Invention

[0003] The purpose of this invention is to provide a method for determining stress migration support in underground engineering, addressing the shortcomings of existing technologies.

[0004] Therefore, the above-mentioned objective of the present invention is achieved through the following technical solution:

[0005] A method for determining stress migration support in underground engineering includes: establishing an in-situ monitoring system for surrounding rock fracture based on the correlation between the fracture depth and support strength of the surrounding rock and the brittle-ductile transformation index of the rock within the confining pressure range, and the correlation between the gradual nature of the surrounding rock fracture and staged support; dynamically optimizing the timing, method, and strength of support to mobilize the self-bearing potential of deep surrounding rock, thereby achieving proactive control of stress migration and ensuring safety and stability in underground engineering; specifically, it includes the following steps:

[0006] S1. Based on the engineering results of typical major underground projects, study the fracture depth and support strength of the surrounding rock, and establish their mapping relationship with the rock brittle-ductile transformation index (BEC) within the confining pressure range of the project.

[0007] The brittle-dullite conversion index (BEC) of rocks within the confining pressure range is the slope of the linear fit between the BR and confining pressure curves, where BR is the ordinate of the curve and confining pressure is the abscissa. The BEC is determined through an indirect conversion of BR.

[0008] S2. Based on the existing engineering rock brittle-ductile conversion index (BEC) and surrounding rock fracture monitoring results, determine the surrounding rock fracture depth and support strength, as well as the timing, method, and strength of primary and secondary support.

[0009] While adopting the above technical solutions, the present invention may also adopt or combine the following technical solutions:

[0010] As a preferred technical solution of the present invention: In step S1, the calculation formula for the brittle-ductile conversion index (BEC) of rocks within the confining pressure range is as follows:

[0011] BEC = -log 10 |k BR(0～50) |

[0012] In the formula:

[0013] BR is an index of rock brittleness;

[0014] k BR(0～50) The linear rate of change of the rock brittleness index BR within the confining pressure range (0-50 MPa) of the project.

[0015] As a preferred embodiment of the present invention, the formula for calculating the rock brittleness index BR is as follows:

[0016]

[0017] In the formula:

[0018] σ p Peak rock strength;

[0019] σ r This represents the residual strength of the rock.

[0020] As a preferred technical solution of the present invention: parameter k BR(0～50) The peak strength σ was determined by conventional triaxial compression tests ranging from 0 to 50 MPa. p and residual strength σ r The confining pressures were set to 0 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, and 50 MPa. The rock brittleness index BR decreased linearly with increasing confining pressure. k was determined by fitting the BR-confining pressure data using a linear function. BR(0～50) .

[0021] As a preferred technical solution of the present invention, step S1 specifically includes the following steps:

[0022] S101. The fracture depth and support strength of the surrounding rock in underground engineering conform to an exponential function relationship with the rock brittle-ductile conversion index (BEC) within the confining pressure range of the project.

[0023] S102. When the excavation tunnel of an underground project is not circular, the fracture depth and support strength of the surrounding rock are divided into the fracture depth and support strength of the top arch, sidewalls and bottom plate.

[0024] As a preferred technical solution of the present invention, step S2 specifically includes the following steps:

[0025] S201. Based on the existing rock brittle-ductile conversion index (BEC) of the existing project, substitute it into the mapping relationship established in step S1 to determine the surrounding rock fracture depth and support strength when the existing project is stable.

[0026] S202. Immediately after the existing project is excavated, spray 5-10cm thick concrete onto the surface surrounding rock.

[0027] S203. Based on the existing monitoring results of the surrounding rock fracture, when the in-situ monitored fracture depth of the surrounding rock reaches 0.5 times the value calculated in step S201, the initial support shall be implemented. The support method shall be mortar anchor bolts, and the support strength of the mortar anchor bolts shall be 0.3 to 0.5 times the value calculated in step S201, so as to actively control the stress concentration zone to migrate to the deeper part of the surrounding rock.

[0028] S204. Based on the existing monitoring results of surrounding rock fracture, when the in-situ monitored fracture depth of the surrounding rock reaches 0.8 times the value calculated in step S201, secondary support shall be implemented. The support method shall be wire mesh and prestressed anchor bolts. A 10-15cm thick layer of concrete shall be sprayed onto the surface surrounding rock, and grouting shall be performed to reinforce the fractured area of ​​the surrounding rock. The support strength of the prestressed anchor bolts shall be the value calculated in step S201. Local anchor cable support may be appropriately increased to actively mobilize the self-bearing potential of the deep surrounding rock.

[0029] As a preferred technical solution of the present invention: In step S2, when the maximum principal stress value is greater than 20MPa and the strength-stress ratio of the surrounding rock is less than 2.5, pressure relief treatment is carried out by surface surrounding rock spraying water and stress relief blasting during the period from the initial support to the secondary support.

[0030] This invention provides a method for determining stress migration support in underground engineering. The method includes: establishing an in-situ monitoring system for surrounding rock fracture based on the correlation between the fracture depth and support strength of the surrounding rock and the brittle-ductile transformation index of the rock within the confining pressure range, and the correlation between the gradual nature of the surrounding rock fracture and the staged support. The method for determining stress migration support in underground engineering provided by this invention can dynamically optimize the timing, method, and strength of support to mobilize the self-bearing potential of deep surrounding rock, thereby achieving active control and safe and stable stress migration in underground engineering. Attached Figure Description

[0031] Figure 1 This is a flowchart illustrating the method for determining stress migration support in underground engineering provided by the present invention. Detailed Implementation

[0032] The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

[0033] The method for determining stress migration support in underground engineering includes the following steps:

[0034] Step S1: Collect engineering results of typical important underground engineering projects, study the fracture depth and support strength of the surrounding rock, and establish a mapping relationship between them and the rock brittle-ductile transformation index (BEC) within the confining pressure range of the project.

[0035] The fracture depth and support strength of the surrounding rock in underground engineering follow an exponential function relationship with the brittle-ductile transformation index (BEC) of the rock within the confining pressure range.

[0036] Step S2: Based on the existing engineering rock brittle-ductile conversion index (BEC) and surrounding rock fracture monitoring results, determine the surrounding rock fracture depth and support strength, as well as the timing, method, and strength of primary and secondary support.

[0037] The peak strength σ was determined by conventional triaxial compression tests ranging from 0 to 50 MPa. p and residual strength σ r The confining pressures were set to 0 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, and 50 MPa. The values ​​of the rock brittleness index BR were determined within different confining pressure ranges. k was determined by fitting the BR-confining pressure data using a linear function. BR(0～50) This allows for the determination of the brittle-ductile transformation index (BEC) of rocks within the confining pressure range of the project.

[0038] The formula for calculating the brittle-ductile conversion index (BEC) of rocks within the confining pressure range of the project is as follows:

[0039] BEC = -log 10 |k BR(0～50) |

[0040] In the formula:

[0041] BR is an index of rock brittleness;

[0042] k BR(0～50) The linear rate of change of the rock brittleness index BR within the confining pressure range (0-50 MPa) of the project.

[0043] The formula for calculating the rock brittleness index BR is as follows:

[0044]

[0045] In the formula:

[0046] σ p Peak rock strength;

[0047] σ r Residual strength of the rock;

[0048] Based on the existing rock brittle-ductile conversion index (BEC) of the existing project, substitute it into the mapping relationship established in step S1 to determine the surrounding rock fracture depth and support strength when the existing project is stable.

[0049] Immediately after the existing project is excavated, spray 5-10cm thick concrete onto the surface surrounding rock.

[0050] Based on the existing monitoring results of surrounding rock fracture, when the in-situ monitored fracture depth of the surrounding rock reaches 0.5 times the value calculated in step S2, the initial support is implemented. The support method is mortar anchor bolts, and the support strength of the mortar anchor bolts is 0.3 to 0.5 times the value calculated in step S2, so as to actively control the migration of the stress concentration zone to the deeper part of the surrounding rock.

[0051] Based on the existing monitoring results of surrounding rock fracture, when the fracture depth of the surrounding rock monitored in situ reaches 0.8 times the value calculated in step S2, secondary support is implemented. The support method is wire mesh and prestressed anchor bolts. A 10-15cm thick layer of concrete is sprayed on the surface surrounding rock and grouting is performed to reinforce the fractured area of ​​the surrounding rock. The support strength of the prestressed anchor bolts is the value calculated in step S2. Local anchor cable support can be appropriately increased to actively mobilize the self-bearing potential of the deep surrounding rock.

[0052] When the maximum principal stress value is greater than 20 MPa and the strength-stress ratio of the surrounding rock is less than 2.5, pressure relief measures such as water spraying on the surface surrounding rock and stress relief blasting are adopted during the period from the initial support to the secondary support.

[0053] The above specific embodiments are used to explain and illustrate the present invention, and are only preferred embodiments of the present invention, not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for determining stress migration support in underground engineering, characterized in that: The method for determining stress migration support in underground engineering includes: establishing an in-situ monitoring system for surrounding rock fracture based on the correlation between the fracture depth and support strength of the surrounding rock and the brittle-ductile transformation index of the rock within the confining pressure range, and the correlation between the gradual nature of surrounding rock fracture and staged support; dynamically optimizing the timing, method, and strength of support to mobilize the self-bearing potential of deep surrounding rock, thereby achieving proactive control and safe stability of stress migration in underground engineering; specifically, it includes the following steps: S1. Based on the engineering results of typical major underground projects, study the fracture depth and support strength of the surrounding rock, and establish their mapping relationship with the rock brittle-ductile conversion index (BEC) within the confining pressure range of the project. S2. Based on the existing engineering rock brittle-ductile conversion index (BEC) and surrounding rock fracture monitoring results, determine the surrounding rock fracture depth and support strength, as well as the timing, method, and strength of primary and secondary support. Step S2 specifically includes the following steps: S201. Based on the existing rock brittle-ductile conversion index (BEC) of the existing project, substitute it into the mapping relationship established in step S1 to determine the surrounding rock fracture depth and support strength when the existing project is stable. S202. Immediately after the existing project is excavated, spray 5-10 cm thick concrete onto the surface surrounding rock. S203. Based on the existing monitoring results of the surrounding rock fracture, when the in-situ monitored fracture depth of the surrounding rock reaches 0.5 times the value calculated in step S201, the initial support shall be implemented. The support method shall be mortar anchor bolts, and the support strength of the mortar anchor bolts shall be 0.3 to 0.5 times the value calculated in step S201, so as to actively control the stress concentration zone to migrate to the deeper part of the surrounding rock. S204. Based on the existing monitoring results of surrounding rock fracture, when the in-situ monitored fracture depth of the surrounding rock reaches 0.8 times the value calculated in step S201, secondary support shall be implemented. The support method shall be wire mesh and prestressed anchor bolts. A 10-15 cm thick layer of concrete shall be sprayed onto the surface surrounding rock, and grouting shall be performed to reinforce the fractured area of ​​the surrounding rock. The support strength of the prestressed anchor bolts shall be the value calculated in step S201. Local anchor cable support may be appropriately increased to actively mobilize the self-bearing potential of the deep surrounding rock.

2. The method for determining stress migration support in underground engineering according to claim 1, characterized in that: In step S1, the formula for calculating the brittle-ductile conversion index (BEC) of rock within the confining pressure area is as follows: In the formula: BR is an index of rock brittleness; The linear rate of change of the rock brittleness index BR within the confining pressure range (0~50MPa) of the project.

3. The method for determining stress migration support in underground engineering according to claim 2, characterized in that: The formula for calculating the rock brittleness index BR is: In the formula: Peak rock strength; This represents the residual strength of the rock.

4. The method for determining stress migration support in underground engineering according to claim 2, characterized in that: parameter Peak strength was determined by conventional triaxial compression tests ranging from 0 to 50 MPa. and residual strength The confining pressures were set to 0 MPa, 10 MPa, 20 MPa, 30 MPa, 40 MPa, and 50 MPa. The rock brittleness index BR decreased linearly with increasing confining pressure. The BR value was determined by fitting the confining pressure data with a linear function. .

5. The method for determining stress migration support in underground engineering according to claim 1, characterized in that: Step S1 specifically includes the following steps: S101. The fracture depth and support strength of the surrounding rock in underground engineering conform to an exponential function relationship with the rock brittle-ductile conversion index (BEC) within the confining pressure range of the project. S102. When the excavation tunnel of an underground project is not circular, the fracture depth and support strength of the surrounding rock are divided into the fracture depth and support strength of the top arch, sidewalls and bottom plate.

6. The method for determining stress migration support in underground engineering according to claim 1, characterized in that: In step S2, when the maximum principal stress value is greater than 20 MPa and the strength-stress ratio of the surrounding rock is less than 2.5, pressure relief treatment is carried out by spraying water on the surface surrounding rock and stress relief blasting during the period from the initial support to the secondary support.

Images