A tunnel stress measurement and support method based on three-dimensional excavation effect

Abstract

A method for tunnel stress measurement and support based on three-dimensional excavation effects, relating to the fields of tunnel engineering and geotechnical mechanics, is disclosed. The method includes: S1, measuring the three-dimensional geostress field of the tunnel area to obtain geostress parameters; S2, establishing a spatial control equation for the three-dimensional excavation stress loss coefficient based on the geostress parameters; S3, designing a support system based on the three-dimensional excavation loss coefficient, including radial and axial support elements; S4, implementing the support system during tunnel excavation and deploying monitoring sensors; and S5, dynamically adjusting support parameters based on monitoring data. This invention quantifies the three-dimensional geostress field to accurately identify excavation effects, avoiding insufficient or excessive support; employs negative Poisson's ratio (NPR) flexible support elements to achieve energy absorption under large deformations; combines monitoring feedback to form a closed-loop control system, improving the adaptability and safety of the support; and is applicable to various geological conditions, such as faults, soft rock, and high geostress areas, reducing engineering risks.

Description

Technical Field

[0001] This invention relates to the fields of tunnel engineering and geotechnical mechanics, specifically a method for tunnel stress measurement and support based on three-dimensional excavation effects, which is particularly suitable for stress monitoring and support of tunnels in deep-buried tunnels, soft surrounding rock, or complex geological conditions. Background Technology

[0002] During tunnel excavation, changes in stress state depend on changes in the excavation space. After excavation to a certain distance, the stress state changes at the free face cease to be affected, which can be abstracted into a two-dimensional state. Within a certain distance, the stress state changes at the free face are affected, which is called a three-dimensional spatial effect. The three-dimensional excavation spatial effect of the three-stage excavation method has three types: ① the transition process from a three-dimensional spatial effect to a two-dimensional state during face advancement; ② the three-dimensional spatial effect of mutual influence between stages under different excavation sequences in the stage excavation method; ③ the three-dimensional spatial effect of excavation under the influence of the pilot tunnel during tunnel excavation. Traditional support methods (such as the New Austrian Tunneling Method) often ignore the dynamic changes in three-dimensional excavation effects, leading to overly conservative or insufficient support designs, which can easily cause large deformations of the surrounding rock, rock bursts, or collapses. In existing technologies, support parameters are mostly based on experience or simplified model designs, failing to fully consider the three-dimensional coupling relationship between the geostress field, the internal forces of the support structure, and the excavation loss coefficient. Existing methods lack a systematic three-dimensional compensation mechanism; although methods such as compensating support and NPR materials are involved, they do not integrate the three-dimensional excavation effect into the overall design. Therefore, there is an urgent need for a support method based on three-dimensional excavation effect to achieve precise stress compensation and dynamic control. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a tunnel stress measurement and support method based on three-dimensional excavation effects. This method achieves effective recovery and control of the surrounding rock stress state by quantifying the three-dimensional geostress field, calculating the excavation loss coefficient, and designing a dynamic compensation support system.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for tunnel stress measurement and support based on three-dimensional excavation effect, which fully monitors the three-dimensional excavation effect of the tunnel to achieve the support purpose, includes the following steps: S1. Measure the three-dimensional geostress field in the tunnel area and obtain geostress parameters; S2. Establish a three-dimensional spatial control equation for the excavation stress loss coefficient based on ground stress parameters; S3. Design the support system based on the three-dimensional excavation loss coefficient, including radial support elements and axial support elements; S4. Implement the support system during tunnel excavation and deploy monitoring sensors; S5. Dynamically adjust support parameters based on monitoring data.

[0005] In S1, the three-dimensional geostress field of the tunnel area is measured using the hydraulic fracturing method or the borehole stress gauge method; the obtained geostress parameters include the maximum principal stress, intermediate principal stress, and minimum principal stress.

[0006] S2 specifically includes the following steps: Based on the data of in-situ stress changes from the three-dimensional stress state to the two-dimensional steady state during the early stage of tunnel excavation, the spatial control equation for the three-dimensional excavation stress loss coefficient is calculated: in: This indicates the location of the point in the tunnel cross-section coordinate system; It is the distance that the tunnel face extends axially towards the excavated portion; The original geostress field of the tunnel cross-section before excavation; This refers to the stress loss caused by excavation disturbance. This refers to the stress compensation term caused by support feedback; The initial distribution of the in-situ stress field at the tunnel cross section is approximately an anisotropic linear field:

[0007] The initial geostress exhibits an exponential decay pattern along the Y-axis: Where: A is the maximum disturbance amplitude, derived from the two-dimensional steady-state condition; λ is the excavation disturbance coefficient; The feedback of the support system is approximately represented by a proportional control term: In summary: in: : represents the original geostress components; : represents the maximum disturbance amplitude in each direction; : represents the disturbance attenuation coefficient in each direction; : This represents the support feedback coefficient in each direction, and is a negative number; k xx : The rate of change of the initial stress component in the x-direction along the X-direction. k xz The rate of change of the initial stress component in the x-direction along the z-direction. k yx The rate of change of the initial stress component in the y-direction along the x-direction. k yz The rate of change of the initial stress component in the y-direction along the Z-direction. k zx The rate of change of the initial stress component in the z-direction along the x-direction. k zz The initial stress component in the z-direction changes at a rate along the Z-direction; the model describes the stress loss due to the spatial change of the excavation disturbance. After obtaining the tunnel stress loss coefficient, the stress loss caused by subsequent excavation is calculated in the same way.

[0008] The radial support elements in S3 include anchor cables or telescopic steel arches made of negative Poisson's ratio (NPR) material, and the axial support elements include pre-grouting or prestressed anchor bolts.

[0009] The constant resistance of the anchor cable is 100-300kN, and the deformation is 500-2000mm.

[0010] The monitoring sensors in S4 include axial force gauges, displacement gauges, or axial force gauges and pressure gauges, and the data is transmitted wirelessly to the central processing system.

[0011] The dynamic adjustment in S5 includes adjusting the anchor cable spacing, grouting pressure, or support stiffness, with the adjustment threshold being a change in monitoring data exceeding 10%.

[0012] The method is applicable to geological conditions such as deep-buried tunnels, weak surrounding rock, or active faults.

[0013] The beneficial effects of this invention are: By quantifying the three-dimensional geostress field, the excavation effect can be accurately identified, avoiding insufficient or excessive support; flexible support elements with negative Poisson's ratio (NPR) materials are used to achieve energy absorption under large deformation; combined with monitoring feedback, a closed-loop control system is formed to improve the adaptability and safety of the support; it is suitable for various geological conditions, such as faults, soft rock, and high geostress areas, reducing engineering risks. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the three-dimensional excavation effect involved in the present invention.

[0015] Figure 2 This is a flowchart of the method of the present invention.

[0016] Figure 3 This is a flowchart illustrating the monitoring, feedback, and adjustment process of this invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0019] Example 1

[0020] A method for tunnel stress measurement and support based on three-dimensional excavation effects, applicable to deep-buried tunnels, weak surrounding rock, or active fault geological conditions, is proposed. This method fully monitors the three-dimensional excavation effects of the tunnel to achieve support objectives. Figure 1 As shown, it includes the following steps: S1. Measure the three-dimensional geostress field in the tunnel area and obtain geostress parameters; S2. Establish a three-dimensional spatial control equation for the excavation stress loss coefficient based on ground stress parameters; S3. Design the support system based on the three-dimensional excavation loss coefficient, including radial support elements and axial support elements; S4. Implement the support system during tunnel excavation and deploy monitoring sensors; S5. Dynamically adjust support parameters based on monitoring data.

[0021] In S1, the three-dimensional geostress field of the tunnel area is measured using the hydraulic fracturing method or the borehole stress gauge method; the obtained geostress parameters include the maximum principal stress, intermediate principal stress, and minimum principal stress.

[0022] S2 specifically includes the following steps: Based on the data of in-situ stress changes from the three-dimensional stress state to the two-dimensional steady state during the early stage of tunnel excavation, the spatial control equation for the three-dimensional excavation stress loss coefficient is calculated: in: This indicates the location of the point in the tunnel cross-section coordinate system; It is the distance that the tunnel face extends axially towards the excavated portion; The original geostress field of the tunnel cross-section before excavation; This refers to the stress loss caused by excavation disturbance. This refers to the stress compensation term caused by support feedback; The initial distribution of the in-situ stress field at the tunnel cross section is approximately an anisotropic linear field:

[0023] The initial geostress exhibits an exponential decay pattern along the Y-axis: Where: A is the maximum disturbance amplitude, derived from the two-dimensional steady-state condition; λ is the excavation disturbance coefficient; The feedback of the support system is approximately represented by a proportional control term: In summary: in: : represents the original geostress components; : represents the maximum disturbance amplitude in each direction; : represents the disturbance attenuation coefficient in each direction; : This represents the support feedback coefficient in each direction, and is a negative number; k xx : The rate of change of the initial stress component in the x-direction along the X-direction. k xz The rate of change of the initial stress component in the x-direction along the z-direction. k yx The rate of change of the initial stress component in the y-direction along the x-direction. k yz The rate of change of the initial stress component in the y-direction along the Z-direction. k zx The rate of change of the initial stress component in the z-direction along the x-direction. k zz : The rate of change of the initial stress component in the z-direction along the Z-direction; The model describes the stress loss as the spatial location of excavation disturbance changes. After obtaining the tunnel stress loss coefficient, the stress loss caused by subsequent excavation can be calculated similarly. Taking the stress component in the z-direction as an example, consider the model:

[0024] The stress loss in the z-direction can be calculated using the following formula: in: Stress loss in the z-direction Measured stress in the z-direction after excavation at the study location The stress loss coefficient in the z-direction is: in: The stress loss coefficient in the z-direction Different from the front of the palm The disturbance attenuation coefficient can be obtained by performing an exponential fit on the measured stress data at the location. Then by

[0025] Calculated disturbance intensity parameters The design objective is to restore the stress in the z-direction at this location after support. Therefore, the support feedback coefficient can be calculated by substituting this into the above formula. .

[0026] The radial support elements in S3 include anchor cables or telescopic steel arches made of negative Poisson's ratio (NPR) material, and the axial support elements include pre-grouting or prestressed anchor bolts.

[0027] The constant resistance of the anchor cable is 100-300kN, and the deformation is 500-2000mm.

[0028] The monitoring sensors in S4 include axial force gauges, displacement gauges, or axial force gauges and pressure gauges, and the data is transmitted wirelessly to the central processing system.

[0029] The dynamic adjustment in S5 includes adjusting the anchor cable spacing, grouting pressure, or support stiffness, with the adjustment threshold being a change in monitoring data exceeding 10%.

[0030] Example 2

[0031] This embodiment demonstrates the application of the method described in Embodiment 1 in the support structure of a deeply buried tunnel. Figure 1 This embodiment illustrates the distribution of the ground stress field before and after excavation in a three-dimensional excavation effect. Taking a tunnel with a burial depth greater than 500m as an example, the specific steps are as follows: S1. Measure the three-dimensional in-situ stress field in the tunnel area and obtain in-situ stress parameters: First, measure the three-dimensional in-situ stress field using the hollow inclusion or hydraulic fracturing method to obtain the initial in-situ stress at the crown. =10MPa, =10MPa, =20MPa. The stress in the Z direction of the tunnel arch is the most important, so only the stress in the Z direction will be discussed. The measured stress disturbance typically reaches -95% within 5 m in front of the tunnel face, with the stress attenuating to 1 MPa. Furthermore, the surrounding rock support needs to maintain the stress at 5 MPa. Therefore, to determine the required support stress at 3 m in front of the tunnel face (Y=3 m), it can be calculated as follows: S2. Establishing a three-dimensional spatial control equation for the excavation stress loss coefficient based on ground stress parameters: Taking directional stress components as an example, consider the following model: Among them, let the initial position of the study location The axial stress is:

[0032] In this embodiment, the initial position is taken at this location. The axial stress is:

[0033] Actual measurement at this location after excavation The axial stress is:

[0034] therefore, The directional stress loss is:

[0035] The directional stress loss coefficient is:

[0036] Stress disturbances typically reach -95% within 5m in front of the tunnel face, meaning that at R=5m, the disturbance term has already decayed to 95% of its amplitude. =-0.95, therefore we get The directional disturbance attenuation coefficient is: .

[0037] Depend on We can obtain: We can obtain:

[0038] If the design goal is to support this location Directional stress restored to: Therefore, without support, arbitrary Location The z-direction stress can be written as: the stress distribution model in the z-direction under unsupported conditions.

[0039] Substituting the parameters, we get:

[0040] when hour:

[0041]

[0042]

[0043] The goal is to maintain until Therefore, the required support compensation stress is:

[0044] Therefore, when Y=3m in front of the tunnel face, the stress in the Z direction at this location without support is approximately 3.31MPa. If the goal of the surrounding rock support is to maintain the stress at this location to 5MPa, then the required support compensation stress is approximately 1.69MPa. S3. Design the support system based on the three-dimensional excavation loss coefficient, including radial support elements and axial support elements: Radial support: If NPR anchor cables are installed, the spacing is 1m and the row spacing is 1m, and the prestress is set to 210kN to compensate for radial stress loss.

[0045] Axial support: Advanced grouting is adopted, taking into account losses, with a grouting pressure of 5MPa and a diffusion radius of 3m to enhance the integrity of the surrounding rock.

[0046] Support structure: Install telescopic steel arch frames (made of NPR material) to adapt to the rheological changes of the surrounding rock.

[0047] S4. Implement the aforementioned support system during tunnel excavation and deploy monitoring sensors: Multiple displacement gauges and axial force gauges are installed at the arch crown and arch waist to monitor deformation and internal force data in real time.

[0048] S5. Dynamically adjust support parameters based on monitoring data: Figure 3 The monitoring and adjustment flowchart illustrates how support parameters are dynamically optimized based on sensor data. Monitoring data is wirelessly transmitted to a cloud-based monitoring and control center, where it is analyzed and outputs early warning information and recommendations for adjusting support parameters. For example, if monitoring shows a 20% increase in steel frame stress, the anchor cable spacing is automatically increased to 1.0m based on experience, or the grouting frequency is increased.

[0049] The method of this invention significantly improves support efficiency and safety through three-dimensional effect integration.

[0050] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for tunnel stress measurement and support based on three-dimensional excavation effects, characterized in that, To achieve the purpose of support, the following steps are included in fully monitoring the three-dimensional excavation effects of the tunnel: S1. Measure the three-dimensional geostress field in the tunnel area and obtain geostress parameters; S2. Establish a three-dimensional spatial control equation for the excavation stress loss coefficient based on ground stress parameters; S3. Design the support system based on the three-dimensional excavation loss coefficient, including radial support elements and axial support elements; S4. Implement the support system during tunnel excavation and deploy monitoring sensors; S5. Dynamically adjust support parameters based on monitoring data.

2. The tunnel stress measurement and support method based on three-dimensional excavation effect according to claim 1, characterized in that, In S1, the three-dimensional geostress field of the tunnel area is measured using the hydraulic fracturing method or the borehole stress gauge method; the obtained geostress parameters include the maximum principal stress, intermediate principal stress, and minimum principal stress.

3. The tunnel stress measurement and support method based on three-dimensional excavation effect according to claim 1, characterized in that, S2 specifically includes the following steps: Based on the data of in-situ stress changes from the three-dimensional stress state to the two-dimensional steady state during the early stage of tunnel excavation, the spatial control equation for the three-dimensional excavation stress loss coefficient is calculated: in: This indicates the location of the point in the tunnel cross-section coordinate system; It is the distance that the tunnel face extends axially towards the excavated portion; The original geostress field of the tunnel cross-section before excavation; This refers to the stress loss caused by excavation disturbance. This refers to the stress compensation term caused by support feedback; The initial distribution of the in-situ stress field at the tunnel cross section is approximately an anisotropic linear field: The initial geostress exhibits an exponential decay pattern along the Y-axis: Where: A is the maximum disturbance amplitude, derived from the two-dimensional steady-state condition; λ is the excavation disturbance coefficient; The feedback of the support system is approximately represented by a proportional control term: In summary: in: : represents the original geostress components; : represents the maximum disturbance amplitude in each direction; : represents the disturbance attenuation coefficient in each direction; : This represents the support feedback coefficient in each direction, and is a negative number; k xx : The rate of change of the initial stress component in the x-direction along the X-direction. k xz The rate of change of the initial stress component in the x-direction along the z-direction. k yx The rate of change of the initial stress component in the y-direction along the x-direction. k yz The rate of change of the initial stress component in the y-direction along the Z-direction. k zx The rate of change of the initial stress component in the z-direction along the x-direction. k zz The initial stress component in the z-direction changes at a rate along the Z-direction; the model describes the stress loss due to the spatial change of the excavation disturbance. After obtaining the tunnel stress loss coefficient, the stress loss caused by subsequent excavation is calculated in the same way.

4. The tunnel stress measurement and support method based on three-dimensional excavation effect according to claim 1, characterized in that, The radial support elements in S3 include anchor cables or telescopic steel arches made of negative Poisson's ratio (NPR) material, and the axial support elements include pre-grouting or prestressed anchor bolts.

5. A method for tunnel stress measurement and support based on three-dimensional excavation effect according to claim 4, characterized in that, The constant resistance of the anchor cable is 100-300kN, and the deformation is 500-2000mm.

6. The tunnel stress measurement and support method based on three-dimensional excavation effect according to claim 1, characterized in that, The monitoring sensors in S4 include axial force gauges, displacement gauges, or axial force gauges and pressure gauges, and the data is transmitted wirelessly to the central processing system.

7. The tunnel stress measurement and support method based on three-dimensional excavation effect according to claim 1, characterized in that, The dynamic adjustment in S5 includes adjusting the anchor cable spacing, grouting pressure, or support stiffness, with the adjustment threshold being a change in monitoring data exceeding 10%.

8. A method for tunnel stress measurement and support based on three-dimensional excavation effect according to any one of claims 1 to 7, characterized in that, The method is applicable to geological conditions such as deep-buried tunnels, weak surrounding rock, or active faults.

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