Method for determining surrounding rock pressure and influence range of shallow-buried tunnel under tunnel face instability
By calculating the surrounding rock pressure and influence range of shallow buried tunnels under face instability, the problem of unreasonable support design caused by face instability that was not considered in the existing technology was solved, and a safe and reasonable support design was achieved, reducing the risk of collapse and surface deformation.
Patent Information
- Application Number
- CN202511811125.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-03-03
AI Technical Summary
Existing technologies fail to effectively consider the calculation of surrounding rock pressure in shallow tunnels under conditions of face instability, resulting in unreasonable support design, which may lead to the expansion of collapse or even surface deformation, posing safety hazards.
A method is provided for calculating the surrounding rock pressure and influence range of shallow tunnels under face instability, including calculation formulas for parameters such as failure range angle, collapse weight, friction force and surrounding rock pressure, which are used to determine reasonable support strength.
This provides a theoretical basis for support design, ensuring that the support strength meets the requirements, reducing the risk of collapse expansion and surface deformation, and improving the safety of tunnel construction.
Smart Images
Figure CN121597948A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of tunnel construction, specifically to a method for determining the surrounding rock pressure and influence range of shallow-buried tunnels under conditions of face instability. Background Technology
[0002] Tunnel face collapse is a common type of accident in tunnels. When the tunnel face becomes unstable, the damage can spread further; in shallow-buried tunnels, deformation of the surrounding rock ahead of the tunnel face can extend to the surface, causing surface deformation and cracking, and even collapse and roof fall. Such collapses seriously endanger tunnel construction. A prime example is the roof fall accident at the Xinglong Tunnel of the Hubei Enshi 351 National Highway Xianfeng Section Reconstruction and Expansion Project, which was under the supervision of the Ministry of Transport. This roof fall accident occurred during the construction of the Xinglong Tunnel of the 351 National Highway Xianfeng Section Reconstruction and Expansion Project, specifically the "August 4th" tunnel face roof fall accident, resulting in the tragic deaths of four construction workers.
[0003] When the tunnel face is unstable or instable, the required support should be stronger than when the face is stable. Determining the magnitude and range of influence of the surrounding rock pressure is a prerequisite for rational support design. However, current conventional calculations of surrounding rock pressure do not consider the case of tunnel face instability. Most existing literature studies the lateral surrounding rock pressure of tunnels, rarely considering the case of tunnel face instability. Summary of the Invention
[0004] The purpose of this invention is to address the aforementioned technical problems in the prior art by providing a method for determining the surrounding rock pressure and influence range of shallow-buried tunnels under conditions of face instability.
[0005] The above-mentioned objective of the present invention is achieved through the following technical solution: The method for determining the surrounding rock pressure and influence range of shallow-buried tunnels under face instability includes the following steps: (1) Determine the failure range angle in front of the working face, which is calculated using the following formula: ; in, β The angle of destruction in front of the palm; The internal friction angle of the surrounding rock at the tunnel face; (2) Calculate the weight of the landslide above, which includes the following steps: (I) Calculate the failure width in front of the tunnel face using the following formula: ; in, L AE The width of the destruction in front of the palm; D This refers to the excavation height at the working face. (II) Calculate the weight of the landslide from above using the following formula: ; in, γ represents the weight of the collapse above; γ represents the unit weight of the surrounding rock; L represents the length of the unsupported section behind the working face. H The tunnel depth is the vertical distance from the ground surface to the tunnel arch. (3) Calculate the frictional force on both sides of the collapsed body above, which is calculated using the following formula: ; in, This refers to the frictional force between the two sides of the collapsed structure above; (4) Calculate the surrounding rock pressure using the following formula: ; Where q is the surrounding rock pressure; (5) Determine the scope of influence, which is calculated using the following formula: ; in, The scope of influence.
[0006] The advantage of this invention compared to existing research methods is that the required support should be stronger when the tunnel face is unstable or instable than when it is stable. Determining the appropriate surrounding rock pressure is a prerequisite for rational support design. However, current conventional surrounding rock pressure calculations do not consider the case of tunnel face instability. Most existing literature studies the lateral surrounding rock pressure of tunnels, rarely considering the case of tunnel face instability.
[0007] This invention provides a method for calculating the surrounding rock pressure and influence range of tunnels under face instability, thus providing a reference for determining the corresponding support strength and parameters. This is beneficial for design and construction units to theoretically optimize support designs. The method of this invention can be applied to the calculation of surrounding rock pressure and the estimation of the influence range in shallow-buried tunnels and underground engineering projects with face instability, such as mining roadways, hydraulic tunnels, and subways. It also provides a theoretical method for determining reasonable support strength and parameters, which is beneficial for tunnel construction safety. Attached Figure Description
[0008] Figure 1 This is a schematic diagram illustrating the calculation of the method for determining the surrounding rock pressure and influence range of shallow buried tunnels under face instability according to the present invention.
[0009] Figure 1 In the middle: 1 is the tunnel; 2 is the working face; 3 is the support lining; 4 is the ground surface; H For tunnel burial depth; D This refers to the excavation height at the working face. β The angle of destruction in front of the palm; L This refers to the length of the unsupported section behind the working face. Detailed Implementation
[0010] The present invention will now be further described with reference to the accompanying drawings and embodiments.
[0011] The method of this invention is applied to an engineering example. Specific data for this example project are as follows: the unit weight γ of the surrounding rock in a tunnel is 18 kN / m³. 3 internal friction angle of the surrounding rock at the working face The angle is 20°, and the tunnel depth is... H The excavation height at the working face is 10m. D The length of the unsupported section behind the working face is 4m. L It is 2m.
[0012] See Figure 1 The method for determining the surrounding rock pressure and influence range of shallow-buried tunnels under face instability is as follows: Step 1: Determine the damage range angle in front of the tunnel face, which is calculated using the following formula: ; in, β The angle of destruction in front of the palm; The internal friction angle of the surrounding rock at the tunnel face; Step 2: Calculate the weight of the landslide debris above, which includes the following steps: (I) Calculate the failure width in front of the tunnel face using the following formula: ; in, L AE The width of the destruction in front of the palm; D This refers to the excavation height at the working face. (II) Calculate the weight of the landslide from above using the following formula: ; in, γ represents the weight of the collapse above; γ represents the unit weight of the surrounding rock; L represents the length of the unsupported section behind the working face. H The tunnel depth is the vertical distance from the ground surface to the tunnel arch. Step 3: Calculate the frictional forces on both sides of the collapsed section above, using the following formula: ; in, This refers to the frictional force between the two sides of the collapsed structure above; Step 4: Calculate the surrounding rock pressure using the following formula: ; Where q is the surrounding rock pressure; Step 5: Determine the scope of influence, which is calculated using the following formula: ; in, The scope of influence.
[0013] Based on the above method and steps, the surrounding rock pressure q under the instability of the tunnel face is obtained as 113.10 kPa.
[0014] Furthermore, determine the scope of impact. It is 18.81m.
[0015] Furthermore, under the condition of instability at the working face, the support force provided by the lining must be greater than 113.10 kPa to ensure safety; the surface monitoring range, i.e. the area of influence, is 18.81 m, and this area should be the focus of monitoring to provide a reference for support design and safe construction.
Claims
1. A method for determining the surrounding rock pressure and influence range of a shallow-buried tunnel under face instability, characterized in that... Includes the following steps: (1) Determine the failure range angle in front of the working face, which is calculated using the following formula: ； in, β The angle of destruction in front of the palm; The internal friction angle of the surrounding rock at the tunnel face; (2) Calculate the weight of the landslide above, which includes the following steps: (I) Calculate the failure width in front of the tunnel face using the following formula: ； in, L AE The width of the destruction in front of the palm; D This refers to the excavation height at the working face. (II) Calculate the weight of the landslide from above using the following formula: ； in, γ represents the weight of the collapse above; γ represents the unit weight of the surrounding rock; L represents the length of the unsupported section behind the working face. H The tunnel depth is the vertical distance from the ground surface to the tunnel arch. (3) Calculate the frictional force on both sides of the collapsed body above, which is calculated using the following formula: ； in, This refers to the frictional force between the two sides of the collapsed structure above; (4) Calculate the surrounding rock pressure using the following formula: ； Where q is the surrounding rock pressure; (5) Determine the scope of influence, which is calculated using the following formula: ； in, The scope of influence.