Comprehensive simulation test system and method for zoning and layered excavation of ultra-large span tunnels

Abstract

The present invention provides a comprehensive simulation test system and method for the zoning, segmentation and layered excavation of an ultra-large span tunnel. The system includes a test model and a tunnel external surrounding rock pressure loading device. The test model includes a tunnel assembled by excavation simulation modules and a simulated rock mass. A number of excavation simulation modules are divided into a minimum construction space, and adjacent excavation simulation modules are isolated by an elastic medium. Each excavation simulation module is provided with an electromagnet group on the horizontal surface and the vertical surface in contact with the elastic medium, and an excavation surface stress monitor is provided on the contact surface between the excavation simulation module and the simulated rock mass. An anchor cable simulation device and a surrounding rock stress monitor are arranged in the simulated rock mass around the tunnel, the fixed end of the anchor cable simulation device is located in the simulated rock mass, and the free force-adding end of the anchor cable simulation device is located on the contour line of the tunnel excavation surface. A tension monitor is provided between the fixed end and the free force-adding end. The tunnel external surrounding rock pressure loading device is used to apply external force to the test model.

Description

Technical Field

[0001] The present invention belongs to the technical field of underground engineering construction, and in particular relates to a comprehensive simulation test system and method for zoning and layered excavation of an ultra-large span tunnel. Background Art

[0002] In my country's railway sector, tunnels with a single span greater than 14 meters are called extra-large span tunnels; in the highway sector, tunnels with a single span greater than 18 meters are called extra-large span tunnels; in the military industry, underground projects with a span greater than 25 meters are called large underground projects. Therefore, the span of most domestic underground projects in the fields of railways and highways does not exceed 25 meters.

[0003] Tunnels exceeding 30 meters are considered ultra-long span tunnels in the industry. Compared to ordinary tunnels, ultra-long span tunnels are significantly different. Due to their large cross-sectional dimensions, ultra-long span tunnels generally require block-by-block, multi-step excavation to form the final cross-sectional profile. Rock pillars within the excavation face are often used as temporary supports, making the construction process complex. Ultra-long span tunnels are excavated in sections and layers, and the surrounding rock is repeatedly disturbed, causing multiple stress redistributions and reducing its self-bearing capacity. Furthermore, as the span increases, the likelihood of unfavorable joints and fissures in the rock mass penetrating to form unstable blocks increases, further compromising tunnel stability. Furthermore, as the span increases, the stress and deformation of the surrounding rock support structure become more complex, increasing the difficulty of designing construction plans, support designs, and determining alarm values for the surrounding rock internal forces for ultra-long span tunnels.

[0004] Currently, most existing experimental research methods are aimed at conducting experimental research on ordinary tunnels, and the improved technologies that have been disclosed also have great limitations: for example, Chinese patent application number 201610551010.3 discloses a tunnel excavation unloading simulation test device and test method. By controlling the rate and position of pulling out the unloading rod, the simulation of different unloading rates and amounts of surrounding rock can be realized, ignoring the influence of friction between the test device and the model material, and is suitable for small-span tunnels; Chinese patent application number 201310425635.1 discloses a deep-buried tunnel excavation simulation experimental device and its application method, which regards the stress, deformation and damage problems of tunnel surrounding rock as axisymmetric problems, and uses parts instead of the whole for research, and the boundary conditions are greatly different from the actual ones; Chinese patent application number 201210097816.1 discloses a geomechanical model chamber excavation device, which realizes the surrounding rock excavation unloading process by first drilling a hole, then pressurizing the hole with an air bag, and then releasing the air bag pressure in the hole, but its loading stress path is different from the actual tunnel excavation stress path. There are large differences in the paths, and it is difficult to simulate the working conditions of ultra-large span tunnels; Chinese patent application number 202411435315.9 discloses a test device for simulating tunnel excavation stress release by releasing the gas in the inflatable airbag to simulate the stress release of the surrounding rock after tunnel excavation and before the installation of the initial support model, but the gas is a compressible medium and it is difficult to truly reflect the stress situation of the excavation surface; Chinese patent application number 202411649113.4 discloses an assembled adjustable tunnel excavation support and protection mechanism, including a tunnel body, a support bottom plate, a vertical lifting mechanism and an adjustable excavation support mechanism. A support bottom plate is installed on the inner bottom of the tunnel body, but it is only for the support structure, and the assembly and construction of the excavation support mechanism is cumbersome, and it cannot simulate the segmented and layered excavation of ultra-large span tunnels. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a comprehensive simulation test system and method for zoning and layered excavation of an ultra-large span tunnel.

[0006] The present invention is achieved through the following technical solutions:

[0007] A comprehensive simulation test system for zoning and layered excavation of ultra-large span tunnels includes a test model and a tunnel external surrounding rock pressure loading device. The test model includes a tunnel assembled from excavation simulation modules made of rigid materials and a simulated rock mass filled around the tunnel. Several excavation simulation modules are divided and layered within the tunnel excavation surface with minimum construction space. Adjacent excavation simulation modules are isolated and filled with elastic medium. Each excavation simulation module is provided with an electromagnet group on the horizontal and vertical surfaces in contact with the elastic medium. An excavation surface stress monitor is provided on the contact surface between the excavation simulation module and the simulated rock mass. An anchor cable simulation device is arranged in the simulated rock mass around the tunnel. The fixed end of the anchor cable simulation device is located in the simulated rock mass, and the free force-adding end of the anchor cable simulation device is located on the tunnel excavation surface. A tension monitor is provided between the fixed end and the free force-adding end. Several surrounding rock stress monitors are pre-buried in the simulated rock mass around the tunnel. The tunnel external surrounding rock pressure loading device is used to apply external force to the test model.

[0008] Furthermore, non-bonding materials are used in the simulated rock mass to simulate rock cracks.

[0009] Furthermore, the elastic medium adopts a rubber cushion layer.

[0010] The present invention also provides a comprehensive simulation test method for zoning and layered excavation of a super-long span tunnel. The method uses the above-mentioned comprehensive simulation test system for zoning and layered excavation of a super-long span tunnel, and includes the following steps:

[0011] Step 1: Determine the material of the simulated rock mass in the test model based on the size and similarity ratio of the test model, cast the simulated rock mass below the bottom of the tunnel excavation surface, and pre-embed the surrounding rock stress monitor;

[0012] Step 2: Arrange the excavation simulation modules in layers and zones, install electromagnet groups on adjacent surfaces of the excavation simulation modules, fill elastic media between adjacent simulation modules, and install excavation surface stress monitors on the contact surfaces between the excavation simulation modules and the simulated rock mass;

[0013] Step 3: pouring simulated rock mass covering the portion above the bottom of the tunnel excavation surface, and pre-embedding surrounding rock stress monitors and anchor cable simulation devices;

[0014] Step 4: Install the tunnel external surrounding rock pressure loading device, calculate the external force of the test model, and apply the external force to the test model through the tunnel external surrounding rock pressure loading device;

[0015] Step 5: Calculate the stress on the contour line of the excavation surface of the test model tunnel. Power is applied to the magnet groups on the horizontal and vertical surfaces of each excavation simulation module, causing the electromagnet groups on both sides of the elastic medium to generate a mutually repulsive force, pressing the contact surface between the excavation simulation module and the simulated rock mass tightly against the simulated rock mass. The original stress state of the surrounding rock before excavation is simulated using the numerical feedback from the excavation surface stress monitor.

[0016] Step 6: Maintain the external loading force of the test model and the loading force between the tunnel internal excavation simulation module for a period of time. After the excavation face stress monitor value stabilizes, record the value of each surrounding rock stress monitor as the data standard for starting the test state;

[0017] Step 7: Based on different layered and zoned excavation schemes and excavation sequences, the electromagnet groups between the excavation simulation modules are controlled to change the originally repulsive forces on both sides of the elastic medium into mutually attractive forces. The elastic medium between the excavation simulation modules is compressed, causing the excavation simulation modules that were originally in close contact with the simulated rock mass to break away from the simulated rock mass, simulating the state after excavation. The surrounding rock stress changes collected by each surrounding rock stress monitor during the entire excavation process are also recorded.

[0018] Step 8: Select the working condition with the smallest change in surrounding rock stress during the entire excavation process as the recommended tunnel construction plan. At the same time, apply a locking force to the free force-adding end of the anchor cable simulation device, monitor the anchor cable tension and surrounding rock stress, and calculate the anchor cable prestressing and surrounding rock pressure warning indicators during the actual construction period through the similarity ratio.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention provides a comprehensive simulation test system and method for zoning, segmenting, and layering excavation of ultra-large-span tunnels. This system includes simulation modules for the original surrounding rock pressure state at the excavation face and the zoning, segmenting, and layering of large-span tunnels, as well as test model creation and selection for multi-condition tunnel excavation simulation. This test system and method can provide a basis for determining key indicators that determine the success and safety of ultra-large-span tunnels, such as optimal excavation plans, anchor cable prestressing settings, and surrounding rock internal force alarm values. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of the comprehensive simulation test system for zoning and layered excavation of ultra-large span tunnels according to the present invention;

[0022] Figure 2 This is a schematic diagram of the stress on the local structure of the test model of the present invention when simulating the initial state without excavation;

[0023] Figure 3 for Figure 2 Enlarged view of point a in the middle;

[0024] Figure 4 This is a schematic diagram of the tunnel excavation zoning and layering plan.

[0025] Reference numerals in the figure: 1-simulated rock mass, 2-excavation simulation module, 3-elastic medium, 4-electromagnet group, 5-excavation face stress monitor, 6-anchor simulation device, 7-surrounding rock stress monitor, 8-tunnel external surrounding rock pressure loading device, 9-rock fissure, 61-free force-adding end of anchor simulation device, 62-anchoring end of anchor simulation device, 63-tension monitor. DETAILED DESCRIPTION

[0026] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art. It should be noted that, unless there is a conflict, the embodiments of the present invention and the features within the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0027] The present invention discloses a specific embodiment of a comprehensive simulation test system for zoning and layered excavation of an ultra-large span tunnel, such as Figures 1 to 3 As shown, the test model includes a test model and a tunnel external surrounding rock pressure loading device 8. The test model includes an excavation simulation module 2 made of rigid material and a simulated rock mass 1 filled around the tunnel. The excavation simulation module 2 is divided into the minimum construction space inside the tunnel excavation surface and the layered excavation area. Multiple excavation simulation modules 2 are assembled to form the entire tunnel. Elastic medium 3 is filled between adjacent excavation simulation modules 2. Electromagnetic iron groups 4 are laid on the contact surfaces of each excavation simulation module 2 on both sides of the elastic medium 3. Electromagnetic iron groups 4 are laid on the contact surfaces between the excavation simulation module 2 and the simulated rock mass 1. An excavation face stress monitor 5 is provided, an anchor cable simulation device 6 is arranged in the simulated rock mass 1 around the tunnel, the anchor cable simulation device anchoring end 62 is located in the simulated rock mass 1, the anchor cable simulation device free force-applying end 61 is located on the longitudinal surface of the tunnel excavation face contour line, a tension monitor 63 is provided between the anchor cable simulation device anchoring end 62 and the anchor cable simulation device free force-applying end 61, a number of surrounding rock stress monitors 7 are pre-buried in the simulated rock mass 1 around the tunnel excavation face, and the tunnel external surrounding rock pressure loading device 8 is used to apply external force to the test model.

[0028] Assume that the excavation simulation modules 2 in the tunnel excavation surface are arranged as follows Figure 4 As shown, elastic medium 3 is filled between each excavation simulation module 2, and an electromagnet group 4 is fixedly installed on the contact surface between each excavation simulation module 2 and the elastic medium 3. The positional relationship between the electromagnet group 4 and the elastic medium 3 is shown in FIG. Figure 3As shown, the electromagnet groups 4 on both sides of the elastic medium 3 can generate mutually repulsive forces or mutually attractive forces after being energized. When the test model simulates the initial state without excavation, the electromagnet groups 4 on both sides of the elastic medium 3 generate mutually repulsive forces. The 1# excavation simulation module and the 5# excavation simulation module are located in the middle, and the excavation simulation modules on both sides are symmetrically arranged. When the same current is passed through all the electromagnet groups 4, the 1# excavation simulation module and the 5# excavation simulation module are subjected to the same force on the left and right sides. Among them, the 1# excavation simulation module is affected by the repulsive force of the bottom surface and is subjected to an upward repulsive force as a whole. The 5# excavation simulation module is affected by the repulsive force of the top and is subjected to a downward repulsive force as a whole. The left 3# excavation simulation module is subjected to both leftward and downward repulsive forces, and the right 3# excavation simulation module is subjected to both leftward and downward repulsive forces. At the same time, they are subjected to repulsive forces to the right and downward, the left 2# excavation simulation module and the left 4# excavation simulation module are subjected to repulsive forces to the upward and left, and the right 2# excavation simulation module and the right 4# excavation simulation module are subjected to repulsive forces to the upward and right. The currents flowing into all the electromagnet groups 4 are adjusted synchronously so that the excavation surface stress monitor 5 on the contact surface between the outermost excavation simulation module and the simulated rock mass 1 meets the requirements. The outside of the test model is loaded by the tunnel external surrounding rock pressure loading device 8, and the inside reaches the state when the tunnel is not excavated under the action of the repulsive force between the excavation simulation modules. The stress state of the left 2# excavation simulation module is as follows: Figure 2 shown. Figure 2 The AB and BC surfaces are Figure 4The horizontal bottom surface and vertical side surface of the middle left 2# excavation simulation module, AC surface is the contact surface between the excavation simulation module 2 and the simulated rock mass 1, and the excavation surface stress monitor 5 is installed on the AC surface. The horizontal AB surface and the vertical BC surface are in contact with the elastic medium 3 respectively, and the electromagnet group 4 is fixedly installed on the AB surface and the BC surface. After the electromagnet group 4 is energized, when repulsive forces are generated between the electromagnet group 4 on the AB surface and the electromagnet group 4 on the top surface of the left 3# excavation simulation module in contact with the elastic medium 3, and between the electromagnet group 4 on the BC surface and the electromagnet group 4 on the leftmost contact surface of the left 4# excavation simulation module in contact with the elastic medium 3, the left 2# excavation simulation module is simultaneously subjected to upward and leftward forces, resulting in the left 2# excavation simulation module as a whole being subjected to a repulsive force to the upper left, and the simulated rock mass 1 and the contact surface AC surface of the excavation simulation module 2 are tightly pressed against each other, which increases the stress on the AC surface and is used to simulate the original surrounding rock pressure of the excavation surface. The elastic medium 3 is compressible under load and rebounds upon unloading. When simulating the unloading state after the excavation of the left 2# and right 2# areas, taking the force on the left 2# excavation simulation module as an example, when attractive forces are generated between the AB surface electromagnet group 4 and the top surface electromagnet group 4 of the left 3# excavation simulation module on the other side of the corresponding elastic medium 3, and between the BC surface electromagnet group 4 and the left surface electromagnet group 4 of the left 4# excavation simulation module on the other side of the corresponding elastic medium 3, the elastic medium 3 is squeezed, and the left 2# excavation simulation module is simultaneously subjected to downward and rightward forces. Driven by the electromagnet group 4, the left 2# excavation simulation module moves inward and downward to the right, causing the contact surface AC of the simulated rock mass 1 to break away from the contact surface AC of the left 2# excavation simulation module, simulating the unloading condition after surrounding rock excavation. The magnitude of the repulsive or attractive force between the electromagnet groups 4 on both sides of the elastic medium 3 is adjusted by controlling the current in the electromagnet group 4. If the unloading state after excavation of area 1# is simulated, it is only necessary to change the repulsive force between the electromagnet group 4 on the bottom surface of the 1# excavation simulation module and the electromagnet group 4 on the top surface of the 5# excavation simulation module into an attractive force to squeeze the elastic medium 3 between the two excavation simulation modules, so that the top surface of the 1# excavation simulation module is separated from the simulated rock mass 1.

[0029] In the simulated rock mass 1, non-bonding materials are used to simulate rock mass cracks, and the elastic medium 3 is a rubber cushion.

[0030] The tunnel external surrounding rock pressure loading device 8 adopts a hydraulic system or a jack.

[0031] The above-mentioned comprehensive simulation test system was used to complete comprehensive simulation tests of ultra-large span tunnel zoning and layered excavation, and the optimal construction plan was determined based on this. The specific process is as follows:

[0032] Step 1: Determine the material of the simulated rock mass 1 in the test model according to the size and similarity ratio of the test model, cast the simulated rock mass 1 to the bottom of the tunnel excavation surface, and embed the surrounding rock stress monitor 7 in the simulated rock mass 1 below the bottom surface.

[0033] Step 2: Set up the excavation simulation module 2 in layers and zones, arrange the electromagnet group 4 at the adjacent interfaces of the excavation simulation module 2, and install the excavation surface stress monitor 5 on the contact surface between the excavation simulation module 2 and the simulated rock mass 1.

[0034] Step three: cast a test model of the part above the bottom of the tunnel excavation surface to simulate the rock mass 1. During the casting process, use non-bonding materials to simulate the rock cracks 9 in the model, and pre-embed the surrounding rock stress monitor 7 and the anchor cable simulation device 6 in the simulated rock mass 1.

[0035] Step 4: Install the tunnel external surrounding rock pressure loading device 8, calculate the external force of the test model, and load vertical and horizontal external forces on the test model through the tunnel external surrounding rock pressure loading device 8.

[0036] Step 5: Calculate the stress on the contour line of the excavation surface of the test model tunnel. By adjusting the electromagnet groups 4 in the horizontal and vertical directions of the excavation simulation module 2, the repulsive force generated by the electromagnet groups 4 on both sides of the elastic medium 3 is used to simulate the original stress state of the surrounding rock inside the tunnel before excavation.

[0037] Step 6: Maintain the external loading of the test model and the internal loading of the excavation simulation module 2 for a period of time. After the value of the excavation surface stress monitor 5 stabilizes, record the value of the surrounding rock stress monitor 7 as the data standard for starting the test state.

[0038] Step seven, according to different layered and zoned excavation schemes and different construction sequences of the same excavation scheme, and in accordance with the principle of simultaneous construction in symmetrical positions, the forces between the electromagnet group 4 on the horizontal surface of the excavation simulation module 2 and the electromagnet group 4 on the vertical surface and the electromagnet group 4 on the other side of the elastic medium 3 at the corresponding position are adjusted to attract each other, and the elastic medium 3 is compressed, so that the surface of the excavation simulation module 2 is out of contact with the simulated rock mass 1, and the unloading condition of the surrounding rock after excavation at the position of the excavation simulation module 2 is simulated, and the surrounding rock stress changes during the construction simulation process of different excavation schemes and different excavation sequences are recorded by the surrounding rock stress monitor 7.

[0039] Step eight, select the excavation scheme and construction sequence with the smallest change in surrounding rock stress as the recommended scheme for layered and zoned excavation of tunnel construction, and simulate the unloading condition of the excavation process by using the excavation simulation module 2 according to the construction sequence of the selected recommended excavation scheme. At the same time, apply a locking force to the free force-applying end 61 of the anchor cable simulation device, monitor the anchor cable tension and surrounding rock stress through the tension monitor 63 and the surrounding rock stress monitor 7, and calculate the anchor cable prestressing and surrounding rock pressure warning indicators during the actual construction period through the similarity ratio.

[0040] If the excavation simulation module 2 of the partitioned and layered excavation areas within the tunnel excavation surface is Figure 4 As shown in the arrangement, when the excavation face stress is unloaded in step 7, the left 2 and right 2 modules are unloaded at the same time, the left 3 and right 3 modules are unloaded at the same time, and the left 4 and right 4 modules are unloaded at the same time. By simulating the changes in surrounding rock stress during different construction sequences, the construction sequence with the smallest fluctuation is selected as the actual construction plan.

[0041] The present invention has been described in detail above through the embodiments, but the contents described are only exemplary embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. The scope of protection of the present invention is defined by the claims. Any use of the technical solution described in the present invention, or any person skilled in the art who, inspired by the technical solution of the present invention, designs a similar technical solution within the essence and scope of protection of the present invention to achieve the above-mentioned technical effects, or any equivalent changes and improvements made to the scope of application, shall still fall within the scope of protection covered by the patent of the present invention. It should be noted that for the sake of clarity, the description of some components and processes that have no direct and obvious connection with the scope of protection of the present invention but are known to those skilled in the art are omitted in the description of the present invention.

Claims

1. A comprehensive simulation test system for zoning and layered excavation of ultra-large span tunnels, characterized by: The invention comprises a test model and a tunnel external surrounding rock pressure loading device. The test model comprises a tunnel assembled by excavation simulation modules made of rigid materials and a simulated rock mass filled around the tunnel. The tunnel excavation surface is divided into several excavation simulation modules by partitioning and layering with the minimum construction space. Adjacent excavation simulation modules are isolated and filled with elastic media. Each excavation simulation module is provided with an electromagnet group on the horizontal and vertical surfaces in contact with the elastic medium. An excavation surface stress monitor is provided on the contact surface between the excavation simulation module and the simulated rock mass. An anchor cable simulation device is arranged in the simulated rock mass around the tunnel. The fixed end of the anchor cable simulation device is located in the simulated rock mass. The free force-adding end of the anchor cable simulation device is located on the contour line of the tunnel excavation surface. A tension monitor is provided between the anchor end and the free force-adding end. Several surrounding rock stress monitors are pre-buried in the simulated rock mass around the tunnel. The tunnel external surrounding rock pressure loading device is used to apply external force to the test model. Non-adhesive materials are used in the simulated rock mass to simulate rock cracks.

2. The comprehensive simulation test system for zoning and layered excavation of ultra-large span tunnels according to claim 1 is characterized in that: The elastic medium adopts a rubber cushion.

3. A comprehensive simulation test method for zoning and layered excavation of ultra-large span tunnels, characterized by: The method adopts the comprehensive simulation test system for zoning and layered excavation of an ultra-large span tunnel according to any one of claims 1 or 2, and comprises the following steps: Step 1: Determine the material of the simulated rock mass in the test model based on the size and similarity ratio of the test model, cast the simulated rock mass below the bottom of the tunnel excavation surface, and pre-embed the surrounding rock stress monitor; Step 2: Arrange the excavation simulation modules in layers and zones, install electromagnet groups on adjacent surfaces of the excavation simulation modules, fill elastic media between adjacent simulation modules, and install excavation surface stress monitors on the contact surfaces between the excavation simulation modules and the simulated rock mass; Step 3: pouring simulated rock mass covering the portion above the bottom of the tunnel excavation surface, and pre-embedding surrounding rock stress monitors and anchor cable simulation devices; Step 4: Install the tunnel external surrounding rock pressure loading device, calculate the external force of the test model, and apply the external force to the test model through the tunnel external surrounding rock pressure loading device; Step 5: Calculate the stress on the contour line of the excavation surface of the test model tunnel. Power is applied to the magnet groups on the horizontal and vertical surfaces of each excavation simulation module, causing the electromagnet groups on both sides of the elastic medium to generate a mutually repulsive force, pressing the contact surface between the excavation simulation module and the simulated rock mass tightly against the simulated rock mass. The original stress state of the surrounding rock before excavation is simulated using the numerical feedback from the excavation surface stress monitor. Step 6: Maintain the external loading force of the test model and the loading force between the tunnel internal excavation simulation module for a period of time. After the excavation face stress monitor value stabilizes, record the value of each surrounding rock stress monitor as the data standard for starting the test state; Step 7: Based on different layered and zoned excavation schemes and excavation sequences, the electromagnet groups between the excavation simulation modules are controlled to change the originally repulsive forces on both sides of the elastic medium into mutually attractive forces. The elastic medium between the excavation simulation modules is compressed, causing the excavation simulation modules that were originally in close contact with the simulated rock mass to break away from the simulated rock mass, simulating the state after excavation. The surrounding rock stress changes collected by each surrounding rock stress monitor during the entire excavation process are also recorded. Step 8: Select the working condition with the smallest change in surrounding rock stress during the entire excavation process as the recommended tunnel construction plan. At the same time, apply a locking force to the free force-adding end of the anchor cable simulation device, monitor the anchor cable tension and surrounding rock stress, and calculate the anchor cable prestressing and surrounding rock pressure warning indicators during the actual construction period through the similarity ratio.

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