A method for predicting and evaluating tunnel large deformation disaster induced by instability of anchoring system

Abstract

This invention provides a method for predicting and assessing tunnel deformation disasters induced by anchorage system instability, relating to the field of tunnel engineering technology. It establishes an assessment model for tunnel deformation disasters induced by anchorage system instability, and predicts the level of large deformation under unsupported conditions by inputting the geological conditions of the tunnel to be predicted. The method uses the long-term deformation and strength of the anchorage system as assessment standards, and calculates the threshold values ​​for long-term deformation and strength failure based on the support design scheme of the anchorage system. It collects measured data on the surrounding rock deformation and radial force of the anchorage system at the site of the tunnel to be predicted, both after excavation without support and after initial support. By comparing and analyzing the measured surrounding rock deformation and radial force of the anchorage system with the calculated long-term deformation and strength threshold values ​​of the anchorage system from the assessment model, it is determined that the large deformation disaster in the tunnel is caused by anchorage system instability.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, and in particular to a method for predicting and assessing large deformation disasters in tunnels induced by instability of the anchoring system. Background Technology

[0002] In mining engineering, water conservancy and hydropower engineering, and tunnel engineering, tunnel excavation is often accompanied by high ground stress, excavation unloading, blasting disturbance, and weak surrounding rock. The superposition of these factors leads to significant deformation of the tunnel surrounding rock, resulting in problems such as cracking of the initial support, arch twisting, anchor bolt breakage, and secondary lining cracking, severely compromising construction quality. Furthermore, excessive deformation of the surrounding rock can cause the tunnel to exceed its limits, requiring additional procedures such as replacing the initial support and reinforcing the surrounding rock, increasing the on-site construction burden, slowing down the construction progress, and causing a huge waste of manpower and financial resources, thus multiplying the tunnel construction cost. To apply reasonable support measures to suppress large deformation of the tunnel surrounding rock, it is necessary to predict the possible large deformation levels of the tunnel surrounding rock.

[0003] The currently accepted method for predicting large deformation levels in tunnels is the strength-stress ratio method. This method determines the tunnel's large deformation level by comparing the ratio of the uniaxial compressive strength of the rock mass to the maximum principal stress of the in-situ stress. However, construction sites often have complex and variable geological conditions, with rapid changes in rock strata. Furthermore, most large deformations occur in sections with weak surrounding rock, making it difficult to obtain the strength values ​​of the surrounding rock mass and the in-situ stress. This makes the accepted strength-stress ratio method unreliable for accurately predicting large deformations. Additionally, this method does not consider the impact of support measures on tunnel deformation. The occurrence of large deformation disasters in tunnels is also closely related to the designed surrounding rock support and control scheme. Reasonable support and control measures can suppress large deformations, while a mismatch between the support and control scheme and the actual deformation level of the surrounding rock can lead to large deformation disasters after tunnel support. Therefore, it is urgently needed at construction sites where large deformation disasters have occurred to use more accurate on-site monitoring data to assess the rationality of the large deformation level and control scheme after tunnel support, moving away from the reliance on experience and semi-experience-based predictions by on-site construction technicians. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for predicting and assessing tunnel deformation disasters induced by anchoring system instability. This method can efficiently and accurately predict the initial deformation level of the tunnel surrounding rock, and simultaneously assess the matching degree between the designed support control scheme and different deformation levels of the surrounding rock, as well as whether the surrounding rock-anchoring system is unstable. This effectively solves the problems of unpredictable large deformation levels and the rationality of support design in tunnel construction sites.

[0005] The present invention adopts the following technical solution:

[0006] A method for predicting and assessing tunnel deformation disasters induced by anchoring system instability includes the following steps:

[0007] Step S1: Establish a disaster assessment model for large deformation of tunnels induced by instability of anchoring system, and predict the level of large deformation of tunnels without support by inputting the geological conditions of the tunnel to be predicted.

[0008] The assessment model for tunnel large deformation disaster induced by anchoring system instability is specifically designed by using three-dimensional discrete element numerical calculation software. It considers three-dimensional constitutive models of different types of surrounding rock, equivalent mechanical models of anchoring systems under different surrounding rock types, and equivalent parameters, and calculates the deformation of the tunnel under the influence of excavation and the support force of the anchoring system. The different types include layered surrounding rock, jointed surrounding rock, and weakly cemented surrounding rock.

[0009] The geological conditions of the large deformation tunnel include the tunnel's ground stress information, the anisotropic mechanical strength parameters of the surrounding rock, the strike and dip angle of the rock strata, faults, the tunnel excavation sequence, and the tunnel size information.

[0010] The anchoring system includes anchor bolts and anchor cables.

[0011] The prediction of the tunnel's large deformation level is based on the strength-stress ratio and the large deformation level standard recognized in the "Technical Specification for Railway Extrusion-Type Surrounding Rock Tunnels"; where the strength-stress ratio refers to the estimation of the natural compressive strength R of the rock mass based on the integrity of the surrounding rock. m With the maximum initial principal stress σ of the rock mass max The ratio is used to classify the tunnel's large deformation level by consulting the high ground stress large deformation classification table;

[0012] Step S2: Using the long-term deformation and strength of the anchoring system as evaluation criteria, and based on the design scheme of the anchoring system support for the tunnel to be built, calculate the threshold for the long-term deformation and the threshold for the failure of the anchoring system strength.

[0013] The long-term deformation threshold and anchorage system strength threshold are the maximum long-term deformation of the surrounding rock and the failure strength of the anchorage system calculated by the tunnel large deformation disaster assessment model induced by anchorage system instability.

[0014] Step S3: Collect measured data on the deformation of the surrounding rock and the radial stress of the anchoring system after the tunnel excavation is completed and before the initial support is completed at the site of the tunnel to be predicted to have large deformation.

[0015] The measured data of surrounding rock deformation and radial force of the anchoring system are as follows: at the tunnel construction site where the large deformation level to be predicted is to be determined, after the excavation of the tunnel face, multiple displacement gauges are installed in the surrounding rock to collect data on the long-term deformation of the surrounding rock; after the initial support is completed, the force monitoring device of the anchoring system is installed to collect the force strength value of the anchoring system as the measured data of radial force of the anchoring system; the surrounding rock deformation collected after the initial support is the surrounding rock deformation including the anchoring system.

[0016] Step S4: Compare and analyze the measured deformation of the surrounding rock on site with the radial force of the anchoring system and the long-term deformation threshold and strength threshold of the anchoring system calculated by the assessment model of the large deformation disaster induced by the instability of the anchoring system. If one of the two measured values ​​exceeds the assessment threshold, it is determined that the anchoring system is unstable, and then it is determined that the large deformation disaster in the tunnel is caused by the instability of the anchoring system.

[0017] The beneficial effects of adopting the above technical solution are as follows:

[0018] This invention provides a method for predicting and assessing tunnel deformation disasters induced by anchorage system instability. This method can accurately predict and determine the tunnel deformation level under different surrounding rock and geological conditions. It can also assess the rationality of the support control scheme under a specific deformation level and its compatibility with the on-site deformation. This not only helps the construction site predict the tunnel deformation level and decide on the corresponding support scheme, but also allows for the assessment of the rationality of the support scheme, timely adjustments, and reduced trial-and-error, ensuring efficient and smooth construction progress and meeting construction quality standards. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the overall process of the prediction and evaluation method of this invention.

[0020] Figure 2 This is a calculation displacement diagram in an embodiment of the present invention. Detailed Implementation

[0021] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0022] A predictive assessment method for tunnel large deformation disasters induced by anchorage system instability, such as... Figure 1 As shown, it includes the following steps:

[0023] Step S1: Establish a disaster assessment model for large deformation of tunnels induced by instability of anchoring system, and predict the level of large deformation of tunnels without support by inputting the geological conditions of the tunnel to be predicted.

[0024] The assessment model for tunnel large deformation disaster induced by anchoring system instability is specifically designed by using three-dimensional discrete element numerical calculation software. It considers three-dimensional constitutive models of different types of surrounding rock, equivalent mechanical models of anchoring systems under different surrounding rock types, and equivalent parameters, and calculates the deformation of the tunnel under the influence of excavation and the support force of the anchoring system. The different types include layered surrounding rock, jointed surrounding rock, and weakly cemented surrounding rock.

[0025] The geological conditions of the large deformation tunnel include the tunnel's ground stress information, the anisotropic mechanical strength parameters of the surrounding rock, the strike and dip angle of the rock strata, faults, the tunnel excavation sequence, and the tunnel size information.

[0026] The anchoring system includes anchor bolts and anchor cables.

[0027] The prediction of the tunnel's large deformation level is based on the strength-stress ratio and the large deformation level standard recognized in the "Technical Specification for Railway Extrusion-Type Surrounding Rock Tunnels"; where the strength-stress ratio refers to the estimation of the natural compressive strength R of the rock mass based on the integrity of the surrounding rock. m With the maximum initial principal stress σ of the rock mass max The ratio is used to classify the tunnel's large deformation level by consulting the high ground stress large deformation classification table;

[0028] Step S2: Using the long-term deformation and strength of the anchoring system as evaluation criteria, and based on the design scheme of the anchoring system support for the tunnel to be built, calculate the threshold for the long-term deformation and the threshold for the failure of the anchoring system strength.

[0029] The long-term deformation threshold and anchorage system strength threshold are the maximum long-term deformation of the surrounding rock and the failure strength of the anchorage system calculated by the tunnel large deformation disaster assessment model induced by anchorage system instability.

[0030] Step S3: Collect measured data on the deformation of the surrounding rock and the radial stress of the anchoring system after the tunnel excavation is completed and before the initial support is completed at the site of the tunnel to be predicted to have large deformation.

[0031] The measured data of surrounding rock deformation and radial force of the anchoring system are as follows: at the tunnel construction site where the large deformation level to be predicted is to be determined, after the excavation of the tunnel face, multiple displacement gauges are installed in the surrounding rock to collect data on the long-term deformation of the surrounding rock; after the initial support is completed, the force monitoring device of the anchoring system is installed to collect the force strength value of the anchoring system as the measured data of radial force of the anchoring system; the surrounding rock deformation collected after the initial support is the surrounding rock deformation including the anchoring system.

[0032] Step S4: Compare and analyze the measured deformation of the surrounding rock on site with the radial force of the anchoring system and the long-term deformation threshold and strength threshold of the anchoring system calculated by the assessment model of the large deformation disaster induced by the instability of the anchoring system. If one of the two measured values ​​exceeds the assessment threshold, it is determined that the anchoring system is unstable, and then it is determined that the large deformation disaster in the tunnel is caused by the instability of the anchoring system.

[0033] Taking a tunnel project under construction as an example, the project is actually classified as a Class I large deformation level. The project overview, ground stress conditions, anisotropic mechanical parameters, and Class I support design scheme are incorporated into the assessment model for tunnel large deformation disaster induced by anchorage system instability. The calculation parameters are as follows:

[0034]

[0035] Among them, d, s1, s2, E b μ b G b and These are the radius, spacing, row spacing, elastic modulus, Poisson's ratio, shear modulus, and tensile strength of the anchor bolt or anchor cable, respectively. r μ r c r , These represent the elastic modulus, Poisson's ratio, cohesion, and internal friction angle of the rock mass, respectively; R0 is the tunnel radius; p1 is the support reaction force provided by the anchor bolt; σ1 and σ3 are the ground stresses; all mechanical parameters are in MPa (internal friction angle is in °); and all geometric parameters are in meters.

[0036] Under this engineering condition, the instability threshold is defined as follows: from excavation to unsupported conditions, the tunnel deformation (unilateral deformation) reaches 0.193m, or the radial stress on the surrounding rock reaches 7.051MPa. After initial anchor bolt support is completed, the instability threshold is defined as follows: the tunnel deformation (unilateral deformation) reaches 0.061m, or the radial stress on the tunnel anchor body reaches 7.814MPa. The displacement calculation diagram is shown below. Figure 2 As shown.

[0037] By selecting on-site monitoring and measurement data of the cross section, the deformation of the surrounding rock after excavation without support and after initial support is compared with the threshold of tunnel surrounding rock deformation when the anchoring system becomes unstable, as calculated by the model. The comparison results are shown in the table below.

[0038]

[0039] Data comparison shows that the deformation of the surrounding rock and the radial stress strength of the anchoring system are both less than the long-term deformation and strength threshold of the anchoring system calculated by the assessment model for large deformation disasters induced by instability of the anchoring system. Therefore, it can be determined that the deformation level of the tunnel is Level 1 large deformation, and the support control measures have not been unstable or damaged, indicating that the support control measures are reasonably matched.

[0040] The above description is merely a preferred embodiment of this disclosure and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in the embodiments of this disclosure is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in the embodiments of this disclosure.

Claims

1. A method for predicting and assessing tunnel deformation disasters induced by anchorage system instability, characterized in that, Includes the following steps: Step S1: Establish a disaster assessment model for large deformation of tunnels induced by instability of anchoring system, and predict the level of large deformation of tunnels without support by inputting the geological conditions of the tunnel to be predicted. Step S2: Using the long-term deformation and strength of the anchoring system as evaluation criteria, and based on the design scheme of the anchoring system support for the tunnel to be built, calculate the threshold for the long-term deformation and the threshold for the failure of the anchoring system strength. Step S3: Collect measured data on the deformation of the surrounding rock and the radial stress of the anchoring system after the tunnel excavation is completed and before the initial support is completed at the site of the tunnel to be predicted to have large deformation. Step S4: Compare and analyze the measured deformation of the surrounding rock on site with the radial force of the anchoring system and the long-term deformation threshold and strength threshold of the anchoring system calculated by the assessment model of the large deformation disaster induced by the instability of the anchoring system. If one of the two measured values ​​exceeds the assessment threshold, it is determined that the anchoring system is unstable, and then it is determined that the large deformation disaster in the tunnel is caused by the instability of the anchoring system.

2. The method for predicting and assessing tunnel deformation disasters induced by anchoring system instability according to claim 1, characterized in that, The assessment model for the tunnel large deformation disaster induced by the instability of the anchoring system in step S1 is specifically as follows: using three-dimensional discrete element numerical calculation software, considering three-dimensional constitutive models of different types of surrounding rock, equivalent mechanical models of the anchoring system under different types of surrounding rock, and equivalent parameters, the deformation of the tunnel under the influence of excavation and the support force of the anchoring system are calculated in the assessment model; among which, different types include layered surrounding rock, jointed surrounding rock, and weakly cemented surrounding rock.

3. The method for predicting and assessing tunnel deformation disasters induced by anchoring system instability according to claim 1, characterized in that, The geological conditions of the large deformation tunnel mentioned in step S1 include the tunnel's geostress information, the anisotropic mechanical strength parameters of the surrounding rock, the strike and dip angle of the rock strata, faults, the tunnel excavation sequence, and the tunnel size information.

4. The method for predicting and assessing tunnel deformation disasters induced by anchoring system instability according to claim 1, characterized in that, The anchoring system described in step S1 includes anchor bolts and anchor cables.

5. The method for predicting and assessing tunnel deformation disasters induced by anchoring system instability according to claim 1, characterized in that, The tunnel large deformation level prediction standard mentioned in step S1 is based on the strength-stress ratio and the large deformation level standard identified in the "Technical Specification for Railway Extrusion-Type Surrounding Rock Tunnels"; where the strength-stress ratio refers to the natural compressive strength of the rock mass. R m With the maximum initial principal stress of the rock mass σ max The ratio is used to classify the tunnel's large deformation level by consulting the high ground stress large deformation classification table.

6. The method for predicting and assessing tunnel deformation disasters induced by anchoring system instability according to claim 1, characterized in that, The long-term deformation threshold and the anchoring system strength threshold mentioned in step S2 are the maximum long-term deformation of the surrounding rock and the failure strength of the anchoring system, respectively, calculated by the tunnel large deformation disaster assessment model induced by anchoring system instability.

7. The method for predicting and assessing tunnel deformation disasters induced by anchoring system instability according to claim 1, characterized in that, The measured data of surrounding rock deformation and radial force of the anchoring system mentioned in step S3 are as follows: at the tunnel construction site where the large deformation level to be predicted is to be determined, after the excavation of the tunnel face, multi-point displacement gauges are installed in the surrounding rock to collect data on the long-term deformation of the surrounding rock; after the initial support is completed, the force monitoring device of the anchoring system is installed to collect the force strength value of the anchoring system as the measured data of radial force of the anchoring system, and the surrounding rock deformation collected after the initial support is the surrounding rock deformation including the anchoring system.

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