Prediction and evaluation method for tunnel large deformation disaster induced by anchoring system instability

Abstract

The invention provides a prediction and evaluation method for tunnel large deformation disasters induced by anchoring system instability, and relates to the technical field of tunnel engineering.The method comprises the steps that a model for evaluating the tunnel large deformation disasters induced by anchoring system instability is established, the geological condition of a large deformation tunnel to be predicted is input, and large deformation grade prediction is conducted under the condition that the tunnel is not supported; the long-term deformation of the anchoring system and the strength of the anchoring system are adopted as evaluation standards, and an anchoring system long-term deformation threshold value and an anchoring system strength damage threshold value are calculated on the basis of a to-be-tunnel anchoring system support design scheme; tunnel excavation is carried out on a to-be-predicted large-deformation tunnel site to complete actual measurement data collection work of surrounding rock deformation and radial stress of an anchoring system after unsupported and primary supporting are completed; and comparing and analyzing the surrounding rock deformation measured on site, the radial stress of the anchoring system, the long-term deformation of the anchoring system calculated by the evaluation model and the strength threshold value of the anchoring system, and judging that the large deformation disaster of the tunnel is induced by the instability of the anchoring system.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a method for predicting and evaluating large deformation disasters of tunnels induced by instability of an anchoring system. Background Art

[0002] In the fields of mining engineering, water conservancy and hydropower engineering, tunnel engineering, etc., tunnel excavation is often accompanied by high ground stress, excavation unloading, blasting disturbance, weak surrounding rock, etc. The superposition of these factors causes the tunnel surrounding rock to produce a large deformation, resulting in cracking of the primary support of the surrounding rock, twisting of the arch frame, breaking of anchor rods, cracking of the secondary lining, etc., which seriously damages the construction quality; in addition, the excessive deformation of the surrounding rock causes the tunnel to exceed the limit, and additional processes such as replacement of the primary support of the arch frame and reinforcement of the surrounding rock are required, which increases the burden of on-site construction, not only reduces the construction progress, but also causes huge waste of manpower and financial resources, and increases the cost of tunnel construction exponentially. In order to impose reasonable support measures to suppress the large deformation of the tunnel surrounding rock, it is necessary to predict the possible large deformation level of the tunnel surrounding rock.

[0003] The currently recognized method for predicting the large deformation level of tunnels is the strength-stress ratio method. Its principle is to judge the large deformation level of the tunnel by the ratio of the uniaxial compressive strength of the rock mass to the maximum principal stress of the in-situ stress. The geology of the construction site is complex and changeable, the rock strata change rapidly, and most of the large deformation of the tunnel occurs in the weak surrounding rock tunnel section. It is inconvenient to obtain the strength value of the surrounding rock mass and the in-situ stress of the tunnel, which leads to the inability to accurately implement the recognized strength-stress ratio method to predict the large deformation of the surrounding rock. At the same time, this method does not consider the influence of support measures on the large deformation of the tunnel. The occurrence of large deformation disasters in tunnels is also closely related to the designed surrounding rock support control scheme. Reasonable support control measures can suppress the large deformation of the surrounding rock. However, if the support control scheme does not match the deformation level of the surrounding rock on site, it will lead to large deformation disasters in the surrounding rock after tunnel support. How to use more accurate on-site monitoring data to evaluate the large deformation level of the surrounding rock and the rationality of the control scheme after tunnel support, and get rid of the experience and semi-empirical prediction and evaluation of on-site construction technicians, is currently an urgent need for construction sites where large deformation disasters of tunnels occur. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides a prediction and assessment method for large deformation disasters in tunnels induced by instability of the anchoring system, which can efficiently and accurately make a preliminary prediction of the large deformation level of the tunnel surrounding rock, and at the same time evaluate and judge the matching degree between the designed support control scheme and the different deformation levels of the surrounding rock, and whether the surrounding rock-anchoring system is unstable, effectively solving the problems of the unpredictable large deformation level and the rationality of the support design at the tunnel large deformation construction site.

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

[0006] A method for predicting and evaluating large deformation disasters of tunnels induced by instability of an anchoring system comprises the following steps:

[0007] Step S1, establishing a disaster assessment model for large deformation of a tunnel induced by instability of the anchoring system, and predicting the large deformation level of the tunnel without support by inputting the geological conditions of the large deformation tunnel to be predicted;

[0008] The anchor system instability-induced tunnel large deformation disaster assessment model is specifically to use three-dimensional discrete element numerical calculation software to consider different types of surrounding rock three-dimensional constitutive models, anchor system equivalent mechanical models under different surrounding rock types and equivalent parameters into the assessment model to calculate the deformation of the tunnel under the influence of excavation and the anchor system support force value; 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 ground stress information of the tunnel, the anisotropic mechanical strength parameters of the surrounding rock, the direction and inclination of the rock formation, faults, tunnel excavation sequence, and tunnel size information;

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

[0011] The prediction of tunnel large deformation level is based on the standard of strength-stress ratio and the large deformation level standard recognized by the Technical Specifications for Railway Squeezing Rock Tunnels; the strength-stress ratio refers to the estimation of the natural compressive strength R of the rock mass based on the degree of integrity of the surrounding rock. m and the maximum initial principal stress σ max The ratio of the tunnel deformation level is determined by searching the high ground stress large deformation classification table.

[0012] Step S2, using the long-term deformation of the anchor system and the strength of the anchor system as evaluation criteria, and calculating the long-term deformation threshold of the anchor system and the strength damage threshold of the anchor system based on the design scheme of the anchor system support of the tunnel to be built;

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

[0014] Step S3, collecting measured data of surrounding rock deformation and radial force of the anchoring system after tunnel excavation is completed without support and after initial support at the site of the tunnel to be predicted with large deformation;

[0015] The measured data of surrounding rock deformation and radial force of the anchoring system are: at the construction site of the tunnel with a large deformation level to be predicted, after the excavation of the face, a multi-point displacement meter is installed in the tunnel surrounding rock to collect data on the long-term deformation of the surrounding rock; after the initial support is completed, a force monitoring device of the anchoring system is installed to collect the force strength value of the anchoring system as the measured data of the 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;

[0016] Step S4, comparing and analyzing the surrounding rock deformation and radial stress of the anchoring system measured on site with the anchoring system long-term deformation threshold and anchoring system strength threshold calculated by the anchoring system instability-induced tunnel large deformation disaster assessment model; if one of the two measured values ​​exceeds the assessment threshold, it is judged that the anchoring system is unstable, and then it is judged 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:

[0018] The present invention provides a prediction and evaluation method for large deformation disasters of tunnels induced by instability of an anchoring system. The method can more accurately predict and judge the large deformation level of the tunnel according to different surrounding rocks and different geological conditions. At the same time, it can evaluate and judge whether the support control scheme is reasonable under a certain deformation level and the degree of matching with the on-site deformation. It can not only help the construction site to predict the deformation level of the tunnel and decide on the support scheme corresponding to the deformation level, but also judge the rationality of the support scheme, make timely adjustments, reduce the number of trial and error, and ensure that the construction progress is efficient and smooth and the construction quality meets the standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the overall flow chart of the prediction and evaluation method of the present invention;

[0020] Figure 2 The displacement map is calculated in the embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0022] A prediction and assessment method for large deformation disasters in tunnels induced by instability of anchoring system, such as Figure 1 As shown, the following steps are included:

[0023] Step S1, establishing a disaster assessment model for large deformation of a tunnel induced by instability of the anchoring system, and predicting the large deformation level of the tunnel without support by inputting the geological conditions of the large deformation tunnel to be predicted;

[0024] The anchor system instability-induced tunnel large deformation disaster assessment model is specifically to use three-dimensional discrete element numerical calculation software to consider different types of surrounding rock three-dimensional constitutive models, anchor system equivalent mechanical models under different surrounding rock types and equivalent parameters into the assessment model to calculate the deformation of the tunnel under the influence of excavation and the anchor system support force value; 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 ground stress information of the tunnel, the anisotropic mechanical strength parameters of the surrounding rock, the direction and inclination of the rock formation, faults, tunnel excavation sequence, and tunnel size information;

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

[0027] The prediction of tunnel large deformation level is based on the standard of strength-stress ratio and the large deformation level standard recognized by the Technical Specifications for Railway Squeezing Rock Tunnels; the strength-stress ratio refers to the estimation of the natural compressive strength R of the rock mass based on the degree of integrity of the surrounding rock. m and the maximum initial principal stress σ max The ratio of the tunnel deformation level is determined by searching the high ground stress large deformation classification table.

[0028] Step S2, using the long-term deformation of the anchor system and the strength of the anchor system as evaluation criteria, and calculating the long-term deformation threshold of the anchor system and the strength damage threshold of the anchor system based on the design scheme of the anchor system support of the tunnel to be built;

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

[0030] Step S3, collecting measured data of surrounding rock deformation and radial force of the anchoring system after tunnel excavation is completed without support and after initial support at the site of the tunnel to be predicted with large deformation;

[0031] The measured data of surrounding rock deformation and radial force of the anchoring system are: at the construction site of the tunnel with a large deformation level to be predicted, after the excavation of the face, a multi-point displacement meter is installed in the tunnel surrounding rock to collect data on the long-term deformation of the surrounding rock; after the initial support is completed, a force monitoring device of the anchoring system is installed to collect the force strength value of the anchoring system as the measured data of the 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;

[0032] Step S4, comparing and analyzing the surrounding rock deformation and radial stress of the anchoring system measured on site with the anchoring system long-term deformation threshold and anchoring system strength threshold calculated by the anchoring system instability-induced tunnel large deformation disaster assessment model; if one of the two measured values ​​exceeds the assessment threshold, it is judged that the anchoring system is unstable, and then it is judged 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 determined to be a first-level large deformation level. The project overview, ground stress conditions, and first-level support design scheme of anisotropic mechanical parameters of the project are brought into the tunnel large deformation disaster assessment model induced by instability of the anchor system for calculation. The calculation parameters are as follows:

[0034]

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

[0036] Under this engineering profile, when the excavation is completed and the unsupported condition is reached, the tunnel deformation (single-sided deformation) reaches 0.193m, or the radial force of the tunnel surrounding rock reaches 7.051MPa, which is the instability threshold; after the initial anchor support is completed, the tunnel deformation (single-sided deformation) reaches 0.061m, or the radial force of the tunnel anchor reaches 7.814MPa, which is the instability threshold. The calculated displacement diagram is shown in Figure 2 shown.

[0037] By selecting the 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, and compared with the threshold of tunnel surrounding rock deformation when the anchor system becomes unstable calculated by the model. The comparison results are shown in the following table.

[0038]

[0039] Through data comparison, on-site monitoring shows that the deformation of the surrounding rock and the radial force strength of the anchoring system are both smaller than the long-term deformation of the anchoring system and the anchoring system strength threshold calculated by the large deformation disaster assessment model of the tunnel induced by instability of the anchoring system. Therefore, it can be judged that the deformation level of the tunnel is the first large deformation level, and the support and control measures have not been unstable and damaged, and the support and control measures are reasonably matched.

[0040] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the above-mentioned inventive concept. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in the embodiments of the present disclosure (but not limited to) to form a technical solution.

Claims

1. A method for predicting and evaluating large deformation disasters in tunnels induced by instability of anchoring systems, characterized in that: The following steps are involved: A method for predicting and evaluating large deformation disasters of tunnels induced by instability of an anchoring system comprises the following steps: Step S1, establishing a disaster assessment model for large deformation of a tunnel induced by instability of the anchoring system, and predicting the large deformation level of the tunnel without support by inputting the geological conditions of the large deformation tunnel to be predicted; Step S2, using the long-term deformation of the anchor system and the strength of the anchor system as evaluation criteria, and calculating the long-term deformation threshold of the anchor system and the strength damage threshold of the anchor system based on the design scheme of the anchor system support of the tunnel to be built; Step S3, collecting measured data of surrounding rock deformation and radial force of the anchoring system after tunnel excavation is completed without support and after initial support at the site of the tunnel to be predicted with large deformation; Step S4, comparing and analyzing the surrounding rock deformation and radial stress of the anchoring system measured on site with the anchoring system long-term deformation threshold and anchoring system strength threshold calculated by the anchoring system instability-induced tunnel large deformation disaster assessment model; if one of the two measured values ​​exceeds the assessment threshold, it is judged that the anchoring system is unstable, and then it is judged that the large deformation disaster in the tunnel is caused by the instability of the anchoring system.

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

3. The method for predicting and evaluating large deformation disasters of tunnels induced by instability of anchoring system according to claim 1 is characterized in that: The geological conditions of the large deformation tunnel in step S1 include the in-situ stress information of the tunnel, the anisotropic mechanical strength parameters of the surrounding rock, the direction and inclination of the rock formations, faults, tunnel excavation sequence, and tunnel size information.

4. The method for predicting and evaluating large deformation disasters of tunnels induced by instability of anchoring system according to claim 1 is characterized in that: The anchoring system in step S1 includes anchor rods and anchor cables.

5. The method for predicting and evaluating large deformation disasters of tunnels induced by instability of anchoring system according to claim 1 is characterized in that: The prediction of the tunnel deformation level in step S1 is based on the strength-stress ratio and the large deformation level standard recognized by the "Technical Specifications for Railway Squeezing Rock Tunnels"; 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 and the maximum initial principal stress σ max The ratio of the tunnel deformation level is determined by consulting the high ground stress large deformation classification table.

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

7. The method for predicting and evaluating large deformation disasters of tunnels induced by instability of anchoring system according to claim 1 is characterized in that: The measured data of surrounding rock deformation and radial force of the anchoring system in step S3 are: at the tunnel construction site with a large deformation level to be predicted, after the excavation of the heading face, a multi-point displacement meter is installed in the tunnel surrounding rock to collect data on long-term deformation of the surrounding rock; after the initial support is completed, a 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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