A method for determining a longitudinal multi-stage damage index threshold of a shield tunnel

Abstract

The present application belongs to the field of shield tunnel anti-seismic design, and discloses a method for determining longitudinal multi-level damage index threshold of shield tunnel, which is implemented according to the following steps: (1) based on longitudinal dynamic response analysis of shield tunnel, a longitudinal random damage index and state distribution sample library of shield tunnel is constructed; (2) based on the sample library, a load-ring opening amount correlation model is established; (3) longitudinal multi-level damage index calibration and shield tunnel performance threshold determination are carried out; (4) a multi-level damage index key threshold probability distribution is established; (5) considering different confidence intervals and guarantee rates, a multi-level damage index threshold system is proposed. The present application considers the longitudinal performance of shield tunnel structure after earthquake, and the proposed method helps to scientifically establish a shield tunnel longitudinal multi-level damage index system with a certain probability guarantee rate, and provides a theoretical reference for future related longitudinal anti-seismic performance research of shield tunnel structure.

Description

Technical Field

[0001] This invention relates to the field of seismic design of shield tunnels, specifically to a method for determining the threshold of longitudinal multi-level damage indicators for shield tunnels. Background Technology

[0002] As critical urban infrastructure and vital lifeline projects, shield tunnels are mostly constructed in seismically active zones, facing severe risks from earthquakes. Historical earthquake damage shows that tunnels and other underground structures can suffer varying degrees of damage or even collapse under strong earthquakes, triggering various secondary disasters and ultimately causing serious economic losses, casualties, and significant negative social impacts. Therefore, a thorough understanding of the seismic performance of tunnel structures is increasingly urgent and of great significance for ensuring the seismic safety of tunnels under earthquake loads.

[0003] Seismic vulnerability expresses the conditional probability of a structure undergoing various failure states under earthquakes of different intensities. It is a powerful tool for quantitatively assessing the seismic performance of structures and has been widely used in seismic risk assessments of infrastructure such as dams, buildings, bridges, and pipelines. In recent years, numerous scholars have conducted extensive research on the seismic vulnerability analysis of tunnels and achieved certain results (Argyroudis et al., 2012; Du Xiuli et al., 2016; Jiang Jiawei et al., 2021; Ding Zude et al., 2020). Among these, tunnel damage indices and their classification standards are key factors in tunnel seismic vulnerability analysis. However, current research on the classification standards of damage indices is based on qualitative analysis of joint waterproofing requirements and seismic performance level classifications in codes. Basic work on the classification of shield tunnel structural performance levels and the calibration of performance indices is very lacking, and a quantitative threshold analysis method has not been established. Meanwhile, current research on seismic vulnerability mainly focuses on the transverse seismic response of tunnels, while research on the longitudinal seismic vulnerability analysis of tunnels started relatively late. Most damage indicators are only applicable to describing the transverse damage state of tunnels, and there are few longitudinal seismic damage indicators. Furthermore, a reasonable quantitative mapping relationship has not been established between seismic response and longitudinal damage indicators, and there is a lack of a multi-level longitudinal damage indicator and threshold system for shield tunnels. Summary of the Invention

[0004] To address the current shortcomings in the quantitative calibration of threshold values ​​for multi-level damage indicators in shield tunnels, and considering the longitudinal performance of shield tunnel structures after earthquakes, this invention proposes a method for determining threshold values ​​for longitudinal multi-level damage indicators in shield tunnels. This method helps to scientifically establish a longitudinal multi-level damage indicator system for shield tunnels with a certain probability guarantee rate, providing a theoretical reference for future research on the longitudinal seismic performance of shield tunnel structures.

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

[0006] A method for determining the threshold of longitudinal multi-level damage indicators in shield tunnels is implemented according to the following steps:

[0007] (1) Based on the longitudinal dynamic response analysis of shield tunnels, a sample library of longitudinal random damage indices and state distributions of shield tunnels was constructed. Among them, a large number of seismic waves were generated by the established seismic ground motion random field model that considers spatial variability, and numerical simulation analysis of the longitudinal dynamic response of the tunnel was carried out on this basis.

[0008] (2) Based on the sample library of longitudinal random damage indices and state distributions of shield tunnels, a load-ring opening amount correlation model was established. The longitudinal damage index is a single index that is sensitive to structural damage of shield tunnels, has clear mechanical significance, is quantifiable, and easily measurable, and is determined based on the results of random simulation of the tunnel's longitudinal dynamic response. The ring opening amount was used as the longitudinal damage index for shield tunnels.

[0009] (3) Calibration of Longitudinal Multi-Level Damage Indicators and Determination of Shield Tunnel Performance Thresholds. Referring to the classification and definition methods for damage performance levels of above-ground structures and in conjunction with seismic codes, a multi-level performance level and qualitative description of damage status of longitudinal damage indicators for shield tunnels were established. Based on the load-ring inter-ring opening correlation model, the origin, concrete cracking point, yield load point, peak load point, and ultimate load point were respectively calibrated on the curve using geometric graphical methods. Combining the multi-level performance level and qualitative description of damage status of longitudinal damage indicators for shield tunnels, a criterion for determining the performance threshold of shield tunnels was defined. When the inter-ring opening is within the range of the origin to the concrete cracking point, the longitudinal performance of the shield tunnel structure is in normal use. The corresponding threshold is the inter-ring opening corresponding to the concrete cracking point. Similarly, the intervals between the concrete cracking point and the yield load point, the yield load point and the peak load point, and the peak load point and the ultimate load point can be defined. The longitudinal performance of the shield tunnel structure is in the functional states of being usable, usable after repair, and unusable, respectively. The corresponding thresholds are the inter-ring opening corresponding to the yield load point, the peak load point, and the ultimate load point, respectively.

[0010] (4) Establish the probability distribution of key thresholds for multi-level damage indicators based on probability statistics. Select multiple shield tunnel projects for longitudinal seismic analysis, statistically analyze the inter-ring opening under each performance state of all projects, study the overall distribution properties of the inter-ring opening under each performance state, perform parameter testing on the sample data, and determine whether it follows a normal distribution. If the sample data does not follow a normal distribution, use probability methods to transform it into a normal distribution through the corresponding function.

[0011] (5) Considering different confidence intervals and guarantee rates, a multi-level damage index threshold system is proposed based on critical values ​​such as "mean, mean + standard deviation, and mean - standard deviation". Based on the judgment criteria of shield tunnel performance threshold determined in step (3) and the calculation results of step (4), considering the reserved safety limit in engineering and different confidence intervals and guarantee rates, and combined with the characteristics of the inter-ring opening amount index, a multi-level damage index threshold system is proposed with "mean - standard deviation" as the critical value.

[0012] Compared with other methods, the present invention has the following characteristics:

[0013] (1) This invention establishes a longitudinal multi-level damage index system for shield tunnels, which deepens the field of seismic vulnerability analysis of shield tunnels;

[0014] (2) This invention is the first to propose a quantitative analysis method for the threshold of longitudinal multi-level damage index of shield tunnel, which makes up for the lack of damage index classification in current research.

[0015] (3) Using this invention, a longitudinal multi-level damage index system for shield tunnels with a certain probability guarantee rate can be established, which is of positive significance for quantitatively assessing the longitudinal seismic vulnerability of shield tunnels and guiding the seismic design of shield tunnels. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method for determining the threshold of longitudinal multi-level damage index for shield tunnels according to the present invention.

[0017] Figure 2 This is a conceptual diagram of the multi-level damage index calibration method of the present invention. Detailed Implementation

[0018] The implementation process of this invention is described in detail below. (See also...) Figure 1 The specific implementation steps are as follows:

[0019] (1) Based on the longitudinal dynamic response analysis of shield tunnels, a sample library of longitudinal random damage indices and state distributions of shield tunnels was constructed. Among them, a large number of seismic waves were generated by the established seismic ground motion random field model that considers spatial variability, and numerical simulation analysis of the longitudinal dynamic response of the tunnel was carried out on this basis.

[0020] (2) Based on the sample library of longitudinal random damage indices and state distributions of shield tunnels, a load-ring opening amount correlation model was established. The longitudinal damage index is a single index that is sensitive to structural damage of shield tunnels, has clear mechanical significance, is quantifiable, and easily measurable, and is determined based on the results of random simulation of the tunnel's longitudinal dynamic response. The ring opening amount was used as the longitudinal damage index for shield tunnels.

[0021] (3) Calibration of Longitudinal Multi-Level Damage Indicators and Determination of Shield Tunnel Performance Thresholds. Referring to the classification and definition methods for damage performance levels of above-ground structures and in conjunction with seismic codes, a multi-level performance level and qualitative description of damage status of longitudinal damage indicators for shield tunnels were established. Based on the load-ring inter-ring opening correlation model, the origin, concrete cracking point, yield load point, peak load point, and ultimate load point were respectively calibrated on the curve using geometric graphical methods. Combining the multi-level performance level and qualitative description of damage status of longitudinal damage indicators for shield tunnels, a criterion for determining the performance threshold of shield tunnels was defined. When the inter-ring opening is within the range of the origin to the concrete cracking point, the longitudinal performance of the shield tunnel structure is in normal use. The corresponding threshold is the inter-ring opening corresponding to the concrete cracking point. Similarly, the intervals between the concrete cracking point and the yield load point, the yield load point and the peak load point, and the peak load point and the ultimate load point can be defined. The longitudinal performance of the shield tunnel structure is in the functional states of being usable, usable after repair, and unusable, respectively. The corresponding thresholds are the inter-ring opening corresponding to the yield load point, the peak load point, and the ultimate load point, respectively.

[0022] (4) Establish the probability distribution of key thresholds for multi-level damage indicators based on probability statistics. Select multiple shield tunnel projects for longitudinal seismic analysis, statistically analyze the inter-ring opening under each performance state of all projects, study the overall distribution properties of the inter-ring opening under each performance state, perform parameter testing on the sample data, and determine whether it follows a normal distribution. If the sample data does not follow a normal distribution, use probability methods to transform it into a normal distribution through the corresponding function.

[0023] (5) Considering different confidence intervals and guarantee rates, a multi-level damage index threshold system is proposed based on critical values ​​such as "mean, mean + standard deviation, and mean - standard deviation". Based on the judgment criteria of shield tunnel performance threshold determined in step (3) and the calculation results of step (4), considering the reserved safety limit in engineering and different confidence intervals and guarantee rates, and combined with the characteristics of the inter-ring opening amount index, a multi-level damage index threshold system is proposed with "mean - standard deviation" as the critical value.

[0024] The invention is further described below through examples.

[0025] Taking a shallow-buried shield tunnel in a certain section of a certain region as an example:

[0026] Step 1: Construct a spatially variable seismic ground motion record and a reasonable random field of soil parameters that conform to the site characteristics of the region. Establish a typical stratum-shield tunnel longitudinal three-dimensional refined nonlinear numerical analysis model. Conduct longitudinal dynamic response analysis of the shield tunnel. Based on the random simulation results of the tunnel's longitudinal dynamic response, and combined with tunnel seismic design specifications and literature review, construct a damage index library characterizing the longitudinal seismic performance of the shield tunnel. This library includes typical indices such as structural ring joint opening, longitudinal curvature, misalignment, longitudinal settlement, bending moment, axial force, and shear force.

[0027] Step 2: Select the inter-ring opening amount as the longitudinal seismic performance damage index of the shield tunnel, which is sensitive to the structural damage of the shield tunnel, has clear mechanical significance, is quantifiable and easy to measure. Based on the sample library of longitudinal random damage index and state distribution of the shield tunnel, establish a load-longitudinal damage index performance correlation model (i.e., load-inter-ring opening amount correlation model).

[0028] Step 3: Referring to the classification and definition methods of damage performance levels of above-ground structures and in conjunction with seismic codes, establish a multi-level performance level and qualitative description of damage status of longitudinal damage indicators for shield tunnels, as shown in Table 1.

[0029] Table 1 Classification of Longitudinal Damage Indicators for Shield Tunnels at Multiple Performance Levels

[0030]

[0031] Based on the load-ring opening correlation model, the origin (O), concrete cracking point (A), yield load point (B), peak load point (C), and ultimate load point (D) are respectively marked on the curve using geometric plotting methods, as shown in the attached figure. Figure 2 As shown. Point A represents the load corresponding to the 10% limit of the curve slope change rate; point C represents the peak load of the shield tunnel structure; after determining points A and C, the yield point B can be obtained through geometric construction; point D represents the load corresponding to the shield tunnel structure's bearing capacity degrading to 85% of the peak load. Combining the multi-level performance levels of the shield tunnel's longitudinal damage index and the qualitative description of the damage state, a performance threshold judgment criterion for shield tunnels is defined. When the inter-ring opening is within the range of origin-concrete cracking point (OA), the longitudinal performance of the shield tunnel structure is in normal use, and the corresponding threshold is the inter-ring opening (d1) corresponding to the concrete cracking point. Similarly, the ranges of concrete cracking point-yield load point (AB), yield load point-peak load point (BC), and peak load point-ultimate load point (CD) can be defined, and the longitudinal performance of the shield tunnel structure is in the functional states of usable, usable after repair, and unusable, respectively. The corresponding thresholds are the inter-ring opening (d2, d3, d4) corresponding to the yield load point, peak load point, and ultimate load point, respectively.

[0032] Step 4: Establish the probability distribution of key thresholds for multi-level damage indicators based on probabilistic statistics. Longitudinal seismic analysis is conducted on multiple shallow-buried shield tunnel sections. The inter-ring opening (d1, d2, d3, d4) under each performance state of all projects is statistically analyzed. The overall distribution characteristics of the inter-ring opening under each performance state are studied. Parameter tests are performed on the sample data to determine whether it follows a normal distribution. If the sample data does not follow a normal distribution, a probabilistic method is used to transform it into a normal distribution through a corresponding function.

[0033] Step 5: Based on the judgment criteria and calculation results of the shield tunnel performance threshold, considering the reserved safety limit in engineering, different confidence intervals and guarantee rates, and combined with the inter-ring opening amount index characteristics d (d1, d2, d3, d4), a multi-level damage index threshold system is proposed with "mean μ - standard deviation σ" as the critical value, as shown in Table 2.

[0034] Table 2 Threshold System for Longitudinal Multi-Level Damage Indicators of Shield Tunnels

[0035] 1 Normal use <![CDATA[0≤d<(μ d1 -s d1 )]]> 2 It can be used <![CDATA[(μ d1 -s d1 )≤d<(μ d2 -s d2 )]]> 3 Use after repair <![CDATA[(μ d3 -s d3 )≤d<(μ d4 -s d4 )]]> 4 Cannot be used <![CDATA[(μ d4 -s d4 )≤d]]>

[0036] The above description is merely a description of preferred embodiments of this application and is not intended to limit the scope of this application in any way. Any changes or modifications made by those skilled in the art based on the above-disclosed technical content should be considered as equivalent and valid embodiments and fall within the scope of protection of the technical solution of this application.

Claims

1. A method for determining the threshold of longitudinal multi-level damage indicators in shield tunnels, characterized in that, Implement the following steps: (1) Based on the longitudinal dynamic response analysis of shield tunnels, a sample library of longitudinal random damage indicators and state distribution of shield tunnels is constructed; (2) Based on the sample library of longitudinal random damage index and state distribution of shield tunnel in step (1), establish the load The model of the interring opening amount correlation; among which, the longitudinal damage index is a single index that is sensitive to the structural damage of the shield tunnel, has clear mechanical significance, is quantifiable and easy to measure, and is determined according to the random simulation results of the longitudinal dynamic response of the tunnel; (3) the calibration of the longitudinal multi-level damage index of the shield tunnel and the determination of the performance threshold of the shield tunnel; among which, the longitudinal multi-level damage index of the shield tunnel is calibrated by combining the key critical points of concrete cracking point, yield load point, peak load point and ultimate load point, and based on the load-interring opening amount correlation model in step (2), the judgment criteria for the performance threshold of the shield tunnel are determined by using the geometric drawing method combined with the method of classifying and defining the damage performance level of the above-ground structure and the seismic code; among which, referring to the method of classifying and defining the damage performance level of the above-ground structure and combined with the seismic code, the multi-level performance level and qualitative description of the damage state of the longitudinal damage index of the shield tunnel are established; the longitudinal multi-level damage index of the shield tunnel The calibration is performed on the load-ring opening curve using a geometric method, calibrating the origin, concrete cracking point, yield load point, peak load point, and ultimate load point respectively. Combining the multi-level performance levels and qualitative description of damage state of the shield tunnel's longitudinal damage index, a performance threshold judgment criterion for the shield tunnel is defined. Specifically, when the ring opening is within the range of the origin to the concrete cracking point, the longitudinal performance of the shield tunnel structure is in a normal usable state, and the corresponding threshold is the ring opening corresponding to the concrete cracking point. Similarly, the ranges of concrete cracking point-yield load point, yield load point-peak load point, and peak load point-ultimate load point are defined, indicating that the longitudinal performance of the shield tunnel structure is in a functional state of "usable," "usable after repair," and "unusable," respectively, with the corresponding thresholds being the ring opening corresponding to the yield load point, peak load point, and ultimate load point, respectively. (4) Establish the probability distribution of key thresholds for multi-level damage indicators based on probability statistics; (5) Considering different confidence intervals and guarantee rates, a multi-level damage index threshold system is proposed based on the critical values ​​of "mean, mean + standard deviation, and mean - standard deviation".

2. The method as described in claim 1, characterized in that, In step (1), specifically, a large number of seismic waves are generated by establishing a seismic ground motion random field model that considers spatial variability. Based on this, numerical simulation analysis of the longitudinal dynamic response of the tunnel is carried out to form a sample of longitudinal random damage index and state distribution of the shield tunnel, so as to construct a sample library of longitudinal random damage index and state distribution of the shield tunnel.

3. The method as described in claim 1, characterized in that, In step (4), multiple shield tunnel projects are selected for longitudinal seismic analysis. The inter-ring opening amount corresponding to each performance state of all projects is statistically analyzed to obtain the inter-ring opening amount index characteristics. The sample data is tested for parameters, and the probabilistic method is used to make the data that does not follow the normal distribution follow the normal distribution after being transformed by the corresponding function.

4. The method as described in claim 1, characterized in that, In step (5): Based on the judgment criteria for the shield tunnel performance threshold determined in step (3) and the calculation results in step (4), considering the reserved safety limit in engineering, different confidence intervals and guarantee rates, and combined with the characteristics of the inter-ring opening amount index, a multi-level damage index threshold system is proposed with "mean - standard deviation" as the critical value.

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