Method for evaluating vulnerability of tunnel under coupling action of dislocation and strong shock

Abstract

The invention relates to the technical field of tunnel safety assessment, in particular to a tunnel vulnerability assessment method under the coupling action of dislocation and strong shock, which comprises the following steps: step 1, determining a typical tunnel structure, collecting physical information of the typical tunnel, and obtaining site rock-soil mechanical characteristic parameters; 2, determining the size of fault dislocation, and reasonably selecting seismic waves conforming to a standard spectrum; 3, constructing a nonlinear dynamic finite element numerical analysis model considering fault dislocation, earthquake and tunnel structure coupling, and performing incremental dynamic time history analysis after fault dislocation application and seismic wave amplitude adjustment; step 4, determining engineering demand parameters of the tunnel structure; 5, obtaining threshold values and standard deviations of the tunnel lining in different damage stages under the condition of considering the coupling effect of fault dislocation and strong shock; step 6, establishing a tunnel vulnerable curved surface considering fault dislocation and strong shock coupling effect; the method is of great significance in guiding risk assessment and optimization design of tunnel system engineering.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel safety assessment, in particular to a method for assessing tunnel vulnerability under the coupling of dislocation and strong earthquake. Background Art

[0002] As an important transportation infrastructure for social and economic development and personnel mobility, tunnels play an increasingly important role in urban development. However, complex geological conditions (such as fault fracture zones) and earthquake disasters have brought many challenges to tunnel safety. Domestic and foreign scholars have proposed an assessment method that only considers the impact of a single disaster for the safety assessment of tunnel structures under occasional disasters. In addition, for railway tunnel structures across active faults, the stick-slip dislocation of the fault fracture zone is very likely to cause tectonic earthquakes, and there is a significant correlation between the dislocation and the earthquake. The traditional assessment method based on a single disaster cannot accurately reflect the influence of tunnel deformation and damage, lining cumulative damage and steel pre-yield under the coupling conditions of fault dislocation and earthquake, and ignores the damage characteristics of tunnel structures such as cumulative damage and pre-destruction during the multi-disaster coupling process, resulting in the inability to further reasonably assess the actual seismic performance of tunnel structures under the coupling conditions of fault dislocation and earthquake. The inaccurate characterization of the seismic performance of tunnels will ultimately lead to the problem of accuracy instability when quantifying the probability of multi-disaster coupling damage in tunnels. The above defects show that there are still deficiencies in the field of tunnel structure safety assessment. Therefore, given the gap between current research and actual needs, the lack of a tunnel vulnerability assessment method that considers the multi-hazard coupling effect will not be able to effectively characterize the risk probability of the tunnel under the combined action of fault dislocation and strong earthquake, resulting in major safety hazards in tunnel operation assurance. Summary of the invention

[0003] The purpose of this application is to provide a method for assessing tunnel vulnerability under the coupling of dislocation and strong earthquake, aiming to solve the problems in the prior art.

[0004] The embodiment of the present application provides a method for evaluating tunnel vulnerability under the coupling of dislocation and strong earthquake, comprising the following steps:

[0005] Step 1: Identify typical tunnel structures, collect key physical information of typical tunnels, and obtain site geotechnical mechanics characteristic parameters;

[0006] Step 2: Determine the size of the fault dislocation and reasonably select the seismic waves that meet the standard spectrum;

[0007] Step 3: Construct a nonlinear dynamic finite element numerical analysis model that considers the coupling of fault dislocation, earthquake and tunnel structure, and perform incremental dynamic time history analysis after applying fault dislocation and adjusting the seismic wave amplitude;

[0008] Step 4: Determine the required parameters of tunnel structure engineering;

[0009] Step 5: Obtain the thresholds and standard deviations of tunnel lining at different damage stages considering the coupling of fault dislocation and strong earthquake;

[0010] Step 6: Establish the tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake.

[0011] Furthermore, in step 2, the amount of fault dislocation is used as a measure of dislocation intensity, and the peak ground acceleration PGA is used as a characterization standard of earthquake intensity; the selected seismic waves must meet the requirements of quantity and waveform, and at least seven seismic waves should be selected.

[0012] Furthermore, the step 3 is specifically to construct a dynamic finite element analysis model that takes into account the nonlinear coupling effect of the soil and tunnel structure system based on the data such as the physical and mechanical parameters of the tunnel structure and surrounding rock obtained in step 1, with the help of numerical simulation software, so as to evaluate the influence of fault dislocation and strong earthquake coupling disasters on the probability of tunnel damage; by selecting the fault dislocation amount determined in step 2 and at least seven seismic waves, the constructed numerical model is used to perform incremental dynamic time history calculations, so as to obtain the dynamic response data of the tunnel lining structure under the action of multiple disasters.

[0013] Furthermore, in step 4, the dual parameter index DM considering the radial convergence of the tunnel and the plastic strain of the lining concrete is used as the tunnel structural engineering demand parameter to measure the performance level of the tunnel lining under the coupling of multiple fault dislocations and strong earthquakes; the expression of the tunnel dual parameter index DM is as follows:

[0014]

[0015] In the above formula, DM is a two-parameter safety index function; P m is the current plastic strain; P u is the maximum plastic strain; θ m is the radial convergence rate of the current tunnel; θ u is the maximum tunnel radial convergence rate; α is the correction coefficient, which is 0.38.

[0016] Furthermore, the plastic strain of concrete is as follows:

[0017] P=P 总 -P 弹

[0018] In the above formula, P 总 is the total strain of concrete, P 弹 is the elastic strain of concrete.

[0019] The calculation formula of tunnel radial convergence rate is as follows:

[0020]

[0021] In the above formula, D1 is the diameter of the tunnel after deformation, and D is the diameter of the tunnel before deformation.

[0022] Furthermore, the step 5 is specifically to obtain a demand model of a typical tunnel structure considering fault dislocation and strong earthquake probability based on the dynamic response data of the tunnel lining structure under the action of multiple disasters determined in step 3 and the tunnel structure engineering demand parameter DM determined in step 4. The tunnel lining probability demand model is shown in the following formula:

[0023] Ln(DM)=aLn(IM S )+bLn(IM M )+c

[0024] In the above formula, parameters a, b, and c are fitting parameters, which can be obtained through log-linear regression analysis; IM S PGA is the earthquake intensity index; IM M It is the fault dislocation strength index, which represents the size of the dislocation;

[0025] Through the tunnel lining probability demand model, the corresponding tunnel lining DM under different earthquake intensities and fault dislocation intensities can be obtained. SM ; Where SM represents the tunnel structure engineering demand parameter DM under the coupling effect of earthquake intensity and fault dislocation intensity; the standard deviation analysis of the tunnel lining probability demand model can obtain the logarithmic standard deviation β of the model, and the relevant calculation formula is as follows:

[0026]

[0027] In the above formula, β is the logarithmic standard deviation, N is the total number of data points, and δ i is the engineering requirement parameter corresponding to data point i.

[0028] Furthermore, step 6 is specifically based on the tunnel lining DM determined in step 5. SM , the tunnel damage state classification table of the dual parameter index DM, and the logarithmic standard deviation β are used to determine the exceedance probability of the relevant tunnel structure under different fault dislocation intensities and earthquake intensities, and the tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake is obtained;

[0029] The calculation formula of the vulnerability surface of the tunnel lining structure considering the coupling disaster of fault dislocation and strong earthquake is as follows:

[0030] Pf=P(D / Ci≥1IM S =i1,IM M =i2)=φ(ln(D)-ln(Ci) / βtot)

[0031] In the above formula, P(·) is the tunnel lining structure exceeding a certain damage state C under a given earthquake intensity and fault dislocation strength.i The probability of IM S PGA is the earthquake intensity index; IM M is the fault dislocation intensity index, which characterizes the size of the dislocation; Φ is the standard normal density cumulative probability function; C is the tunnel lining engineering demand parameter under given earthquake intensity and fault dislocation intensity; β is the logarithmic standard deviation, which expresses the variability of the fragility surface.

[0032] The beneficial effects of the present invention are as follows: the present invention fully considers the uncertainty of seismic waves and the variability of the size and material properties of non-structural components, and uses the finite element method to carry out the incremental dynamic time history analysis of tunnels under different strike-slip dislocation momentums and different PGA intensities; on this basis, the influence of multiple disasters such as strong earthquakes and dislocations on the dynamic response of tunnels is further explored, and the engineering demand parameters of tunnels under different dislocations and earthquake intensities are extracted and analyzed, and a tunnel vulnerability assessment function considering the coupling effects of fault dislocations and strong earthquakes is constructed, thereby realizing the quantitative assessment of the tunnel damage probability considering the coupling effects of fault dislocations and strong earthquakes. This method meets the current requirements of "performance-based seismic design", fully considers the influence of the coupling effects of strong earthquakes and dislocations on tunnel risk assessment, and is of great significance for guiding the risk assessment and optimal design of tunnel system engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The figure is a flow chart of the analysis method of the tunnel vulnerability assessment method of the present invention.

[0034] Figure 2 This is the tunnel probability demand model diagram.

[0035] Figure 3 Schematic diagram of tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake; a is slight damage, b is moderate damage, and c is severe damage. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The present invention provides a tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake, the flow chart of which is as follows: Figure 1 As shown, the following steps are included:

[0038] Step 1: After defining the typical tunnel structure, key physical information such as typical tunnel dimensions and material parameters needs to be collected; in addition, the site geotechnical mechanics characteristic parameters need to be obtained in one step.

[0039] A typical highway tunnel in a western mountainous area was selected as a research case. The diameter of the highway tunnel was selected as the standard 15.68m, the lining thickness was selected as 0.6m, and its buried depth was assumed to remain unchanged at about 75m. The concrete strength of the highway tunnel lining is C35. In terms of the rock and soil media around the highway tunnel, there are two main rock and soil types, namely ordinary rock and soil layer and broken zone rock and soil. The rock and soil thickness is consistent with the model height, both of which are 150m.

[0040] The lining and geotechnical related material properties in the study case are shown in the following table.

[0041]

[0042] Step 2: Determine the size of the fault dislocation and reasonably select seismic waves that conform to the standard spectrum.

[0043] The dislocation direction and amplitude of the fault fracture zone, as well as the intensity and waveform characteristics of the seismic waves, are all key factors affecting the degree of damage to the tunnel structure under multiple disaster conditions. The present invention uses the amount of dislocation as a measure of dislocation intensity, and uses the peak ground acceleration as a characterization standard for earthquake intensity; the selected seismic waves must meet the requirements of quantity and waveform. According to the "GB / T 38591-2020 Building Seismic Resilience Evaluation Standard", at least seven seismic waves should be selected to fully reflect the impact of the uncertainty of the seismic wave waveform on the structure.

[0044] In this embodiment, the selected fault slip mode is strike-slip, and the slip amplitudes are 0.0 m, 0.1 m, 0.2 m, 0.3 m, 0.4 m and 0.5 m.

[0045] In addition, in terms of seismic waveform and intensity, 8 measured seismic waves were selected from the Pacific Earthquake Engineering Research Center in the United States to meet the uncertainty of seismic waves when earthquake disasters occur. The source site of the seismic waves is similar to the underlying bedrock conditions of the model. At the same time, the mean value of the amplification factor response spectrum of the selected seismic waves is consistent with the standard spectrum. The detailed information of the seismic waves is shown in the following table.

[0046]

[0047] Step 3: Establish a nonlinear dynamic finite element numerical analysis model considering the coupling of fault dislocation-earthquake-tunnel structure, and carry out incremental dynamic time history calculation after applying fault dislocation and seismic wave amplitude modulation.

[0048] Based on the geometric characteristics, structural material properties, selected seismic waves, fault slip direction and amplitude, and boundary conditions of the mountain tunnel project in step 1, a nonlinear dynamic finite element numerical analysis model considering fault dislocation, earthquake and tunnel structure coupling is constructed with the help of numerical simulation software, such as ABAQUS or other numerical simulation software. Using the determined fault dislocation and 8 seismic waves, after adjusting the seismic wave amplitude by 0.1g, the incremental dynamic time history calculation of the numerical model is carried out to obtain the dynamic response results of the tunnel structure under the coupling of different fault dislocations and earthquake disasters (where the fault dislocation is 0.0m-0.5m and the PGA is 0.1PGA-1.0PGA).

[0049] In the process of establishing the finite element model, in order to avoid the reflection waves caused by the contact between the seismic waves and the boundary from interfering with the calculation results, the size of the numerical model is usually set to more than five times the tunnel size. In addition, in the setting of boundary conditions, the fault dislocation is specified as a mandatory displacement boundary condition. After the dislocation analysis, the restart strategy of the numerical analysis is adopted to inherit various vector fields such as stress and velocity in the calculation. At the same time, in the boundary condition setting of the finite element model, special attention should be paid to avoiding the reflection phenomenon of seismic waves, such as by using the built-in multi-point constraints in ABAQUS to achieve motion coupling.

[0050] Step 4: Determine the required parameters of tunnel structure engineering.

[0051] Under the coupling of fault dislocation and strong earthquake load, the failure form of tunnel engineering structure is mainly the overall radial convergence of the tunnel and local collapse failure. Therefore, the dual parameter index DM considering the radial convergence of the tunnel and the plastic strain of the lining concrete is used as the required parameter of the tunnel structure engineering to measure the performance level of the tunnel lining under the coupling of multiple fault dislocations and strong earthquakes. The expression of the tunnel dual parameter index DM is as follows:

[0052]

[0053] In the above formula, DM is a two-parameter safety index function, P m is the current plastic strain, P u is the maximum plastic strain, θ m is the radial convergence rate of the current tunnel, θ u is the maximum tunnel radial convergence rate, α is the correction coefficient, and its value is 0.38.

[0054] The plastic strain of concrete is given by:

[0055] P=P 总 -P 弹

[0056] In the above formula, P 总 is the total strain of concrete, P弹 is the elastic strain of concrete.

[0057] The calculation formula of tunnel radial convergence rate is as follows:

[0058]

[0059] In the above formula, D1 is the diameter of the tunnel after deformation, and D is the diameter of the tunnel before deformation.

[0060] The classification of tunnel damage states based on the dual parameter index DM considering the radial convergence of the tunnel and the plastic strain of the lining concrete is shown in the following table.

[0061]

[0062] Step 5: Obtain the thresholds and standard deviations of tunnel lining at different damage stages under the coupling of fault dislocation and strong earthquake.

[0063] Based on the dynamic response data of the tunnel lining structure under multiple disasters determined in step 3 and the tunnel structure engineering demand parameters (tunnel dual parameter index DM) determined in step 4, a typical tunnel structure demand model considering fault dislocation and strong earthquake probability is obtained. The relevant schematic diagram is shown in Figure 2 As shown in the figure, the fitting parameters a=0.326, b=0.673, c=-0.188 obtained through logarithmic linear regression analysis are substituted into the tunnel lining probability demand model as shown in the following formula:

[0064] Ln(DM)=0.326Ln(IM S )+0.637Ln(IM M )-0.188

[0065] In the above formula, IM S is the earthquake intensity index PGA, in g; IM M It is the fault dislocation strength index, which represents the size of the dislocation. The unit is m. The size of the fault dislocation and the PGA strength range are determined according to step 3.

[0066] Through the tunnel lining probability demand model and the tunnel damage state classification table, the corresponding tunnel lining DM under different earthquake intensities and fault dislocation intensities can be obtained. SM , where SM represents the engineering demand parameter DM of the tunnel structure under the coupling of earthquake intensity and fault dislocation intensity. The thresholds of slight damage, moderate damage and severe damage are 0.11, 0.21 and 0.38 respectively.

[0067] By performing standard deviation analysis on the tunnel lining probability demand model, the logarithmic standard deviation β of the model can be obtained. The relevant calculation formula is as follows:

[0068]

[0069] In the above formula, β is the logarithmic standard deviation, N is the total number of data points, and δ i is the engineering requirement parameter corresponding to data point i.

[0070] Step 6: Establish the tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake.

[0071] Based on the tunnel structure determined in step 5, the corresponding tunnel lining DM under different earthquake intensities and fault dislocation intensities SM , the tunnel damage state classification table of the dual parameter index DM, and the logarithmic standard deviation β are used to determine the exceedance probability of the relevant tunnel structure under different fault dislocation intensities and earthquake intensities, and the tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake is obtained. The tunnel vulnerability surface under different damage states is as follows Figure 3 shown.

[0072] The calculation formula of the probability surface of slight damage to the tunnel lining structure under the action of fault dislocation and strong earthquake coupling disaster is as follows:

[0073] Pf=P(D / Ci≥1IM S =i1,IM M =i2)=φ(ln(DM)-ln(0.11) / 0.41)

[0074] The calculation formula of the medium damage probability surface is as follows:

[0075] Pf=P(D / Ci≥1IM S =i1,IM M =i2)=φ(ln(DM)-ln(0.21) / 0.41)

[0076] The calculation formula of severe damage probability surface is as follows:

[0077] Pf=P(D / Ci≥1IM S =i1,IM M =i2)=φ(ln(DM)-ln(0.38) / 0.41)

[0078] In the above formula, P(·) is the tunnel lining structure exceeding a certain damage state C under a given earthquake intensity and fault dislocation strength. i The probability of IM S is the earthquake intensity index PGA, in g; IM M is the fault dislocation intensity index, which characterizes the size of the dislocation, and its unit is m; Φ is the standard normal density cumulative probability function, C is the tunnel lining engineering demand parameter under given earthquake intensity and fault dislocation intensity, and β is the logarithmic standard deviation, which expresses the variability of the fragility surface.

[0079] Based on the above evaluation method, a systematic analysis of the influence of strong earthquake and dislocation coupling effect can be realized, so as to quantify the damage probability of tunnel lining under different damage states and the coupling of fault dislocation and strong earthquake.

[0080] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake, characterized in that: The following steps are involved: Step 1: Identify typical tunnel structures, collect key physical information of typical tunnels, and obtain site geotechnical mechanics characteristic parameters; Step 2: Determine the size of the fault dislocation and reasonably select the seismic waves that meet the standard spectrum; Step 3: Construct a nonlinear dynamic finite element numerical analysis model that considers the coupling of fault dislocation, earthquake and tunnel structure, and perform incremental dynamic time history analysis after applying fault dislocation and adjusting the seismic wave amplitude; Step 4: Determine the required parameters of tunnel structure engineering; Step 5: Obtain the thresholds and standard deviations of tunnel lining at different damage stages considering the coupling of fault dislocation and strong earthquake; Step 6: Establish the tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake.

2. The tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake according to claim 1 is characterized in that: In step 2, the fault dislocation amount is used as a measure of the dislocation intensity, and the peak ground acceleration PGA is used as a characterization standard of earthquake intensity; the selected seismic waves must meet the requirements of quantity and waveform, and at least seven seismic waves should be selected.

3. The tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake according to claim 1 is characterized in that: The step 3 specifically includes constructing a dynamic finite element analysis model that takes into account the nonlinear coupling effect of the soil and tunnel structure system based on the data such as the physical and mechanical parameters of the tunnel structure and surrounding rock obtained in step 1, with the help of numerical simulation software, so as to evaluate the influence of fault dislocation and strong earthquake coupling disasters on the probability of tunnel damage; by selecting the fault dislocation amount determined in step 2 and at least seven seismic waves, using the constructed numerical model to perform incremental dynamic time history calculations, thereby obtaining the dynamic response data of the tunnel lining structure under the action of multiple disasters.

4. The tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake according to claim 1 is characterized in that: In step 4, the dual parameter index DM considering the radial convergence of the tunnel and the plastic strain of the lining concrete is used as the tunnel structural engineering demand parameter to measure the performance level of the tunnel lining under the coupling of multiple fault dislocations and strong earthquakes; the expression of the tunnel dual parameter index DM is as follows: In the above formula, DM is a two-parameter safety index function; P m is the current plastic strain; P u is the maximum plastic strain; θ m is the radial convergence rate of the current tunnel; θ u is the maximum tunnel radial convergence rate; α is the correction coefficient, which is 0.

38.

5. The tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake according to claim 4 is characterized in that: The plastic strain of concrete is given by: P=P 总 -P 弹 In the above formula, P 总 is the total strain of concrete, P 弹 is the elastic strain of concrete. The calculation formula of tunnel radial convergence rate is as follows: In the above formula, D1 is the diameter of the tunnel after deformation, and D is the diameter of the tunnel before deformation.

6. The tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake according to claim 1 is characterized in that: The step 5 is specifically to obtain a demand model of a typical tunnel structure considering fault dislocation and strong earthquake probability based on the dynamic response data of the tunnel lining structure under the action of multiple disasters determined in step 3 and the tunnel structure engineering demand parameter DM determined in step 4. The tunnel lining probability demand model is shown in the following formula: Ln(DM)=aLn(IM S )+bLn(IM M )+c In the above formula, parameters a, b, and c are fitting parameters, which can be obtained through log-linear regression analysis; IM S PGA is the earthquake intensity index; IM M It is the fault dislocation strength index, which represents the size of the dislocation; Through the tunnel lining probability demand model, the corresponding tunnel lining DM under different earthquake intensities and fault dislocation intensities can be obtained. SM ; Where SM represents the tunnel structure engineering demand parameter DM under the coupling effect of earthquake intensity and fault dislocation intensity; the standard deviation analysis of the tunnel lining probability demand model can obtain the logarithmic standard deviation β of the model, and the relevant calculation formula is as follows: In the above formula, β is the logarithmic standard deviation, N is the total number of data points, and δ i is the engineering requirement parameter corresponding to data point i.

7. The tunnel vulnerability assessment method under the coupling of dislocation and strong earthquake according to claim 1 is characterized in that: The step 6 is specifically based on the tunnel lining DM determined in step 5. SM , the tunnel damage state classification table of the dual parameter index DM, and the logarithmic standard deviation β are used to determine the exceedance probability of the relevant tunnel structure under different fault dislocation intensities and earthquake intensities, and the tunnel vulnerability surface considering the coupling effect of fault dislocation and strong earthquake is obtained; The calculation formula of the vulnerability surface of the tunnel lining structure considering the coupling disaster of fault dislocation and strong earthquake is as follows: Pf=P(D / Ci≥1IM S =i1,IM M =i2)=ϕ(ln(D)-ln(Ci) / βtot) In the above formula, P(·) is the tunnel lining structure exceeding a certain damage state C under a given earthquake intensity and fault dislocation strength. i The probability of IM S PGA is the earthquake intensity index; IM M is the fault dislocation intensity index, which characterizes the size of the dislocation; Φ is the standard normal density cumulative probability function; C is the tunnel lining engineering demand parameter under given earthquake intensity and fault dislocation intensity; β is the logarithmic standard deviation, which expresses the variability of the fragility surface.

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