Evaluation method of gas pipeline under landslide action based on structural vulnerability theory

Abstract

The present invention discloses a method for evaluating a gas pipeline under landslide based on structural vulnerability theory, comprising the following steps: S1, performing vulnerability demand analysis on the gas pipeline under landslide; S2, performing vulnerability capacity analysis on the gas pipeline under landslide; S3, performing vulnerability evaluation on the gas pipeline under landslide. According to pipeline vulnerability demand analysis and vulnerability capacity analysis, the present invention establishes a vulnerability demand-capacity model of the gas pipeline under landslide based on different response parameters, proposes a pipeline damage degree classification standard, can intuitively reflect the damage state and exceedance probability of the pipeline under different landslide intensities, and can predict the damage and vulnerability probability of the pipeline within a certain period of time in the future.

Description

Technical Field

[0001] The invention relates to the technical field of pipeline safety prediction, in particular to an evaluation method for a gas pipeline under landslide action based on a structural vulnerability theory. Background Art

[0002] Gas pipelines are prone to rupture and failure accidents under the action of landslide geological disasters, causing casualties and economic losses. At present, there are many studies on the mechanical response analysis and risk assessment of pipelines under landslide disasters at home and abroad, but there are few studies on the vulnerability characteristics of pipelines under landslide geological disasters based on structural vulnerability theory. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the present invention provides an evaluation method for gas pipelines under landslides based on the structural vulnerability theory. For the risk assessment of landslide geological disasters, especially for the quantitative evaluation of the vulnerability of the disaster-bearing body, the present invention can intuitively reflect the damage state and exceedance probability under different landslide intensities, and can predict the damage state and vulnerability probability of the gas pipeline under the action of landslide within a certain period of time in the future.

[0004] The technical solution adopted by the present invention is:

[0005] An evaluation method for gas pipelines under landslide action based on structural vulnerability theory includes the following steps:

[0006] S1. Conduct vulnerability analysis on gas pipelines under landslides;

[0007] S2. Conduct vulnerability analysis on gas pipelines under landslides;

[0008] S3. Conduct vulnerability assessment of gas pipelines under landslides;

[0009] Wherein, step S1 comprises the following steps:

[0010] S11, random sampling, selecting multiple parameters of the pipeline as random variables, and extracting multiple samples using the optimal Latin hypercube sampling method according to the distribution characteristics of the selected multiple random variables, each sample including the selected multiple random variables and the landslide displacement intensity parameter, to generate a landslide-pipeline sample pair;

[0011] S12. Finite element analysis of pipelines: the parameters of each sample are respectively brought into the landslide pipeline model for simulation analysis to obtain the response parameters of the pipeline, and the pipeline response parameters are used as the required parameters for vulnerability analysis;

[0012] S13, constructing a vulnerable demand probability model, performing regression analysis on the landslide displacement intensity parameter and the pipeline demand parameter, and obtaining the vulnerable demand probability model;

[0013] Step S2 includes the following steps:

[0014] Taking pipeline demand parameters as capacity index parameters, quantifying capacity index parameters, and partitioning the quantified capacity index parameters, different partitions correspond to different damage levels;

[0015] Step S3 includes the following steps:

[0016] S31. Taking landslide displacement as the disaster intensity parameter, based on the vulnerability demand probability model and combined with the capacity index parameter limit, the vulnerability probability model of pipeline based on the demand-capacity of response parameters under different landslide displacement intensity parameters is obtained;

[0017] S32. When the landslide displacement intensity parameter takes different values, the probability of the pipeline exceeding different damage levels is calculated respectively.

[0018] Preferably, the plurality of random variables include yield strength, pipe diameter, wall thickness and elastic modulus.

[0019] Preferably, the response parameter is maximum axial strain or maximum displacement.

[0020] Preferably, the simulation analysis in step S12 is performed using ABAQUS software.

[0021] The beneficial effects of the present invention are:

[0022] According to the pipeline vulnerability demand analysis and vulnerability capacity analysis, a vulnerability demand-capacity model of the gas pipeline under landslide based on different response parameters is established, and a pipeline damage degree classification standard is proposed, which can intuitively reflect the damage status and exceedance probability of the pipeline under different landslide intensities, and can predict the damage status and vulnerability probability of the pipeline in a certain period of time in the future. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below in conjunction with the embodiments.

[0024] Example 1

[0025] 1. Analysis of gas pipeline vulnerability requirements under landslides:

[0026] ① Random sampling: Taking the X70 pipe gas pipeline as an example, the four parameters of the X70 pipe, namely, yield strength, pipe diameter, wall thickness, and elastic modulus, are selected. The four random variables are normally distributed, as shown in Table 1.

[0027] Table 1 Distribution characteristics of structural parameters of X70 gas pipeline

[0028]

[0029] The initial displacement of the landslide soil is 0.1m, the maximum displacement is 1.5m, and the step increment is 0.2m to analyze the response state of the pipeline under different landslide intensities. The optimal Latin hypercube sampling method is used to extract 80 sample points for each random variable to generate the "landslide-pipeline" sample pairs, as shown in Table 2.

[0030] Table 2 Random combination sample pairs of landslide displacement and pipeline parameters

[0031]

[0032]

[0033]

[0034] ② Pipeline vulnerability analysis: Based on ABAQUS software simulation analysis, 80 groups of “landslide-pipeline” sample parameters were brought into the landslide pipeline model for simulation analysis, and the maximum axial strain of the gas pipeline was obtained. The pipeline burial depth was 2m and the internal pressure of the pipeline was 8MPa. The statistical results of the maximum axial strain of all samples are shown in Table 3.

[0035] Table 3 Statistical results of maximum strain simulation of gas pipeline under landslide

[0036]

[0037] ③ Vulnerability demand probability model: The landslide displacement intensity parameter and the maximum axial strain of the pipeline are regressed and the maximum axial strain of the pipeline is set as the dependent variable ε, and the landslide displacement intensity is set as the independent variable U. The functional relationship expression is obtained as shown in formula (1):

[0038] ε=0.00576U 2 +0.00288U+0.00063 (1)

[0039] The standard unbiased estimator of ε is σ = 0.000273.

[0040] Substituting formula (1) into the vulnerability demand model formula (2), the probability model of vulnerability demand based on strain under landslide is obtained (3):

[0041]

[0042]

[0043] 2. Vulnerability analysis of gas pipelines under landslides:

[0044] The maximum axial strain of the pipeline obtained in step 1 is used as the capacity index parameter, and the capacity index parameter is quantified to define the gas pipeline under the action of landslide into four damage levels: basically intact, generally damaged, moderately damaged, and severely damaged;

[0045] The empirical values ​​and calculation formulas for the compression and tensile failure limit strains of pipelines in CSA Z662-2007, Oil and Gas Pipeline Systems, and the tensile limit strain of pipelines are adopted. The calculation formula is shown in formula (4):

[0046]

[0047] The strain-based failure judgment criterion stipulates that the maximum axial strain generated by the pipeline during operation should be less than the allowable strain of the pipeline. The allowable strain of the pipeline can be obtained based on the pipeline limit strain value and a certain safety factor. Therefore, the strain-based failure judgment criterion for the pipeline under the action of landslide is shown in formula (5):

[0048]

[0049] In formula (5), ε tf is the tensile strain generated during pipeline operation; [ε t ] is the required tensile strain generated during pipeline operation; φ ε is the safety factor, which is 1.25 (derived from Comparative Analysis of Domestic and International Oil and Gas Pipeline Standards, published by Petroleum Industry Press in 2010, author is China Petroleum Pipeline Company).

[0050] Considering the actual parameters of the tie line, it can be calculated that the maximum tensile strain [ε t ] v =2%, maximum allowable compressive strain [ε c ] v = 0.7% and yield strain ε y =0.23%. During the landslide, the tensile strain on the pipeline is the main cause of its failure, and in reality, it is difficult for compressive strain to break, so tensile strain failure is the main cause.

[0051] The damage level classification is shown in Table 4.

[0052] Table 4 Damage level classification of gas pipelines under landslide based on strain index

[0053]

[0054] 3. Vulnerability assessment of gas pipelines under landslides:

[0055] Taking the displacement intensity of the landslide body as the disaster intensity parameter and the maximum axial strain of the pipeline under the action of the landslide as the demand parameter, a strain-based vulnerability assessment model for the pipeline is established:

[0056]

[0057] In formula (6), ε i is the logarithmic mean of the maximum strain capacity parameter of the pipeline under limit state i; β ε is the logarithmic standard deviation of the maximum strain capacity parameter of the pipeline under the corresponding limit state.

[0058] Probabilistic vulnerability model of pipeline based on strain demand-capacity under different landslide displacement intensities:

[0059]

[0060] Standard deviation β ε =0.0013

[0061] When the landslide displacement U takes different values, the probability of the gas pipeline being basically intact is:

[0062]

[0063] When the landslide displacement U takes different values, the probability of the gas pipeline exceeding the general damage is:

[0064]

[0065] When the landslide displacement U takes different values, the probability of the gas pipeline exceeding the medium damage is:

[0066]

[0067] Example 2

[0068] 1. Analysis of gas pipeline vulnerability requirements under landslides:

[0069] ① Random sampling: Taking the X70 pipe gas pipeline as an example, the four parameters of the X70 pipe, namely, yield strength, pipe diameter, wall thickness, and elastic modulus, are selected. The four random variables are normally distributed, as shown in Table 1.

[0070] The initial displacement of the landslide soil is 0.1m, the maximum displacement is 1.5m, and the step increment is 0.2m to analyze the response state of the pipeline under different landslide intensities. The optimal Latin hypercube sampling method is used to extract 80 sample points for each random variable to generate the "landslide-pipeline" sample pairs, as shown in Table 2.

[0071] ② Pipeline vulnerability analysis: Based on ABAQUS software simulation analysis, 80 groups of “landslide-pipeline” sample parameters were brought into the landslide pipeline model for simulation analysis to obtain the maximum displacement of the gas pipeline. The pipeline burial depth was 2m and the internal pressure was 8MPa. The maximum displacement of the midpoint of each sample pipeline was recorded as S. The simulation statistical results of all samples are shown in Table 5.

[0072] Table 5 Statistical results of maximum displacement simulation of gas pipeline under landslide

[0073]

[0074]

[0075] ③ Vulnerability demand probability model: The landslide displacement intensity parameter and the maximum displacement of the pipeline are regressed and the maximum displacement of the pipeline is set as the dependent variable and the landslide displacement intensity is set as the independent variable to obtain the functional relationship expression (12):

[0076] S=0.76354U-0.01944 (11)

[0077] The standard unbiased estimator of S is σ = 0.007.

[0078] Substituting formula (11) into the vulnerable demand model formula (2), the probability demand model of the pipeline based on the maximum displacement under the action of landslide is obtained. The conditional distribution probability function of the maximum displacement of the pipeline to the landslide displacement intensity can be expressed as formula (12):

[0079]

[0080] 2. Vulnerability analysis of gas pipelines under landslides:

[0081] The maximum displacement of the pipeline obtained in step 1 of this embodiment is used as the capacity index parameter, and the capacity index parameter is quantified to define the gas pipeline under the action of the landslide into four damage levels: basically intact, generally damaged, moderately damaged, and severely damaged;

[0082] When the pipeline reaches the yield strain, the maximum displacement of the landslide body is 0.38m, and the corresponding displacement offset of the pipeline is 0.28m. The pipeline is in the small deformation stage; when the pipeline reaches the intermediate strain between the yield limit and the tensile limit, the maximum displacement of the landslide body is 1.1m, and the corresponding displacement offset of the pipeline is 0.85m. The pipeline is in the elastic-plastic large deformation stage; when the pipeline reaches the ultimate tensile strain, the maximum displacement of the landslide body is 1.65m, and the corresponding displacement offset of the pipeline is 1.26m. The pipeline will undergo huge deformation and even be in danger of fracture and damage.

[0083] Table 6 Limit displacement values ​​of gas pipeline under landslide

[0084]

[0085] 3. Conduct vulnerability assessment on gas pipelines under landslide conditions.

[0086] Taking the displacement of the landslide body as the disaster intensity parameter and the maximum displacement of the pipeline under the action of the landslide as the demand parameter, a strain-based vulnerability assessment model for the pipeline is established:

[0087]

[0088] In formula (13), ε i is the logarithmic mean of the maximum displacement capacity parameter of the pipeline under limit state i; β ε It is the logarithmic standard deviation of the maximum displacement capacity parameter of the pipeline under the corresponding limit state.

[0089] Vulnerability probability model of gas pipeline based on displacement demand-capacity under different landslide displacement intensities:

[0090]

[0091] When the landslide displacement U takes different values, the probability of the gas pipeline being basically intact is:

[0092]

[0093] When the landslide displacement U takes different values, the probability of the gas pipeline exceeding the general damage is:

[0094]

[0095] When the landslide displacement U takes different values, the probability of the gas pipeline exceeding the medium damage is:

[0096]

[0097] The above-mentioned embodiments only express the specific implementation of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A method for evaluating a gas pipeline under landslide action based on structural vulnerability theory, characterized in that: The steps include: S1. Conduct vulnerability analysis on gas pipelines under landslides; S2. Conduct vulnerability analysis on gas pipelines under landslides; S3. Conduct vulnerability assessment of gas pipelines under landslides; Wherein, step S1 comprises the following steps: S11, random sampling, selecting multiple parameters of the pipeline as random variables, and extracting multiple samples using the optimal Latin hypercube sampling method according to the distribution characteristics of the selected multiple random variables, each sample including the selected multiple random variables and the landslide displacement intensity parameter, to generate a landslide-pipeline sample pair; S12. Finite element analysis of pipelines: the parameters of each sample are respectively brought into the landslide pipeline model for simulation analysis to obtain the response parameters of the pipeline, and the pipeline response parameters are used as the required parameters for vulnerability analysis; S13, constructing a vulnerable demand probability model, performing regression analysis on the landslide displacement intensity parameter and the pipeline demand parameter, and obtaining the vulnerable demand probability model; Step S2 includes the following steps: Taking pipeline demand parameters as capacity index parameters, quantifying capacity index parameters, and partitioning the quantified capacity index parameters, different partitions correspond to different damage levels; Step S3 includes the following steps: S31. Taking landslide displacement as the disaster intensity parameter, based on the vulnerability demand probability model and combined with the capacity index parameter limit, the vulnerability probability model of pipeline based on the demand-capacity of response parameters under different landslide displacement intensity parameters is obtained; S32. When the landslide displacement intensity parameter takes different values, the probability of the pipeline exceeding different damage levels is calculated respectively.

2. The method for evaluating a gas pipeline under landslide based on structural vulnerability theory according to claim 1 is characterized in that: The plurality of random variables include yield strength, pipe diameter, wall thickness, and elastic modulus.

3. The method for evaluating a gas pipeline under landslide action based on structural vulnerability theory according to claim 2 is characterized in that: The response parameter is the maximum axial strain or the maximum displacement.

4. The method for evaluating a gas pipeline under landslide action based on structural vulnerability theory according to claim 3 is characterized in that: The simulation analysis in step S12 is performed using ABAQUS software.

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