Gas pipe vertical incidence seismic wave analysis method, device and readable medium

Abstract

This invention discloses a method, equipment, and readable medium for analyzing vertically incident seismic waves in gas pipelines, belonging to the field of pipeline integrity evaluation and seismic analysis technology. The method establishes a three-dimensional pipe-soil interaction finite element model based on pipeline geometric parameters, material properties, and corrosion defect characteristics; it uses viscoelastic artificial boundaries to simulate the radiation damping effect of a semi-infinite foundation, and derives the equivalent nodal force calculation formulas for vertically incident SV and SH waves based on wavefield decomposition theory; it develops an automated program to apply viscoelastic boundary conditions and input seismic waves; and it reveals the differentiated sensitivity of internal and external corrosion defects to SV and SH waves by analyzing strain response and stress distribution. This invention, employing the aforementioned method, equipment, and readable medium for analyzing vertically incident seismic waves in gas pipelines, improves the accuracy and modeling efficiency of seismic wave simulation, ensures computational reliability, and establishes a quantitative assessment system for pipeline seismic response.

Description

Technical Field

[0001] This invention belongs to the field of pipeline integrity evaluation and seismic analysis technology, specifically involving a method, equipment, and readable medium for analyzing vertically incident seismic waves from gas pipelines. Background Technology

[0002] Urban gas pipelines are vital urban lifeline infrastructure, but they commonly suffer from severe corrosion as their service life increases. Corrosion defects reduce pipeline strength and threaten pipeline integrity. At the same time, the combined effect of corrosion defects and strong earthquakes can easily lead to the failure of buried gas pipelines, causing safety accidents such as leaks, fires, and explosions.

[0003] However, existing technologies have the following shortcomings: most studies focus on intact buried pipelines and do not consider corrosion damage in actual service; a few studies involving corrosion only analyze single internal or external corrosion, without conducting systematic comparisons of double external corrosion, double internal corrosion, and internal-external composite corrosion, nor revealing the interaction mechanism of composite corrosion; shear waves (S-waves) are the dominant seismic waves that cause deformation of buried pipelines, which can be decomposed into vertically polarized shear waves (SV waves) and horizontally polarized shear waves (SH waves), which will induce different stress states in the pipeline, but existing studies have not systematically compared the differential effects of the two on different corrosion types under vertical incidence; finite element simulation of seismic waves requires the application of artificial boundaries on the cross-section. Although viscoelastic boundaries can simultaneously simulate wave radiation and foundation elastic recovery, which is superior to viscous boundaries (low-frequency instability) and transmission boundaries (complex formulas and sensitive to incident angle), traditional methods require cross-platform data processing when implementing viscoelastic boundary conditions and seismic wave input, which is cumbersome, error-prone, and has low modeling efficiency and reliability.

[0004] Therefore, a new method is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a method, equipment, and readable medium for analyzing vertically incident seismic waves from gas pipelines. This method improves the accuracy and efficiency of seismic wave simulation and ensures the reliability of calculations. It also establishes a quantitative evaluation system for pipeline seismic response and improves the calculation and verification system for viscoelastic boundary parameters.

[0006] To achieve the above objectives, the present invention provides a method, apparatus, and readable medium for analyzing vertically incident seismic waves from gas pipelines, comprising the following steps: S1. Construct a three-dimensional pipe-soil interaction finite element model of a buried gas pipeline with four corrosion conditions. Use the surface-to-surface contact algorithm to simulate the pipe-soil interaction and perform local mesh refinement on the corrosion defect area; output the model file. S2. Using the model file output from S1 as input, calculate and apply three-dimensional viscoelastic artificial boundary conditions at the cut-off boundary of the soil model. First, calculate the physical parameters of the medium foundation, then calculate the stiffness coefficient and damping coefficient of the boundary nodes. Determine the control area of ​​the nodes through the uniformly distributed pressure loading method. Output the model file with boundary parameters and parameter table. S3. Using the model file with boundary parameters and parameter table output from S2 as input, derive the equivalent nodal force formula for SV and SH waves under perpendicular incidence based on wave field decomposition theory, as well as the free field displacement and velocity correction formulas considering wave superposition and time delay, and organize the wave type adaptation rules; output the formula calculation system file. S4. Using the model file with boundary parameters output from S2 and the formula calculation system file output from S3 as input, develop a Python automated program based on the ABAQUS script interface to automate the entire process of applying viscoelastic boundaries and inputting seismic waves, and verify the reliability of the program's calculations; output a finite element calculation model file with seismic wave loads. S5. Using the finite element calculation model file with seismic wave load output from S4 as input, determine the ground motion parameters according to the seismic design code, process the ground motion record, and perform numerical calculations of the dynamic response under vertical incidence of SV wave and SH wave for four working conditions; output the original dataset of dynamic calculation. S6. Using the original dynamic calculation dataset output from S5 as input, select axial strain as the evaluation index, extract the response data at the corrosion defect location and calculate the strain amplification factor; output the corrosion defect location response data calculation table. S7. Using the corrosion defect location response data calculation table output from S6 as input, calculate the SV / SH ratio to quantify the seismic wave direction sensitivity of corrosion defects, analyze the response law under different corrosion conditions, reveal the composite corrosion load sharing mechanism and evaluate the seismic safety margin of the pipeline; output a seismic response law analysis report of corrosion defects. S8. Using the seismic response law analysis report output from S7 as input, compile a comprehensive seismic response analysis report for corroded buried gas pipelines, propose engineering application suggestions, and form a theoretical research framework for pipeline response analysis under oblique incident seismic waves.

[0007] Preferably, in S1, the pipe model of the three-dimensional pipe-soil interaction finite element model is made of L360 steel with an outer diameter of 323.8 mm and a wall thickness of 7.9 mm. The burial depth is 1.2 m from the vertical distance from the center line of the pipe to the ground surface, and a uniform internal pressure of 3 MPa is applied. The soil model is silty clay with dimensions of 20 m × 4 m × 3 m along the axial, transverse, and vertical directions of the pipe. The Mohr-Coulomb elastoplastic constitutive model is adopted, and the pipe model adopts a linear elastic constitutive model.

[0008] Preferably, in S1, the four corrosion conditions include intact condition, double external corrosion condition, double internal corrosion condition, and internal and external combined corrosion condition; Corrosion defects are idealized as elliptical geometries; the axial length of corrosion defects in double external corrosion, double internal corrosion, and combined internal and external corrosion conditions is 30mm, the circumferential width is 24mm, and the depth is 5mm. The two corrosion defects are aligned along the pipe axis and the longitudinal spacing is 40mm. In the surface-to-surface contact algorithm, the outer surface of the pipe is set as the master surface and the inner surface of the soil is set as the slave surface. The normal direction adopts the hard contact model, and the tangential direction adopts the penalty function method with a friction coefficient of 0.3.

[0009] Preferably, in step S2, the basic physical parameters of the calculated medium include the medium shear modulus, shear wave velocity, and longitudinal wave velocity. The formula for calculating the shear modulus of a medium is: ; In the formula, ; The elastic modulus of the medium; Poisson's ratio of the medium; The formula for calculating shear wave velocity is: ; In the formula, The shear wave velocity of the medium; The density of the medium; The formula for calculating the longitudinal wave velocity is: ; In the formula, The longitudinal wave velocity of the medium; Boundary node stiffness and damping coefficients, including tangential and normal coefficients, are calculated using the following formulas: The formulas for calculating the stiffness and damping coefficient of a tangential spring are as follows: ; ; In the formula, The stiffness coefficient of the viscoelastic artificial boundary tangential spring; This is the tangential correction factor for the viscoelastic artificial boundary; This represents the distance from the wave source to the artificial boundary node. The tangential damping coefficient of the viscoelastic artificial boundary The formulas for calculating the stiffness and damping coefficient of a normal spring are as follows: ; ; In the formula, The normal stiffness coefficient of the viscoelastic artificial boundary spring; This is the correction factor for the viscoelastic artificial boundary normal. The normal damping coefficient of the viscoelastic artificial boundary; Among them, the tangential correction coefficient of the three-dimensional pipe-soil interaction finite element model Normal correction factor .

[0010] Preferably, in S2, the uniform pressure loading method involves applying a 1Pa uniform normal pressure to the surface of the viscoelastic artificial boundary, constraining all degrees of freedom of the boundary nodes, extracting the node reaction forces, and the node reaction force values ​​being the node control area values. The spring stiffness coefficient and damping coefficient are then multiplied by the corresponding node control area to obtain the actual parameters.

[0011] Preferably, in step S3, the total formula for the equivalent nodal force is expressed as: ; In the formula, Let be the free field displacement vector of the boundary node; The free field velocity vector of the boundary node; The spring stiffness coefficient at the boundary node; The boundary node damping coefficient; This is the reaction force generated by the spring due to its free-field motion; This is the reaction force generated by the damper due to free field motion; The control area of ​​the boundary nodes; The surface force on the boundary surface is the stress tensor of the free field. For the free field stress tensor; The outward normal unit vector of the boundary is determined by the geometric features of the model boundary of S1; The formula for correcting free field displacement is: ; In the formula, This represents the displacement caused by the earthquake. For the free field displacement of a node at any height; The height of the artificial boundary node; This represents the total height of the model; This is the time delay for the incident wave to propagate from the bottom to the node; This is the time delay for the reflected wave to return from the free surface to the node; This refers to the propagation time of seismic waves; The formula for correcting free field velocity is: ; In the formula, Input the velocity of the ground motion; Let be the free field velocity of a node at any height.

[0012] Preferably, in step S4, the Python automation program performs operations through the ABAQUS script interface without cross-platform data transmission; the boundary node identification module automatically matches the node coordinates with the viscoelastic artificial boundary parameters; and the equivalent node force application module automatically calculates and applies the dynamic loads corresponding to the SV wave and SH wave according to the equivalent node force total calculation formula. A 50m×50m×50m three-dimensional homogeneous soil model was constructed as a three-dimensional verification model, with the material parameter set to a density of 2000 kg / m³. 3 With an elastic modulus of 200 MPa and a Poisson's ratio of 0.25, an SV wave pulse propagating vertically upward was input at the bottom boundary of the model, and 10 monitoring points were selected on the top and bottom surfaces to compare the numerical solution with the theoretical solution.

[0013] Preferably, in step S7, the formula for calculating the SV / SH ratio is: ; In the formula, A quantitative index for the sensitivity of corrosion defects to the direction of seismic waves; The dynamic strain range at the location of corrosion defects under SV wave excitation. The dynamic strain range at the location of corrosion defects under SH wave excitation; A higher ratio indicates a stronger sensitivity to SV waves, while a ratio close to 1 indicates equal sensitivity to both SV and SH waves.

[0014] Therefore, by employing the aforementioned method, equipment, and readable medium for analyzing vertically incident seismic waves from gas pipes, the present invention offers the following advantages compared to existing technologies: (1) The technical means of adopting four typical working conditions of good design / double external corrosion / double internal corrosion / internal and external composite corrosion and systematically analyzing the different effects of vertical incidence of SV wave and SH wave are used to overcome the technical problems of incomplete research on seismic response of corrosion pipelines, failure to compare the response differences of different corrosion types, and failure to systematically distinguish the different effects of the orthogonal component of S wave on different corrosion defects. Thus, the technical effects of revealing the load sharing mechanism of internal and external composite corrosion for the first time, clarifying the pipeline deformation mechanism of SV wave and SH wave, and revealing the significant directional sensitivity of external corrosion to SV / SH wave and the equilibrium sensitivity of internal corrosion to it for the first time are achieved. (2) By adopting the technical means of accurately deriving the equivalent nodal force calculation formula for vertical incidence of SV / SH waves under viscoelastic artificial boundary and optimizing the details of three-dimensional pipe-soil finite element modeling, we have overcome the technical problems of insufficient accuracy in seismic wave simulation and artificial boundary implementation, failure to consider the superposition and time delay of incident and reflected waves in the derivation of equivalent nodal force, and distortion of corrosion defect stress simulation caused by simplification of modeling details. In this way, we have achieved the technical effect of perfecting the engineering application of wave field decomposition theory, accurately simulating the stress distribution of the penetration wall thickness of corrosion defects and the interaction between pipe and soil, effectively capturing stress concentration at the defect, and greatly improving the accuracy of seismic wave simulation and artificial boundary implementation. (3) By adopting the technical means of developing Python automated programs based on the ABAQUS script interface, the technical problems of low efficiency in the traditional viscoelastic boundary condition application and seismic wave input methods and easy error in cross-platform data exchange are overcome. In this way, the technical effect of completing the entire process of boundary node identification in a unified computing environment is achieved, completely eliminating cross-platform data exchange, and greatly improving modeling efficiency and computational reliability is achieved. (4) By adopting the technical means of selecting axial strain E33 as the core evaluation index and proposing the SV / SH ratio quantitative index for the first time, the technical problem of lack of unified quantitative index for seismic response evaluation of corrosion pipelines, and the fact that most of them are qualitative / semi-quantitative analysis, has been overcome. This has achieved the technical effect of establishing a quantitative evaluation system for seismic response of corrosion pipelines, accurately quantifying the strain amplification effect of corrosion defects and the sensitivity of different corrosion defects to the direction of seismic waves, and providing a unified quantitative standard for seismic safety evaluation of pipelines. (5) By adopting a clear three-dimensional viscoelastic artificial boundary parameter calculation formula, proposing a boundary node control area determination method of “applying a uniform pressure of 1 Pa and extracting nodal reaction force”, and establishing a three-dimensional verification model, the technical problems of no clear standard for viscoelastic artificial boundary parameter calculation and lack of reliability verification of implementation method are overcome. In this way, the parameter calculation and verification system of viscoelastic artificial boundary is improved, the reliability of the boundary implementation method is verified, and the average absolute error between numerical solution and theoretical solution is less than 2.5%.

[0015] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the technical process of an embodiment of the present invention. Figure 2 This is a schematic diagram accompanying the three-dimensional pipe-soil interaction finite element model of a corroded buried gas pipeline according to an embodiment of the present invention. Figure 2 (a) shows a schematic diagram of the geometric dimensions of a three-dimensional pipe-soil finite element model; Figure 2 (b) shows a schematic diagram of the mesh generation for the finite element model; Figure 2(c) shows a schematic diagram of the arrangement of viscoelastic artificial boundary spring-damper; Figure 3 This is a schematic diagram of corrosion defect configuration for four working conditions according to an embodiment of the present invention; Figure 3 (a) indicates a pipe in good working order; Figure 3 (b) indicates a dual external corrosion condition; Figure 3 (c) indicates a double internal corrosion condition; Figure 3 (d) indicates a combined internal and external corrosion condition; Figure 4 This is a detailed execution flowchart of the Python automation program according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the physical scenario of the vibration and deformation mechanism of buried gas pipelines under vertical incidence of SV and SH waves according to an embodiment of the present invention. Figure 6 Numerical results and visualization analysis of the reliability verification of the Python automated program in this embodiment of the invention; Figure 6 (a) shows a schematic diagram of the geometry and node layout of the three-dimensional homogeneous soil verification model; Figure 6 (b) shows the SV wave pulse input time history curve; Figure 6 (c) shows a comparison of the response time history curves of the monitoring points; Figure 6 (d) represents the displacement contour plots of the validation model at different times; Figure 7 This is a comparison of the time history curves of axial strain (E33) at the location of corrosion defects in a corroded buried gas pipeline under different working conditions under vertical incidence of SV and SH waves, according to an embodiment of the present invention. Figure 7 (a) shows the time history curves of axial strain (E33) at the location of corrosion defects under four working conditions under vertical SV wave incidence; Figure 7 (b) shows the time history curves of axial strain (E33) at the location of corrosion defects under four working conditions with vertical SH wave incidence; Figure 8 This is a comparison of peak Mises stress distribution cloud maps under different corrosion conditions for SV wave and SH wave vertical incidence in embodiments of the present invention; Figure 8 (a) shows the equivalent stress distribution of an intact pipeline under SV waves; Figure 8 (b) shows the equivalent stress distribution of a pipeline with double external corrosion defects under SV waves; Figure 8 (c) represents the equivalent stress distribution of a pipeline with double internal corrosion defects under SV waves; Figure 8 (d) represents the equivalent stress distribution of a pipeline with combined internal and external corrosion defects under SV waves; Figure 8 (e) represents the equivalent stress distribution of an intact pipeline under SH waves; Figure 8 (f) represents the equivalent stress distribution of a pipeline with double external corrosion defects under SH waves; Figure 8(g) represents the equivalent stress distribution of a pipeline with double internal corrosion defects under SH waves; Figure 8 (h) represents the equivalent stress distribution of a pipeline with combined internal and external corrosion defects under SH waves. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used in the present invention should have the ordinary meaning understood by those skilled in the art.

[0018] Example 1 like Figures 1-2 As shown, this embodiment provides a method, equipment, and readable medium for analyzing vertically incident seismic waves from gas pipes. It should be understood that the specific parameters, models, and protocols mentioned in this embodiment are merely examples to help those skilled in the art understand the present invention, and are not intended to limit the present invention.

[0019] The present invention provides a method, apparatus, and readable medium for analyzing vertically incident seismic waves from gas pipes, comprising the following steps: S1. Construct a three-dimensional pipe-soil interaction finite element model of a corroded buried gas pipeline; This step is performed using ABAQUS finite element analysis software to construct a three-dimensional pipe-soil interaction finite element model that includes both a pipe model and a soil model. Specifically: The overall geometric structure of the model was determined, including the parameters of the pipeline model and the soil model. In the pipeline model parameters, the outer diameter of the pipeline was set to 323.8 mm, the wall thickness to 7.9 mm, and the burial depth of the pipeline was defined as the vertical distance from the center line of the pipeline to the ground surface, which was taken as 1.2 m. The pipeline material was L360 (X52) steel, which is commonly used for buried gas pipelines in cities. In order to reduce the influence of boundary effects on the subsequent dynamic calculation results, the dimensions of the soil model were set to 60 times, 11 times, and 8 times the diameter of the pipeline along the axial direction (Z-axis), the transverse direction (X-axis), and the vertical direction (Y-axis), respectively, i.e., 20 m × 4 m × 3 m. The soil medium was selected as the typical silty clay around buried pipelines in cities.

[0020] Model element discretization and mesh processing: The pipe model and soil model are discretized globally using eight-node reduced integral solid elements (C3D8R). Solid elements are used in the pipe model instead of shell elements to accurately simulate the stress distribution characteristics of corrosion defects penetrating the pipe wall thickness. A local mesh refinement strategy is adopted for the corrosion defect area of ​​the pipe model, with the mesh density gradually transitioning to a normal mesh density along the pipe axis and circumference towards the non-defect area. The mesh is refined in the area around the pipe in the soil model, with the mesh density gradually transitioning to a coarse mesh density along the soil radial direction towards the artificial boundary area to avoid calculation distortion in stress concentration areas.

[0021] Model material parameters and constitutive model assignment: The soil model uses silty clay and employs the Mohr-Coulomb elastoplastic constitutive model, with the following physical and mechanical parameters assigned: density is... The elastic modulus is 23.4 MPa and the Poisson's ratio is... Internal friction angle 26°; The pipe model adopts a linear elastic constitutive model, and the assigned physical and mechanical parameters are: density is The elastic modulus is 206000 MPa, the Poisson's ratio is 0.3, and the yield strength is 360 MPa. To characterize the typical operating conditions of urban buried gas pipelines, a uniform internal pressure of 3 MPa was applied inside the pipeline model.

[0022] Simulation setup for soil-pipe interaction: The surface-to-surface contact algorithm is used to simulate the interaction between the outer surface of the pipe model and the inner surface of the soil model. The outer surface of the pipe model is set as the master surface, and the inner surface of the soil model is set as the slave surface. The normal contact adopts a hard contact model, which allows the model to be completely closed when compressed and to be freely separated when stretched. The tangential contact adopts the penalty function method to simulate the friction behavior, and the friction coefficient is taken as the commonly used value of 0.3 in engineering.

[0023] Model construction for multiple corrosion conditions: Corrosion defects in actual engineering are idealized into elliptical geometry, and the geometric dimensions of corrosion defects are uniformly set as follows: axial length 30mm, circumferential width 24mm, and corrosion depth 5mm. Two corrosion defects are aligned along the pipe axis. In this embodiment, 2√(Dt)≈101mm and the longitudinal spacing SL=40mm are used to ensure that the defects interact with each other and that the configuration of each working condition model is consistent.

[0024] like Figure 3 As shown, Figure 3 (a) A complete pipeline model is shown. Figure 3 (b) A model of a pipe with double external corrosion is shown. Figure 3(c) A model of a pipe with double internal corrosion is shown. Figure 3 (d) shows a pipeline model with combined internal and external corrosion; Four comparative working conditions were constructed, with condition 1 serving as the baseline condition and conditions 2 through 4 as corrosion conditions, all with identical geometric dimensions of corrosion defects. Condition 1: Intact pipeline model, used as a comparison baseline; Working condition 2: Dual external corrosion pipe model, with both corrosion defects located on the outer surface of the pipe model; Working condition 3: Dual internal corrosion pipe model, with both corrosion defects located on the inner surface of the pipe model; Working condition 4: Internal and external composite corrosion pipeline model, with one corrosion defect located on the outer surface of the pipeline model and one corrosion defect located on the inner surface of the pipeline model.

[0025] Generate a 3D pipe-soil interaction finite element model file in the native format of the ABAQUS finite element analysis software. This file contains model node / element coordinate information, pipe-soil contact setting parameters, material parameters and constitutive model information, and corrosion defect geometry information for four working conditions. Use this model file as the base model carrier for S2 and import it into S2 for applying 3D viscoelastic artificial boundary conditions.

[0026] S2 receives the three-dimensional pipe-soil interaction finite element model file output by S1, which includes core parameters such as model geometry, node coordinates, medium density, elastic modulus, and Poisson's ratio; as well as the values ​​of the three-dimensional viscoelastic artificial boundary correction coefficients known in elastic dynamics theory.

[0027] Based on the theory of elastic dynamics, three-dimensional viscoelastic artificial boundary conditions are calculated and applied on the truncated boundary of the soil model. The viscoelastic boundary is equivalent to a continuously distributed parallel system of springs and dampers on the truncated boundary, specifically: Determine the location where the artificial boundary is applied: Three-dimensional viscoelastic artificial boundary conditions are applied to the bottom and four sides of the soil model, and the top surface of the soil model is set as a free boundary to simulate the surface conditions in actual engineering.

[0028] Calculate the basic physical parameters of the medium: Based on the medium's elastic modulus, Poisson's ratio, and density input by S1, the medium's shear modulus, shear wave velocity, and longitudinal wave velocity are calculated respectively, providing a basis for subsequent stiffness / damping coefficient calculations; Shear modulus is expressed as: ; In the formula, ; The elastic modulus of the medium; Poisson's ratio of the medium; Shear wave velocity is expressed as: ; In the formula, The shear wave velocity of the medium; The density of the medium; The longitudinal wave velocity is expressed as: ; In the formula, The longitudinal wave velocity of the medium; Calculate the spring stiffness coefficients of the boundary nodes: Calculate the spring stiffness coefficients in the tangential and normal directions of the viscoelastic artificial boundary, and the tangential correction coefficient in the three-dimensional pipe-soil interaction finite element model scenario. Normal correction factor The distance from the wave source to the artificial boundary node is calculated and extracted from the model node coordinates of S1; The formulas for calculating the stiffness and damping coefficient of a tangential spring are as follows: ; ; In the formula, The stiffness coefficient of the viscoelastic artificial boundary tangential spring; This is the tangential correction factor for the viscoelastic artificial boundary; This represents the distance from the wave source to the artificial boundary node. The tangential damping coefficient of the viscoelastic artificial boundary; The formulas for calculating the stiffness and damping coefficient of a normal spring are as follows: ; ; In the formula, The normal stiffness coefficient of the viscoelastic artificial boundary spring; This is the correction factor for the viscoelastic artificial boundary normal. is the normal damping coefficient of the viscoelastic artificial boundary.

[0029] Determine the control area of ​​the boundary nodes: The control area of ​​the boundary nodes was determined using the uniformly distributed pressure loading method: a uniformly distributed normal pressure of 1 Pa was applied to the viscoelastic artificial boundary surface of the soil model, constraining the degrees of freedom of all nodes on the boundary, and the reaction force values ​​of each node were extracted. The node reaction force values ​​(unit: N) and the node control area values ​​(unit: m²) were then compared. 2 The spring stiffness coefficient and damping coefficient are equal; multiply the spring stiffness coefficient and damping coefficient by the control area of ​​the corresponding node to obtain the actual stiffness / damping parameters of each boundary node in the finite element model.

[0030] Assigning viscoelastic artificial boundary conditions: The calculated tangential / normal actual stiffness parameters and damping parameters are associated one-to-one with the corresponding boundary nodes on the bottom surface and four sides of the soil model to complete the global application of the three-dimensional viscoelastic artificial boundary conditions. Generate a core parameter table for the viscoelastic artificial boundary and import the parameter table into S3 as the basic parameters for deriving the equivalent nodal force calculation formula. Extract the core geometric parameters of the soil model, including the height y of the artificial boundary nodes and the total height H of the soil model. Import these parameters into S3 for the derivation of the free field displacement / velocity correction formula.

[0031] Generate a pipe-soil finite element model file with three-dimensional viscoelastic artificial boundary parameters, and import the file into S4 as the base model for parameter assignment in the Python automation program.

[0032] S3 receives the core parameter table of the viscoelastic artificial boundary and the geometric core parameters of the soil model output by S2; as well as the basic characteristic parameters of the seismic wave.

[0033] Based on wavefield decomposition theory, the seismic wave input problem is transformed into a wave source problem. The equivalent nodal force calculation formulas and free field displacement / velocity correction formulas under perpendicular incidence conditions for SV and SH waves are derived, specifically: Transformation of wavefield decomposition and seismic wave input problem: The total wave field at the viscoelastic artificial boundary is decomposed into a free field and a scattered field. The free field is the wave field of seismic waves propagating in a semi-infinite medium without any structure, which can be directly determined by the input ground motion. The scattered field is the wave field disturbance caused by the presence of the pipe structure, which is considered by the boundary spring-damper system itself; therefore, the equivalent nodal force only characterizes the contribution of the free field. The total wave field satisfies: ; In the formula, This represents the displacement field vector of seismic waves propagating in a semi-infinite medium when there is no structure. The displacement field vector of the wave field disturbance caused by the existence of the pipeline structure; Let be the total displacement field vector at the viscoelastic artificial boundary.

[0034] The formula for calculating the total equivalent nodal force is as follows: Based on the viscoelastic artificial boundary core parameters input by S2, the formula for calculating the equivalent total nodal force is derived, as follows: ; In the formula, Let be the free field displacement vector of the boundary node; The free field velocity vector of the boundary node; This refers to the spring stiffness coefficient of the boundary node, which is the combined stiffness coefficient of the artificial boundary node integrating tangential and normal directions. This refers to the boundary node damping coefficient, which is the integrated damping coefficient of the artificial boundary node combining tangential and normal directions. This is the reaction force generated by the spring due to its free-field motion; This is the reaction force generated by the damper due to free field motion; The control area of ​​the boundary nodes; The surface force on the boundary surface is the stress tensor of the free field. For the free field stress tensor; The outward normal unit vector of the boundary is determined by the geometric features of the model boundary of S1.

[0035] The equivalent nodal force, as represented by the overall formula for calculating equivalent nodal forces, consists of two parts: the reaction force of the spring-damped system to the free field motion and the surface force of the free field stress on the boundary surface. Calculated using the theory of free-field propagation of seismic waves.

[0036] Derivation of the formula for calculating free field displacement / velocity correction: For technical scenarios involving perpendicular incidence of SV and SH waves, considering the superposition effect of incident waves from the lateral and front / back boundaries of the soil model and reflected waves from the free surface, as well as the time delay of wave propagation, corrected calculation formulas for free field displacement and velocity are derived. The derivation process for SH waves is consistent with that for SV waves, only the vibration direction differs: The free field displacement correction is expressed as: ; In the formula, This represents the displacement caused by the earthquake. For the free field displacement of a node at any height; The height of the artificial boundary node; This represents the total height of the model; This is the time delay for the incident wave to propagate from the bottom to the node; This is the time delay for the reflected wave to return from the free surface to the node; This represents the propagation time of the seismic waves.

[0037] Free field velocity correction, expressed as: ; In the formula, Input the velocity of the ground motion; Let be the free field velocity at any node height; Generate an equivalent nodal force calculation system file under perpendicular incidence of SV / SH waves, including the general formula for equivalent nodal forces, the free field displacement / velocity correction formula, the formula parameter description, and the wave type adaptation rules. Import this file into S4 as the algorithm basis for the development of Python automated programs.

[0038] Generate a formula parameter association table to clarify the one-to-one correspondence between each parameter in the calculation system and the boundary parameters and model geometric parameters output by S2. Import this table into S4 for code parameter mapping in Python automation programs.

[0039] S4 receives the pipe-soil finite element model file with three-dimensional viscoelastic artificial boundary parameters and the viscoelastic artificial boundary core parameter table output by S2, as well as the equivalent nodal force calculation system file and formula parameter association table output by S3.

[0040] like Figure 4 As shown, a Python automation program was developed based on the ABAQUS script interface to automate the entire process of applying viscoelastic boundary conditions and inputting seismic waves within the ABAQUS unified computing environment, eliminating errors caused by cross-platform data exchange. Specifically: Setting up the program development and runtime environment: A Python program development environment is built based on the native script interface of the ABAQUS finite element analysis software, ensuring seamless integration between the program and the ABAQUS software. All operations are performed within the unified ABAQUS computing environment, with no cross-platform data transfer required.

[0041] Based on the S3 calculation system files and parameter association tables, five functional modules were developed to work in conjunction with the finite element model, enabling fully automated operation throughout the entire process: (1) Boundary node identification module: Automatically identify viscoelastic artificial boundary nodes on the bottom surface and four sides of the soil model, and match the node coordinates with the boundary parameters of S2; (2) Control area calculation module: Automatically executes the operation of “applying 1Pa uniform pressure - constraining node degrees of freedom - extracting node reaction force” to complete the automatic calculation and assignment of the control area of ​​the boundary node; (3) Spring damping parameter assignment module: Based on the formula parameter association table, assign the spring damping parameter value. , , , Automatically assign values ​​to the corresponding boundary nodes without manual intervention; (4) Time delay interpolation module: Automatically calculates the wave propagation time delay of each boundary node according to the formula, and completes the automatic interpolation correction of free field displacement / velocity; (5) Equivalent nodal force application module: Automatically calculates the equivalent nodal force of each boundary node under the vertical incidence of SV wave and SH wave according to the formula, and automatically applies it as a dynamic load to the corresponding node of the finite element model.

[0042] Numerical verification of program reliability: A three-dimensional homogeneous soil verification model was constructed to verify the accuracy and reliability of the program's calculation results. Specific verification steps included: (1) Verification of model parameters: A three-dimensional homogeneous soil model of 50m×50m×50m was constructed, and the material parameters were assigned as follows: density of 2000kg / m³. 3 The elastic modulus is 200 MPa, the Poisson's ratio is 0.25, and the corresponding shear wave velocity is 200 m / s; (2) Verification method: Input the SV wave pulse that propagates vertically upward at the bottom boundary of the model, select 10 monitoring points on the top and bottom surfaces of the model, and extract the numerical solution (calculated by this program) and theoretical solution (obtained by the analytical solution of elastic wave propagation theory) of the displacement time history curve of the monitoring points. (3) Verification criteria: The average absolute error between the numerical solution and the theoretical solution should be less than 2.5%; (4) Verification results: The numerical solutions of the displacement time history curves of each monitoring point are in good agreement with the theoretical solutions, with an average absolute error of 2.1%, which meets the verification criteria and proves that the program calculation is reliable.

[0043] Generate executable Python automation program files; Generate a finite element calculation model file with seismic wave load after processing by a Python program. The model has completed the precise application of viscoelastic boundary conditions and the loading of equivalent nodal force loads of SV wave / SH wave. It is configured according to the four corrosion conditions of S1. Import the file into S5 as the calculation model for dynamic response analysis. Generate a Python program reliability verification report, including verification model parameters, comparison results between numerical and theoretical solutions, and error analysis, to corroborate the reliability of the computational model.

[0044] S5: Receive the finite element calculation model file with seismic wave load output by S4; The seismic records were selected using the response spectrum matching method, and the dynamic response numerical calculations were carried out under vertical incidence of SV and SH waves for four corrosion conditions. Specifically: Selection and processing of seismic motion data: The response spectrum matching method was used to select ground motion records, and finally RSN4207 (ground motion record number) was determined as the input ground motion. The scaling factor is set to 1.282, and the peak ground acceleration is adjusted to 0.30g to match the design requirements of a rare earthquake of magnitude 8. The strongest response period of 20 seconds in the ground motion record was extracted as the core input data. The ground motion time interval was set to 0.01 seconds, and the total calculation time was 20 seconds.

[0045] Definition of the mechanism of seismic wave incidence and pipeline deformation: Define the incident plane as the YOZ plane, and let the seismic wave propagate vertically upward along the soil model (Y direction). Determine the particle vibration direction of SV wave and SH wave and the corresponding pipeline deformation mechanism: SV wave perpendicular incidence: The particle vibrates along the pipe axis (Z direction), causing axial tensile and compressive deformation of the pipe; SH wave perpendicular incidence: The particle vibrates laterally (X direction) along the pipe, causing the pipe to bend and deform laterally.

[0046] Parameter settings for dynamic calculation: In the ABAQUS finite element analysis software, set the relevant parameters for dynamic calculation: calculation duration 20s, time step 0.01s, enable the stress / strain time history data recording function, and enable the accurate extraction function of corrosion defect location data to ensure that the calculation results can extract stress and strain response data of the defect location throughout the entire time period.

[0047] Numerical calculation of dynamic response under all working conditions: The processed ground motion data were loaded into the finite element calculation models of four corrosion conditions in SV and SH wave forms respectively through a Python automated program. The dynamic response numerical calculations were then executed sequentially, completing the entire process of 8 sets of calculations for 4 conditions × 2 wave types, with the calculation data being automatically recorded throughout.

[0048] A raw dataset for full-condition dynamic calculations was generated and stored in ABAQUS post-processing format (.odb). It was categorized by "corrosion condition - seismic wave type" and includes the following core data: Time history data of axial strain (E33) at the location of corrosion defects under SV wave and SH wave excitation for four working conditions; Peak Mises stress distribution cloud map data and peak Mises stress values ​​at corrosion defect locations under SV wave and SH wave excitation for four working conditions; Stress and strain data for all nodes of the model over all time periods.

[0049] Import this dataset into S6 as the raw data for seismic response analysis of corrosion defect locations; S6: Receive the raw dataset for full-condition dynamic calculation output by S5; Axial strain, which closely matches the pipeline deformation mechanism, was selected as the core evaluation index. Key data on the location of corrosion defects were extracted, and basic quantitative calculations were completed. Specifically: Axial strain (E33) was selected as the core evaluation index for the seismic response at the location of corrosion defects (this index has the largest dynamic amplitude under SV wave and SH wave excitation, and is highly matched with the deformation mechanism of axial tension and compression and lateral bending of pipelines); node data of areas without corrosion defects were removed from the original dataset, and only node data of corrosion defect locations under four working conditions were retained to reduce interference from non-target data.

[0050] From the target dataset after filtering out the data, the following core data are precisely extracted: (1) Time history curves of axial strain (E33) at the location of corrosion defects under SV wave and SH wave excitation for four working conditions; (2) Peak Mises stress values ​​and stress distribution characteristics at the location of corrosion defects under SV wave and SH wave excitation in four working conditions; (3) The dynamic strain range (maximum strain fluctuation range) of axial strain (E33) at the location of corrosion defects under SV wave and SH wave excitation in four working conditions.

[0051] Using the dynamic strain range of axial strain (E33) of condition 1 (intact pipeline model) as a benchmark, the strain amplification factors of condition 2 (dual external corrosion), condition 3 (dual internal corrosion), and condition 4 (combined internal and external corrosion) under SV wave and SH wave excitation are calculated respectively. The strain amplification effect of corrosion defects relative to intact pipeline is quantified and expressed as: ; In the formula, This refers to the dynamic strain range under corrosive conditions. For the dynamic strain range under good working conditions.

[0052] A core response data calculation table for corrosion defect locations is generated, containing data such as the dynamic strain range of axial strain (E33), peak Mises stress value, and strain amplification factor for four working conditions. This calculation table is then imported into S7 as the basic data for analyzing the seismic response law of corrosion defects and calculating quantitative indicators.

[0053] S7, Calculation table of core response data for corrosion defect location received from S6; The directional sensitivity of corrosion defects is quantified by calculating the SV / SH ratio, and the load-sharing mechanism of internal and external combined corrosion and the safety of pipeline structure are analyzed. Specifically: The formula for calculating the SV / SH ratio under the four operating conditions is as follows: ; In the formula, A quantitative index for the sensitivity of corrosion defects to the direction of seismic waves; The dynamic strain range at the location of corrosion defects under SV wave excitation. The ratio represents the dynamic strain range of the corrosion defect location under SH wave excitation; this ratio is a quantitative index of the directional sensitivity of the corrosion defect to different seismic wave types. The higher the ratio, the stronger the sensitivity to SV waves, and a ratio close to 1 indicates that the corrosion defect is equally sensitive to SV and SH waves.

[0054] Analysis of the directional sensitivity of corrosion defects: By comparing the SV / SH ratios under four operating conditions, and analyzing the differences in the directional sensitivity of external corrosion, internal corrosion, and combined internal and external corrosion defects to the SV and SH waves, it is clarified that: (1) External corrosion defects are significantly sensitive to the direction of SV waves (SV / SH ratio = 1.91). (2) Internal corrosion defects are equally sensitive to SV and SH waves (SV / SH ratio = 1.59). (3) The SV / SH ratio of the intact pipeline is 1.58, which serves as the benchmark for comparison under corrosive conditions.

[0055] Analysis of the load sharing mechanism in combined internal and external corrosion: By comparing the peak strain and dynamic strain range at the corrosion defect location under SV wave excitation for conditions 2 (dual external corrosion), 3 (dual internal corrosion), and 4 (internal and external combined corrosion), the strain reduction was calculated, revealing the load sharing mechanism of internal and external combined corrosion: (1) The peak strain at the external corrosion defect was 21% lower than that in condition 2; (2) The peak strain at the internal corrosion defect is 6% lower than that in condition 3.

[0056] Analysis of the seismic safety of the pipeline structure: (1) By comparing the peak Mises stress at the location of corrosion defects under various working conditions under SV wave and SH wave excitation, it is clear that SV wave poses a more severe test to the longitudinal structural integrity of the corroded pipeline; (2) The peak Mises stress at the corrosion defect locations under each working condition was compared with the yield strength (360MPa) of L360 steel to verify the safety margin of the pipeline: the peak Mises stress at all defect locations was less than 37% of the yield strength, with the highest being 134.71MPa, indicating that the pipeline maintained fully elastic behavior under the level of a rare earthquake of magnitude 8 and had sufficient seismic safety margin. (3) Analysis of the reasons for the residual strain shift after earthquake excitation: The residual strain is caused by the plastic deformation of the surrounding soil using the Mohr-Coulomb constitutive model, and is not caused by the yielding of the non-pipe material.

[0057] Generate a seismic response analysis report on corrosion defects, including SV / SH ratio calculation results, directional sensitivity patterns, composite corrosion load sharing mechanisms, and seismic safety analysis of pipeline structures; import this report into S8 as the core theoretical basis for engineering application.

[0058] S8 receives the seismic response law analysis report of corrosion defects output by S7.

[0059] The technical analysis results are transformed into engineering application outcomes, generating a comprehensive analysis report and proposing targeted engineering application suggestions, specifically: Compile a comprehensive analysis report on the seismic response of corroded buried gas pipelines: Integrate all calculation data, analysis results, and pattern conclusions from S1 to S7 to compile a standardized comprehensive analysis report. The core of the report includes: (1) Description of technical solution and calculation parameters; (2) Core quantitative indicators for four working conditions (dynamic strain range, strain amplification factor, SV / SH ratio, peak Mises stress); (3) Seismic response characteristics of corrosion defects (direction sensitivity, composite corrosion load sharing mechanism). (4) Conclusion of seismic safety assessment of pipeline structure; (5) Specific recommendations for engineering applications.

[0060] Targeted recommendations for the application of urban gas pipeline network engineering are proposed: Based on the analysis results, engineering application suggestions are proposed from three dimensions: seismic design, integrity management, and post-earthquake monitoring, so as to realize the implementation of the technical achievements: (1) Seismic design: Design to enhance the axial seismic resistance of externally corroded pipelines and optimize the axial protection structure of the pipeline; (2) Integrity management: The SV / SH ratio is incorporated into the seismic safety assessment index system for corroded buried gas pipelines, and externally corroded pipelines with high SV / SH ratios are given priority maintenance; (3) Post-earthquake inspection: The externally corroded pipelines in the SV wave-affected area are listed as the priority level for post-earthquake inspection to improve the efficiency of post-earthquake emergency response.

[0061] A comprehensive analysis report on the seismic response of vertically incident seismic waves to corroded buried gas pipelines is generated, providing theoretical basis and technical support for the seismic design, integrity management, and post-earthquake detection of urban gas pipeline networks.

[0062] like Figure 5 As shown in the figure, this is a schematic diagram of the seismic wave incident scene in the three-dimensional pipe-soil coupled dynamic analysis model. It clearly shows the propagation path and particle motion direction of the SH wave (particle vibrating along the X direction) and SV wave (particle vibrating along the Z direction) when the seismic wave is perpendicularly incident on the YOZ plane along the Y direction, thus constructing a clear physical scene for the pipe-soil dynamic response analysis.

[0063] like Figure 6 As shown, Figure 6 (a) A three-dimensional cubic homogeneous soil model of 50m×50m×50m is shown. Five monitoring points A, B, C, D and E are set on the top surface, and five monitoring points F, G, H, I and J are set on the bottom surface for subsequent displacement response comparison. Figure 6 (b) Presents the SV wave pulse input load applied to the bottom of the model; Figure 6(c) The accuracy of the numerical method on single-point responses was verified; Figure 6 (d) The propagation process of SV wave pulses in soil is presented intuitively: the wavefront advances from bottom to top over time, and the displacement field distribution conforms to the propagation law of elastic waves, further verifying the overall wave field simulation capability of the method.

[0064] like Figure 7 As shown, Figure 7 (a) shows the strain time history curves under vertical incidence of SV waves; Figure 7 (b) shows the strain time history curve under vertical incidence of SH wave; under the action of both types of seismic waves, the strain amplitude of the pipeline with corrosion defects is significantly higher than that of the intact pipeline, showing an obvious strain amplification effect; in comparison, the strain peak value of the pipeline is higher and the fluctuation is more violent under the action of SV wave, and the dynamic impact effect is stronger, while the strain amplitude is lower and the curve is flatter under the action of SH wave.

[0065] like Figure 8 As shown, Figure 8 (a) and Figure 8 (e) shows the peak Mises stress distribution of the intact pipeline, which has the lowest stress level. The maximum stress on the inner side is only 87.89 MPa under SV wave action and 86.34 MPa under SH wave action. The overall stress distribution is uniform, with no obvious stress concentration. In pipelines with corrosion defects, the peak stress is significantly increased, and the stress concentration locations correspond perfectly to the defect locations. in, Figure 8 (b) and Figure 8 (f) shows the stress distribution of the double-corroded pipeline. The stress concentration is most severe at the outer defect, and the peak stress under the action of SV wave can reach more than 134.70 MPa. Figure 8 (c) and Figure 8 (g) shows the stress distribution of the double internal corrosion pipeline. There is obvious stress concentration at the inner defect. The peak stress under the action of SV wave is about 121 MPa. Figure 8 (d) and Figure 8 (h) shows the stress distribution of the pipeline with combined internal and external corrosion. Stress concentration occurs on both the inner and outer sides, and the peak stress is between the conditions of double external corrosion and double internal corrosion.

[0066] Under the action of SV wave, the peak stress of each working condition is generally higher than that of SH wave (such as the double external corrosion condition, the peak value of SV wave is ~134.7MPa, and that of SH wave is ~132.1MPa), indicating that SV wave has a stronger dynamic impact on the pipeline, which is consistent with the conclusion of the previous strain time history curve.

[0067] Therefore, this invention adopts the above-mentioned method, equipment and readable medium for analyzing vertically incident seismic waves in gas pipelines. This method improves the accuracy of seismic wave simulation and modeling efficiency, ensures the reliability of calculation, establishes a quantitative evaluation system for pipeline seismic response, and improves the calculation and verification system for viscoelastic boundary parameters.

[0068] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for analyzing vertical incidence seismic waves in a gas pipe, characterized by, Includes the following steps: S1. Construct a three-dimensional pipe-soil interaction finite element model of a buried gas pipeline with four corrosion conditions. Use the surface-to-surface contact algorithm to simulate the pipe-soil interaction and perform local mesh refinement on the corrosion defect area; output the model file. S2. Using the model file output from S1 as input, calculate and apply three-dimensional viscoelastic artificial boundary conditions at the cut-off boundary of the soil model. First, calculate the physical parameters of the medium foundation, then calculate the stiffness coefficient and damping coefficient of the boundary nodes, and determine the control area of ​​the nodes by the uniform pressure loading method. Output the model file with boundary parameters and the parameter table; S3. Using the model file with boundary parameters and parameter table output from S2 as input, derive the equivalent nodal force formula for SV and SH waves under perpendicular incidence based on wave field decomposition theory, as well as the free field displacement and velocity correction formulas considering wave superposition and time delay, and organize the wave type adaptation rules; output the formula calculation system file. S4. Using the model file with boundary parameters output from S2 and the formula calculation system file output from S3 as input, develop a Python automated program based on the ABAQUS script interface to automate the entire process of applying viscoelastic boundaries and inputting seismic waves, and verify the reliability of the program's calculations. Output finite element model file with seismic wave load; S5. Using the finite element calculation model file with seismic wave load output from S4 as input, determine the ground motion parameters according to the seismic design code, process the ground motion record, and perform numerical calculations of the dynamic response under vertical incidence of SV wave and SH wave for four working conditions; output the original dataset of dynamic calculation. S6. Using the original dynamic calculation dataset output from S5 as input, select axial strain as the evaluation index, extract the response data at the location of corrosion defects, and calculate the strain amplification factor. Output a table showing the response data for the location of corrosion defects; S7. Using the corrosion defect location response data calculation table output by S6 as input, calculate the SV / SH ratio to quantify the seismic wave direction sensitivity of corrosion defects, analyze the response law under different corrosion conditions, reveal the composite corrosion load sharing mechanism, and evaluate the seismic safety margin of the pipeline. Output a report analyzing the seismic response patterns of corrosion defects; S8. Using the seismic response law analysis report output from S7 as input, compile a comprehensive seismic response analysis report for corroded buried gas pipelines, propose engineering application suggestions, and form a theoretical research framework for pipeline response analysis under oblique incident seismic waves.

2. The gas pipe vertical incidence seismic wave analysis method according to claim 1, characterized by, In S1, the pipe model of the three-dimensional pipe-soil interaction finite element model is made of L360 steel with an outer diameter of 323.8 mm and a wall thickness of 7.9 mm. The burial depth is 1.2 m from the vertical distance from the center line of the pipe to the ground surface, and a uniform internal pressure of 3 MPa is applied. The soil model is silty clay with axial, transverse and vertical dimensions of 20 m × 4 m × 3 m along the pipe. The Mohr-Coulomb elastoplastic constitutive model is adopted, and the pipe model adopts a linear elastic constitutive model.

3. The gas pipe vertical incidence seismic wave analysis method according to claim 2, characterized by, In S1, the four corrosion conditions include intact condition, double external corrosion condition, double internal corrosion condition, and internal and external combined corrosion condition; Corrosion defects are idealized as elliptical geometries; the axial length of corrosion defects in double external corrosion, double internal corrosion, and combined internal and external corrosion conditions is 30mm, the circumferential width is 24mm, and the depth is 5mm. The two corrosion defects are aligned along the pipe axis and the longitudinal spacing is 40mm. In the surface-to-surface contact algorithm, the outer surface of the pipe is set as the master surface and the inner surface of the soil is set as the slave surface. The normal direction adopts the hard contact model, and the tangential direction adopts the penalty function method with a friction coefficient of 0.

3.

4. The gas pipe vertical incidence seismic wave analysis method according to claim 3, characterized by, In S2, the basic physical parameters of the calculated medium include the medium shear modulus, shear wave velocity, and longitudinal wave velocity. The formula for calculating the shear modulus of a medium is: ； wherein ; is the medium Poisson's ratio; and is the medium Poisson's ratio; and The formula for calculating shear wave velocity is: ； In the formula, The shear wave velocity of the medium; The density of the medium; The formula for calculating the longitudinal wave velocity is: ； In the formula, The longitudinal wave velocity of the medium; Boundary node stiffness and damping coefficients, including tangential and normal coefficients, are calculated using the following formulas: The formulas for calculating the stiffness and damping coefficient of a tangential spring are as follows: ； ； In the formula, The stiffness coefficient of the viscoelastic artificial boundary tangential spring; This is the tangential correction factor for the viscoelastic artificial boundary; This represents the distance from the wave source to the artificial boundary node. The tangential damping coefficient of the viscoelastic artificial boundary The formulas for calculating the stiffness and damping coefficient of a normal spring are as follows: ； ； In the formula, The normal stiffness coefficient of the viscoelastic artificial boundary spring; This is the correction factor for the viscoelastic artificial boundary normal. The normal damping coefficient of the viscoelastic artificial boundary; Among them, the tangential correction coefficient of the three-dimensional pipe-soil interaction finite element model Normal correction factor .

5. The method for analyzing vertically incident seismic waves from a gas pipeline according to claim 4, characterized in that, In S2, the uniform pressure loading method involves applying a 1Pa uniform normal pressure to the surface of the viscoelastic artificial boundary, constraining all degrees of freedom of the boundary nodes, extracting the node reaction forces, and the node reaction force values ​​are the node control area values. The spring stiffness coefficient and damping coefficient are multiplied by the corresponding node control area to obtain the actual parameters.

6. The method for analyzing vertically incident seismic waves from a gas pipeline according to claim 5, characterized in that, In S3, the total formula for the equivalent nodal force is expressed as: ； In the formula, Let be the free field displacement vector of the boundary node; The free field velocity vector of the boundary node; The spring stiffness coefficient at the boundary node; The boundary node damping coefficient; This is the reaction force generated by the spring due to its free-field motion; This is the reaction force generated by the damper due to free field motion; The control area of ​​the boundary nodes; The surface force on the boundary surface is the stress tensor of the free field. For the free field stress tensor; The outward normal unit vector of the boundary is determined by the geometric features of the model boundary of S1; The formula for correcting free field displacement is: ； In the formula, This represents the displacement caused by the earthquake. For the free field displacement of a node at any height; The height of the artificial boundary node; This represents the total height of the model; This is the time delay for the incident wave to propagate from the bottom to the node; This is the time delay for the reflected wave to return from the free surface to the node; This refers to the propagation time of seismic waves; The formula for correcting free field velocity is: ； In the formula, Input the velocity of the ground motion; Let be the free field velocity of a node at any height.

7. The method for analyzing vertically incident seismic waves from a gas pipeline according to claim 6, characterized in that, In S4, the Python automation program performs operations through the ABAQUS script interface without cross-platform data transmission. The boundary node identification module automatically matches the node coordinates with the viscoelastic artificial boundary parameters. The equivalent node force application module automatically calculates and applies the dynamic loads corresponding to SV wave and SH wave according to the equivalent node force total calculation formula. A 50m×50m×50m three-dimensional homogeneous soil model is constructed, with material parameters set as density 2000kg / m 3 , elastic modulus 200MPa, and Poisson's ratio 0.

25. An SV wave pulse propagating upward vertically is input at the bottom boundary of the model, and 10 monitoring points are selected on the top and bottom surfaces to compare the numerical solution with the theoretical solution.

8. The method for analyzing vertically incident seismic waves from a gas pipeline according to claim 7, characterized in that, In S7, the formula for calculating the SV / SH ratio is: ； In the formula, A quantitative index for the sensitivity of corrosion defects to the direction of seismic waves; The dynamic strain range at the location of corrosion defects under SV wave excitation. The dynamic strain range at the location of corrosion defects under SH wave excitation; A higher ratio indicates a stronger sensitivity to SV waves, while a ratio close to 1 indicates equal sensitivity to both SV and SH waves.

9. A computer device, characterized in that, include: A processor configured to be coupled to memory, read and execute instructions and / or program code in the memory to perform the method as described in any one of claims 1-8.

10. A computer-readable medium, characterized in that, The computer-readable medium stores computer program code that, when executed on a computer, causes the computer to perform the method as described in any one of claims 1-8.

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