A method for judging the safety status of buried gas pipelines by surface vibration velocity

Abstract

The present invention provides a method for determining the safety status of a buried gas pipeline by surface vibration velocity. The method calculates the on-site P-wave and S-wave velocities to obtain the time difference between the time when the P wave arrives at the surface monitoring point and the time when the direct P wave, the reflected P wave, and the reflected SV wave arrive at the buried gas pipeline; the vibration velocity of the direct P wave, the reflected P wave, and the reflected SV wave is obtained by calculating the reflection coefficient and time difference of the vibration wave, and the vibration velocity of the soil beside the buried gas pipeline is obtained by vector calculation, and the empirical coefficient of the difference in vibration velocity between the soil around the buried gas pipeline and the pipeline is obtained by numerical simulation calculation, and then the vibration velocity threshold of the buried gas pipeline is obtained, and compared with the theoretical threshold of the buried gas pipeline, so as to judge the safety status of the buried gas pipeline. The patent of the present invention can judge the safety status of the buried gas pipeline by monitoring the surface vibration velocity, and has high economic value and strong practicality.

Description

Technical Field

[0001] The invention relates to the field of bored pile construction vibration and buried gas pipeline safety, and in particular to a method for calculating the vibration velocity of a buried gas pipeline from the surface vibration velocity above the buried gas pipeline to determine the safety status of the buried gas pipeline. Background Art

[0002] The rapid development of various linear projects in my country conflicts with the oil and gas pipelines planned and built in the early years. Therefore, it is inevitable that some major engineering projects need to be parallel to or cross the buried oil and gas pipelines. Such newly built engineering projects that are parallel to or cross the pipelines generally take the form of bridges to cross the pipelines. When constructing the pile foundation of the bridge, my country often uses the method of punched cast-in-place piles, but the punched cast-in-place piles have a greater impact on the adjacent buried gas pipelines. At present, the safety monitoring of buried gas pipelines is mainly carried out by directly connecting vibration sensors to the pipelines. Although this method has high accuracy, it is difficult to excavate pipelines and has high monitoring costs in some areas. Therefore, it is a key technical issue to control economic costs while ensuring accuracy. If the vibration velocity of the buried gas pipeline can be calculated by monitoring the surface vibration velocity during the construction of the punched cast-in-place piles, and its safety can be determined, it will be of great significance to control the monitoring cost and pipeline safety.

[0003] The Chinese invention patent application with publication number CN112130207B discloses a method for calculating underground vibration from ground vibration under spherical charge conditions. The patent only calculates the underground vibration velocity through the ground vibration point, and does not propose how to convert the underground vibration velocity and the buried gas pipeline vibration velocity, nor does it determine where the vibration source is located to have the greatest impact on the buried gas pipeline. Therefore, it is impossible to determine the safety status of the buried gas pipeline. Therefore, a method is needed to convert the surface vibration velocity into the peak vibration velocity of the buried gas pipeline to determine the safety status of the buried gas pipeline. Summary of the invention

[0004] In order to solve the problems existing in the above background technology, the present invention proposes a method for judging the safety status of a buried gas pipeline by the ground vibration velocity. The method can calculate the corresponding vibration velocity of the buried gas pipeline by the ground vibration velocity above the buried gas pipeline, and then compare it with the vibration threshold of the buried gas pipeline, so as to achieve the purpose of judging the safety status of the buried gas pipeline.

[0005] In order to achieve the above technical objectives, the present invention provides a method for determining the safety status of a buried gas pipeline by using the surface vibration velocity, which is characterized by the following specific steps:

[0006] S1. Measure the rock and soil properties on site, and calculate the velocity of the compression wave P wave and the velocity of the shear wave S wave of the rock and soil on site through the density, Poisson's ratio, and elastic modulus parameters of the rock and soil, as follows:

[0007]

[0008]

[0009] Where C p is the P wave velocity of the rock and soil medium, in m / s; Cs is the S wave velocity of the rock and soil medium, in m / s;

[0010] ρ is the density of rock and soil medium, unit: kg / m 3 ; u is the Poisson's ratio of rock and soil medium;

[0011] E is the elastic modulus of the rock sample medium, in MPa;

[0012] S2. The incident angle of the incident P wave and the exit angle of the reflected SV wave, the reflection coefficient of the P wave and the reflection coefficient of the S wave at the ground monitoring point are calculated by the horizontal distance H1 between the buried gas pipeline and the vibration source of the bored pile construction and the buried depth D1 of the buried gas pipeline. The expressions are as follows:

[0013]

[0014]

[0015]

[0016]

[0017] Where θ P is the incident angle of the incident P wave at the ground monitoring point;

[0018] θ S is the reflection angle of the reflected SV wave at the ground monitoring point;

[0019] H1 is the horizontal distance between the vibration source of the bored pile construction and the buried gas pipeline;

[0020] D1 is the vertical distance between the vibration source of bored pile construction and the ground and the buried depth of the pipeline;

[0021] R pp is the reflection coefficient of the reflected P wave at the ground monitoring point;

[0022] R ps is the reflection coefficient of the reflected SV wave at the ground monitoring point;

[0023] S3. Determine that the incident P wave reaches the buried gas pipeline after being reflected by the ground vibration wave with vertical polarization, which is called the reflected P wave, and the ground excitation point is point P; determine that the incident P wave reaches the buried gas pipeline after being reflected by the ground vibration wave with vertical polarization, which is called the reflected SV wave, and the ground excitation point is point S; the P wave incident at point P has no vertical polarization, so the incident angle is consistent with the exit angle, and point P is directly obtained as the center point of the horizontal distance H1 between the buried gas pipeline and the ground monitoring point, that is, the horizontal distance H1 from point P to the vibration source of the bored pile construction is obtained. p :

[0024]

[0025] The P wave velocity C of the rock medium calculated in step S1 is calculated by the buried depth D1 of the buried gas pipeline, the horizontal distance H1 between the buried gas pipeline and the ground monitoring point, and the P wave velocity C of the rock medium calculated in step S1. p , S wave velocity C of rock and soil medium s Calculate the horizontal distance H between the ground excitation point S of the reflected SV wave and the center of the vibration source of the bored pile construction s and the incident angle θ′ of the incident P wave at the ground excitation point P p , the reflection angle θ″ of the reflected SV wave at the ground excitation point S s ; The specific calculation formula is as follows:

[0026]

[0027] D1(tanθ″ p +tanθ″ s )=H1

[0028] C p sinθ″ s -C s sinθ″ p =0

[0029] H s =D1·tanθ″ p

[0030] In the formula, H p It is the horizontal distance from the ground excitation point P to the vibration source of bored pile construction;

[0031] H s It is the horizontal distance from the ground excitation point S to the center of the vibration source of bored pile construction;

[0032] S4. Calculate the time difference between the direct P wave emitted by the bored pile construction vibration source and directly reaching the buried gas pipeline, the reflected P wave reflected by the ground excitation point P, and the reflected SV wave reflected by the ground excitation point S and the time difference between the incident P wave emitted by the bored pile construction vibration source and reaching the ground monitoring point directly above the pipeline. The calculation formula is as follows:

[0033]

[0034]

[0035]

[0036] Where Δt0 is the time difference between the direct P wave reaching the buried gas pipeline and the incident P wave reaching the ground monitoring point;

[0037] Δt1 is the time difference between the reflected P wave reflected by the ground excitation point P and the arrival of the incident P wave at the ground monitoring point;

[0038] Δt2 is the time difference between the reflected SV wave reflected by the ground excitation point S and the arrival of the buried gas pipeline and the incident P wave at the ground monitoring point;

[0039] S5. Calculate the waveform of the incident P wave based on the vertical vibration velocity of the ground surface measured by the vertical vibration sensor installed at the ground monitoring point. The expression is as follows:

[0040]

[0041] Where V y (t) is the vertical vibration velocity waveform of the ground monitoring point;

[0042] V p (t) is the vibration velocity waveform of the incident P wave at the ground monitoring point;

[0043] S6. The vibration velocity components of the soil vibration velocity at the underground gas pipeline in the horizontal and vertical directions are obtained by emitting the direct P wave directly reaching the buried gas pipeline through the punched cast-in-place pile construction vibration source, the reflected P wave reflected at the ground excitation point P, and the reflected SV wave reflected at the ground excitation point S.

[0044]

[0045]

[0046]

[0047] In the formula, It is the vibration velocity component of the underground gas pipeline in the horizontal direction;

[0048] It is the vibration velocity component of the underground gas pipeline in the vertical direction;

[0049] It is the soil vibration velocity at the underground gas pipeline;

[0050] V 0x (t) is the vibration velocity component of the direct P wave in the underground gas pipeline along the horizontal direction;

[0051] V 0z (t) is the vibration velocity component of the direct P wave in the underground gas pipeline along the vertical direction;

[0052] V 1x (t) is the vibration velocity component of the reflected P wave reflected at the ground excitation point P in the underground gas pipeline along the horizontal direction;

[0053] V 1z (t) is the vibration velocity component of the reflected P wave reflected at the ground excitation point P in the underground gas pipeline in the vertical direction;

[0054] V 2x (t) is the vibration velocity component of the reflected SV wave reflected at the ground excitation point S in the underground gas pipeline along the horizontal direction;

[0055] V 2z (t) is the vibration velocity component of the reflected SV wave reflected at the ground excitation point S in the underground gas pipeline along the vertical direction;

[0056] S7. The soil vibration velocity at the underground gas pipeline calculated in step S6 Combined with the established three-dimensional model of the buried gas pipeline, the relationship between the vibration velocity of the buried gas pipeline and the soil is obtained, and the peak vibration velocity V of the buried gas pipeline is obtained. 管 , which is calculated as follows:

[0057]

[0058] K t is the empirical coefficient of pipeline-soil vibration velocity difference;

[0059] S8. By adjusting the peak vibration velocity V of the buried gas pipeline 管 The buried gas pipeline vibration threshold V 阈值 Compare and judge the pipeline safety status:

[0060] If V 管 >V 阈值 , the pipeline is in an unsafe state;

[0061] If V 管 <V 阈值 , the pipeline is in a safe state;

[0062] Wherein, the buried gas pipeline vibration threshold V 阈值 It is the vibration speed when the buried gas pipeline is damaged.

[0063] A further technical solution of the present invention is as follows: when the peak vibration velocity of the buried gas pipeline corresponding to the peak vibration velocity of the surface of the buried gas pipeline reaches the maximum, the impact vibration source of the bored piles and the buried gas pipeline are in the same horizontal plane. Therefore, during the calculation, it is set that the impact vibration source of the bored piles and the buried gas pipeline are in the same horizontal plane.

[0064] A further technical solution of the present invention is as follows: the ground monitoring point in step S2 is a vibration sensor installed in the vertical direction of the ground surface just above the buried gas pipeline; the horizontal distance H1 between the vibration source of the bored pile construction and the buried gas pipeline is the horizontal distance between the vibration source of the bored pile construction and the ground monitoring point; the buried depth D1 of the buried gas pipeline is the vertical distance between the vibration source of the bored pile construction and the ground.

[0065] A further technical solution of the present invention is as follows: in the step S6, the vibration source of the bored pile construction emits a direct P wave that directly reaches the buried gas pipeline, a reflected P wave reflected at the ground excitation point P, and a reflected SV wave reflected at the ground excitation point S. The vibration velocity components V in the horizontal and vertical directions of the buried gas pipeline are 0x (t), V 0z (t), V 1x (t), V 1z (t), V 2x (t), V 2z (t) is calculated according to the following process:

[0066]

[0067] V 0x (t) = V0(t)

[0068] V 0z (t) = 0

[0069]

[0070]

[0071] V1x(t)=V1(t)·sinθ′p

[0072] V1z(t)=V1(t)·cosθ′ p

[0073]

[0074]

[0075] V2x(t)=V2(t)·cosθ″ s

[0076] V2z(t)=V2(t)·sinθ″ s

[0077] Where V0(t) is the vibration velocity waveform of the direct P wave at the underground buried gas pipeline;

[0078] V P (t-Δt0) is the vibration velocity waveform of the P wave incident on the ground monitoring point, which is translated by Δt0 in the positive direction of the time axis;

[0079] V1(t) is the vibration velocity waveform of the reflected P wave reflected at the ground excitation point P at the underground buried gas pipeline;

[0080] V P (t-Δt1) is the vibration velocity waveform of the P wave incident on the ground monitoring point, which is translated by Δt1 in the positive direction of the time axis;

[0081] R' pp is the reflection coefficient of the reflected P wave reflected from the ground excitation point P;

[0082] V2(t) is the vibration velocity waveform of the reflected SV wave reflected at the ground excitation point S at the underground buried gas pipeline;

[0083] V P (t-Δt2) is the vibration velocity waveform of the P wave incident on the underground gas pipeline, which is translated by Δt2 in the positive direction of the time axis;

[0084] R” ps is the reflection coefficient of the reflected SV wave reflected from the ground excitation point S.

[0085] The preferred technical solution of the present invention is: the buried gas pipeline vibration threshold V in step S8 阈值 The vibration velocity of the buried gas pipeline when it is damaged is calculated by two methods: the "Code for Seismic Design of Oil / Gas Steel Pipelines" and the numerical simulation method to establish a three-dimensional model of the buried gas pipeline. The smaller vibration velocity of the two is selected as the vibration velocity threshold of the buried gas pipeline to judge the safety status of the pipeline; that is:

[0086] If V m >V s , then V 阈值 =V s ;

[0087] If V m <V s , then V 阈值 =V m ;

[0088] Where V m is the vibration velocity corresponding to pipeline damage obtained through numerical simulation;

[0089] V s It is the vibration velocity corresponding to pipeline damage calculated by the "Seismic Design Code for Oil / Gas Steel Pipelines";

[0090] V 阈值 It is the vibration velocity threshold of buried gas pipeline.

[0091] A preferred technical solution of the present invention: the method of establishing the three-dimensional model of the buried gas pipeline in step S6 and step S8 is the same, and the specific steps are as follows:

[0092] (1) Test the properties of the on-site rock and soil and obtain the pipeline properties, burial depth, and bored pile construction conditions, and establish a three-dimensional numerical model of the buried gas pipeline;

[0093] (2) According to the calculation amount and calculation accuracy, the three-dimensional geometric model of the buried pipeline is meshed and the mesh independence is analyzed to obtain the stable state grid, that is, the number of grids and nodes used for calculation; during the test, soil stress, soil vibration velocity, soil displacement, pipeline stress, and pipeline vibration velocity are used as references.

[0094] The preferred technical solution of the present invention is to extract the vibration velocity of the buried gas pipeline at different times and the vibration velocity of the soil around the pipe at the corresponding time according to numerical simulation calculation, and use Origin software to perform linear fitting on a series of data to obtain the relationship between the vibration velocity of the buried gas pipeline and the vibration velocity of the soil around the pipe as V 管 =(1+K t )Vt, and K t is the empirical coefficient of pipeline-soil vibration velocity difference.

[0095] The present invention selects the situation that has the greatest impact on the buried gas pipeline, that is, the underground test point (buried gas pipeline) and the impact vibration source (punching cast-in-place pile construction vibration source) are located in the same horizontal plane, and the wave velocity of the on-site P wave and S wave is calculated to obtain the time difference between the time when the P wave reaches the surface vibration sensor (ground monitoring point) and the time when the direct P wave, the reflected P wave, and the reflected SV wave propagate to the buried gas pipeline; the vibration velocity of the direct P wave, the reflected P wave, and the reflected SV wave is obtained by calculating the reflection coefficient and time difference of the vibration wave, and the vibration velocity of the soil beside the buried gas pipeline is obtained by vector calculation; then, the empirical coefficient of the difference in vibration velocity between the soil around the buried gas pipeline and the pipeline is obtained by numerical simulation calculation, and then the vibration velocity threshold of the buried gas pipeline is obtained and compared with the buried gas pipeline threshold obtained by numerical simulation calculation and theoretical calculation, so as to judge the safety state of the buried gas pipeline.

[0096] The present invention can arrange vibration sensors on the surface above the buried gas pipeline to obtain the surface vibration velocity, thereby calculating the corresponding buried gas pipeline vibration velocity and comparing it with the buried gas pipeline vibration threshold, thereby judging the safety status of the buried gas pipeline; compared with the traditional monitoring method of excavating pipelines and burying vibration sensors, the present invention can judge the safety status of buried gas pipelines through surface vibration velocity monitoring, without excavating pipelines, and compared with traditional monitoring, the number of sensors is reduced, thereby reducing monitoring costs and monitoring difficulties, and has higher economic value and stronger practicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0097] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, in which:

[0098] Figure 1 It is an overall flow chart of an embodiment of the present invention;

[0099] Figure 2 It is a three-dimensional numerical simulation diagram of the bored pile-buried gas pipeline-soil in the example of the present invention;

[0100] Figure 3 A three-dimensional numerical simulation grid division diagram of a bored pile-buried gas pipeline-soil body in an example of the present invention;

[0101] Figure 4 It is a schematic diagram of the propagation and reflection law of vibration waves in rock and soil in an example of the present invention;

[0102] Figure 5 It is a waveform diagram of the measured surface vibration velocity in an example of the present invention.

[0103] Figure numbers: 101-buried gas pipeline; 102-bored cast-in-place pile construction area; 103-soil; 201-ground monitoring point; 202-buried gas pipeline monitoring point; 203-bored cast-in-place pile construction vibration source; 204-incident P wave at the ground excitation point P; 205-incident SV wave at the ground excitation point S; 206-incident P wave at the ground monitoring point 201; 207-reflected P wave reflected at the ground excitation point P; 208-reflected SV wave reflected at the ground excitation point S; 209-reflected SV wave at the ground monitoring point 201. DETAILED DESCRIPTION

[0104] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0105] In this embodiment, the construction of bored cast-in-place piles beside the West-East Gas Pipeline II pipeline at the intersection of the West-East Gas Pipeline II and the newly built Wuhan-Daigu Expressway is taken as an example to illustrate the specific implementation methods of the present invention.

[0106] First, let's introduce the project overview: Wuhan-Dawu Expressway (referred to as Wuhan-Dawu Expressway) is located in the north of Wuhan City. It starts at the end of the lower extension of Hankou North Jiefang Avenue in Huangpi District, Wuhan City, and ends at Liuji where it intersects with the Mazhu Expressway. The expressway intersects with the West-East Gas Pipeline at Xiangdian Village Zhongqiao and pile number K29+327, with an intersection angle of 85°. The West-East Gas Pipeline II uses X80 steel, a pipe diameter of 1219mm, a design pressure of 10MPa, a buried depth of about 2m, and a pipeline length of 36m within the bridge span. The new expressway is spanned by a bridge. When constructing the pile foundation of the bridge, the punched cast-in-place pile method is used, but the punched cast-in-place pile has a greater impact on the adjacent buried gas pipeline. If the conventional buried vibration sensor method is used for underground gas pipeline safety monitoring, it is necessary to excavate the area to bury the vibration sensor, which has the problems of greater excavation difficulty and higher monitoring cost. Therefore, this project adopts the method of judging the safety status of the buried gas pipeline by the surface vibration velocity in the present invention, which can calculate the vibration velocity of the buried gas pipeline by monitoring the surface vibration velocity during the construction of the bored piles, thereby judging its safety. The specific steps of the method are as follows:

[0107] S1: According to the site environment, the vibration velocity threshold of the buried gas pipeline is determined by numerical simulation and calculation according to the "Seismic Design Code for Oil (Gas) Steel Pipelines", which specifically includes the following steps:

[0108] Step S1.1: Test the properties of the on-site rock and soil and obtain the pipeline properties, burial depth, bored pile construction conditions, etc., and establish Figure 2The three-dimensional numerical model of the buried gas pipeline is shown; according to the existing technical research, when the pipeline vibration velocity reaches the maximum, that is, when the vibration velocity threshold is reached, the impact vibration source of the bored piles and the buried gas pipeline are in the same horizontal plane, and the vibration velocity of the buried gas pipeline calculated corresponding to the surface vibration velocity at this time is the maximum; therefore, when the numerical simulation model is established, it is set that the impact vibration source of the bored piles and the buried gas pipeline are in the same horizontal plane.

[0109] Step S1.2: According to the calculation amount and calculation accuracy, the three-dimensional geometric model of the buried pipeline is meshed and the mesh independence analysis is performed. After multiple mesh comparisons, a relatively stable mesh is obtained, which is used as the number of meshes and nodes for this calculation. The specific steps for meshing the three-dimensional geometric model of the buried pipeline and the mesh independence analysis according to the calculation amount and calculation accuracy are as follows:

[0110] The simulation was carried out for 0.05s to verify the independence of the four grid numbers A, B, C, and D. The soil stress, soil vibration velocity, soil displacement, pipeline stress, and pipeline vibration velocity were used as references. The results obtained after the simulation reached a stable state are shown in Table 1.

[0111] Table 1 Verification results of grid independence of buried pipeline system

[0112]

[0113] It can be seen from Table 1 that the number of grids has a great influence on the results of the simulation output. When the number of grids is below 65371, the output data is extremely unstable and the difference is large; when the number of grids is 65371 or above, the output data is relatively stable, the difference is not large, and it is accurate. Therefore, considering the calculation time and the error of the simulation, it can be approximately considered that the number of grids type C can meet the requirements of grid independence. The number of grids in the three-dimensional system of the buried gas pipeline is 65371, and the number of nodes is 85620. Figure 3 .

[0114] Step S1.3: Set the boundary conditions of the buried pipeline three-dimensional system and the parameters of the soil and pipeline according to the site conditions; use the buried pipeline three-dimensional system model to calculate the vibration threshold of the buried gas pipeline. The specific steps are as follows:

[0115] The material parameters of the numerical simulation calculation in the patent example of the present invention are selected from the parameters of the West-East Gas Transmission Line 2 pipeline and the soil properties of the site where the Wuhan-Dalian Expressway crosses the West-East Gas Transmission Line 2. The materials used for each component are shown in Table 2. The outer diameter of the pipeline is D = 1219 mm, the inner diameter is d = 18 mm; p is the gas transmission pressure in the pipe, p = 10 MPa;

[0116] Table 2 Physical properties of buried pipeline system

[0117]

[0118] In the numerical simulation calculation of the patent example of the present invention, the boundary conditions of the three-dimensional system of the buried gas pipeline are as follows: the four sides of the soil model are set as normal constraints, the bottom surface is set as a completely fixed constraint, and the upper surface is a free surface without constraints; the two ends of the pipeline model are set as axial constraints, the friction coefficient between the buried gas pipeline and the soil is set to 0.4; the internal friction angle of the soil is set to 30°; the soil cohesion is set to 18KPa;

[0119] In the numerical simulation calculation of the patent example of this invention, pipeline damage actually means that the stress on the pipeline is greater than the yield strength of the pipeline; therefore, when calculating the vibration velocity threshold, the theory is applied to the numerical simulation calculation, and the yield strength of the pipeline to be damaged by vibration is set. At this time, the corresponding vibration velocity is the vibration velocity threshold of the pipeline. Therefore, the yield strength of the buried gas pipeline is set to the minimum yield strength of the West-East Gas Pipeline Line 2, 555MPa. According to the numerical simulation calculation, when the yield strength reaches 555MPa, the pipeline vibration velocity is 2.14cm / s. The vibration velocity threshold of the buried gas pipeline is 2.14cm / s through numerical simulation calculation.

[0120] Step S1.4: According to the numerical simulation calculation, the vibration velocity of the buried gas pipeline at different times and the vibration velocity of the soil around the pipeline at the corresponding time are extracted. A series of data are linearly fitted using Origin software to obtain the relationship between the vibration velocity of the buried gas pipeline and the vibration velocity of the soil around the pipeline: V 管 =(1+K t )Vt, and the empirical coefficient of pipeline-soil vibration velocity difference K t =0.03;

[0121] Step S1.5: According to the on-site rock and soil properties and pipeline properties, the vibration velocity threshold of the buried gas pipeline is calculated to be 2.30 cm / s through the "Code for Seismic Design of Oil / Gas Steel Pipelines". The specific calculation steps are as follows:

[0122] (1) Pipeline parameters: outer diameter of buried gas pipeline D = 1219 mm, inner diameter of buried gas pipeline d = 1182.2 mm, wall thickness of buried gas pipeline δ n =18.4mm, Poisson's ratio μ is 0.3, the pressure in the pipeline is P = 10MPa, the temperature t1 of the pipeline during excavation, construction, installation and backfilling is 25℃, and the working temperature t2 of the pipeline during gas transmission is 50℃; At present, the West-East Gas Pipeline II mainly uses X80 steel. In the elastic zone of the buried gas pipeline steel: elastic modulus E1 = 2.07×10 5 MPa, stress σ1=555MPa; elastic-plastic zone: stress σ2=625MPa; plastic zone: stress σ b=565MPa, working temperature limit 50℃, pipe laying temperature is room temperature 25℃, linear expansion coefficient of steel α = 1.2×10 -5 (C -1 );

[0123] (2) Allowable axial strain of buried pipeline against vibration:

[0124] ① Allowable tensile strain

[0125] Because σ b =555MPa<625MPa

[0126] As the vibration-resistant allowable tensile stress-strain of the buried gas pipeline, it is taken as 40-50 stress cycles corresponding to the stress cycle number of the fatigue curve of the design:

[0127] [ε t ] v =1%;

[0128] ② Allowable compressive strain

[0129] Because the deformation of underground direct buried pipelines under earthquake action is homogeneous tensile deformation or compressive deformation on the entire cross section; therefore, in the plastic zone, if the deformation is lower than the allowable low-cycle fatigue limit, axial compressive instability is likely to occur. Therefore, it is necessary to calculate the allowable deformation of the buried gas pipeline under pressure:

[0130] [ε t ] v =0.35δ / D=0.35×18.4 / 1219=0.52%;

[0131] (3) Stress and strain under operating conditions

[0132] ① Hoop stress: δ h =Pd / 2δ n =10×1182.2 / 2×1.219=484.9MPa

[0133] ②Axial stress: σ L =μσ h +Eα(t1-t2)

[0134] =0.3×484.9+2.07×10 5 ×1.2×10 -5 ×(50-25)=207.57MPa

[0135] ③Axial strain:

[0136] (4) Axial strain combination: Without affecting the integrity and continuity of the soil, due to the influence of external factors, and the buried gas pipeline is still buried in the soil, all loads during operation will be borne by the buried pipeline; therefore, the maximum stress generated under working conditions should be combined with the stress generated under working conditions; if compression occurs, that is: ε max +ε L ≤0,|ε max +ε L |≤[ε c ] v

[0137] Because [ε c ] v =0.52%, ε L =10.65×10 -4

[0138] Then we can get: cmax ≥-4.14×10 -3

[0139] If stretching occurs, then: ε max +ε L >0,|ε max +ε L |≤[ε c ] v

[0140] Because [ε t ] v =1.0%,ε L =10.65×10 -4

[0141] Then we can get: tmax ≤8.94×10 -3 ;

[0142] (5) The particle vibration acceleration that the pipeline can withstand; because the bending deformation of the underground pipeline caused by the shear wave caused by the bored pile is much smaller than its axial deformation, this patent only analyzes the axial strain of the pipeline. According to the calculation formula for the maximum axial deformation of the buried pipeline under the action of seismic waves in the "Seismic Design Code for Buried Oil Pipelines" (SYT0450-2004), the calculation method is as follows:

[0143]

[0144] Where: a—peak acceleration of ground motion;

[0145] T g — Characteristic period of earthquake response spectrum;

[0146] C—site shear wave velocity;

[0147] If stretching occurs, then:

[0148] If compression occurs, then:

[0149] (6) According to the relationship between the peak surface vibration velocity V and the peak seismic acceleration a, we can obtain:

[0150] The excitation frequency of bored piles is generally between 10 and 50 Hz. By substituting the shear velocity and characteristic period corresponding to different soil types in Table 3 into the formula, the maximum vibration velocity of the particle corresponding to the extreme value of pipeline strain that may cause pipeline damage can be obtained. The results are shown in Table 4.

[0151] Table 3 Site soil types and characteristic period values

[0152]

[0153] Table 4 Maximum vibration velocity of the particle that may cause pipeline damage due to extreme pipeline strain

[0154]

[0155] According to the bored cast-in-place pile construction of Wuhan-Dalian Expressway in this paper, combined with the on-site topography and lithology conditions, the construction section of Wuhan-Dalian Expressway belongs to medium-hard soil, with an ultimate tensile particle peak velocity of 6.0 cm / s and an ultimate compression particle peak velocity of 2.3 cm / s.

[0156] Step S1.6: Compare the buried gas pipeline vibration velocity threshold value of 2.14 cm / s obtained by numerical simulation with the buried gas pipeline vibration velocity threshold value of 2.3 cm / s calculated in the "Code for Seismic Design of Oil (Gas) Steel Pipelines", and take the smaller value of 2.14 cm / s as the buried gas pipeline vibration velocity threshold value for the West-East Gas Pipeline II and the newly built Wuhan-Dawu Expressway.

[0157] S2. Measure the peak vibration velocity of the ground surface directly above the buried gas pipeline, and calculate the peak vibration velocity of the buried gas pipeline corresponding to the peak vibration velocity of the ground surface by using the law of vibration wave reflection in rock and soil media; according to previous studies, when the pipeline vibration velocity reaches the maximum, that is, when the vibration velocity threshold is reached, the impact vibration source of the bored pile and the buried gas pipeline are at the same horizontal plane, and the vibration velocity of the buried gas pipeline corresponding to the calculated surface vibration velocity at this time is the maximum; therefore, if Figure 4As shown in the figure, during the calculation, it is assumed that the impact vibration source of the bored pile and the buried gas pipeline are located at the same horizontal plane. Elastic waves propagating in the stratum medium can be divided into body waves and surface waves; body waves can be further divided into compression waves (P waves) and shear waves (S waves), and surface waves are divided into Rayleigh (R waves) and love (L waves), but surface waves propagate on the stratum surface; since the present invention mainly considers the waves that occur below the surface and have a greater impact on the buried gas pipeline, the influence of surface waves is not considered, and only body waves, namely P waves and S waves, are calculated; the source of the P waves and S waves in the present application is the vibration generated by the hammer during the construction of bored piles, and the same P waves and S waves will be generated in all directions during the vibration, so the wave velocities of all incident P waves in the present application are the same, and the wave velocities of the incident S waves are also the same; but because different ground excitation points have different incident angles and different exit angles, the wave velocities of the reflected P waves and reflected SV waves after reflection are different, and the incident angles and exit angles must be calculated according to different ground excitation points.

[0158] The specific calculation process of the peak vibration velocity of the buried gas pipeline corresponding to the peak vibration velocity of the surface vibration is calculated by the law of vibration wave reflection in rock and soil media as follows:

[0159] Step S2.1: Measure the rock and soil properties on site and obtain the density of the rock and soil ρ = 1800 kg / m 3 , Poisson's ratio u=0.25, elastic modulus E=20Gpa, and substitute into the following formula to calculate the P wave velocity C of the rock and soil medium caused by the hammer vibration during the construction of bored piles: p (m / s) and S wave velocity Cs (m / s) of rock and soil media:

[0160]

[0161]

[0162] Calculate C p =3652m / s, C s =2108m / s.

[0163] Step S2.2: Measure the horizontal distance H1=6.5m between the buried gas pipeline and the vibration source, and the buried depth D1=2m of the buried gas pipeline. Since this calculation assumes that the impact vibration source of the bored piles and the buried gas pipeline are located in the same horizontal plane, it can be known that the buried depth D1 of the buried gas pipeline is the vertical distance between the bored pile construction vibration source and the ground.

[0164] Step S2.3: Based on the buried depth D1=2m of the buried gas pipeline obtained in step S2.2 and the distance H1=6.5m between the buried gas pipeline and the vibration source of the bored pile, the P wave velocity C calculated in step S2.1 is p =3652m / s and S wave speed Cs =2108m / s, the incident angle θ of the incident P wave at the ground monitoring point (i.e. the point where the vibration sensor is buried) is calculated according to the following formulas: p , the emission angle θ of the reflected SV wave at the ground monitoring point (i.e. the point where the vibration sensor is buried) s :

[0165]

[0166]

[0167] The incident angle θ of the incident P wave at the ground monitoring point is calculated p =72.9°, the outgoing angle θ of the reflected SV wave at the ground monitoring point s =33.5°, and calculate the reflection coefficient R of the P wave at the ground monitoring point pp and the S-wave reflection coefficient R ps , and its calculation formula is as follows:

[0168]

[0169]

[0170] Calculate the reflection coefficient R of the P wave at the ground monitoring point pp = 0.10 and the reflection coefficient of S wave R ps =0.51.

[0171] Step S2.4: In the present application, the reflected P wave is the wave that arrives at the buried gas pipeline after the incident P wave is reflected by the vertical polarization of the ground vibration wave, and the ground excitation point is point P; the reflected SV wave is the wave that arrives at the buried gas pipeline after the incident P wave is reflected by the vertical polarization of the ground vibration wave, and the ground excitation point is point S;

[0172] (1) According to the pipeline burial depth D1=2m obtained in step S2.2 and the distance H1=6.5m between the buried gas pipeline and the vibration source of the bored pile, the distance H between the excitation point position P on the ground and the vibration source received by the buried gas pipeline is calculated according to the following formula: p The incident angle θ of the reflected P wave received by the buried gas pipeline at the excitation point P on the ground P ';

[0173] Since the P wave incident at point P has no vertical polarization, the incident angle is consistent with the exit angle. Therefore, it can be intuitively obtained that point P is the center point of H1, that is:

[0174]

[0175] The distance H between the excitation point P on the ground and the vibration source of the reflected P wave at the buried gas pipeline is calculated. p =3.25m and incident angle θ′ p =58.4°, the emission angle θ's = θ' p =58.4°;

[0176] (2) The distance H1 between the position S of the ground excitation point of the reflected SV wave received by the buried gas pipeline and the vibration source is calculated according to the following formula based on the pipeline burial depth D1, the distance H1 between the vibration source and the ground vibration sensor during the bored pile construction, and the P wave velocity and S wave velocity of the rock and soil medium. s , the P wave incident at point S takes vertical polarization into consideration, so the incident angle is inconsistent with the outgoing angle, and the reflection is the reflected SV wave, which is obtained by the following calculation formula:

[0177] D1(tanθ″ p +tanθ″ s )=H1

[0178] C p sinθ″-C s sinθ″ p =0

[0179] H s =D1·tanθ″

[0180] According to the above formula, the horizontal distance H from the ground excitation point S to the vibration source center of the reflected SV wave is calculated s =5.0m and the incident angle θ″ of the reflected SV wave at the ground excitation point S p =68.2° and the emission angle θ″ s =32.0°.

[0181] Step S2.5: Based on the parameters in step S2.2, the time t at which the incident P wave emitted by the bored pile vibration source reaches the ground monitoring point directly above the pipeline is calculated according to the following formula:

[0182]

[0183] The calculation shows that the time t = 0.0018s when the incident P wave emitted by the bored pile vibration source reaches the ground monitoring point directly above the pipeline;

[0184] Step S2.6: Based on the parameters in step S2.3, the time t1, t2, and t3 for the direct P wave emitted by the bored pile vibration source, the reflected P wave reflected by the ground excitation point P, and the reflected SV wave reflected by the ground excitation point S to reach the buried gas pipeline are calculated respectively according to the following formulas:

[0185]

[0186]

[0187]

[0188] The time t1=0.0017s when the direct P wave emitted by the bored pile vibration source reaches the buried gas pipeline, the time t2=0.0020s when the reflected P wave reflected by the ground excitation point P reaches the buried gas pipeline, and the time t3=0.0027s when the reflected SV wave reflected by the ground excitation point S reaches the buried gas pipeline.

[0189] Step S2.7: Based on the parameters calculated in steps S2.5 and S2.6, calculate the difference between the time t1 when the direct P wave arrives at the buried gas pipeline and the time t when the incident P wave arrives at the ground monitoring point directly above the pipeline Δt0=t1-t=-0.0001s according to the following formulas; the difference between the time t2 when the reflected P wave arrives at the buried gas pipeline and the time t when the incident P wave arrives at the ground monitoring point directly above the pipeline Δt1=t2-t=0.0002s; the difference between the time t3 when the reflected SV wave arrives at the buried gas pipeline and the time t when the incident P wave arrives at the ground monitoring point directly above the pipeline Δt2=t3-t=0.0009s.

[0190] Step S2.8: Figure 5 The vertical surface vibration velocity waveform diagram is measured on site. According to the vertical surface vibration velocity waveform V y (t), the reflection coefficient R of the P wave at the ground monitoring point calculated in step S2.3 pp = 0.10, S wave reflection coefficient R ps =0.51, and the incident angle θ of the incident P wave at the ground monitoring point is calculated p =72.9°, the outgoing angle θ of the reflected SV wave at the ground monitoring point s =33.5°Substitute it into the following formula to calculate the waveform of the incident P wave to be V p (t); the calculation formula is as follows:

[0191]

[0192] The calculated waveform of the incident P wave is V p (t)=1.64V y (t).

[0193] Step S2.9: According to steps S2.7 and S2.8, calculate the vibration velocity V0(t) of the soil beside the buried gas pipeline and its horizontal velocity component V0(t) of the direct P wave emitted by the bored pile vibration source and directly reaching the buried gas pipeline. 0x (t) and the vertical velocity component V0z (t); the calculation formula is as follows:

[0194]

[0195] V 0x (t) = V0(t)

[0196] V 0z (t) = 0

[0197] Calculate the vibration velocity of the soil beside the buried gas pipeline, as well as its horizontal and vertical velocity components V, emitted by the bored pile vibration source and reaching the buried gas pipeline directly. 0x (t)=1.72V y (t-Δt0), V 0z (t)=0.

[0198] Step S2.10: Substitute the incident angle θ′ of the reflected P wave calculated in step S2.4 at the excitation point P on the ground p =58.4°, emission angle θ' S =58.4°, and the P-wave velocity and S-wave velocity calculated in step S2.1 are substituted into the first formula in step 2.4 to calculate the reflection coefficient R' of the reflected P-wave at the ground excitation point P. pp = 0.13; the incident angle θ″ of the reflected SV wave at the ground excitation point S calculated in step S2.4 p =68.2° and the emission angle θ″ s =32.0°, and the P-wave velocity and S-wave velocity calculated in step S2.1 are substituted into the second formula in step 2.4 to calculate the reflection coefficient R" of the SV wave reflected by the ground excitation point S ps =0.87;

[0199] Step S2.11: Then use the reflection coefficient R' of the reflected P wave calculated in step S2.10 at the ground excitation point P pp =0.13 Substitute into the following formula to calculate the vibration velocity V1(t) of the soil body beside the buried gas pipeline and its horizontal velocity component V1(t) of the reflected P wave reflected at the ground excitation point P 1x (t) and the vertical velocity component V 1z (t):

[0200]

[0201] V1x(t)=V1(t)·sinθ′ p

[0202] V1z(t)=V1(t)·cosθ′ p

[0203] The vibration velocity component V of the reflected P wave reflected at the ground excitation point P at the underground buried gas pipeline along the horizontal direction is calculated. 1x (t)=0.16V y (t-Δt1);

[0204] The vibration velocity component V of the reflected P wave reflected at the ground excitation point P at the underground buried gas pipeline in the vertical direction 1z (t)=0.10V y (t-Δt1);

[0205] Then the reflection coefficient R" of the reflected SV wave calculated in step S2.10 at the ground excitation point S ps =0.13 Substitute into the following formula to calculate the vibration velocity V2(t) of the soil body beside the buried gas pipeline and its horizontal velocity component V of the reflected SV wave reflected at the ground excitation point S 2x (t) and the vertical velocity component V 2z (t):

[0206]

[0207] V2x(t)=V2(t)·cosθ″ s

[0208] V2z(t)=V2(t)·sinθ″ s

[0209] The vibration velocity component V of the reflected SV wave reflected at the ground excitation point S at the underground buried gas pipeline along the horizontal direction is calculated. 2x (t)=0.58V y (t-Δt2);

[0210] V is the vibration velocity component of the reflected SV wave reflected at the ground excitation point S in the underground gas pipeline along the vertical direction 2z (t)=0.36V y (t-Δt2);

[0211] Then, the vibration velocity components of the underground buried gas pipeline in the horizontal direction are calculated according to the following formula: The vibration velocity component of the underground gas pipeline in the vertical direction

[0212]

[0213]

[0214] Substituting the above calculation results into the formula Calculate the soil vibration velocity at the underground gas pipeline

[0215] Step S2.12: Since the greater the vibration velocity of the buried gas pipeline, the greater the impact on the pipeline, the less safe the pipeline is. Therefore, in order to determine the safety status of the buried gas pipeline, the time when the surface vibration velocity reaches the peak value is selected during the calculation, t = 0.108s; Substitute it into the formula to calculate Substitute it into step S1.4 to obtain the relationship between the vibration velocity of the buried gas pipeline and the soil around the pipe: The peak vibration velocity V of the buried gas pipeline is calculated. 管 =1.87cm / s;

[0216] S3. The pipeline safety status is obtained by comparing the buried gas pipeline vibration peak velocity with the buried gas pipeline vibration threshold; due to V 管 =1.87cm / s <V 阈值 =2.14cm / s, so the buried gas pipeline is in a safe state.

[0217] It should be noted that the above description is only an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the specification and content of the present invention, or directly or indirectly applied in other related technical fields, is also included in the patent protection scope of the present invention.

Claims

1. A method for determining the safety status of a buried gas pipeline by using the ground vibration velocity, characterized in that: The specific steps are as follows: S1. Measure the rock and soil properties on site, and calculate the velocity of the compression wave P wave and the shear wave S wave of the rock and soil on site through the density, Poisson's ratio, and elastic modulus parameters of the rock and soil, as follows: Where C p is the P wave velocity of the rock and soil medium, in m / s; Cs is the S wave velocity of the rock and soil medium, in m / s; ρ is the density of rock and soil medium, unit: kg / m 3 ; u is the Poisson's ratio of rock and soil medium; E is the elastic modulus of the rock sample medium, in MPa; S2. The incident angle of the incident P wave and the exit angle of the reflected SV wave, the reflection coefficient of the P wave and the reflection coefficient of the S wave at the ground monitoring point are calculated by the horizontal distance H1 between the buried gas pipeline and the vibration source of the bored pile construction and the buried depth D1 of the buried gas pipeline. The expressions are as follows: Where: θ P is the incident angle of the incident P wave at the ground monitoring point; θ S is the reflection angle of the reflected SV wave at the ground monitoring point; H1 is the horizontal distance between the vibration source of the bored pile construction and the buried gas pipeline; D1 is the vertical distance between the vibration source of bored pile construction and the ground and the buried depth of the pipeline; R pp is the reflection coefficient of the reflected P wave at the ground monitoring point; R ps is the reflection coefficient of the reflected SV wave at the ground monitoring point; S3. Determine that the incident P wave reaches the buried gas pipeline after being reflected by the ground vibration wave with vertical polarization, which is called the reflected P wave, and the ground excitation point is point P; determine that the incident P wave reaches the buried gas pipeline after being reflected by the ground vibration wave with vertical polarization, which is called the reflected SV wave, and the ground excitation point is point S; the P wave incident at point P has no vertical polarization, so the incident angle is consistent with the exit angle, and point P is directly obtained as the center point of the horizontal distance H1 between the buried gas pipeline and the ground monitoring point, that is, the horizontal distance H1 from point P to the vibration source of the bored pile construction is obtained. p : The P wave velocity C of the rock medium calculated in step S1 is calculated by the buried depth D1 of the buried gas pipeline, the horizontal distance H1 between the buried gas pipeline and the ground monitoring point, and the P wave velocity C of the rock medium calculated in step S1. p , S wave velocity C of rock and soil medium s Calculate the horizontal distance H between the ground excitation point S of the reflected SV wave and the center of the vibration source of the bored pile construction s and the incident angle θ' of the incident P wave at the ground excitation point P p 、Reflection angle θ of the reflected SV wave at the ground excitation point S” s ; The specific calculation formula is as follows: D1(tanθ” p +tanθ” s )=H1 C p sinθ” s -C s sinθ” p =0 H s =D1·tanθ” p In the formula, H p It is the horizontal distance from the ground excitation point P to the vibration source of the bored pile construction; H s It is the horizontal distance from the ground excitation point S to the center of the vibration source of bored pile construction; S4. Calculate the time difference between the direct P wave emitted by the bored pile construction vibration source and directly reaching the buried gas pipeline, the reflected P wave reflected by the ground excitation point P, and the reflected SV wave reflected by the ground excitation point S and the time difference between the incident P wave emitted by the bored pile construction vibration source and reaching the ground monitoring point directly above the pipeline. The calculation formula is as follows: Where Δt0 is the time difference between the direct P wave reaching the buried gas pipeline and the incident P wave reaching the ground monitoring point; Δt1 is the time difference between the reflected P wave reflected by the ground excitation point P and the arrival of the incident P wave at the ground monitoring point; Δt2 is the time difference between the reflected SV wave reflected by the ground excitation point S and the arrival of the buried gas pipeline and the incident P wave at the ground monitoring point; S5. The vertical vibration velocity V of the ground surface measured by the vertical vibration sensor installed at the ground monitoring point y (t) Calculate the waveform of the incident P wave, the expression is as follows: Where V y (t) is the vertical vibration velocity waveform of the ground monitoring point; V p (t) is the vibration velocity waveform of the incident P wave at the ground monitoring point; S6. The vibration velocity components of the soil vibration velocity at the underground gas pipeline in the horizontal and vertical directions are obtained by emitting the direct P wave directly reaching the buried gas pipeline through the punched cast-in-place pile construction vibration source, the reflected P wave reflected at the ground excitation point P, and the reflected SV wave reflected at the ground excitation point S. In the formula, It is the vibration velocity component of the underground gas pipeline in the horizontal direction; It is the vibration velocity component of the underground gas pipeline in the vertical direction; It is the soil vibration velocity at the underground gas pipeline; V 0x (t) is the vibration velocity component of the direct P wave in the underground gas pipeline along the horizontal direction; V 0z (t) is the vibration velocity component of the direct P wave in the underground gas pipeline along the vertical direction; V 1x (t) is the vibration velocity component of the reflected P wave reflected at the ground excitation point P in the underground gas pipeline along the horizontal direction; V 1z (t) is the vibration velocity component of the reflected P wave reflected at the ground excitation point P in the underground gas pipeline in the vertical direction; V 2x (t) is the vibration velocity component of the reflected SV wave reflected at the ground excitation point S in the underground gas pipeline along the horizontal direction; V 2z (t) is the vibration velocity component of the reflected SV wave reflected at the ground excitation point S in the underground buried gas pipeline along the vertical direction; S7. The soil vibration velocity at the underground gas pipeline calculated in step S6 Combined with the established three-dimensional model of the buried gas pipeline, the relationship between the vibration velocity of the buried gas pipeline and the soil is obtained, and the peak vibration velocity V of the buried gas pipeline is obtained. 管 , which is calculated as follows: K t is the empirical coefficient of pipeline-soil vibration velocity difference; S8. By setting the buried gas pipeline vibration peak velocity V 管 The buried gas pipeline vibration threshold V 阈值 Compare and judge the pipeline safety status: If V 管 >V 阈值 , the pipeline is in an unsafe state; If V 管 <V 阈值 , the pipeline is in a safe state; Wherein, the buried gas pipeline vibration threshold V 阈值 It is the vibration speed when the buried gas pipeline is damaged.

2. A method for determining the safety status of a buried gas pipeline by using the ground vibration velocity according to claim 1, characterized in that: When the peak vibration velocity of the buried gas pipeline corresponding to the peak vibration velocity of the buried gas pipeline surface reaches the maximum, the impact vibration source of the bored piles and the buried gas pipeline are in the same horizontal plane. Therefore, when calculating, it is set that the impact vibration source of the bored piles and the buried gas pipeline are in the same horizontal plane.

3. The method for determining the safety status of a buried gas pipeline by using the ground vibration velocity according to claim 2, characterized in that: The ground monitoring point in step S2 is a vibration sensor installed in the vertical direction of the ground just above the buried gas pipeline; the horizontal distance H1 between the vibration source of the bored pile construction and the buried gas pipeline is the horizontal distance between the vibration source of the bored pile construction and the ground monitoring point; the buried depth D1 of the buried gas pipeline is the vertical distance between the vibration source of the bored pile construction and the ground.

4. The method for determining the safety status of a buried gas pipeline by using the ground vibration velocity according to claim 2, characterized in that: In step S6, the vibration source of the bored pile construction emits a direct P wave that directly reaches the buried gas pipeline, a reflected P wave reflected at the ground excitation point P, and a reflected SV wave reflected at the ground excitation point S. The vibration velocity components V in the horizontal and vertical directions of the buried gas pipeline are: 0x (t), V 0z (t), V 1x (t), V 1z (t), V 2x (t), V 2z (t) is calculated according to the following process: V 0x (t)=V0(t) V 0z (t)=0 V1x(t)=V1(t)·sinθ′ p V1z(t)=V1(t)·cosθ′ p V2x(t)=V2(t)·cosθ″ s V2z(t)=V2(t)·sinθ″ s Where V0(t) is the vibration velocity waveform of the direct P wave at the underground buried gas pipeline; V P (t-Δt0) is the vibration velocity waveform of the P wave incident on the ground monitoring point, which is translated by Δt0 in the positive direction of the time axis; V1(t) is the vibration velocity waveform of the reflected P wave reflected at the ground excitation point P at the underground buried gas pipeline; V P (t-Δt1) is the vibration velocity waveform of the P wave incident on the ground monitoring point, which is translated by Δt1 in the positive direction of the time axis; R' pp is the reflection coefficient of the reflected P wave reflected from the ground excitation point P; V2(t) is the vibration velocity waveform of the reflected SV wave reflected at the ground excitation point S at the underground buried gas pipeline; V P (t-Δt2) is the vibration velocity waveform of the P wave incident on the underground gas pipeline, which is translated by Δt2 in the positive direction of the time axis; R” ps is the reflection coefficient of the reflected SV wave reflected from the ground excitation point S.

5. The method for determining the safety status of a buried gas pipeline by using the ground vibration velocity according to claim 2, characterized in that: The buried gas pipeline vibration threshold V in step S8 阈值 The vibration velocity of the buried gas pipeline when it is damaged is calculated by two methods: the "Code for Seismic Design of Oil / Gas Steel Pipelines" and the numerical simulation method to establish a three-dimensional model of the buried gas pipeline. The smaller vibration velocity of the two is selected as the vibration velocity threshold of the buried gas pipeline to judge the safety status of the pipeline; that is: If V m >V s , then V 阈值 =V s ; If V m <V s , then V 阈值 =V m ; Where V m is the vibration velocity corresponding to pipeline damage obtained through numerical simulation; V s It is the vibration velocity corresponding to pipeline damage calculated by the "Seismic Design Code for Oil / Gas Steel Pipelines"; V 阈值 It is the vibration velocity threshold of buried gas pipeline.

6. A method for determining the safety status of a buried gas pipeline by using the ground vibration velocity according to claim 5, characterized in that: The method of establishing the three-dimensional model of the buried gas pipeline in step S6 and step S8 is the same, and the specific steps are as follows: (1) Test the properties of the on-site rock and soil and obtain the pipeline properties, burial depth, and bored pile construction conditions, and establish a three-dimensional numerical model of the buried gas pipeline; (2) According to the calculation amount and calculation accuracy, the three-dimensional geometric model of the buried pipeline is meshed and the mesh independence is analyzed to obtain the stable state grid, that is, the number of grids and nodes used for calculation; during the test, soil stress, soil vibration velocity, soil displacement, pipeline stress, and pipeline vibration velocity are used as references.

7. A method for determining the safety status of a buried gas pipeline by using the ground vibration velocity according to claim 6, characterized in that: The vibration velocity of the buried gas pipeline at different times and the vibration velocity of the soil around the pipeline at the corresponding time are extracted according to numerical simulation calculation. A series of data are linearly fitted using Origin software to obtain the relationship between the vibration velocity of the buried gas pipeline and the vibration velocity of the soil around the pipeline: V 管 =(1+K t )Vt, and K t is the empirical coefficient of pipeline-soil vibration velocity difference.

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