CN106777454B - Design method for pipeline crossing slip fault - Google Patents
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Abstract
The invention discloses a design method for a pipeline to cross a slip fault, and belongs to the technical field of oil and gas pipeline crossing. The method comprises the following steps: calculating the maximum dislocation amount of the earth surface where the slip fault is located, and determining the type of backfill soil, the buried depth of a pipeline, the type of a contact surface between the pipeline and the soil and the included angle between the slip fault and the pipeline; acquiring pipeline parameters passing through a slip fault, and calculating fault displacement parallel to the axial direction of the pipeline and fault displacement in the normal direction of the pipeline; establishing a finite element model, simulating the maximum strain of the pipeline when the slip fault slides by using the finite element model, establishing an empirical formula of the maximum strain of the pipeline passing through the slip fault, and fitting the parameters to be determined to obtain the specific numerical relationship between the maximum strain and each parameter. The method simulates the actual change condition of the pipeline after the slip fault slips through the finite element model, and fits a pipeline design formula suitable for the slip fault, so that the pipeline corresponding to the fault under specific conditions is accurately designed.
Description
Technical Field
The invention relates to the technical field of oil and gas pipeline crossing, in particular to a design method for a pipeline crossing slip fault.
Background
Oil and natural gas have been increasingly demanded as strategic energy sources in the past decades. The buried pipeline as one of the lifeline projects is responsible for the main transportation task of oil and gas resources, and provides an important energy guarantee for the production construction, the economic development and the social stability of China. In the process of construction and operation of a long oil and gas transmission pipeline, the long oil and gas transmission pipeline is possibly damaged by various adverse geological conditions due to changes of natural environment, and serious threats are brought to the safe operation of the pipeline. Earthquake is a sudden natural disaster which has the greatest harm to society and human beings, and the earthquake disaster in China, which is taken as a national earthquake disaster with stronger earthquake activity in the world, is one of the most serious natural disasters in China. According to a large number of earthquake damage statistics, the damage of the pipeline mainly comes from two aspects: one aspect is pipe failure due to wave effects and the other aspect is pipe failure due to large deformations, whereas pipe failure through a fracture zone is a typical example of large deformation failure. When the long-distance buried pipeline crosses a fault, the buried pipeline deforms along with the deformation of a soil body due to large dislocation of the ground of the fault area, and the buried pipeline is subjected to the action of soil reaction force from the transverse direction and the axial direction of the pipeline. When the pipe is pulled, if the tensile strain exceeds a limit value, the pipe is damaged; buckling failure can occur when the pipe is compressed due to buckling of the shell. Theoretically, the method can reduce the threat of the earthquake to the pipeline by reducing the burial depth, improving the ductility of the pipe, changing the included angle between the fault plane and the pipe shaft, selecting the position of the pipeline crossing the fault, increasing the wall thickness of the pipeline, adjusting the positions of the anchoring point and the fixed pier and the like.
The underground pipeline is affected by adverse factors such as environmental load, corrosion, fatigue, material aging and the like, so that the shock resistance of the pipeline is seriously weakened. How to avoid the damage of the pipeline is a subject of research of engineering designers. For the buried pipeline crossing the fault, the following anti-seismic measures are mainly included:
1) when the pipeline is buried, the active fault zone is avoided as much as possible. If the existing active fault data or earthquake safety evaluation results are fully utilized, earthquake fortification is carried out, and meanwhile, the intersection angle of the pipeline and the fault is correctly selected, so that the pipeline is pulled when the fault moves, and the pipeline is prevented from being pressed. Because the prediction result of the fault trend has certain error compared with the actual situation, the earthquake-proof purpose can not be achieved by only selecting a proper intersection angle of the pipeline and the fault.
2) The pipeline should be buried as shallow as possible and preferably in loose or medium density non-sticky soil to reduce the binding force of the soil on the pipeline when fault motion occurs. Reducing the angle of friction at the interface between the pipe and the soil may increase the ability of the pipe to withstand fault displacements, for example by using an epoxy jacket around the pipe at the intersection with the fault. The loose sand is compacted under horizontal load, and during compaction, the friction angle increases, producing a maximum pipe force consistent with the case of higher density sand initially. It is advantageous to reduce the angle of friction between the pipe and the soil, but it is mainly embodied in the axial direction, while the lateral resistance of the soil to the pipe is not greatly changed.
3) The pipe with good shock resistance (high strength and good ductility) is used. The greater wall thickness is the most favorable factor affecting the tube reaction when the tube is under tension. In the case of compressed pipes, the smaller the diameter to wall thickness ratio, the more advantageous it is, so that in practice, thick-walled pipes with good ductility are preferably used. Thick-walled pipelines can greatly improve the seismic capacity of the pipeline, but the increase in thickness is limited, and the requirements may not be met for large dislocation.
4) The capability of the pipeline to adapt to faults is inversely proportional to the friction coefficient between the pipeline and the soil body and the volume weight of the backfill soil, and soil materials with low friction coefficient and low volume weight of the backfill soil are selected as the backfill soil as far as possible. Generally, the backfill soil of the pipeline passing through the active fault is preferably loose to medium-density and non-viscous soil.
5) The actual anchoring point, i.e. the anchor block, should be located as far away from the fault as possible, at least 1.5L from the fault on each sidee(Lt)—2.0Le(Lt). Wherein L iseIs the sliding length of the elastic part of the pipe, LtThe sliding length of the pipeline at one side of the fault. If the pipeline has enough sliding length, the allowable dislocation displacement is provided for the pipeline, and the pipeline can be prevented from being sheared due to the transverse dislocation of the fault. Increasing the non-anchored length may increase the tolerance of the pipeline to fault motion. However, it is usually only up to about the length from the faultAt 200 meters, the effect is achieved and the continued increase in length results in little additional capacity (both lateral and axial).
It follows that, under large fault dislocation, the above measures may not meet the requirements, i.e. there is no reliable and effective anti-seismic measure at present. With the development of society, the requirements for the functions of pipelines are higher and higher, and many important and dangerous long-distance pipelines (conveying media are toxic, harmful, inflammable and explosive) have higher requirements for the seismic performance of the pipelines, and the traditional seismic structure and seismic method are not necessarily effective due to the unpredictability of earthquake faults and the complexity of seismic reaction of the pipelines. When an earthquake occurs, soil load around the pipeline acts on the pipeline, and the pipeline still can generate complex displacement forms such as transverse displacement, longitudinal displacement, space displacement and the like, so that instability damage of the pipeline is caused.
In view of the vulnerability of buried pipelines under fault action and the great harm of damage to society, more reliable and effective measures are needed to improve and ensure the earthquake-proof safety of the cross-fault buried pipelines under fault dislocation. Since the 'norm' and 'guide rule' issued by China, the earthquake-proof design level of pipelines in China is improved, but a plurality of new research results are not included in the norm, for example, new research in the earthquake engineering world shows that when a fracture zone has sudden dislocation, if a surface soil layer has certain thickness, the fracture angle, the fracture direction and the displacement of a surface fracture surface are different from those of bedrock. This result shows that the site conditions not only affect the seismic response spectrum, but also affect the surface fracture and displacement amplitude, and similarly, for different active fault types (such as normal fault, slip fault, reverse fault, etc.), the method for seismic design of pipelines has great difference due to different surface fractures with soil layers of a certain thickness. For a long-distance pipeline to pass through a sliding fault area, a Newmark method and a kennedy method are more classical methods, and the Newmark method is still adopted in the specifications of the United states and China at present. However, the analysis result has a large error with the actual test condition, so that an effective pipeline seismic design method cannot be provided, the cost waste is easily caused, and a large amount of manpower and material resources are consumed.
Disclosure of Invention
In order to solve the problems of large anti-seismic design error, easy cost waste and the like of the existing long-distance pipeline crossing slip fault, the invention provides a design method of a pipeline crossing slip fault, which comprises the following steps:
calculating the maximum dislocation amount of the earth surface where the slip fault is located, and determining the type of backfill soil, the buried depth of a pipeline, the type of a contact surface between the pipeline and the soil and the included angle between the slip fault and the pipeline;
acquiring pipeline parameters passing through the walk-slip fault, and calculating fault displacement parallel to the axial direction of the pipeline and fault displacement in the normal direction of the pipeline;
establishing a finite element model of a pipeline passing through the slip fault layer, and carrying out parameterization processing on the finite element model by using the acquired pipeline parameters;
and simulating the maximum strain of the pipeline when the sliding fault slides by using the finite element model, establishing an empirical formula of the maximum strain of the pipeline passing through the sliding fault according to a simulation result, and fitting undetermined parameters in the empirical formula to obtain a specific numerical relationship between the maximum strain of the pipeline passing through the sliding fault and each parameter.
The steps of simulating the maximum strain of the pipeline when the slip fault slides by using the finite element model and establishing an empirical formula of the maximum strain of the pipeline passing through the slip fault according to a simulation result are as follows:
introducing parameters such as different pipe stress-strain relation curves, pipe diameters D, wall thicknesses t and the like into a finite element model to obtain the maximum strain of the pipeline crossing the walk-slip fault under different working conditions; according to different maximum strains, an empirical formula of the maximum strain epsilon of the pipeline passing through the slip fault is established, and the empirical formula is as follows:
1) when the included angle between the slip fault layer and the pipeline is less than 90 degrees:
2) when the included angle between the slip fault layer and the pipeline is larger than 90 degrees:
wherein: x is the number of1,x2,...x14D is the undetermined coefficient, D is the diameter of the pipeline in m, t is the wall thickness of the pipeline in m, f is the displacement of the slip fault in m, α is the included angle between the slip fault and the pipeline in radian, p is the internal pressure of the pipeline in MPa, t is the internal pressure of the pipeline in radianuIs an axial soil spring with the unit of KN/m; p is a radical ofuIs a lateral soil spring in the horizontal direction, and the unit is KN/m; c is the characteristic bonding strength of the backfill soil; h is the buried depth of the central line of the pipeline; gamma is the effective weight of the soil; f. ofrIs a coefficient associated with the pipeline soil interface; phi is the internal friction angle of the soil; c0～C4The coefficient is taken as a value related to the internal friction angle.
The maximum dislocation amount is calculated according to geological data and seismic data of the earth surface where the walk-slip fault is located, and the specific calculation formula is as follows: log (M) -4.8+0.69MwWherein: log (M) is the common logarithm to base 10, MwThe seismic moment magnitude is shown.
The backfill soil types include dense sand, loose sand, hard clay and loose clay; the types of the contact surface of the pipeline and the soil comprise a concrete layer, coal tar, a rough steel surface, a smooth steel surface and sintered epoxy powder.
The pipeline parameters comprise a pipe stress-strain relation curve, a pipe diameter D, a wall thickness t, a working pressure elastic modulus E and a maximum tensile strain epsilon allowed by the pipelinemax；
The stress-strain relationship curve of the pipe is measured through experiments and is fitted by using a Ramberg-Osgood equation:
wherein: ε is strain, σ is stress, E is working pressure elastic modulus, σsα and N are Ramberg-Osgood parameters, N is a hardening parameter of a nonlinear term, α is yield offset;
the maximum tensile strain εmaxComprises the following steps:
εmax＝δ(2.36-1.58λ-0.101ξη)(1+16.1λ-4.45)(-0.157+0.239ξ-0.241η-0.315)
wherein λ is the yield ratio, η is the ratio of the defect depth to the wall thickness, ξ is the ratio of the defect length to the wall thickness, and δ is the apparent fracture toughness.
The step of establishing a finite element model of the pipeline passing through the slip fault and carrying out parameterization processing on the finite element model by using the acquired pipeline parameters specifically comprises the following steps: establishing a finite element model by using finite element software, and in the process of establishing the finite element model, dispersing a pipeline far away from a slip fault layer by adopting a pipe unit and dispersing a pipeline near the slip fault layer by adopting a bent pipe unit according to the surface dislocation quantity of the slip fault layer; introducing the backfill soil type, the pipeline burial depth, the type of a pipeline-soil contact surface, the included angle between the slip fault and the pipeline, the fault displacement of the slip fault and the obtained pipeline parameters into a finite element model, and realizing the parameterization processing of the finite element model.
According to the design method for the pipeline to penetrate through the slip fault, the actual change condition of the pipeline after the slip fault slides is simulated by establishing the finite element model, and the pipeline design formula suitable for the slip fault is fitted, so that the pipeline corresponding to the fault under the specific condition is accurately designed; various links are tightly buckled, the logic is smooth, the conception is strict, the design has good guiding significance on the pipeline design in the sliding fault layer, and the actual technical requirement is completely met.
Drawings
FIG. 1 is a flow chart of a design method for a pipeline crossing a slip fault according to an embodiment of the invention.
Detailed Description
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
The embodiment of the invention is mainly applied to how to design a proper pipeline to be installed in the active fault when the active fault is a walk-slip fault, so that the pipeline in the walk-slip fault has good anti-seismic performance. The design method for the pipeline to pass through the sliding fault provided by the embodiment of the invention specifically comprises the following steps:
step S1: and calculating the maximum dislocation quantity M of the earth surface where the slip fault is located, and determining the type of the backfill soil, the buried depth of the pipeline, the type of the contact surface between the pipeline and the soil and the included angle between the slip fault and the pipeline.
The maximum dislocation amount M needs to be calculated according to geological data and seismic data of the surface where the walk-slip fault is located, and the calculation formula is as follows: log (M) -4.8+0.69Mw(log (M) is the common logarithm to the base 10, MwSeismic moment magnitude). Backfill soil types include dense sand, loose sand, hard clay, and loose clay. The types of the pipe-soil interface include concrete layers, coal tar, rough steel surfaces, smooth steel surfaces, and sintered epoxy powders. In practical application, the soil type of the backfill soil and the type of the contact surface between the pipeline and the soil need to be determined according to the actual soil condition on site, and the included angle between the pipeline buried depth and the slip fault and the pipeline needs to be determined according to the design requirement of site construction.
Step S2: and acquiring the pipeline parameters passing through the slip fault.
The pipeline parameters comprise a stress-strain relation curve of the pipe, the pipe diameter D, the wall thickness t, the working pressure elastic modulus E and the maximum tensile strain epsilon allowed by the pipelinemaxAnd the like. The stress-strain relationship curve of the pipe can be measured through experiments and is fitted by using a Ramberg-Osgood equation:
wherein: ε is strain, σ is stress, E is working pressure elastic modulus, σsα and N are Ramberg-Osgood parameters, N is the hardening parameter of the nonlinear term, α is the yield offset.
Maximum tensile strain epsilonmax＝δ(2.36-1.58λ-0.101ξη)(1+16.1λ-4.45)(-0.157+0.239ξ-0.241η-0.315) Wherein λ is the yield ratio, η is the ratio of the defect depth to the wall thickness, ξ is the ratio of the defect length to the wall thickness, and δ is the apparent fracture toughness in mm.
Step S3: and calculating the fault displacement delta X parallel to the axial direction of the pipeline and the fault displacement delta Y in the normal direction of the pipeline.
Δ X ═ Mcos θ, Δ Y ═ Msin θ; wherein: m is the maximum dislocation amount calculated in the step S1, and theta is the included angle between the slip layer and the pipeline.
Step S4: and establishing a finite element model of the pipeline crossing the slip fault, and carrying out parameterization processing on the finite element model by using the acquired pipeline parameters.
Finite element models are built using finite element software (e.g., ABAQUS). In the process of establishing a finite element model, according to the amount of surface dislocation of a slip fault, dispersing pipelines far away from the slip fault (1000 meters on the left and right) by adopting a pipeline unit PIPI31, wherein the length of the pipeline unit is 1 meter; the pipelines near the slip fault (100 meters on the left and the right) are dispersed by adopting an ELBOW unit ELBOW31, and the length of the pipeline unit is 0.1 meter. Introducing the backfill soil type, the pipeline burial depth, the type of a pipeline-soil contact surface, the included angle between the slip fault and the pipeline, the fault displacement of the slip fault and the obtained pipeline parameters into a finite element model, and realizing the parameterization processing of the finite element model.
Step S5: and simulating the maximum strain of the pipeline when the slip fault slides by using a finite element model, and establishing an empirical formula of the maximum strain of the pipeline passing through the slip fault according to a simulation result.
Introducing parameters such as different pipe stress-strain relation curves, pipe diameters D, wall thicknesses t and the like into a finite element model to obtain the maximum strain of the pipeline crossing the walk-slip fault under different working conditions; according to different maximum strains, an empirical formula of the maximum strain epsilon of the pipeline passing through the slip fault is established, and the empirical formula is as follows:
1) when the included angle between the slip fault layer and the pipeline is less than 90 degrees:
2) when the included angle between the slip fault layer and the pipeline is larger than 90 degrees:
wherein: x is the number of1,x2,...x14D is the undetermined coefficient, D is the diameter of the pipeline in m, t is the wall thickness of the pipeline in m, f is the displacement of the slip fault in m, α is the included angle between the slip fault and the pipeline in radian, p is the internal pressure of the pipeline in MPa, t is the internal pressure of the pipeline in radianuIs an axial soil spring with the unit of KN/m; p is a radical ofuIs a lateral soil spring in the horizontal direction, and the unit is KN/m; c is the characteristic bonding strength of the backfill soil; h is the buried depth of the central line of the pipeline; gamma is the effective weight of the soil; f. ofrIs a coefficient associated with the pipeline soil interface; phi is the internal friction angle of the soil; c0～C4The coefficient is a value related to the internal friction angle and related to the friction angle.
Step S6: use of non-linear fitting toolkit in MATLAB to determine parameters (x) to be determined in empirical formula1,x2,...x14) And fitting to obtain the specific numerical relationship between the maximum strain of the pipeline crossing the slip fault and each parameter.
In the specific design, objective conditions such as the maximum fault displacement of the walk-slip fault, the included angle between the pipeline and the walk-slip fault, the backfill property of the pipe ditch and the like are used as limiting conditions, and different pipeline parameters are substituted into a maximum strain empirical formula to obtain the maximum strain of the pipeline under the walk-slip fault. Comparing the maximum strain with the allowable strain, and if the maximum strain is greater than the allowable strain, indicating that the designed pipeline parameters do not meet the technical requirements and needing to redesign the pipeline parameters; if the maximum strain is less than or equal to the allowable strain, the designed pipeline parameters meet the technical requirements, and the most appropriate pipe is selected by combining economic factors to achieve the most perfect design scheme.
In order to facilitate understanding of the technical solution of the embodiment of the present invention and to embody the accuracy of the embodiment of the present invention in terms of pipeline design, the implementation process of the present invention is described below by taking a formula fitting process of an X90 steel pipeline crossing a slip fault as an example, and the parameters of the pipeline and the fault are selected as follows: surface dislocation amount M: 0-5 m; the included angle between the slip fault and the pipeline is as follows: 0-pi (two formulas are respectively fit by taking a right angle as a boundary in order to more accurately describe the change of the pipeline); burying depth of the pipeline: 0-2.5 m; type of backfill soil: loosening sand; type of pipe-soil interface: sintering the epoxy powder; pipe diameter D: 1219mm, 1422 mm; wall thickness: 19.1mm, 23.8mm, 26.4mm, 33.0 mm; working pressure: 4MPa, 8MPa and 12 MPa; soil type: the backfill soil is medium density sandy soil; soil volume weight γ: 18kN/m 3; friction angle phi: 35 degrees; lateral soil pressure coefficient K0: 0.5. the soil spring parameters obtained from the soil parameters are as follows 1:
TABLE 1
| Serial number | Direction of earth spring | Ultimate resistance (kN/m) | Yield displacement (m) |
| 1 | Axial direction | 47.180 | 0.003 |
| 2 | Lateral direction | 570.801 | 0.122 |
| 3 | Vertically upwards | 89.489 | 0.025 |
| 4 | Vertically downwards | 2424.275 | 0.122 |
Combining the parameters one by one to simulate all working conditions of the pipeline crossing the sliding fault; fitting all the obtained working condition data to obtain the following formula:
1) when the included angle between the slip fault layer and the pipeline is less than 90 degrees:
x1＝95.4972，x2＝-0.1977，x3＝-0.8451，x4＝0.0195，x5＝0.8515，x6＝0.0900，x7＝0.6008，x8＝1.7538×10-4，x9＝4.7833×10-5，x10＝2.5214×10-4，x11＝0.0503，x12＝-5.2163×10-8，x13＝1.0288×10-7，x14＝1.3131×10-7。
2) when the included angle between the slip fault layer and the pipeline is larger than 90 degrees:
x1＝1.5453×10-9，x2＝-0.4233，x3＝-0.7434，x4＝0.8645，x5＝0.4135，x6＝0.2708，x7＝1.3674，x8＝0.0372，x9＝1，x10＝-18.3886，x11＝356.8678，x12＝1，x13＝-1.6799，x14＝0.0796。
3) and substituting known data in the formula, changing the parameters of the pipe and the pipeline to obtain the maximum strain of the pipeline under the fault, comparing the maximum strain with the allowable strain, if the maximum strain is greater than the allowable strain, converting the parameters until the maximum strain is less than the allowable strain, and selecting the most appropriate pipe by considering economic factors to achieve the most perfect design scheme.
The design method for the pipeline to pass through the sliding fault provided by the embodiment of the invention has the following advantages:
1) aiming at the characteristics of the slip fault, a designer simulates the actual change condition of the pipeline after the slip fault slips by establishing a finite element model, and fits a pipeline design formula suitable for the slip fault through massive data collection, data analysis, regression statistics, research and calculation, so that the pipeline corresponding to the fault under specific conditions is accurately designed; various links are tightly buckled, the logic is smooth, the conception is strict, the design has good guiding significance on the pipeline design in the sliding fault layer, and the actual technical requirement is completely met.
2) The embodiment of the invention researches the pipeline crossing the slip fault, so that the fitted formula is particularly suitable for the pipeline design crossing the slip fault, and the practicability is higher than that of other ground displacement modes. The embodiment of the invention also considers the influence factors such as the type of the contact surface between the pipeline and the soil, the type and the property of the backfill soil, the backfill depth and the like, and well makes up the defects of the design of the pipeline crossing in the existing slip fault area.
3) The method has strong universality and applicability, and suitable pipelines can be designed according to the method provided by the embodiment of the invention aiming at different types of strike-slip faults no matter technicians involved in seismic pipeline design engineering research work or experienced technical experts. For a technician with little experience, the pipeline may need to be selected for multiple times and calculated one by one, so that a proper pipeline can be designed. And technicians with abundant experience can reduce the times of selecting the pipelines and design the proper pipelines according to the knowledge of the characteristics of the earthquake area and the characteristics of the pipelines.
4) According to the embodiment of the invention, finite element software is used for simulating the change condition of the pipeline, and then a large amount of simulation data are integrated, so that the accuracy is high, the error with the actual condition is small, the practicability is strong, a computer is taken as an auxiliary means to meet the technological development trend, and the effective pipeline seismic design greatly saves the cost.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are only exemplary embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A design method for a pipeline to pass through a slip fault is characterized by comprising the following steps:
calculating the maximum dislocation amount of the earth surface where the slip fault is located, and determining the type of backfill soil, the buried depth of a pipeline, the type of a contact surface between the pipeline and the soil and the included angle between the slip fault and the pipeline;
acquiring pipeline parameters passing through the walk-slip fault, and calculating fault displacement parallel to the axial direction of the pipeline and fault displacement in the normal direction of the pipeline;
establishing a finite element model of a pipeline passing through the slip fault layer, and carrying out parameterization processing on the finite element model by using the acquired pipeline parameters;
simulating the maximum strain of the pipeline when the sliding fault slides by using the finite element model, establishing an empirical formula of the maximum strain of the pipeline passing through the sliding fault according to a simulation result, and fitting undetermined parameters in the empirical formula to obtain a specific numerical relationship between the maximum strain of the pipeline passing through the sliding fault and each parameter;
the steps of simulating the maximum strain of the pipeline when the slip fault slides by using the finite element model and establishing an empirical formula of the maximum strain of the pipeline passing through the slip fault according to a simulation result are as follows:
introducing parameters of stress-strain relation curves, pipe diameters D and wall thicknesses t of different pipes into a finite element model to obtain the maximum strain of the pipeline crossing a sliding fault under different working conditions; according to different maximum strains, an empirical formula of the maximum strain epsilon of the pipeline passing through the slip fault is established, and the empirical formula is as follows:
1) when the included angle between the slip fault layer and the pipeline is less than 90 degrees:
2) when the included angle between the slip fault layer and the pipeline is larger than 90 degrees:
wherein: x is the number of1,x2,...x14D is the undetermined coefficient, D is the diameter of the pipeline in m, t is the wall thickness of the pipeline in m, f is the displacement of the slip fault in m, α is the included angle between the slip fault and the pipeline in radian, p is the internal pressure of the pipeline in MPa, t is the internal pressure of the pipeline in radianuIs an axial earth spring unitKN/m; p is a radical ofuIs a lateral soil spring in the horizontal direction, and the unit is KN/m; c is the characteristic bonding strength of the backfill soil; h is the buried depth of the central line of the pipeline; gamma is the effective weight of the soil; f. ofrIs a coefficient associated with the pipeline soil interface; phi is the internal friction angle of the soil; c0～C4The coefficient is taken as a value related to the internal friction angle.
2. The method for designing a pipe-through slip fault according to claim 1, wherein the maximum dislocation amount is calculated according to geological data and seismic data of the surface of the slip fault, and the specific calculation formula is as follows: log (M) -4.8+0.69MwWherein: log (M) is the common logarithm to base 10, MwThe seismic moment magnitude is shown.
3. The method of designing a pipe traversing slip-fault of claim 1, wherein the backfill soil types comprise dense sand, loose sand, hard clay, and loose clay; the types of the contact surface of the pipeline and the soil comprise a concrete layer, coal tar, a rough steel surface, a smooth steel surface and sintered epoxy powder.
4. The method of claim 1, wherein the pipeline parameters include stress-strain relationship curve of the pipe, pipe diameter D, wall thickness t, working pressure elastic modulus E, and maximum allowable tensile strain epsilon of the pipelinemax；
The stress-strain relationship curve of the pipe is measured through experiments and is fitted by using a Ramberg-Osgood equation:
wherein: ε is strain, σ is stress, E is working pressure elastic modulus, σsα and N are Ramberg-Osgood parameters, N is a hardening parameter of a nonlinear term, α is yield offset;
the maximum tensile strain εmaxComprises the following steps:
εmax＝δ(2.36-1.58λ-0.101ξη)(1+16.1λ-4.45)(-0.157+0.239ξ-0.241η-0.315)
wherein λ is the yield ratio, η is the ratio of the defect depth to the wall thickness, ξ is the ratio of the defect length to the wall thickness, and δ is the apparent fracture toughness.
5. The method according to claim 1, wherein the step of establishing a finite element model of the pipeline crossing the slip fault and performing parameterization on the finite element model by using the acquired pipeline parameters specifically comprises: establishing a finite element model by using finite element software, and in the process of establishing the finite element model, dispersing a pipeline far away from a slip fault layer by adopting a pipe unit and dispersing a pipeline near the slip fault layer by adopting a bent pipe unit according to the surface dislocation quantity of the slip fault layer; introducing the backfill soil type, the pipeline burial depth, the type of a pipeline-soil contact surface, the included angle between the slip fault and the pipeline, the fault displacement of the slip fault and the obtained pipeline parameters into a finite element model, and realizing the parameterization processing of the finite element model.
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