A method for anti-sliding of aviation fuel pipelines through push-type landslides based on combined pile walls

Abstract

The present invention discloses a method for preventing aviation fuel pipelines from sliding across a push-type landslide based on a combined pile wall, including setting a combined pile wall behind the aviation fuel pipeline that crosses the push-type landslide; designing the size parameters of retaining walls and anti-sliding piles according to landslide parameters and aviation fuel pipeline parameters; using finite element software to calculate according to the pipe-soil-oil-anti-sliding measures multi-physics field fully coupled model, and extracting the pipeline equivalent stress cloud map and displacement cloud map; analyzing the pipeline stress distribution and deformation according to the pipeline equivalent stress cloud map and displacement cloud map; optimizing and upgrading the combined pile wall. The present invention performs segmented protection and treatment for aviation fuel pipeline landslides, and adopts retaining walls for anti-sliding protection in the layer through which the aviation fuel pipeline passes, which can effectively reduce the damage to the aviation fuel pipeline caused by the sliding of the landslide soil body and improve the stability of the aviation fuel pipeline; adopts anti-sliding piles for anti-sliding protection when the aviation fuel pipeline passes through the lower layer, which can reduce the moisture content of the soil body and save the cost of anti-sliding for landslides.

Description

Technical Field

[0001] The invention relates to an anti-sliding method for an aviation fuel pipeline that crosses a push-type landslide based on a combined pile wall, and belongs to the technical field of aviation fuel pipeline protection. Background Art

[0002] The long-distance aviation fuel pipeline (hereinafter referred to as the "aviation fuel pipeline") is the lifeline project of the aviation industry. It is undoubtedly unique and plays a prominent role in the modernization of national defense and aviation fuel logistics. Its safety management is very different from that of oil fields, refining enterprises, and ordinary logistics enterprises. First, the aviation fuel pipeline has a long transportation distance (from the refinery to the airport, dozens to hundreds of kilometers), a large geographical span (various landforms, geological units, and multiple administrative divisions), and a complex social environment and changeable natural environment along the pipeline; second, aviation fuel is a refined oil product, and has the characteristics of being flammable, explosive, volatile, and easy to accumulate static electricity, and aircraft have high requirements for its quality; third, aviation fuel pipeline transportation is usually a point-to-point series relay transportation method, that is, as long as there is a problem in any link or point in the aviation fuel pipeline system, the safe operation of the entire system will be affected.

[0003] Among the various factors that constitute the operational risks of aviation fuel pipelines, environmental and geological disaster factors occupy an absolute dominant position. Among environmental and geological disasters, soil landslides are the most widely distributed, most frequently occurring, and most complex landslide type in my country, which makes the catastrophic process of soil slopes more diverse during landslides. Therefore, when crossing soil landslide bodies and their catastrophic impact zones, the potential risk factors faced by pipeline integrity management will also become more complex. For the safety of oil and gas pipelines, the design must follow the requirements of the specifications to avoid areas with poor engineering geology. However, in the widely distributed mountainous and hilly areas, although pipelines can be bypassed, it costs a considerable amount of money economically. Sometimes, when it is impossible to avoid, it is still necessary to cross small landslide areas. Slopes are often affected by geological activities, climate change, human activities and other factors, and often become unstable and deformed, and develop into landslides. Some ancient landslides will also revive under characteristic conditions. All of these make landslide disasters occur from time to time in the slope areas where pipelines pass. At the same time, pipeline construction will inevitably affect the stability of the slope, which poses a greater threat to the transportation safety of the pipeline. If an accident occurs, it will not only cause huge economic losses to the pipeline operation companies and pose a great threat to the lives and property of the people along the line, but will also cause the airport to stop flying and bring great negative impacts on the ecological environment, social stability, public safety and other aspects along the pipeline, and even cause social disasters due to explosion accidents. Similarly, to a certain extent, it will also greatly affect the safe, healthy, rapid and sustainable development of the pipeline logistics industry.

[0004] At present, the treatment of push-type landslide disasters of aviation fuel pipelines generally adopts the same means as simple landslide treatment, often combining fire load reduction with retaining walls or anti-slide piles. Aviation fuel pipelines are often shallowly buried in the soil and are easily affected by landslide soil. Simple landslide treatment methods are not effective in protecting aviation fuel pipelines under push-type landslides, and they are prone to instability and damage under the action of sliding force. When the aviation fuel pipeline has been damaged and deformed in the landslide, a single landslide treatment method is difficult to meet the protection requirements for the aviation fuel pipeline.

[0005] Therefore, for the anti-sliding control measures of the aviation fuel pipeline crossing the push-type landslide, it is proposed to combine the retaining wall with the anti-sliding piles for protection. A numerical model is established based on the particle method to analyze the anti-sliding force. According to the analysis results, the combined pile wall is optimized to achieve the best protection effect. Summary of the invention

[0006] In order to overcome the defects in the prior art, the present invention aims to provide an anti-sliding method for an aviation fuel pipeline passing through a push-type landslide based on a combined pile wall.

[0007] The technical solution provided by the present invention to solve the above technical problems is: a method for preventing aviation fuel pipelines from sliding across a push-type landslide based on a combined pile wall, comprising:

[0008] S1. A combined pile wall is set behind the aviation fuel pipeline that crosses the push-type landslide, and the combined pile wall is composed of a retaining wall and anti-slide piles;

[0009] S2. Design the size parameters of retaining walls and anti-slide piles according to the landslide parameters and aviation fuel pipeline parameters;

[0010] S3. Establish a fully coupled multi-physics model of pipe-soil-oil-anti-slip measures based on the particle method;

[0011] S4. Calculate using finite element software based on the fully coupled model of multi-physics fields of pipe-soil-oil-anti-slip measures, and extract the equivalent stress cloud map and displacement cloud map of the pipeline;

[0012] S5. Analyze the stress distribution and deformation of the aviation fuel pipeline crossing the push-type landslide under the action of sliding force on the sliding soil according to the pipeline equivalent stress cloud map and displacement cloud map;

[0013] S6. Based on the pipeline stress distribution and deformation of S5, the combined pile wall is optimized and upgraded. The thickness of the retaining wall in the combined pile wall is increased at the location where the pipeline stress is concentrated to limit the deformation of the pipeline.

[0014] A further technical solution is that the combined pile wall is located 3-5 m behind the aviation fuel pipeline.

[0015] A further technical solution is that the retaining wall is arranged behind the layer through which the aviation fuel pipeline passes, and the anti-slide piles are arranged below the layer through which the aviation fuel pipeline passes.

[0016] A further technical solution is that the landslide parameters include density, internal friction angle, cohesion, water content, landslide length, landslide width, sliding body thickness, and landslide angle.

[0017] A further technical solution is that the aviation fuel pipeline parameters include density, elastic modulus, Poisson's ratio, initial yield stress, tangent modulus, internal pressure, pipe diameter, and wall thickness.

[0018] A further technical solution is that the soil material in the pipe-soil-oil-anti-slip measure multi-physics field fully coupled model adopts the MAT_FHWA_SOIL model;

[0019] The pipeline material adopts the MAT_PLASTIC_KINEMATIC model;

[0020] The oil body material adopts the MAT_NULL model;

[0021] The OHNSON_HOLMQUIST_CONCRET model is used as the composite pile wall material.

[0022] A further technical solution is that the process of establishing the pipe-soil-oil-anti-slip measure multi-physics field fully coupled model is as follows:

[0023] S71. Use the Mechanical APDL Product Launcher module in ANASYS software to establish the entity models of sliding soil, sliding bed, aviation fuel pipeline, aviation fuel body, and anti-skid measures;

[0024] S72. Use the Mesh Tool provided in the module to divide each part of the model and the reverse mesh;

[0025] S73. Save the established mesh model in a K file format.

[0026] A further technical solution is that in step S5, the saved K file is imported into the LS-PREPOST software to set parameters, the mesh model file with set parameters is submitted to the LS-DYNA solver in the ANSYS software for solution calculation, the calculation result file is extracted, and imported into the LS-PREPOST software to obtain the pipeline equivalent stress cloud map and displacement cloud map.

[0027] A further technical solution is that the parameter setting includes model boundary conditions, contact forms, selection of constitutive model parameters of each part, material parameter setting, and time step setting.

[0028] The present invention has the following beneficial effects:

[0029] 1. Carry out segmented protection and treatment for aviation fuel pipeline landslides. The aviation fuel pipeline crosses the layer with retaining walls for anti-slip protection, which can effectively reduce the damage to the aviation fuel pipeline caused by the sliding of the landslide soil and improve the stability of the aviation fuel pipeline. The aviation fuel pipeline crosses the lower layer with anti-slip piles for anti-slip protection, which can reduce the moisture content of the soil and save the cost of landslide anti-slip.

[0030] 2. The particle method is used to simulate and calculate the anti-sliding measures of the combined pile wall. It is not affected by the random distribution of particles, has strong adaptability, and can solve related problems such as large deformation;

[0031] 3. Multi-physics field coupling can overcome the various limitations of a single method and has greater advantages in accuracy and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flow chart of an embodiment of the present invention;

[0033] Figure 2 It is a three-dimensional diagram of a modular pile wall;

[0034] Figure 3 It is a cross-sectional view of the combined pile wall;

[0035] Figure 4 It is a schematic diagram of the arrangement position of the combined pile wall;

[0036] Figure 5 It is a schematic diagram of the mesh of the combined pile wall numerical model;

[0037] Figure 6 This is the displacement cloud diagram of the aviation fuel pipeline at different times;

[0038] Figure 7 It is the stress cloud diagram of the front / back sliding surface of the aviation fuel pipeline at different times;

[0039] Figure 8 This is the curve of axial stress variation of the pipeline sliding surface at 300ms;

[0040] Fig. 9 This is the axial stress variation curve of the back sliding surface of the pipeline at 300ms;

[0041] Fig.10 This is the pipe axial displacement change curve at 300ms. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The present invention discloses an anti-sliding method for an aviation fuel pipeline crossing a push-type landslide based on a combined pile wall. The method divides the push-type landslide into a layer through which the aviation fuel pipeline crosses and a lower layer through which the aviation fuel pipeline crosses, and arranges different anti-sliding measures for protection; a retaining wall is arranged behind the layer through which the aviation fuel pipeline crosses for protection, and anti-sliding piles are arranged at the lower layer through which the aviation fuel pipeline crosses for protection; a numerical model of the combined pile wall and a numerical model of the push-type landslide with a single anti-sliding measure are established based on a particle method for calculation and analysis, and the combined pile wall is optimized according to the specific analysis results.

[0044] like Figure 1 As shown, the specific steps include:

[0045] S1. Analyze the regional geological conditions, geotechnical properties, and aviation fuel pipeline laying conditions in the landslide study area, collect and determine relevant technical parameters, and set up a combined pile wall 3-5m behind the aviation fuel pipeline that crosses the push-type landslide;

[0046] The geological conditions of the landslide area include: topography, stratigraphic structure, rock and soil type, geological structure, neotectonic movement and earthquake, hydrogeology, human engineering activities, etc.;

[0047] Geotechnical properties include: soil corrosion, natural water content, natural density, specific gravity, natural void ratio, degree of saturation, plastic limit, liquid limit, plasticity index, liquid index, quick shear and residual shear, compression coefficient, compression modulus, natural and saturated compressive strength, etc.;

[0048] The laying conditions of aviation fuel pipelines include: burial depth, diameter-thickness ratio, crossing angle, internal pressure, pipe flow velocity, etc.;

[0049] S2, calculating and determining the size of the retaining wall in the combined pile wall according to the data collected in S1;

[0050] The design of retaining walls can refer to a series of design specifications such as "Design and Construction Specifications for Highway Retaining Walls";

[0051] S3, calculating and determining the size of the anti-slide piles in the combined pile wall according to the data collected in S1;

[0052] The design of anti-slide piles can refer to a series of design specifications such as the "Code for Design of Landslide Prevention and Control" (GB / T 38509-2020). At the same time, the anti-slide piles in this method also serve as the load-bearing pile foundation of the retaining wall, and must be designed and checked in accordance with the "Code for Design of Building Pile Foundations";

[0053] S4. Establish a fully coupled multi-physics model of pipe-soil-oil-anti-slip measures based on particle method;

[0054] In the fully coupled model of pipe-soil-oil-anti-slip measures multi-physics field, the soil model adopts the modified Mohr-Coulomb model, and its yield expression is:

[0055]

[0056] Where: p is pressure; K(θ) is the function of the tensor plane angle; φ is the internal friction angle; c is the cohesion; J2 is the second invariant of the stress deviator tensor; Ahyp is the modified yield surface coefficient.

[0057] The aviation fuel pipeline material adopts the PLASTIC_KINEMATIC model, which follows the Mises (VM) yield criterion. The model equation is:

[0058]

[0059] Where: σ0 is the initial yield stress, MPa; is the effective plastic strain; σ y is the yield stress, MPa; β is the hardening parameter; E P is the plastic hardening modulus.

[0060] The aviation fuel body material adopts the MAT_NULL model. While considering the dynamic viscosity of the fluid, it does not need to calculate the deviatoric stress. However, in order to describe the relationship between volume deformation and pressure, it is necessary to combine the state equation EOS_GRUNEISEN.

[0061] The equations for retaining walls, anti-slide piles, and combined pile walls adopt the JOHNSON_HOLMQUIST_CONCRE T model, and its equivalent stress is defined as:

[0062] σ=[A(1-D)+BP *N ](1+Cln(ε * )) (3)

[0063] Where: A is the cohesive strength; D is the damage parameter; B is the pressure hardening parameter; P * =P / f c ' is the standard pressure; C is the strain rate coefficient; ε * =ε / ε0 is the dimensionless strain rate.

[0064] S41. Unit selection: Before solid modeling, you need to select the appropriate unit type. The unit type selected for the model built in this case is solid164 unit.

[0065] S42, Modeling: The physical models of sliding soil, sliding bed, aviation fuel pipeline, aviation fuel body and anti-skid measures were established respectively through the Mechanical APDL Product Launcher module in ANASYS software, mainly using the bottom-up modeling steps;

[0066] S43, Mesh division: Use the Mesh Tool tool in the module to divide each part of the model and the reverse mesh. To ensure the final calculation accuracy of the model, divide the model into hexahedral meshes;

[0067] S44, save mesh file: save the established mesh model in the format of K file;

[0068] S5. Calculate using finite element software based on the fully coupled model of multi-physics fields of pipe-soil-oil-anti-slip measures, and extract the equivalent stress cloud map and displacement cloud map of the pipeline;

[0069] S51, parameter setting: import the saved K file into LS-PREPOST software to set parameters;

[0070] Specific parameters include model boundary conditions, contact form, selection of constitutive model parameters for each part, material parameter settings, and time step, etc.;

[0071] S52, submit calculation: submit the mesh model file with set parameters to the LS-DYNA solver in ANSYS software for solution calculation;

[0072] S53, post-processing: extract the calculation result file and import it into LS-PREPOST software to perform stress analysis on each structure;

[0073] S6. By analyzing the stress and deformation of the pipeline, the weak parts of the aviation fuel pipeline under the action of the push-type landslide are obtained. The combined pile wall structure is strengthened and optimized for the weak parts of the aviation fuel pipeline. By changing the thickness of the retaining wall at the corresponding part, its anti-sliding effect on the soil is increased.

[0074] Example

[0075] The parameters of a landslide and an aviation fuel pipeline are shown in Table 1:

[0076] Table 1 Case parameters

[0077]

[0078] (1) Investigate the actual data on site and determine the layout of the combined pile wall.

[0079] The data of this specific case are shown in Table 1. Other situations need to be investigated and obtained according to the actual situation on site. The landslide slope here is small, and the combined pile wall can be set 3m behind the pipeline.

[0080] (2) Based on the known relevant parameters, the design retaining wall dimensions are calculated according to the design specifications.

[0081] Based on the relevant design specifications of the retaining wall and the on-site topography and landform conditions, the relevant dimensional parameters of the retaining wall, such as height, length, wall top width and toe board width, are preliminarily determined.

[0082] (3) Based on the known relevant parameters, the design anti-slide pile dimensions are calculated in accordance with the design specifications.

[0083] Combined with the relevant design specifications of anti-slide piles and the on-site topography and geomorphology, the relevant dimensional parameters of the anti-slide piles such as height, length, and width are preliminarily determined. The anti-slide piles here also serve as combined pile wall foundations, which need to be verified and designed.

[0084] (4) Based on the on-site data of landslide control, a fully coupled model of the aviation fuel pipeline with a single anti-slip measure and a fully coupled model of the multi-physics field of pipe-soil-oil-anti-slip measures were established, and the calculation results were analyzed;

[0085] (5) Identify weak points in the pipeline based on simulation results and strengthen protection by adjusting and optimizing the structure of the retaining wall at the corresponding point in the combined pile wall;

[0086] It can be seen from the pipeline stress distribution and displacement cloud map that there is stress concentration in the middle of the pipeline and around the landslide boundary. The stress is close to the yield limit of the pipeline. It is the weak part of the pipeline and needs to be strengthened and optimized. The combined pile wall can be increased by increasing the thickness of the corresponding retaining wall to increase the anti-sliding effect.

[0087] (6) The optimized composite pile wall was modeled and verified. When the maximum stress value error of the aviation fuel pipeline before and after the verification was kept within 10%, the structure could be considered to meet the setting requirements.

[0088] The above description is not intended to impose any form of limitation on the present invention. Although the present invention has been disclosed through the above embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A method for anti-sliding of aviation fuel pipelines through push-type landslides based on combined pile walls, characterized in that: The following steps are involved: S1. A combined pile wall is set behind the aviation fuel pipeline that crosses the push-type landslide, and the combined pile wall is composed of a retaining wall and anti-slide piles; S2. Design the size parameters of retaining walls and anti-slide piles according to the landslide parameters and aviation fuel pipeline parameters; S3. Establish a fully coupled multi-physics model of pipe-soil-oil-anti-slip measures based on the particle method; In the fully coupled model of pipe-soil-oil-anti-slip measures multi-physics field, the soil model adopts the modified Mohr-Coulomb model, and its yield expression is: (1) Where: For pressure; is a function of the tensor plane angle; is the internal friction angle; for cohesion; is the second invariant of the stress deviator; is the modified yield surface coefficient; The aviation fuel pipeline material adopts the PLASTIC_KINEMATIC model, which follows the Mises (VM) yield criterion. The model equation is: (2) Where: is the initial yield stress, MPa; is the effective plastic strain; is the yield stress, MPa; is the hardening parameter; is the plastic hardening modulus; The aviation fuel body material adopts the MAT_NULL model. While considering the dynamic viscosity of the fluid, it does not need to calculate the deviatoric stress. However, in order to describe the relationship between volume deformation and pressure, it is necessary to combine the state equation EOS_GRUNEISEN. The equations for retaining walls, anti-slide piles, and combined pile walls use the JOHNSON_HOLMQUIST_CONCRET model, and its equivalent stress is defined as: (3) Where: is the cohesive strength; is the damage parameter; is the pressure hardening parameter; To regulate pressure; is the strain rate coefficient; is the dimensionless strain rate; S31. Unit selection: Before solid modeling, you need to select the unit type first. The unit type selected for the model is solid164 unit; S32, Modeling: Use the Mechanical APDL Product Launcher module in ANASYS software to build the solid models of sliding soil, sliding bed, aviation fuel pipeline, aviation fuel body, and anti-skid measures, mainly using bottom-up modeling steps; S33, Mesh division: Use the Mesh Tool tool in the module to divide each part of the model and the reverse mesh. To ensure the final calculation accuracy of the model, divide the model into hexahedral meshes; S34, save the grid file: save the established grid model in the format of K file; S4. Calculate using finite element software based on the fully coupled model of multi-physics fields of pipe-soil-oil-anti-slip measures, and extract the equivalent stress cloud map and displacement cloud map of the pipeline; S41, parameter setting: import the saved K file into LS-PREPOST software to set parameters; Specific parameters include model boundary conditions, contact form, selection of constitutive model parameters for each part, material parameter settings, and time step; S42, submit calculation: submit the mesh model file with set parameters to the LS-DYNA solver in ANSYS software for solution calculation; S43, post-processing: extract the calculation result file and import it into LS-PREPOST software to perform stress analysis of each structure; S5. Analyze the stress distribution and deformation of the aviation fuel pipeline crossing the push-type landslide under the action of sliding force on the sliding soil according to the pipeline equivalent stress cloud map and displacement cloud map; S6. Based on the pipeline stress distribution and deformation of S5, the combined pile wall is optimized and upgraded. The thickness of the retaining wall in the combined pile wall is increased at the location where the pipeline stress is concentrated to limit the deformation of the pipeline.

2. The anti-sliding method for aviation fuel pipelines crossing push-type landslides based on combined pile walls according to claim 1 is characterized in that: The combined pile wall is located 3-5m behind the aviation fuel pipeline.

3. The anti-sliding method for aviation fuel pipelines crossing push-type landslides based on combined pile walls according to claim 1 is characterized in that: The retaining wall is arranged behind the layer through which the aviation fuel pipeline passes, and the anti-slide piles are arranged below the layer through which the aviation fuel pipeline passes.

4. The anti-sliding method for aviation fuel pipelines crossing push-type landslides based on combined pile walls according to claim 1 is characterized in that: The landslide parameters include density, internal friction angle, cohesion, water content, landslide length, landslide width, sliding body thickness, and landslide angle.

5. The anti-sliding method for aviation fuel pipelines crossing push-type landslides based on combined pile walls according to claim 1 is characterized in that: The aviation fuel pipeline parameters include density, elastic modulus, Poisson's ratio, initial yield stress, tangent modulus, internal pressure, pipe diameter, and wall thickness.

Images