Stress Analysis Of Gas Pipelines In Landslide Sections Based On Finite Element Analysis

Landslide is one of the major geologic hazards that pose a threat to the integrity of pipelines. The pipeline failures caused by landslide tend to bring about a tremendous economic loss as well as negative social impact. In particular, the geological conditions are extremely complicated in the western region of China. Therefore, the mechanical properties analysis for buried pipelines subjected to landslides is of great significance.Based on finite element theory, the general finite element program ANSYS is used to analyze the mechanical properties of pipelines subjected to landslides. In order to simulate the interaction between pipeline and soil,3D surface-to-surface contact element is utilized in the FEA model. In terms of pipe-soil interaction, this paper illustrates the surface-to-surface contact model's advantages over the nonlinear soil spring model. It also offers the details about the building of model and contact pairs, the selection of element type and materials, and the applying of boundary conditions and loads.For the pipeline parallel to the landslide, these influential factors on response are studied: landslide displacement, pipe diameter, pipe wall thickness and soil properties of landslide. For the pipeline perpendicular to the landslide, these influential factors on response are studied: landslide displacement, internal pressure, pipeline material and buried depth. At the same time, FEA is also conducted for the condition that no landslide occurs, and the results can be compared with those with landslide.Through the study, we can obtain these main conclusions:(1) Under the effect of longitudinal landslide, the maximum equivalent stress strain and displacement of the pipeline appear in the elbow, which indicates that the bend pipe is stress-risk cross section, but the yield stress has not been reached, the plastic displacement has not happened; The greater the stress, the greater the possibility of failure; vertical landslide lots should be laid a small diameter pipe, and increase the wall thickness can significantly reduce the peak stress and strain, so the diameter to thickness ratio D/t bias Hour, the better the safety and stability of the pipeline; the friction coefficient between the soil and the pipeline of the landslide plays a decisive role in the pipeline stress, and the density of the soil affects the sinking amount of the pipeline due to the casing pressure.(2) the lateral landslide is much more dangerous than the vertical landslide, which may result in the local buckling and even the tensile fracture of the pipeline. The load of the pipeline is not necessarily increased continuously during the lateral landslide. The effect of the internal pressure on the stress of the pipe is similar to that of the parabola, and reaches the peak value at 8MPa. The internal pressure may affect the landslide body to be affected by the internal pressure, so the load will not be affected. The maximum stress and strain at the top of the pipe and the bottom of the pipe occurred at the junction of the landslide and the non-landslide area. The buckling deformation of the pipe in the landslide area is very great. Using shallow-buried landslide-prone areas and ancient landslides.