A study on stress of buried oil and gas pipeline crossing a fault based on thin shell FEM model

With the large deformation of the thin shell and the coupling interaction between pipe and soil considered, a FEM model based on shell elements is established for different conditions. These conditions include whether the site located on each side of the seismic fault is consistent or different and whether the fault zone exists at the intermediate areas of the fault. The strain response of large diameter oil and gas pipeline of grade X80 steel passing through seismic fault is studied using the shell elements of large deformation in finite element method (FEM). Considering the nonlinearity of pipeline and soil interaction, the influences on the strain response from the parameters including the pipe wall thickness, buried depth, width of the fault zone, fault displacement, intersection angle of pipe and fault under the corresponding site conditions, as well as the tendency curves, are systematically analyzed. The seismic strain responses of pipeline are compared under different conditions and the sensitivity of each influencing factor are discussed. When the width of fault zone is wider, the axial deformation of the pipeline is smaller. It means pipeline crossing a wider fault zone can resist against the earthquake better. Simultaneously, the pipeline in a large diameter is more likely to become deformed with different soil properties on either side of the fault than that with same soil properties on either side of the fault. The maximum strain response occurs on the side with harder soil, where the damage is more serious.