Study On Seismic Responses Of Buried Segmented Pipelines Crossing Fault

Buried pipelines are typical underground lifeline engineering. The study of buried pipelines crossing fault is always hot topic in the field of lifeline engineering. Buried pipelines consist of continuous pipelines and segmented pipelines. In the research at home and abroad, research solutions on buried continuous pipelines consist of experiment, analytical analysis and finite element analysis. However, the research achievements of segmented pipelines crossing fault is less. And more attention should be paid to this field.Firstly, the finite element model which is applied to resist seismic for buried continuous pipelines crossing fault is established. The model is composed of beam or shell element which can analyze the large deformation, soil-spring elements in three directions which can analyze the pipe-soil interaction and an equivalent spring at two ends of the pipeline. Based on buried continuous pipelines’ model and considering the non-linearity of joint, joint spring elements are established, composed by axial spring, bend spring and shear spring in three directions. At the location of joints, joint spring elements are applied to link up the beam or shell elements to obtain the failure mechanism of segmented pipelines objected to fault.The model is applied to three typical examples, such as an example of an oil-gas pipeline crossing a fault, a simulation experiment of buried concrete segmented pipelines crossing the fault and an example of PVC deformation under subsidence. The results are listed as follows.1. Compared to tensile state, buried steel pipelines may produce stress concentration and buckling failure under the compression state.2. Damage of concrete segmented pipelines mainly occurs near the fault surface, the damage of the joint is often the coupling failure mode which is due to the action of axial and rotational direction.3. In the transition zone of subsidence and no-subsidence, the pipe body of PVC appears stress concentration. Compared to the pipe body, the joint is more easily to be destroyed.Lastly, in order to obtain the failure mechanism of segmented pipelines crossing fault, a finite element model of a diameter of200mm PVC is established. Both the angel between fault and pipeline and the location of the fault through pipeline are changed. The results show that both the angel between fault and pipeline and the location of the fault through pipeline are the crucial factors which can decide the failure mechanism. For segmented pipelines, failure mechanisms mainly include joint pull-out, joint contraction, joint rotation and pipe failure. In addition, the better angel between fault and pipeline is from sixty degrees to ninety degrees. In this situation, the pipeline is in the tensile state and can resist large fault displacement.