Earthquake Liquefaction Caused By The Large Ground Displacement And Its Impact On Underground Pipelines

Liquefaction of sandy soil deposits is one of the most severe disasters during earthquake, and liquefaction-induced large ground displacement has more destroy. Among many seismic disaster, Liquefaction-induced permanent ground displacement have damaged some lifeline engineering, especially buried pipeline. Since the earthquake in Niigata of Japan, A new seismic disasters captured more and more attention of geotechnical engineering community. However, due to the complex mechanism and to the limited research, Study on this subject is quite limited.On the base of the mechanism of liquefaction-induced large ground displacement, the paper divides large ground displacement into two parts: One is the ground displacement occurring during earthquake time, which lasts from soil deposits liquefaction to the end of earthquake. Another is the ground displacement taking place after earthquake, which lasts from the end of earthquake to the period of excess pore pressures in sandy soil diffused out. As to the first ground displacement, the mechanism of sandy soil liquefaction-induced large ground displacement is highlighted and analyzed. The program of soil dynamic FEM is utilized to calculate the ground earthquake acceleration respond and excess pore pressure in liquefied soil, according to which the residual shear resistance of soil is revised, the yield acceleration of Newmark's rigid slide block is identified. Appling the model of Newmark's rigid slide block, the lateral displacement is calculated. As to the second ground displacement, the theory of soil consolidation is utilized to analyze the diffusing course of excess pore pressures, the shear resistance is revised and the yield acceleration is identified. The value of ground displacement could be predicted through the model of Newmark's rigid slide block similarly. At last, two parts of ground displacement is added up as the liquefaction-induced large ground displacement. Additionally the possible factors, which may influent the large ground displacement, are well studied. All of that provides theory foundation for studying buried pipeline's seismic damage due to large ground displacement.The impartment of liquefaction-induced large ground displacement to buried pipeline is a foreland subject of earthquake engineering. Firstly, the bending stiffness of pipeline is so small that the damage of pipeline often is nolinear generational large deformation, such as pipeline buckling. The next, the soil-pipe interaction is nolinear, which shows in the friction effect between soil and buried pipeline, and in the contact situation between them. The following, soil is nolinear material, whose stress-strain constitution modeling is affected by all kinds of factors. The paper utilizes ANSYS to erase the FEM model to simulate the impartment of large ground displacement to buried pipeline. And lateral displacement is subjected to soil around buried pipeline step by step, to simulate stress and strain situation of buried pipeline during large ground displacement. In order to test the validity of numerical analysis, the numerical results are compared with catastrophic damages of buried pipeline in earthquake. Lastly, the possible factors, which may influent the anti-seismic ability of buried pipeline paving in liquefied ground, are studied.On the base of numerical results and summarizing some relative measurement, the paper gives some measures for paving buried pipeline in liquefied ground.