Shaking table test of earthquake input acceleration effect on uplift of buried pipes in liquefiable soils

During past earthquakes, several types of underground structures were damaged by uplift movement, because they were relatively light resulting from liquefaction of the adjacent subsoil.In this study, a series of shaking table tests in physical modeling laboratory of the university of Tabriz were conducted in order to investigate the effects of earthquake input acceleration on uplift movement of buried pipes in liquefiable soils. To acquire the displacement vector fields and strain contours in the soil around pipes, particle image velocimetry technique was applied. The models were prepared in a rigid plexiglass container with dimentions of 100cm long, 62cm wide, 64cm high. Ghom tapeh sand was used in the present study. The sand was prepared by the pluviation method in order to get a constant relative density of 30%. The soil was saturated by deaired water after vacuuming the soil in order to get full saturation. A small scale of model pipe from PVC with 6cm in diameter and 60cm in length was buried in the soil to a depth of 15cm from the ground surface. 1D shaking motion was applied parallel to horizontal axis at a frequency of 8 hz with accelerations of 0.35g, 0.5g, 0.65g to know the effect of severity of liquefaction on the speed and amount of floatation.The results show that the magnitude of pipe uplift is significantly influenced by the input acceleration. The amount and speed of uplift displacements increase with increasing the input acceleration. The liquefied subsoil displaces from the both side toward the bottom of the pipe which causes the uplift movement of the pipe and the soil above the pipe was raised by uplifting pipe. In this paper, the displacement patterns obtained from PIV and their comparison with each other are shown.

کلیدواژه ها:

Earthquake ، Liquefaction ، Uplift ، PIV ، Shaking table