Centrifugal model tests on countermeasure against liquefaction-induced uplift of underground structures using sheet piles

摘要

During past earthquakes, several types of buried structures including sewage treatment pipelines and petroleum tanks were damaged by buoyant force induced by liquefaction of subsoil. Among the preventive measures including densification, deep soil mixing, gravel dram and sheet pile driving, the sheet piling method is often used for underground structures especially in urban areas where workspace is limited. A series of dynamic centrifugal model tests was conducted in order to investigate the behavior of underground structures, sheet piles installed vertically at the sides of underground structures and its effects as a counter-measure against liquefaction-induced uplift of underground structures. The factors investigated in the tests included thickness and depth of sheet piles and amplitude of input acceleration. The test results showed that the sheet piles reduced uplift displacement of underground structures by suppression of lateral deformation of liquefied soil. The amount of uplift displacement was lower when the thickness of sheet piles was large. Cyclic component of earth pressure acting on sheet pile, which was back-calculated from bending strain of sheet pile observed in the tests, decreased as the thickness of sheet piles decreases and as thickness of liquefied layer increased.