Seismic behavior of irregular underground structures in saturated sand

Abstract

Sand liquefaction is one of the leading causes of severe earthquake damage. In this study, shaking table tests were carried out to investigate the dynamic interaction between the saturated sand and the irregular subway stations. In this test, a method for the preparation of a liquefiable foundation based on a flexible sensing chain combined with water sedimentation was proposed. Typical test results were interpreted, including the development and spatial distribution of pore pressure, surface subsidence, acceleration, deformation, and dynamic earth pressure. Results show that the spatial distribution of excess pore water pressure is changed by the irregular underground structure, and the liquefiable soil below the bottom plate of the structure can be divided into I, II, and III areas based on the degree of liquefication. The surface subsidence is significantly related to Arias intensity and is concentrated within the range of 5 %–95 % of the intensity. The structural floating is synchronized with the liquefaction of the saturated sand, and the uneven floating and inclination of the underground structure are remarkable, anti-flotation design of underground structures should take into account differences in section forms. During the liquefaction of saturated sand, the foundation soil has conspicuous lateral deformation, especially in the deep soil layer. The shape of the dynamic earth pressure increments turns from triangular to linear, when the foundation soil changes from non-liquefied to liquefied. Compared with the limiting values of the elastic inter-story drift ratio, the maximum inter-story drift ratio of the structure is smaller. The tensile strain responses on the columns, particularly in the lower layer, are more prominent than those at the slabs and side walls.