The effect of stratum organization on the occurrence of liquefaction in subsurface silty sand

首先，在钻孔调查和室内试验的基础上，建立了浦安土的弹塑性模型。之后，对其进行地震反应分析，以了解2011年东日本大地震中浦安市发生广泛且不均匀液化破坏的原因。主要结论如下：1)粘土层的存在导致地震波在较长周期范围内的放大，即使在中间土体中也会产生较大的塑性应变，足以引起液化；2)不规则倾斜边界的存在产生面波，导致加速度局部放大，地表连续振荡，液化扩大；3)在均匀的地面条件下，面波与体波的复杂干涉导致地表变形不均匀。

Firstly, elasto-plastic modelling of Urayasu soils based on the boring survey and laboratory testing was conducted. After then, its seismic response analysis was conducted for the purpose of understanding why extensive and non-uniform liquefaction damage was occurred at Urayasu city during 2011 Great East Japan Earthquake. The main conclusions are as follows, 1) existence of the clay layer caused amplification of the seismic wave in the somewhat long-period ranges, leading to large plastic strains sufficient to cause liquefaction even in intermediate soils, 2) existence of the sloped irregularly-shaped boundary generates surface waves which causes localized amplification of the acceleration, continuous oscillation at the ground surface and expansion of the liquefaction, 3) complicated interposition of the surface waves and body waves result in non-uniform ground deformation even for homogeneous ground conditions.