自由场地液化响应特性的离心机振动台试验

利用ZJU-400土工离心机振动台,对相对密度为40%的福建中细砂自由场地模型,进行5次动态加载的液化试验.分析试验中土的动力特性和地震动特性,得到土体不同深度范围内加速度、超静孔隙水压力随时间的发展规律,以及土体加速度、沉降与超静孔隙水压力增长之间的关系,增强了对地震过程中土体加速度、沉降与孔隙水之间相互作用的理解.结果表明：场地放大作用受超静孔隙水压力增长和土体软化的共同作用,液化破坏了土颗粒的联结强度和结构稳定性,再次沉积形成的结构不稳定易再次液化|峰值过后切应力对超静孔隙水压力增长仍起到不可忽视的作用；土体超静孔隙水压力增长和土体沉降是外荷由土颗粒到孔隙水再到土颗粒传递的结果|液化后固结完成,场地土体自振频率增加；基于剪切波速确定CRR曲线的方法是合理的.

Centrifuge shaking table modeling of liquefaction characteristics of free field

A free-field model whose relative density is 40% with Fujian sand was constructed, and five dynamic loading liquefaction tests were performed in ZJU-400 geotechnical centrifuge shaking table. By analyzing dynamic soil features and seismic motion character in the tests, the development and variation rules of acceleration, excess pore-water pressure (EPWP) with time were obtained at different soil depth for a few of seismic vibrations, as well as the relationship between soil acceleration, settlement and EPWP increasing, which help improving our comprehension of interaction of soil acceleration, settlement and pore-water during earthquake. Results are as follows: the site amplification depends on a combination of soil softening and EPWP increasing; liquefaction destroys connection strength and structural stability of soil grain, and resedimentation soil fabric isn’t stable and is easy to liquefy again; effect of shear stress after peak on EPWP increasing can’t be neglected; EPWP increasing and soil settlement is result of external load shift from soil grain to pore-water, and then to soil grain; site soil natural frequency increases when consolidation is finished after liquefaction; it’s reasonable to determine cyclic resistance ratio (CRR) curve based on shear wave.