原生各向异性地基条件下条形基础动力试验研究

Dynamic test study of strip foundation on fabric anisotropic ground

地震液化现象一直是土动力学的一个热门研究课题,前期研究表明由砂土颗粒之间接触的法向分布和颗粒形状所引起的原生各向异性对砂土动力学特性有影响。而现有的液化判别方法没有考虑砂土的原生各向异性,使得地震对上部结构的影响很难准确的评价。本研究通过制作专门设计的离心机模型箱控制砂土的不同沉积方向,模拟地基的原生各向异性,并且通过6个离心机振动模型试验再现了砂土原生各向异性对条形基础和地层的动力学特性的影响,包括对条形基础的加速度、水平位移、地层加速度、沉降和超孔隙水压力的影响。与前期的无条形基础的研究结果相似,尤其在饱和情况下,砂土的原生各向异性对条形基础的动力学特性影响非常大,加速度和超孔隙水压力表明,沉积方向为90°的地基使得条形基础的破坏较为严重,引发严重的地表沉降和基础的水平残余位移。为了更加准确预测结构物在地震区的动力特性,工程勘察和设计人员应考虑地基原生各向异性对结构物的影响。

Seismic Liquefaction is a hot topic in soil dynamics. Some past researches show that fabric anisotropy of sandy soil due to normal distribution of contact and particle shape may affect its dynamic characteristic. To explore the effects of fabric anisotropy on dynamic response of the superstructure and its ground, six centrifuge tests were performed on scaled model with different directions of sandy soil deposition to simulate its anisotropy and could reproduce the influences of fabric anisotropy on dynamic characteristics of strip foundation and ground, including accelerations and horizontal displacements of the strip founda- tion, accelerations, subsidence and excess pore water pressure of the ground. It was concluded that fabric anisotropy greatly in- fluenced the dynamic characteristics of strip foundation and ground especially in the saturation case. The liquefaction resistance of model in 90~deposition direction is lower than those of other models from observation of acceleration and pore pressure evolu- tion, which were indicated by serious subsidence and residual horizontal displacement of the ground. It is recommended that in order to precisely predict the dynamic performance of structure in earthquake area, the effect of fabric anisotropy on dynamic response of ground should be incorporated in the site investigation.