CFG桩加固饱和粉土地基的动力特性试验研究

以京沪高速铁路液化土地基加固为背景，利用大型堆叠式剪切变形模型箱，进行了模型比例1:10的CFG桩桩网结构地基加固饱和粉土地基的振动台模型试验，得出各级加载情况下地基路基响应加速度幅值放大系数的分布以及响应加速度幅值放大系数与各级加载加速度幅值的关系，分析了CFG桩桩网结构地基加固饱和粉土地基在地震作用下的加速度传递规律，得到了以下结论：（1）在加载加速度小于0.101g时，地基路基响应加速度幅值基本不放大，且加速度放大系数云图呈现水平状分布；（2）当加载加速度为0.161g时，桩间土的液化引起地基路基的响应加速度幅值放大系数的较大增加；（3）当加载加速度为0.210g时，桩间土液化的同时部分CFG桩发生剪断破坏，从而引起了地基路基的各响应加速度幅值放大系数的增大；（4）当加载加速度为0.324g和0.363g时，地基整体刚度的大幅度减小，在一定程度上降低了桩网结构地基传递振动的能力，从而导致加速度幅值放大系数相对前一级加载时减小；（5）整个加载过程中，粉土层的放大效应显著，而黏土层对加载加速度几乎没有放大作用。

Study of dynamic characteristics of saturated silty soil ground treated by CFG columns

A 1:10 scale shaking table model test was conducted by a large-scale laminar shear box; the test mainly researched on cement fly-ash gravel (CFG) column-net composite foundation, with the saturated silty soil ground of the Beijing-Shanghai High Speed Railway which was treated by CFG column-net. It has been plot that the amplification coefficient distribution of response acceleration under a series of input acceleration seismic loads, and the relation between the series of input accelerations and its corresponding amplification coefficient of response acceleration. The results show that: (1) at less than 0.101g loading acceleration, the response acceleration scarcely enlarge and its nephogram presents a horizontal type distribution; (2) at 0.161g loading acceleration, as a result of liquefaction of soil between piles, the respone acceleration greatly increase; (3) at 0.210g loading acceleration, the response acceleration increase result from liquefaction of soil between piles and shear break of CFG column; (4) at 0.324g, 0.363g loading acceleration, the integral rigidity of foundation decreases greatly, which reduces its capability of the shock transferred and result in the response acceleraton is less than that at the former loading acceleration; (5) during the course of loading acceleration, amplification effect of response acceleration is obvious in silty soil, but not in clay layer.