碎石桩复合地基桩体减震作用研究

地震引起的土体液化和地基失效对岩土工程师而言仍是一个热点问题。地震液化及地基变形可以采用多种地基加固方法防治，碎石桩技术是常用方法之一。碎石桩复合地基抗液化效用主要是增加桩周土体的密度、桩体的排水以及桩体分担地震水平剪应力作用(桩体减震作用)。目前，以抗液化为主的碎石桩复合地基的设计以及效果评价方法仍只考虑加密作用。首先通过3个模型(1个饱和砂土地基模型、2个碎石桩复合地基模型)的振动台试验研究抗液化碎石桩的减震作用。然后以试验记录的模型动力反应以及建立的理论模型为基础，分析碎石桩复合地基的桩体减震作用。试验及理论分析结果表明，复合地基中的碎石桩可以明显地降低作用在桩间可液化土上的地震剪应力。

Study on effect of reducing the total cyclic shear stress in thesoil for stone columns

The soil liquefaction induced from earthquake and associated ground failure have been a major concern for geotechnical engineers in seismically-active regions. The harm of liquefaction and associated ground deformation can be controled using various ground-reinforcement methods; the macadam pile is the one that is commonly used. The effectiveness of macadam piles for the prevention of soil liquefaction during vibration period is often of three folds: densification, drainage and the reduction of the total cyclic shear stress in the soil. However, the design and evaluation methods remain focused on the densification of in-situ soils at present. In this study, the shaking table test is conducted to assess the effect of reducing the total cyclic shear stress in the soil for macadam piles as a liquefaction countermeasure. In a series of three separate model tests, the saturated sand is studied first without, then with stone columns. The effect of reducing the total cyclic shear stress is discussed based on the recorded dynamic responses and established theory model. The test and theoretical analysis results demonstrate that macadam piles can reduce the total cyclic shear stress in the liquefiable soil remarkably.