作　　者： ; ; ; ; ;

机构地区： 浙江大学建筑工程学院岩土工程研究所

出　　处： 《岩土工程学报》 2009年第5期764-771,共8页

摘　　要： 初始动剪模量是土体多种结构性因素的综合反映,除固结压力和孔隙比(密度)这两个主要因素外,还受循环振动影响。以往对该因素的研究偏重于干砂,且预振时施加的剪应变幅多低于10-3;对于饱和土体,尤其是对经受过较大振幅振动后土体初始动剪模量的研究十分有限。本文利用安装弯曲元的动三轴仪,在等向固结条件下对不同相对密度的饱和粉土进行不排水循环三轴试验,同时监测试样的剪切波速,获得循环动力加载过程中土的初始动剪模量。为保证试验结果的可靠性,同时进行了共振柱试验,比较确定弯曲元接收信号的到达点;评估了不同孔压发展程度下试验暂停时间对测试结果的影响。结果表明:在一定次数大振幅循环荷载作用下观察到初始动剪模量有别于相同应力下固结后得到的模量值,出现附加衰减或增长,正是循环荷载作用下土微观结构变化的外部宏观表现。这种附加变化由土颗粒接触行为决定,受到试样初始条件和振动幅值等多种因素的影响,表现出不同的变化模式。 The small strain shear modulus is one of the most important parameters reflecting soil structure. It is primarily a function of the effective confining stress and void ratio （density）, while the dynamic loading history is another important factor. Many experiments have been conducted to investigate the small strain shear modulus of dry sands due to prestraining with prestrain amplitude below 10-3, though the results for the effects on those of saturated soils subjected to a higher amplitude dynamic loading are limited and somewhat contradictory. An attempt is made to study the influence of seismic vibration on the small strain shear modulus of the saturated silt specimens with different relative densities. The shear wave velocity of the specimens are monitored with bender elements equipped on the dynamic triaxial apparatus as soon as the undrained cyclic triaxial testing is interrupted. To ensure the credibility, the reach points of shear wave velocity are examined through the comparison of resonant column tests. The effects of interrupting time at different pore pressure developing stages are also evaluated. It can be observed in the tests that under large amplitude cyclic loading cycles, the small strain shear modulus has a dissimilar degradation or increament changes compared with that under the same static stress without cyclic loading history. This is attributed to the changes in soil microstructure during cyclic loading. The variation modes for the small strain shear modulus are initial specimen condition and cyclic amplitude dependant, decided by the soil particle contact behaviour.

关 键 词： 初始动剪模量 地震振动 预振 弯曲元 粉土

领　　域： [建筑科学] [建筑科学]