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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。
Initial dynamic shear modulus is a comprehensive reflection of many structural factors of soil, except for the two main factors of consolidation pressure and void ratio (density), but also affected by cyclic vibration. Previous research on this factor has focused on dry sand, and the amplitude of shear strain applied during pre-vibration is more than 10-3. For saturated soils, especially for the initial dynamic shear modulus of soil subjected to large amplitude vibration Research is very limited. In this paper, the triaxial test of undrained saturated silt with different relative density under the condition of isotropic consolidation was carried out by using the moving triaxial apparatus with curved element. Meanwhile, the shear wave velocity of the sample was monitored, The initial dynamic shear modulus. In order to ensure the reliability of the test results, the resonance column test was carried out at the same time to determine the arrival point of the received signal of the bent element. The influence of the test pause time on the test results under different pore pressure development was evaluated. The results show that the initial dynamic shear modulus under a large number of cyclic loading is observed to be different from the modulus obtained after consolidation under the same stress, and the additional attenuation or increase is the change of soil micro-structure under cyclic loading External macro performance. This additional change is determined by the contact behavior of soil particles and is influenced by many factors, such as the initial conditions of the sample and the amplitude of the vibration, showing different modes of change.