Comparison of dynamic characteristics of the silty clay before and after freezing and thawing under the subway vibration loading
Comparison of dynamic characteristics of the silty clay before and after freezing and thawing under the subway vibration loading
复制标题
地铁振动荷载作用下粉质黏土冻融前后动力特性对比
DOI：
10.1016/j.coldregions.2015.07.004
复制
发表时间：
2015-11-01
影响因子：
4.1
通讯作者：
Zhang, Zhong-Liang
中科院分区：
文献类型：
--
作者：
Cui, Zhen-Dong;Zhang, Zhong-Liang
近年来，软土在地铁振动荷载作用下的长期变形问题越来越受到研究人员和工程技术人员的关注。上海有14条以上的地铁线路投入运营，一些新线路正在建设中。地铁隧道大部分埋于软土层中，隧道旁路采用人工冻结法施工。本文对上海地区约10m深的5层粉质粘土进行了循环三轴试验，研究了冻融前后粉质粘土的动力特性。在弹塑性Iwan模型的基础上，讨论了H-D模型与M-D模型之间的转换。用这两种模型对循环三轴试验数据进行了拟合，并分析了主干曲线模型在上海软土中的适用性。考虑振动次数、偏应力频率和偏应力幅值的影响，通过分析超孔压和轴向应变发展曲线，详细比较了冻融前后粉质粘土的动力特性。结果表明，在相同的试验条件下，冻融粘土产生的应变比原状粘土大26.7%，超孔压高53%。随着振动次数的增加，轴向应变和超孔压的增加率逐渐减小。偏应力的频率越低、幅值越大，传递给土体的能量越多，变形拐点出现的时间越早。(C)2015爱思唯尔B.V.保留所有权利。
The long-term deformation of soft clay under the subway vibration loading has been paid more attention by researchers and engineers recently. More than 14 subway lines are in operation and some new lines are being built in Shanghai. Most of the subway tunnel are buried in the soft clay layer and the by-pass of tunnel is constructed by the artificial freezing method. In this paper, cyclic triaxial tests for the silty clay of layer No. 5 about 10 m in depth in Shanghai were conducted to study the dynamic behaviors of the silty clay before and after freezing and thawing. Based on the elastic-plastic Iwan model, the conversion between H-D model and M-D model was discussed. The cyclic triaxial tests data were fitted by the two models and the applicability of the backbone curve models to Shanghai soft clay was analyzed. Considering the influence of number of vibration, the frequency and the amplitude of deviator stress, the dynamic behaviors of the silty clay before and after freezing and thawing were compared in details through analyzing the excess pore water pressure and the axial strain development curves. The results show that the freezing-thawing clay can produce up to 26.7% larger strain and 53% higher excess pore pressure than the undisturbed clay under the same test conditions. The rates of increasing of the axial strain and the excess pore pressure decrease gradually with the increase of the number of vibration. The lower the frequency and the larger the amplitude of deviator stress are, the more energy transferred to soil is and the earlier the inflection points of deformation appear. (C) 2015 Elsevier B.V. All rights reserved.