摘要
以青藏高原粉质黏土为对象,进行冻融循环试验和三轴固结不排水剪切试验,研究冻融循环对压实粉质黏土应力-应变关系、孔隙水压力-应变关系、有效应力路径、临界状态线及抗剪强度指标等的影响。研究结果表明:试样在冻融循环前后的应力-应变关系分别为应变硬化型和应变软化型,抗剪强度随冻融循环次数增加而逐渐减小;剪切产生的孔隙水压力和破坏时的孔隙水压力系数均随冻融循环次数或围压增加而增大。应力空间p'-q平面上的有效应力路径在冻融循环后逐渐向左下侧移动,低围压下路径形态由单调增大型过渡为"S"型。孔隙水压力和有效应力路径特征均表明试样在冻融循环下由超固结状态向正常固结状态发展。临界状态线位置随冻融循环次数增加而逐渐下降,临界状态应力比也随之减小;与总应力强度指标相比,有效应力强度指标可以更准确地反映冻融循环和围压对土体力学性质的综合影响;黏聚力和内摩擦角的劣化规律可以采用Logistic函数拟合与预测。
In order to study the freeze-thaw cycling effect on stress-strain relationship, pore water pressure-strain relationship, effective stress path, critical state line and shear strength index of soil, freeze-thaw cycling tests and consolidation-undrained triaxial shear tests were conducted on compacted silty clay from Qinghai—Tibet Plateau. The results show that stress-strain curves of samples before and after freeze-thaw cycling are strain hardening type and strain softening type, respectively. The undrained shear strength decreases continuously with each additional freeze-thaw cycle. The pore water pressure keeps increasing with the increase of both number of freeze-thaw cycles and confining pressure, and so is the pore water pressure coefficient in shear failure. The effective stress path in p＇-q plane also develops towards the lower left, and in low confining pressure it will transfer from monotonously increasing type to ＂S＂ type at the same time. Both the characteristics of pore water pressure and effective stress path reflect that the degree of consolidation decreases with freeze-thaw cycling. The positions of critical state lines in p＇-q plane are lowered, and the critical state stress ratio keeps decreasing by freeze-thaw cycling. Compared with the total stress strength index, the effective stress strength index can reflect the comprehensive effect of freeze-thaw cycling and confining pressure on soil mechanical properties more accurately. The variation regularity of cohesion and internal friction angle versus number of freeze-thaw cycles can both be fitted and further predicted by the Logistic model.
作者
胡田飞
刘建坤
王青志
房建宏
HU Tianfei1,2,LIU Jiankun1,2,WANG Qingzhi1,2,FANG Jianhong2(1. School of Civil Engineering,Beijing Jiaotong University,Beijing 100044,China; 2. Transportation Industry Laboratory of Highway Construction and Maintenance Technology in Permafrost Regions-Qinghai Research Observation Base,Qinghai Research Institute of Transportation,Qinghai 810000,Chin)
出处
《中南大学学报（自然科学版）》
EI
CAS
CSCD
北大核心
2018年第6期1481-1490,共10页
Journal of Central South University:Science and Technology
基金
交通运输部应用基础研究计划(重点平台)项目(2014319363200)
国家自然科学基金资助项目(51378057,41371081)
关键词
粉质黏土
冻融循环
孔隙水压力
有效应力路径
临界状态线
不排水抗剪强度指标
silty clay
freeze-thaw cycling
pore water pressure
effective stress path
critical state line
undrained shear strength index
