非饱和击实粉土的强度和屈服特性研究

Strength and yielding characteristics of unsaturated compacted silts

由于吸力量测技术的困难,对京―九线粉土在不同含水率下击实并进行三轴不排水剪切试验,研究其强度和屈服特性,为非饱和击实粉土力学模型的建立提供依据。试验结果表明:该击实粉土在剪切过程中,在最优含水率干侧击实的土样具有较高的强度,应力-应变关系曲线呈软化趋势,土样先剪缩后剪胀,湿侧击实的土样具有较低的强度,应力-应变关系曲线呈硬化趋势,土样不断剪缩;随着试样击实含水率的增加,击实粉土的强度和屈服应力不断减小,水对土体具有一定的软化作用;不同击实含水率下,土样在q-p平面内破坏时的屈服轨迹为近似平行的斜直线,含水率对临界状态线的斜率没有影响;含水率对击实粉土抗剪强度的贡献表现为土体的似黏聚力的增加,似黏聚力与含水率之间呈乘幂关系,得出以含水率为变量的击实粉土强度计算公式,可在实际工程中推广应用。

through the triaxial CU tests of compacted silts under different water content by using an unsaturated GDS triaxial apparatus,the strength and yielding characteristics of the silts taken from Beijing-Kowloon-Railway subgrade are analyzed,which provide an experimental basis for the establishment of soil mechanics model.Some conclusions can be made from the research as follows：（1） Higher strength and a tendency to work softening of stress and strain curves are shown of the samples compacted dry side of the optimum water content,which also exhibit shearing dilatation initially and then shearing shrinkage;but for samples compacted wet side of the optimum water contents,lower strength and work harding trend are observed and the samples always exhibit shearing shrinkage characteristics.（2） The strength and yielding stress decrease with the water content increasing,which shows the softening effect of water on the soils behavior.（3） The yield loci at failure on q-p plane of different water contents exhibit linear relationship.The slopes of the critical state lines are independent of the water contents.（4） Cohesive increasing reflects the contribution of the water content to shear strength,and a power relation is shown between the cohesive and water content.（5） A formula taken water content as variable is deduced for calculating the shear strength,which shows good agreement with the testing data and can be used in practice.