基于吸应力的非饱和黄土抗剪强度研究  

Study of shear strength of unsaturated and undisturbed loess based on suction stress

作　　者：袁志辉[1] 倪万魁[1] 刘茹[1] 李焕焕[1] 

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054

出　　处：《合肥工业大学学报（自然科学版）》2015年第5期648-653,共6页Journal of Hefei University of Technology：Natural Science

基　　金：国家重点基础研究发展计划(973计划)资助项目(2012CB026101);陕西省科技统筹创新工程计划资助项目(2012KTDZD03-03)

摘　　要：文章通过滤纸法与直剪试验相结合的方法,得到了非饱和原状黄土土水特征曲线和抗剪强度,分析了基于吸应力下的非饱和原状黄土的抗剪强度。试验结果表明:非饱和原状黄土的抗剪强度随基质吸力的增大表现为非线性增大,并逐渐趋于稳定,与土水特征曲线的变化规律基本一致;表观黏聚力随基质吸力的增大表现为非线性增大,尤其在毛细发挥段和水膜吸附段该趋势变得非常明显;表观内摩擦角随基质吸力的增大呈稍微增大的趋势;与表观内摩擦角相比,表观黏聚力的增加幅度较大,因此基质吸力对抗剪强度的贡献更多地体现在表观黏聚力上。通过吸应力概念得到了非饱和原状黄土的表观黏聚力;当土体含水率大于塑限时,基于吸应力公式计算的表观黏聚力与试验结果基本一致;当土体含水率小于塑限时,运用吸应力公式计算的表观黏聚力远远大于试验结果。因此,在含水率较高时,可用吸应力下的抗剪强度公式预测非饱和原状土抗剪强度;在含水率较低时,基于吸应力下的抗剪强度公式是不适用的。The soil-water characteristic curve（SWCC） and shear strength of unsaturated and undis- turbed loess are obtained by using filter paper method and direct shear test. The shear strength of un- saturated and undisturbed loess based on suction stress is analyzed. The results show that the shear strength increases nonlinearly with the increase of matric suction and gradually tends to a stable state, its variation is consistent with the change rule of SWCC~ apparent cohesion increases nonlinearly with the increasing matric suction, especially in capillarity stage and water film adsorption stage, this trend is obvious; apparent internal friction angle shows a slightly increasing trend with the increase of ma- tric suction; the increasing extent of apparent cohesion is greater than that of apparent internal friction angle, so the contribution of matric suction to the shear strength is more reflected in the apparent co- hesion. The apparent cohesion of unsaturated and undisturbed loess is obtained by using suction stress concept. The apparent cohesion of shear strength formula based on suction stress and experimental re- sults are basically the same when water content is greater than plastic limit of soil sample; the appar- ent cohesion is much larger than experimental results when water content is less than plastic limit of soil sample. Therefore, the shear strength formula based on suction stress is suitable for calculating the shear strength of unsaturated and undisturbed loess soil with high water content, and the shear strength formula is not suitable for low water content.

关 键 词：滤纸法 土水特征曲线 抗剪强度 基质吸力 吸应力 

分 类 号：TU432[建筑科学—岩土工程]