粉质黏土强度指标的水化学敏感性研究  

A study of water chemical sensitivity of strength indices of silty clay

作　　者：杨德欢[1] 颜荣涛[1] 韦昌富[1,2] 张敏[1] 张芹[1] 

机构地区：[1]桂林理工大学广西建筑新能源与节能重点实验室,广西桂林541004 [2]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071

出　　处：《岩土力学》2016年第12期3529-3536,共8页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.11372078;No.51309055);广西自然科学基金创新研究团队项目(No.2012GXNSFGA060001);广西自然科学基金青年项目(No.2014GXNSFBA118236)~~

摘　　要：通过对重塑粉质黏土的液、塑限和固结慢速直剪试验,探讨了粉质黏土液限、塑性指数及抗剪强度与不同浓度Na Cl孔隙溶液的关系。试验结果表明,随着孔隙溶液浓度增加,液限随之减小,塑性指数表现出粉土的性质;不同竖向正应力下的强度随浓度变化表现出较大的差异,正应力较低时,强度不断减小,而正应力较高时,则强度不断增大,正应力介于二者之间强度则先降后升;内摩擦角随浓度增加而增大,最终趋于稳定;黏聚力先迅速减小后逐渐回升,且均为负值。其性质变化主要是因为扩散双电层、颗粒间作用力以及孔隙比发生了改变。基于Terzaghi的有效应力原理,对饱和粉质黏土固结慢速直剪试验测得的负值黏聚力进行了分析和讨论,认为渗透压力对黏聚力起了非常重要的作用,从而使黏聚力成为负值。A series of direct shear experiments was performed to investigate the influences of pore fluid concentration on the liquid limit, plastic index and shear strength of remolded silty clay. The experimental results indicate that the liquid limit decreases with the increase of pore solution concentration, and the plastic index is similar to that of silt. It is found that the variation of the shear strength with the concentration depends upon the vertical stress applied. For a low vertical stress, the shear strength decreases slightly as the concentration increases; for a medium vertical stress, the shear strength first decreases and then increases as the concentration increases; for a high vertical stress, however, the strength constantly increases as the concentration increases. In addition, the internal friction angle increases with the pore fluid concentration and approaches toward a stable value, while the cohesion decreases rapidly in the early stage, and gradually increases again, remaining at a negative values all the time. These features of the soil behavior can be attributed to the combing effect of electric diffuse double layers, the intergranular stress variation and the void ratio change under coupled chemical and mechanical interactions. Based on the Terzaghi＇s effective stress principle, the shear strength parameters of the tested saturated silty clay are analyzed, suggesting that the osmotic pressure plays an important role in the occurrence of the negative cohesion of clayey soils.

关 键 词：水-土化学作用 粉质黏土 液塑限试验 直剪试验 渗透压力 

分 类 号：TU411[建筑科学—岩土工程]