纳米黏土改良黄土力学性能试验研究

在陕西安塞地区黄土中掺入两种不同纳米黏土材料,设计不同掺量、含水率、养护龄期等多因素影响下的正交试验,并对改良后黄土进行三轴试验,分析凹凸棒土和纳米蒙脱土改善黄土无侧限抗压强度指标以及抗剪强度指标的变化特征,并采用SEM对两种纳米黏土改良黄土进行改善机理微观分析。结果表明:掺量为1%的凹凸棒土、掺量为2%的纳米蒙脱土对黄土抗压强度影响最为显著,在一定含水率下可使素黄土的抗压强度分别提高21%和42.3%; 两种纳米黏土改良黄土应力-应变曲线受试样干密度、围压及掺量的影响,干密度为1.35 g?cm^-3、围压为50 kPa的改良黄土有应变软化现象,干密度达到1.65 g?cm^-3时,4种不同围压下改良黄土应力-应变曲线均有应变硬化的趋势; 两种纳米黏土对改良黄土的抗剪强度指标影响效果显著,其中1%掺量的凹凸棒土、2%掺量的纳米蒙脱土可以使改良黄土的黏聚力分别提升61.02%和81.70%,内摩擦角分别提升27.86%和21.31%。

Experimental study on mechanical properties of loess improved by nano clays

Two different nano clay materials were mixed into the loess soil in the Ansai area of Shaanxi Province, and an orthogonal test was designed to investigate the effects of different factors, such as mixing ratio, water content, and curing time on the modified loess. Three-axis tests were conducted to analyze the changes in the unconfined compressive strength and shear strength of the modified loess after mixing the attapulgite and nano montmorillonite, and the improvement mechanisms were microscopically analyzed by SEM. The results show that the addition of 1% attapulgite and 2% nano montmorillonite have the most significant influence on the compressive strength of the loess. Under certain water content, the compressive strength of the plain loess increase by 21% and 42.3%, respectively. The stress-strain curve of the modified loess with the two types of nano clay is affected by dry density, confining pressure, and mixing ratio. The modified loess with a dry density of 1.35 g?cm^-3 and a confining pressure of 50 kPa exhibit a strain softening phenomenon, while the stress-strain curves of the modified loess at four different confining pressures show strain hardening tendency when the dry density reached 1.65 g?cm^-3. The two types of nano clay significantly affect the shear strength index of the modified loess. The addition of 1% attapulgite and 2% nano montmorillonite increase the cohesion of the modified loess by 61.02% and 81.70%, respectively, and the internal friction angle increase by 27.86% and 21.31%, respectively.