膨胀土胀缩性指标的试验研究及变异性分析

Experimental study and variability analysis of swell-shrinkage indices of expansive soil

为研究膨胀土的胀缩性大小及其影响因素,对合肥某工地膨胀土在初始含水率为13%、15%、17%、19%、21%和23%的条件下进行无荷膨胀率试验及收缩试验,提出求解土样缩限的曲线拟合法,分析膨胀土的胀缩性指标与土样初始含水率的关系,并对胀缩性指标的变异性进行了统计分析。结果表明:Weibull模型的拟合相关系数为0.996 6,能较好地拟合收缩试验过程中线缩率与含水率的关系,根据此模型并结合曲线拟合法能快速、准确地求解土样的缩限,避免了传统作图法求解土样缩限过程中的人为影响因素。土样的最大无荷膨胀率随着初始含水率的增大从25.6%减小到15.7%;最大线缩率随初始含水率的增大从1.1%增大到4.7%;胀缩总率随着初始含水率的增大从26.7%减小到20.4%。土样缩限的变异系数相对较小,最大的变异系数为8.0%;而膨胀率及线缩率的变异程度中等,其最大变异系数小于15.1%。膨胀率及线缩率的相关系数为-0.988 3,具有负相关性。

In order to investigate the swell-shrinkage characteristics and its factors, a no-load swell- ing ratio test and a shrinkage test on expansive soil samples of a construction site in Hefei at different initial water contents （ 13% , 15% , 17% , 19% , 21% and 23% ） were conducted. A curve-fitting method was put forward to obtain the shrinkage limit, and the relationship between the swell-shrink- age characteristic index and the initial water content of soil samples was analyzed. The variability of swell-shrinkage characteristic indices was obtained by using the statistical method. The results show that the relationship between shrinkage limit and water content can be fitted by the Weibull Model. And the relevant coefficient is 0. 996 6. The proposed curve-fitting method to obtain the shrinkage limit can give the shrinkage limit of soil samples quickly and accurately to avoid the human factors while using the traditional hand-drawing method. The maximum swelling ratio of soil sample decrea- ses from 25.6% to 15.7% with the increase of initial water content; the maximum linear shrinkage ratio increases from 1.1% to 4.7% with the increase of initial water content; and the swellingshrinkage ratio decreases slightly from 26.7% to 20. 4% with the increase of initial water content. The variability of shrinkage limit is less tan 8.0% , which is relatively low. The variability of swell ratio and linear shrinkage ratio are moderate, and the maximum are less than 15.1%. The relevant coefficient of the swelling ratio and the linear shrinkage ratio is -0. 988 3, showing a negative rela- tionship.