土水特征曲线的概率分析

Probabilistic analysis of the soil-water characteristic curve

土水特征曲线(SWCC)反映非饱和土基质吸力与含水率的关系,是非饱和土研究中重要的关系曲线。为进行与非饱和土有关工程的可靠度分析,需要对土水特征曲线进行概率分析。文章基于理论分析及数值模拟试验,分析比较了求解曲线拟合参数的直接回归法及数理统计法,探讨了试验点数量及位置对计算结果的影响。研究了求解响应量置信带的直接回归法,以及由自变量的置信区间求解响应量置信带的间接方法,指出了考虑变量间相关性的重要性,提出了由相关非正态变量求解响应量置信带的方法。通过土水特征试验,对合肥非饱和土的SWCC概率特征进行了分析,求得了SWCC拟合参数的均值、变异系数及相关系数,绘出了SWCC响应量的置信范围与基质吸力的关系。

The soil-water characteristic curve（ SWCC） reflects the relationship between the matrix suction and the water content of unsaturated soil. It is a very important curve for the studyh of unsaturated soil. To carry out the reliability analysis of engineering related to unsaturated soil,it is necessary to perform the probabilistic analysis of the soil-water characteristic curve. Based on theoretical analyses and numerical simulations of linear and nonlinear examples,two methods for getting the curve fitting parameters are examined. These two methods are the direct regression method and the mathematical statistical method,respectively. The effect of the number and locations of the test points on the fitting parameters are analyzed. The confidence belt of the dependent variable can be obtained with the direct regression method,or with the undirected method of using the confidence interval of each fitting parameter. The difference in the confidence belts between the direct and undirected methods indicates the importance of consideration of the correlation among each fitting parameters.A method for obtaining the confidence belt from non-normal correlated variables is proposed. Through soilwater characteristic curve tests,the probabilistic features of SWCC of the Hefei unsaturated soil are analyzed,and the mean value,the coefficient of variation and the coefficient of correlation are obtained. The confidence belt of the depend variable along the whole suction range is also plotted.