土水特征曲线参数的概率统计及敏感性分析

Probability Statistics and Sensitivity Analysis of Parameters of Soil-Water Characteristic Curves

为了研究不同类型土体的土水特征曲线(SWCC)特性,以Fredlund-Xing模型的3种模式及van Genuchten模型的3种模式为SWCC拟合模型,以MATLAB编程语言中的3种函数为拟合方法,以UNSODA数据库中的黏土、砂土、广西膨胀土及合肥膨胀土为研究对象,对大量的基质吸力-体积含水率数据进行了曲线拟合及参数统计,分析了拟合模型与拟合方法对模型参数的影响,得到了这4类土的SWCC参数概率分布特征;提出了考虑变量间相关性时对体积含水率进行参数敏感性分析的计算公式。拟合结果表明:拟合方法对SWCC参数有一定影响;在低吸力部分,各种拟合模型的SWCC基本一致;在高吸力部分,FX2与VG2、FX3与VG3的SWCC基本一致;体积含水率对参数a的敏感性很小,对参数n与m的敏感性较大。

To study the characteristic of soil-water characteristic curves （SWCC） of several different types of soils, a number of data sets of matric suction-volume water content were studied for UNSODA clay, UNSODA sand, Guangxi expansive soil and Hefei expansive soil. Three types of Fredlund-Xing models and three types of van Genuchten models were used to study the influence of SWCC models, and three types of functions in the scientific programming language MATLAB were applied to analyze the effect of different fitting methods. Through the data fitting and statistic analysis, the probabilistic characteristics of the fitting parameters of SWCCs for the four types of soils were obtained. For analyzing the relative sensitivity of the normalized volume water content to the three fitting parameters of SWCC, a formula which considers the correlation of parameters was proposed. Through the data fitting of many data sets, it is found that the fitting methods influence the value of parameters of SWCC, while the influence is less than that of fitting models from the statistical point of view. The SWCCs of all the models are nearly the same when the suction is low. With the increase of the suction, the SWCCs of FX2 and VG2 are very close, and the SWCCs of FX3 and VG3 are the same. The sensitivity analysis shows that the normalized volume water content is more sensitive to parameters n and m than to parameter a.