修正Van Genuchten模型拟合干旱、半干旱地区遗址土颗分曲线的可靠性研究

Reliability research on fitting particle size distribution curves of relic soils in arid and semi-arid regions by modified Van Genuchten model

不均匀系数、曲率系数在土力学中的应用很广,但对精确求解d_(10)、d_(30)、d_(60) 3个参数的方法研究较少。提出了一种修正Van Genuchten(MVG)方程描述颗分曲线。以Matlab编程语言中的cftool为拟合工具,以青海黄土、青海遗址土、甘肃遗址土和新疆遗址土等33组土为研究对象,对比拟合方程描述遗址土颗分曲线的效果,分析MVG模型中3个参数a、m、n对曲线的影响。结果表明:MVG模型在拟合33组土的颗分曲线时均具有较好的效果,相关系数2R(29)0.98;参数a导致曲线偏移并可以推测土粒中的最大粒径,参数m影响土中的各颗粒组分的比例,参数n影响曲线的斜率。提出的MVG方程能够精确地求解d_(10)、d_(30)、d_(60) 3个参数。

The nonuniform coefficient and curvature coefficient are very useful coefficients in soil mechanics. However, the precise approach to calculating d_（10）, d_（30）, d_（60） is seldom studied. A modified Van Genuchten（MVG） equation is proposed to fit the particle size distribution curves. Cftool in the scientific programming language MATLAB is applied to fit the function. This paper analyzes the influence of three parameters of a, m, n in MVG model on the particle size distribution curves of the thirty-three types of soils, which including the Qinghai loess, the Qinghai relic soil, the Gansu relic soil and the Xinjiang relic soil and so on. It is shown that the fitted curves of MVG equation perform well in predicting the particle size distribution curves, the square of the correlation coefficients are all bigger than 0.98. The parameter a causes the curves to migrate from the left to the right and vice versa, and can also indicate the maximum particle sizes. The parameter m influences the proportion of every group with the different particle sizes and the parameter n affects the slopes of curves. The proposed MVG equation is a precise approach to calculating d_（10）, d_（30）, d_（60）.