单峰和双峰土水特征曲线基本参数的确定

土水特征曲线基本参数(如进气值、残余吸力值和过渡区脱湿曲线的斜率等)的确定是预测非饱和土强度、渗透性以及本构关系的基础。基于修正Fredlund和Xing拟合方程,提出单峰和双峰土水特征曲线基本参数的确定方法。首先,对试验数据点进行最优化拟合,获取拟合方程的参数,对于双峰土水特征曲线,根据试样的孔径分布特征将其分段进行拟合;其次,根据拟合方程的几何关系求出过渡区和残余区土水特征曲线的斜率及其切线方程;再根据切线方程可以准确地确定单峰和双峰土水特征曲线的进气值、残余吸力值等。最后,利用单峰和双峰土水特征曲线的试验数据,验证了此方法的可行性。

Determination of basic parameters of unimodal and bimodal soil water characteristic curves

The determination of basic parameters (such as air-entry value, residual suction, slope at transition zone, etc.) of soil-water characteristic curve (SWCC) is the most fundamental for predicting the strength, permeability and constitutive relation of unsaturated soils. In this paper a method is proposed to determine the basic parameters of unimodal and bimodal SWCCs based on the modified Fredlund and Xing’s fitting equation. Firstly, the parameters of the fitting equation can be obtained by the optimal fitting of experimental data. For the bimodal SWCC, the piecewise fitting method is adopted based on the pore size distribution characteristics of soils. Secondly, the slopes and equations of tangent lines are obtained in the transition and residual zones based on the geometric relationship of the fitting equation. Furthermore, the air-entry value and residual suction of SWCCs are determined by the geometric relationship of tangent lines. Finally, the proposed method is validated to be feasible by use of the experimental data of unimodal and bimodal SWCCs.