具有参数独立性的双峰土水特征曲线预测模型

Prediction Model of the Bimodal Soil⁃Water Characteristic Curve with Parameter Independence

双孔结构土内部存在集聚体内孔隙和集聚体间孔隙,其土水特征曲线呈现双峰特征。现有双峰土水特征曲线模型多采用将2个单峰土水特征曲线线性叠加的方法建立,参数较多且不具备独立性,用其拟合试验数据时可能存在不收敛问题。基于毛细管理论提出了一个新的双峰土水特征曲线预测模型。首先,通过在单峰孔径分布函数中引入双曲三角函数的数学方法,在几何上将单峰孔径分布曲线的单峰分割为双峰,从而获得了双峰孔径分布函数;其次,将新提出的双峰孔径分布函数进行累积积分,建立了双峰土水特征曲线模型;最后,分析了该模型参数的物理意义及其对预测结果的影响,发现该模型参数相互独立。使用新模型预测多种双孔结构土的土水特征曲线试验数据,取得了良好的预测效果。

In the soil with a dual⁃porosity structure,there are intra⁃aggregate pores and inter⁃aggregate pores,and the soil⁃water characteristic curve(SWCC)exhibits bimodal characteristics.The existing models of the bimodal SWCC are mostly established by linearly stacking two unimodal SWCC,having too many parameters of no independence.Thus,when they are used to fit experimental data,non⁃convergence may be caused.In the study,a novel prediction model of the bimodal SWCC was proposed based on the capillary theory.Firstly,by introducing hyperbolic trigonometric functions into a unimodal pore size distribution(PSD)function,the single peak of the unimodal PSD curve was geometrically split into two peaks so that a bimodal PSD function was obtained.Secondly,a bimodal SWCC model was built by accumulatively integrating the newly proposed bimodal PSD function.Finally,physical meanings of the parameters in the new model and their influences on the prediction results were analyzed.It was found that the model has parameters that are independent of each other.This new model was used to predict test data of SWCC of various soils with double⁃pore structure,achieving a good prediction agreement.