考虑接触角及粒径级配影响的土水特征曲线滞回模型  

Hysteretic model for fitting soil-water characteristic curves considering contact angle and grain-size distribution

作　　者：伏映鹏 廖红建[1] 吕龙龙 柴小庆[2] FU Ying-peng;LIAO Hong-jian;LYU Long-long;CHAI Xiao-qing(School of Human Settlements and Civil Engineering,Xi’an Jiaotong University,Xi'an 710049,China;College of Geology Engineering and Geomatics,Chang’an University,Xi'an 710054,China)

机构地区：[1]西安交通大学人居环境与建筑工程学院,陕西西安710049 [2]长安大学地质工程与测绘学院,陕西西安710054

出　　处：《岩土工程学报》2022年第3期502-513,共12页Chinese Journal of Geotechnical Engineering

基　　金：国家自然科学基金项目(51879212,41630639);中央高校基本科研业务费专项资金项目(xzy022019009);陕西省国际科技合作计划重点项目(2019KWZ-09)。

摘　　要：土水特征曲线描述了非饱和土中含水率(或饱和度)与基质吸力(或土水势)之间的关系。土水特征曲线存在滞回效应,即在相同的吸力下,土体在蒸发或重力排水的脱湿过程中赋存的水量比土体在入渗、毛细上升的增湿过程中所赋存的水量多。针对影响土水特征曲线滞回特性的两个关键因素--接触角及由颗粒粒径级配(孔隙分布)引起的墨水瓶效应,首先,基于势能最小原理采用数值模拟方法研究了斜面液滴行为,提出了增湿、脱湿过程微细观界面关键参数接触角与含水率的演化关系;其次,通过修正颗粒间液桥体积表达式,使Young-Laplace方程可用于计算w-lns平面上边界影响区、过渡区及部分残余区的基质吸力;最后,通过引入Rosin-Rammler颗粒粒径分布函数,建立了考虑接触角及粒径级配影响的土水特征曲线滞回模型,该模型参数物理意义明确,能够较好地描述接触角及颗粒粒径对土水特征曲线滞回特性的影响。以西安曲江某基坑压实黄土土水特征曲线为例进行模型验证,结果表明该模型能够很好地反映基质吸力与含水率的非线性关系,该模型可进一步用于非饱和土抗剪强度、本构模型等的研究。The soil-water characteristic curve(SWCC)describes the relationship between water content(or saturation)and matric suction(or soil-water potential)in unsaturated soils.It is worth noting that the amount of water stored in soils during the drying process caused by evaporation or gravity drainage is more than that during the wetting process caused by infiltration and capillary rise under the same matric suction level.This phenomenon is described by the hysteretic behavior of the SWCCs.Based on existing knowledge,the contact angle and the ink-bottle effect caused by the grain-size distribution(or pore-size distribution)are the two main factors that affect the hysteretic behaviors of the SWCCs.First,the behaviors of a liquid drop sitting on an inclined surface are investigated by the numerical method,and a relationship between the contact angle and the water content during the wetting and drying processes is proposed based on the principle of the minimum potential energy.Second,the expression for the volume of the liquid bridge is modified to make the Young-Laplace equation keep valid in calculating the matric suction in the boundary affected zone,transition zone and the part of the residual zone on the w-lns plane.Finally,an analytical model for analyzing the hysteretic behaviors of SWCCs is proposed after introducing the Roshin-Rammler grain-size distribution function.The model has a clear physical meaning,and the parameters can be obtained easily.Moreover,the model can describe the hysteretic behaviors of the SWCCs.Taking the SWCC of recompacted loess in a foundation pit in Qujiang,Xi’an as an example,the model is verified.The results show that the proposed model can well reflect the nonlinear relationship between the matric suction and the water content.The model can also be used for studying the shear strength and the constitutive model for unsaturated soils.

关 键 词：土水特征曲线 滞回模型 接触角 粒径级配 Young-Laplace方程 Rosin-Rammler分布 

分 类 号：TU431[建筑科学—岩土工程]