竖向应力及干密度对砾石土土-水特征曲线的影响研究

Influence of vertical stress and dry density on soil-water characteristic curve of gravelly soil

利用SWC-150 Fredlund土-水特征曲线压力仪,对不同干密度的砾石土进行不同竖向应力作用下的土-水特征试验,探讨了干密度和竖向应力对土-水特征曲线(SWCC)的影响。采用Fredlund&Xing三参数模型对试验所得的土-水特征曲线进行最小二乘法拟合,获得了土-水特征曲线的模型参数,并探讨了其变化规律。随着竖向应力及干密度的增大,模型参数n增大,m减小。除吸湿阶段拟合参数a随干密度略微减小外,其余情况a随竖向应力和干密度密度的增大而增大。结合土-水特征曲线拟合函数,分析研究了竖向应力和干密度对土-水特征曲线的进气值或进水值以及斜率的影响规律,提出了土-水特征曲线的进气值或进水值以及过渡段斜率与竖向应力和干密度的定量关系。结果表明:进气值或进水值与竖向应力和干密度呈线性关系,但吸湿阶段的进水值随干密度变化不明显;土-水特征曲线的斜率与竖向应力呈双曲线关系,与干密度呈直线关系。

SWC-150 Fredlund soil water characteristic cell is used to test the soil-water characteristic curve （SWCC） of gravelly soils with different densities under different vertical stresses. The influence of the vertical stress and dry density on the SWCCs is investigated. The SWCCs are fitted based on Fredlund＆amp;Xing tri-parameter model using least-square method. The parameters of the model are determined and discussed. With the increase in the vertical stress and dry density, the model parameter n increases while m decreases. Except that the parameter a slightly decreases with the increase in the dry density during wetting process, it increases with the increase in the vertical stress and dry density. Based on the fitting results, the influence of the vertical stress and dry density on the air or water entry value and the slope of the SWCC are studied. The quantitative relationships between the air or water entry value, the slope of transition segment of the SWCC and the vertical stress, dry density are proposed. The results show that the air or water entry value has a positive linear relationship with the vertical stress and dry density. Nevertheless, the water entry value has little change with the change in the dry density. The slope of transition segment of the SWCC presents hyperbolic relationship with the vertical stress, while the relationship between the slope and the dry density is linear.