由土–水特征曲线预测上海非饱和软土渗透系数

Predicting coefficient of permeability from soil-water characteristic curve for Shanghai soft soil

在分析总结由土–水特征曲线预测非饱和土渗透系数方法的基础上,根据Childs和Collis-George(1950)利用充水孔隙空间形状提出的、并经多次修改的预测渗透系数模型,预测了上海非饱和软土的相对渗透系数。上海非饱和软土渗透性参数随吸力(含水率)变化呈现非线性变化,吸力增加(含水率降低)渗透性快速降低。对不同粒径的上海非饱和软土层,在减饱和初期(低吸力阶段),土体中骨架颗粒大小对渗透性影响不大;但随着减饱和过程的进行,大骨架颗粒的土体的渗透性衰减速率大于小颗粒土体;而减饱和后期,这种衰减速率上的差异又趋于不明显。这一衰减特征主要与参与减饱和的土中水的赋存状态有关。

Childs and Collis-George（ 1950）proposed a model for predicting the coefficient of permeability based on the random variation of pore size. It was then improved several times and proved to be effective. Based on this model, the relative coefficients of permeability of Shanghai soft soil were predicted from the soil-water characteristic curves. It was shown that permeability parameter of Shanghai soft soil varied nonlinearly with suction（water content）, and it decreased quickly with increasing of suction（decreasing of water content）. For different grain sizes of Shanghai soft soil, at the beginning of de-saturation（low suctions）, the size of soil grains had little influence on permeability. But with the progress of de-saturation, the decreasing rate of permeability of large grain soil was larger than that of small grain soil. At the last stage of de-saturation, the difference of the decreasing rate became unobtrusive. This decreasing phenomenon was mainly related to the character of water that participated in the process of de-saturation.