基于微观孔隙通道的饱和/非饱和土渗透系数模型及其应用

从微观角度揭示土体变形对饱和/非饱和渗透系数的影响机理,建立相应的预测方法,对于饱和/非饱和土的渗流分析及水力耦合研究具有重要的科学意义。利用流体力学理论,建立了微观孔隙通道渗透系数与等效孔径的关系,在此基础之上,结合毛细理论建立了饱和/非饱和渗透系数与土-水特征曲线的关系模型,并利用已有试验数据验证了模型的合理性。结合该模型与变形条件下土-水特征曲线预测方法,对变形条件下武汉黏性土饱和/非饱和渗透系数进行预测,结果表明黏性土在压缩变形条件下:饱和渗透系数呈数量级的减小,预测值与实测值均吻合较好;双对数坐标下,非饱和相对渗透系数在进气值之后随基质吸力增加而减小,不同初始孔隙比条件下其斜率近似不变,整体呈现"毛刷型"分布,相同基质吸力条件下,初始孔隙比越小,相对渗透系数越大;非饱和渗透系数,进气值之前近似为饱和渗透系数,进气值之后随基质吸力增大而减小,不同初始孔隙比的变化线近似重合。

A model for determining the permeability coefficient of saturated and unsaturated soils based on micro pore channel and its application

To reveal the influence mechanism of deformation on the saturated and unsaturated permeability and establish the corresponding prediction method from the micro perspective is of great significance for seepage analysis and hydro-mechanical coupling study of saturated and unsaturated soils. Using the fluid mechanics theory, the relation between the permeability coefficient and the equivalent pore-size of micro pore channel has been established. On this basis, by using the capillary theory, a new model was presented to determine the permeability coefficient of saturated and unsaturated soils from soil-water characteristic curve (SWCC), which was testified to be reasonable based on existing experimental data. Combining this model with prediction method of SWCCs of deformation soils, the saturated and unsaturated permeability coefficients of Wuhan deformation clay were predicted. The results show that the predictions of the saturated permeability coefficients are in good agreement with the experimental results,which decrease in orders of magnitude under compression deformation condition. In double logarithmic coordinate,unsaturated relative permeability coefficients decrease with the increase of matric suction for the suction stage greater than the air entry value, which has the approximately same slope for different initial void ratio and present as a "brush" profile. In condition of the same matric suction,the smaller initial void ratio is,the greater unsaturated relative permeability coefficient is. In the suction stage smaller than the air entry value,unsaturated permeability coefficient is approximately equal to the saturated permeability coefficient. In the suction stage greater than the air entry value, unsaturated permeability coefficient decrease with the increase of matric suction, which show the approximately coincident line in the condition of different initial void ratio.