干湿循环对非饱和黄土渗透系数的影响研究

针对不同干密度的重塑非饱和黄土，利用GCTS压力仪研究非饱和黄土在干湿循环条件下的土－水特征曲线，选用van Genuchten模型拟合体积含水量与基质吸力的关系，结合Childs & Collis-Geroge模型预测黄土的非饱和渗透系数，进而分析干湿循环作用及干密度对非饱和渗透系数的影响。研究结果表明：试验地区非饱和黄土的土－水特征曲线拟合相关度高达0.97以上，有良好的适用性；黄土的非饱和渗透系数与干湿循环次数及干密度之间均符合指数函数关系；相同基质吸力条件下，干密度大的黄土非饱和渗透系数大，基质吸力较小时，干密度为1.74 g/cm³的黄土比干密度为1.56 g/cm³的黄土非饱和渗透系数大10²数量级；当干密度保持不变时，随着干湿循环次数的增加，渗透系数逐渐增大，其增幅随体积含水量的增大而增大，随基质吸力的增大而减小；当非饱和黄土试样的体积含水量接近残余含水量时，土体的渗透系数趋于稳定。

Influence of dry-wet cycles on the permeability coefficient of unsaturated loess

Regarding to remolded unsaturated loess with different dry densities, a GCTS pressionmeter was used to study the permeability coefficient of unsaturated loess under the treatments of different dry-wet cycles, and the relationship between volumetric water content and matrix suction was fitted by the van Genuchten model. Combined with Childs & Collis-Geroge model, the influence of dry-wet cycles and dry density on the unsaturated permeability coefficient was analyzed. The results show that the fitting correlation of the soil-water characteristic curve(SWCC) of the unsaturated loess in the test site is above 0.97 and the fitting effect is satisfactory for the loess. The unsaturated permeability coefficient of the loess is exponentially related to the number of dry-wet cycles and dry density. Under the same matrix suction, the unsaturated loess with higher dry density has larger permeability coefficient. When the matrix suction is small, the permeability coefficient of the unsaturated loess with a dry density of 1.74 g/cm³ is more than 100 times greater than that with a dry density of 1.56 g/cm³. When the dry density remains constant, the permeability coefficient increases gradually with the increase of dry-wet cycles, and its increase rate rises with the increase of the volumetric water content, decreases with the increase of the matrix suction. When the volumetric water content of unsaturated loess samples is close to the residual water content, the permeability coefficient of the soil tends to stabilize.