南阳膨胀土冻融循环后的土水特征试验研究

南水北调中线工程的膨胀土渠道容易遭受季节性冻融的影响。为探究冻融作用对膨胀土土水特征的影响规律,以南阳膨胀土为试验对象,采用滤纸法测定经历不同冻融次数的膨胀土土样的总吸力和基质吸力,绘制其试验散点图,并分别采用VG模型和幂函数模型对基质吸力及总吸力与土体含水率的关系进行拟合。结果表明:随着冻融循环次数的增加,基质吸力和总吸力土水曲线整体向左下方偏移,进气值逐渐减小,持水性能降低;渗透吸力在含水率增大时逐渐减小,但不同冻融次数的渗透吸力数值并无显著差别;采用VG模型和幂函数模型分别拟合本试验中的基质吸力土水曲线和总吸力土水曲线,相关系数高,形式简单,模型参数在冻融循环中逐渐趋于稳定值。研究成果可供处在季节性冻土区的膨胀土工程建设及维护提供参考。

Experimental Research on Soil-Water Characteristics of Nanyang Expansive Soil Subjected to Freeze-Thaw Cycles

The expansive soil canal in the Middle Route of South-to-North Water Transfer Project is easily subjected to the effect of freeze-thaw cycles. In order to investigate the influence of freeze-thaw cycles on soil-water characteristics of expansive soil, we measured the total suction and matric suction of Nanyang expansive soil subjected to different freeze-thaw cycles using the filter paper method, and fitted the relationship between matric suction, total suction and water content with Van Genuchten model and power function model, respectively. Results show that as the freeze-thaw cycle proceeds, the soil and water characteristic curves (SWCCs) of the matric suction and total suction shifted to the lower left side, with the air entry value and water holding capacity both declining. The osmotic suction decreased gradually with the increase of water content, but the osmotic suction at different freeze-thaw cycles did not vary significantly. Finally, the fitting models used in the paper are of high correlation coefficients and simple forms, and the parameters of the models tend to be stable as the number of freeze-thaw cycles increases.