积水入渗稳定时近饱和土中封闭气泡含量试验研究

Experimental study on entrapped air content in quasi-saturated soil subjected to steady ponded water infiltration

含有与大气不相连通的封闭气泡且饱和度接近100%的土体称为近饱和土体。通过室内土柱一维积水入渗模型试验,研究了入渗稳定时土壤类型、干密度和初始含水率对近饱和土体中封闭气泡的含量以及气相逸出率的影响,分析了3种影响因素对封闭气泡体积的影响趋势和影响机理。试验结果表明:土样孔隙中封闭气泡的体积随土样干密度的增大而减小;当土样初始含水率超过某一临界含水率时,土样孔隙中封闭气泡的逸出随初始含水率的增加显著减少;由于黏性土达到渗流稳定需要的时间较砂性土长,因而砂性土的气相逸出率要明显小于黏性土的气相逸出率。通过试验揭示了实际土体入渗中的一些物理现象,为更好地理解土壤入渗过程和建立数值模拟模型提供了试验数据。

The quasi-saturated soil is defined as a soil with entrapped air and saturation close to 100%. A series of one-dimensional ponded water infiltration tests are designed and conducted in laboratory. The influence factors of entrapped air content in the quasi-saturated soil, such as soil types, dry density and the initial water content, are studied. The influence mechanisms are analyzed and discussed. The results show that the volume of entrapped air decreases as dry density increase; the escape of entrapped air is more difficult when the initial water content increases above a critical water content; the escape ratio of entrapped air in sand is smaller than that in clay because of the relatively longer time to reach stable state of infiltration for the clay. Some physical phenomena in real soil infiltration are shown. The results provide test data for better understanding of soil infiltration process and numerical modelling.