土壤中空气对土结构和入渗过程的影响

Experimental study of the air entrapment effects on soil structure and infiltration

分析了土壤表面积水入渗过程中压缩气体对土体结构的影响理论,并通过二维土柱入渗试验对其进行了分析及验证。在积水深度为2.8 cm的条件下,对2个初始含水量、3个孔隙率下的土柱进行了试验,测量出其在试验过程中的气体压力和入渗量,并同时观察土体结构的变化。理论和试验结果表明,气体出现突破之前,土壤内气体压缩产生的气压对湿润区土体的顶托作用会破坏土体的平衡,从而在湿润锋处产生水平裂缝,破坏入渗土体的连续性。试验还发现,入渗过程中土体结构变化大小受土壤初始结构和含水率的影响,初始结构越牢固、含水量越大,结构和气压变化越小,根据结构变化不同,可以划分出两种不同的试验过程。同时入渗土体内出现裂缝时,气压的减渗作用尤为显著,甚至会导致试验过程的停止。

The theoretical analysis and experiments are conducted to study the effects of the entrapped air on the soil structure and infiltration. We apply the 2.8 cm ponding depth at the soil surface to two the antecedent water contents and three porosities soil columns and measure the air pressure ahead of the wet front, the cumulative infiltration, and the change of soil structure. The theoretical and experimental results indicate that the air pressure can lift the saturated layer of soil near the surface to cause an upward disruption in the soil column in the wet front before the air pressure head reaches the air-breaking value. The disruption makes the bottom layer discontinuous with the top layer. The data from the infiltration experiments generally indicate that the structure changes of the infiltration soil are affected by the antecedent structure and water contents. For the consolidated and high water content materials, the change of the structure and air pressure is smaller, vice versa. In addition, the disruption lifts the soil in the surface and, in some cases, stops infiltration.