降雨条件下含大孔隙土柱水-气两相流试验

为揭示降雨条件下含大孔隙土中水—气两相流运移机制，基于室内人工降雨试验，通过自行设计试验装置并借助各类试验设备，对不同工况下大孔隙和基质域的含水率、孔隙水压力、孔隙气压力分别进行实时监测.结果表明：大孔隙的存在可明显加快水分入渗速率，使土柱湿润锋呈现漏斗状，大孔隙附近水分入渗速率明显较快(即产生优先流),但是降雨需持续一定时间才会产生优先流；模型箱底部边界开通有利于气体的排出，可降低孔隙气压力，从而更有利于水分的入渗；大孔隙存在情况下，增加降雨强度可加快优先流的产生，使水分更快地沿着大孔隙入渗至土壤深层，并沿着大孔隙壁向周围基质扩散.此外当降雨强度大于水分入渗速度时，会在土体表面形成积水，一定程度上增加孔隙气压力.

Experiment on water-air two-phase flow in soil column with macropores under rainfall condition

In order to reveal the migration mechanism of water air two-phase flow in soil with macropores under rainfall conditions, based on the indoor artificial rainfall experiment, the water content, pore water pressure and pore air pressure of macropores and matrix under different working conditions were monitored in real time by self-designed test device and various test equipment. The results show that: 1) The existence of macropores can significantly accelerate the water infiltration rate, making the wetting front of soil column funnel-shaped. The water infiltration rate near macropores is significantly faster (i.e. preferential flow), but it takes a certain period of rainfall to produce preferential flow; 2) The opening of the bottom boundary of the model box is conducive to the discharge of gas and the reduction of pore gas pressure, which is more conducive to the infiltration of water; 3) In the case of macropores, increasing rainfall intensity can accelerate the generation of preferential flow, make water infiltrate into the deep soil along the macropores faster, and diffuse to the surrounding matrix along the macropore wall. In addition, when the rainfall intensity is greater than the water infiltration rate, water will form on the soil surface, which will increase the pore gas pressure to a certain extent. The results lay a foundation for further study of water-air two-phase flow in macroporous soil.