非饱和土降雨诱发塌陷成因探讨

有些土体塌陷由降雨诱发，特别是久旱无雨后突降暴雨，有时会导致岩溶塌陷成群出现。同样，在干旱季节农田灌溉也会导致塌陷大量出现，可见塌陷的产生与土壤的干湿状态密切相关。自然土层接近地表部位为非饱和的包气带，以下才是饱水带，大气降雨及农田灌溉水入渗地下要有一个由非饱和带向饱水带运动的过程。由于土体为固气液和收缩膜四相体系，在地表水入渗地下的过程中，入渗的水峰会对土体结构中的气体产生驱动作用，对固体骨架也会产生动力作用。本文采用非饱和土力学的基本原理，对于非饱和土中吸力和水压传递机理以及降雨诱发塌陷进行了分析，并按提出的成因机制对暴雨诱发塌陷实例进行了分析。

THE GROUNDWATER PRESSURE TRANSFERENCE IN UNSATURATED SOIL AND GENESIS OF KARST COLLAPSE

Collapses in soil may be induced by heavy rainfall and appear in large numbers, especially after a long time's drought. Similarly, they also can be induced by irrigation in drought seasons. So it can be inferred that the appearance of collapses in soil is connected with the moisture content of soil closely. Soil is made up of three zones:the aerated zone, capillary zone and saturated zone. The rainwater supplying the aquifer must run through the unsaturated zone to reach the saturated one. The infiltration water drives the movements of solid,liquid and air of soil. When the soil is far from saturated, the cracks in the soil will be open and their suction force reaches the maximum value. When the rainwater is attracted by unsaturated soil and the soil gets saturated, the linkup of soil grains goes down, which leads to the decrease of ability to resist corrosion and collapse in soil. The transference of hydraulic pressure in unsaturated soil and the formation of collapses in soil induced by rainfall are discussed in detail in the paper.