地下水扰动作用下地基土体渗透破坏试验研究

Seepage Failure Test of Foundation Soil Under Ground Water Perturbation

为分析近年来中国西南地区频繁发生的"天坑"形成原因,从渗流破坏理论出发,通过自主设计循环变水压渗透试验装置模拟地下水扰动过程,研究了地下水扰动作用下地基土体的变形破坏机制。首先通过现场和室内试验获得土样的基本物理化学性质,排除由碳酸盐溶洞导致地表塌陷的可能性。在此基础上,为模拟地下水循环扰动对土体的渗透破坏作用,采用饱和土渗流理论,设计了1种变压型常水头渗透试验装置,通过自动循环地改变水头大小模拟地下水扰动对土体的破坏机制,分析实验前后土样级配组成、水头变化和土样变形破坏特性,试验表明土样在地下水扰动作用下细颗粒明显减少,土体级配结构发生改变,土体承载力降低并最终导致土体塌陷。变压型常水头渗透破坏试验研究表明,该方法较好地阐明了该地区"天坑"形成机制。

In order to find out the reason of many ＂tiankeng＂ in southwest of china in recent years, based on seepage damage theory, the theory of saturated soil seepage and changed water head equipment were used to simulate the change process of water head in geologic norm, considering the influence of vacuum erosion as well. At first, physical property and chemical composition of soil samples were got by in-situ test and laboratory test before destroy test, and the result shows that the surface subsidence is not caused by carbonate karst cave. Then changed water head equipment was designed to simulate the change process of water head automatically. The gradation, water head and sample deformation characteristic of soil before the destroy experiment were compared with those after the destroy experiment. It is show that soil sample chemical property changes little, but little soil particles reduce significantly. With the change of gradation and structure of soil, the bearing capacity decreases and eventually it leads to the soil mass collapse. The changed water head test clarifies the reason and mechanism of ＂tiankeng＂ phenomenon reasonably.