膨胀土损伤增量规律试验研究

Experimental investigation on the damage variance change of expansive soil

进行了原状膨胀土浸水及不浸水的三轴剪切试验过程的CT扫描。提出了密度损伤增量、空隙损伤增量和总损伤增量的概念。发现在剪切过程中随着轴向位移的增大,对于干土样,密度损伤增量开始缓慢地增大,当达到峰值强度后,密度损伤增量开始迅速减小;孔隙体积在一直增大,裂隙在不断扩展;膨胀土的总损伤增量随着剪切位移的增大开始有微小的增量,但是峰值强度过后,开始大幅度的减小,说明开始时,密度损伤增量占优势,且试样被压密,后来孔隙的发展占优势,直接导致膨胀土的破坏。对于湿样,密度损伤增量随加水量的增大呈先增加后减少的变化,空隙损伤增量随加水量的增加而增加,总损伤增量随加水量的增加呈先增加后减少变化趋势,说明后期膨胀占优势,最终导致试样的破坏。

Triaxial compress shear test on original expansive soil and another test on the soil immersed by distilled water are finished , and in the process of which, the CT scanning the two specimens is being carried out at the same time. Basing on the data of the CT scanning, density damage increment, pore damage increment and total damage increment are defined. For original expansive soil specimen, with the development of shearing, at beginning, the density damage increment continuously increases slowly, and when the stress is over peak strength, it does in the exact opposite direction. Pore volume enlarges continuously, the cracks swells, total damage increment develops like density damage increment does, which shows that at first, the density dominates the deformation of the specimen, and then the void dominates the deformation, at last, the void swells greatly, the specimen is destroyed. For the soil specimen immersed by distilled water, the density damage increment increases with the increasing of water quantity, and then decreases, pore damage increment increases with the increasing of water quantity continuously, total damage increment develops just like density damage increment does, so the specimen is destroyed.