Study Of The Cracking And Infiltration Characteristic Of Expansive Soil Under Wetting-drying Cycles

Expansive soil is rich in clay(< 2 microns) and strong hydrophilic clay minerals, which is low-permeability in the case of dense and low permeability. While in the practical engineering, expansive soil will cause a large number of cracks under the action of wetting-drying cycles of atmospheric. Crisscros cracks make its permeability increasing greatly. Rainfall penetration often causes crowds of collapsing on the cutting slope. In order to make out the special engineering properties of expansive soils, the article takes expansive soils in the outer of Nanning as the main research subject, and simulates atmospheric effects indoor for conducting experiments, and explores the expansive soil’s cracks rule and penetrating quality which is of different densities under wetting-drying cycles.First of all, the article compares quantitative description of the existing cracks with the collection method, and determines to leave surface crack rate as index to describe cracks quantitative. Next, the article captures the sample surface crack by using the digital camera, and the internal cracks of sample by ICT. The entire experimental research project is designed by simulating the actual atmosphere as much as possible.The article gets permeability change rule and fracture laws of both inside and outside the sample under wetting-drying cycles by completing a series of trials in strict accordance with existing plan. It shows that SD value which was obtained by ICT can characterize the situation of fracture better. There is a close relationship between fracture crack&permeability change and the initial density of sample under wetting-drying cycles. When density increases, the crack and saturated infiltration coefficient decreases. The result shows that surface crack and saturated infiltration coefficient are in good logarithmic relationship. There is a peak value in the absolute growth rate of saturated infiltration coefficient as the change dry density. The smaller absolute growth rate is, the more important dry density is when filling-construvtion of expansive soil.To verify whether the testing result has universal relevance, we further the program by having carried out two more comparative experiments with expansive soil from Baise area in Guangxi province and Fengtai Area in Beijing respectively. And the two results turn out to be in accordance with the conclusion in my essay.Finally, the article analyzes the incidence from density of expansive soil and soil mechanical parameters to crack and absolute growth rate by using gray correlation theory. As well as, the article discusses the reasons about the change of cracks and permeability coefficient under wetting-drying cycles.