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| Experimental research of cracking process of expansive soil under rainfall infiltration and evaporation |
| CAO Ling1，2，WANG Zhijian2，ZHANG Zhenhua2 |
| (1. Department of Civil Engineering，Shanghai Jiaotong University，Shanghai 200240，China；2. Collaborative Innovation Center for Geo-hazards and Eco-environment in Three Gorges Area，China Three Gorges University，Yichang，Hubei 443002，China) |
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Abstract To better understand the cracking process of expansive soil，rainfall-evaporation tests in laboratory were conducted to expansive soil. The specimen was weighed and photographed regularly during the test process in order to record the development of cracks. The image processing technique was employed to quantitatively extract the parameters of crack features，such as the crack ratio. In addition，the method of wax filling was used to observe the ultimate shape and measure the volume of cracks. It was found that the cracking process consisted of phases of slow→rapid→slow growth. 80%–90% of cracks appeared in the 2nd phase. The cracks appeared when the matric suction approached to the air-entry pressure and the development almost stopped when the water content was close to the shrinkage limit. During the drying-wetting cycles，the new cracks did not always grow along the old tracks. In the drying-wetting cycle，the cracks of expansive soil developed gradually，the crack ratio and the total number of cracks were increased. The development of cracks ceased when it reached a certain stage. The iterative presence and healing of cracks significantly weakened the soil structure that resulted in the reduction of tensile energy. The volume of the cracks is 167.8 cm3 and about 4.8% of the total volume of the sample.
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2016, Vol. 35 
