Investigation of soil desiccation cracking using an environmental chamber

Soil desiccation cracking due to loss of water is a common natural phenomenon, and can significantly affect the soil performance in various geotechnical, geological and environmental engineering applications. In this investigation, a large-scale environmental chamber (1 m × 0.8 m × 1.5 m) was developed for carrying out physical model desiccation tests. This chamber was instrumented by various sensors allowing the soil volumetric water content and suction to be monitored at various depths. The air temperature and relative humidity at the inlet, in the chamber and at the outlet can also be monitored. The development of cracks on soil surface was monitored by a camera which was fixed above the chamber. The soil column was subjected to a 30-day drying under controlled air conditions. The results show that the average actual evaporation rate of soil column is constant at the initial stage of drying and then tends to decrease with decreasing water content. Cracks initiate at very high water content (about 60 %) when the soil is still saturated and the corresponding evaporation rate is constant. By image processing, the evolution of geometrical and morphological parameters of the crack networks was quantitatively analysed. It is found that the crack parameters reach stabilization at different water contents during drying. The number of clods, nodes and crack segments reach stabilization earlier than the average crack length and crack density. The evolution characteristics of surface crack ratio and average crack width are highly consistent, and in addition, they are the last to reach stabilization. The results indicate that the developed environmental chamber constitutes an effective tool for studying the desiccation cracking behaviour of soil in large scale, and provides useful data for the investigation of soil-atmosphere interactions content.