Behaviors and mechanisms of desiccation cracking of soils

The desiccation cracking of soils is a common natural phenomenon. The presence of cracks in soils can significantly destroy integrity of the soil mass and weaken their engineering properties. In this investigation, laboratory desiccation tests are conducted. It is found that the desiccation cracking process takes place at three typical stages and presents evident time-order characteristics. New cracks always start perpendicularly from the existing cracks. Based on the fundamental principles of water-soil interaction and soil mechanics, the mechanisms of desiccation cracking are discussed. A series of conceptual models are established to provide insights behind the laboratory and field observations. The following conclusions can be drawn: (1) The space for soil shrinkage deformation is the basis of cracking that is conditioned by soil nature. (2) The desiccation cracking is one form of tensile failures. Surface tension of pore water and drying-induced metric suction (capillary force) can lead to the development of tensile stress field in soils, which is the main mechanical cause of cracking. (3) Cracking occurs once the drying-induced tensile stress exceeds the tensile strength of soil, or the connection strength between soil particles. After that, the gathered local strain energy releases and the stress field tends to readjust. From macroscopic scale, the matric suction and tensile strength of soils are the two key mechanical parameters controlling the desiccation cracking behaviors, while from microscopic scale, the geometric and morphologic characteristics of crack pattern are strongly linked to the homogenous and microstructure features of soils. Generally, most of the cracks initiate when the soils are still fully saturated. The corresponding critical water content at onset of cracking is likely higher than the liquid limit. The flaws on soil surface can result in stress concentration and trigger the initiation of cracks. (4) The surface curling like “pancake effect” may occur during drying. The combined effects of tensile stress field in soil surface and crack face are responsible for this phenomenon. Moreover, the