STUDY ON DESICCATION CRACKING BEHAVIOUR OF EXPANSIVE SOIL

Upon drying, the evaporation of soil water results in volumetric shrinkage and desiccation cracks on expansive soils. The presence of crack can significantly weaken the engineering properties of soil, and cause various problems in geological, geotechnical, hydraulic, environmental engineering fields. With the increasing frequency of severe drought climate, the engineering problems that induced by desiccation cracking can be more and more, worse and worse. The study of desiccation cracking is therefore very significant for revealing the intrinsic mechanisms behind this common natural phenomenon, and plays an important role in engineering practice in clayey soil areas and especially in expansive soil areas. Generally, the initiation and propagation of desiccation cracks show evident dynamic characteristics and significantly depend on soil water evaporation rate, stress state and shrinkage property. The cracks initiate at constant evaporation rate stage. Soil suction and tensile strength are the two key mechanical parameters that control the cracking behavior. Cracking is likely to occur if the tensile stress which is induced by soil suction reaches the tensile strength of soil. Intrinsically, cracking is the result of pore shrinkage. It is believed that the mechanical effect and shrinkage potential are the two necessary factors for crack initiation. It is found that the desiccation cracking behaviour is affected by many factors including soil materials, mechanical properties, structures, test conditions, and test methods. Quantitative characterization of crack patterns is required for desiccation cracking investigation, and plays very important role in understanding the cracking mechanism and constructing the relevant model. Image processing is a powerful, efficient and high-accurate tool for quantitative description crack patterns. In the next stage, more attention should be paid to the dynamic characteristics of cracking, and more work should be done on water-soil interaction, mechanical mechanism, shrinkage mechanism, large scale field test and 3D quantification technique that related to soil desiccation cracking. It is also important to study desiccation cracking behaviour on the basis of soil materials, mechanics and structures, to integrate macro-observation with micro-analysis and to construct perfect theory for characterizing desiccation cracking.