An effective stress constitutive framework for the prediction of desiccation crack in lime-treated soil: Experimental characterization and constitutive prediction

The present work investigates the desiccation effects on a lime-treated silty clay. Original experimental techniques have been developed to control suction conditions (with osmotic technique), to track volume variations and cracks occurrence upon drying. Free and constrained desiccations are performed to evaluate the shrinkage potential (for free drying) and the conditions of desiccation crack triggering (upon constrained drying). Also, indirect tensile tests and uniaxial compression tests are carried out to evaluate the strength and stiffness at various suctions. Those investigations have been performed on natural and lime-treated compacted silty clay in order to emphasize the benefits of the lime treatment in the triggering and/or mitigation of the cracking process. To simulate the field conditions of compaction and obtain specimens having geomechanical properties as close as possible of the real material on site, the particular kneading compaction process in a CBR mould was used, and the final specimens were cut at required sizes with a milling machine numerically controlled by computer (CNC). At the end, generalized effective stress framework with an effective stress parameter χ calibrated according to a power law is used to provide a constitutive interpretation of the occurrence of desiccation cracks in relation with the water retention properties, the soil stiffness, the tensile strength and the geometrical constraints of the soil specimens. It is observed that the cracks initiate under positive (compressive) effective stress. For the used compacted materials, it is demonstrated that the lime treatment postpones the occurrence of desiccation cracks, that are triggered at higher suctions. So, lime treatment plays a favourable role in the reduction of shrinkage and crack occurrence of soft soils subject to drying.