Patterns of cracking in soils due to drying and wetting cycles

Abstract

There is a well reported evidence of cracking in clayey or silty soils when drying. Shrinkage in the soil mass and also boundary conditions generate a nonhomogeneous stress state locally producing tensile stresses and eventually cracking. This process has been analysed in detail by several authors. However, the evolution of such cracks due to further relative humidity changes (i.e. wetting and drying again) has been rarely considered in the reported experiments. This paper describes a particular type of experiments developed in an environmental chamber with a cylindrical soil specimen 80 cm in diameter and 10 cm in height, of Barcelona silty clay. Relative humidity was imposed in the chamber by controlling the flows of dry and wet air applied, whereas the main soil and chamber variables were recorded (temperature, suction, water content). A cycle of desiccation, wetting and further desiccation was considered and the paper describes the evolution of the cracking pattern during this process. It is shown that the pattern of cracks changes dramatically when cycles of relative humidity are imposed. In particular, soil cracking increases when soil is wetted after a dry period. An explanation of this behaviour based on Unsaturated Soil Mechanics concepts is also presented in the paper.