Determination of J-integral for clay during desiccation

Fracture behaviour of clay during desiccation is an important area in soil mechanics that needs further development. The current approach is to use linear elastic fracture mechanics involving parameters such as fracture toughness, measured from load tests for analysis and modelling of crack propagation. However, the importance of taking crack tip plasticity of the material into consideration has been highlighted by several researchers. This may be especially true for soft and/or slurry clay. The recently developed double ring test is the only desiccation test available today that enables determination of the elastoplastic fracture mechanic parameter J-integral. This parameter accounts for the change in potential energy with fracture propagation. Currently, there are no data for J-integral in the literature as applicable to desiccation cracking. This paper fills this gap by presenting a set of J-integral data for Churchill clay and kaolin clay measured from the double ring test. J-integral values have been calculated for both slurry and compacted clay using corresponding coefficients of linear shrinkage. The challenging task of calculating strains and stresses has been dealt with by using image analysis. In addition, the path independence for J-integral calculation and the behaviour of J-integral with the moisture content are also discussed.