Evaluation of J integral for clay soils using a new ring test

Fracture behaviour of clay soils is an important area in soil mechanics that needs further development. Currently, there is no test method to determine fracture properties of clay soils during desiccation. The past work has been mostly on the use of fracture toughness as applicable to linear elastic fracture mechanics using external loading of specimens. However, importance of considering likely plasticity in fracture propagation, especially with soft soils, has been highlighted. J integral is an important parameter in elasto-plastic fracture mechanics, which accounts for the change in potential energy with fracture propagation. This paper presents an innovative test method to evaluate the fracture behaviour, in particular to determine J integral, as applicable to desiccating soils. The challenging task of calculating strains and stresses of slurry clays has been dealt with using an image-analysis technique. Starting from the fundamentals of fracture mechanics, J integral is expressed as a summation of several line integrals. The major advantage of the new method is its suitability for wet or slurry soils for which load tests are impossible. Copyright © 2012 by ASTM International.