Fracture toughness of compacted cohesive soils using ring test

Testing procedures and methd off of analysis for determining the fracture toughness of soils using the ring test are described and values of fracture toughness measured for 132 compacted specimens of two cohesive soils are presented. The critical mode I stress-intensity factor, the critical J integral, and the tensile strength can be determined simultaneously from a single ring-test specimen. The critical J integral was approximately equal to the energy-release rate computed from the critical mode [ stress-intensity factor measured for the same specimen. A strong correlation between fracture toughness and ring-specimen tensile strength was found. Effects of material type, water content, soil-placement conditions, rate of loading, and specimen size have been studied, and values of fracture toughness measured by bending tests are compared to ring-test results. Test results show that fracture toughness of cohesive soils is affected significantly by material type and water content at time of fracture. In contrast, effects of material-placement conditions, molding water content, and molding compactive effort are relatively unimportant.