FRACTURE-TOUGHNESS OF COMPACTED COHESIVE SOILS USING RING TEST

Testing procedures and methods of analysis for determining the fractur e toughness of soils using the ring test are described and values of f racture 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 simul taneously from a single ring-test specimen. The critical J integral wa s approximately equal to the energy-release rate computed from the cri tical mode I stress-intensity factor measured for the same specimen. A strong correlation between fracture toughness and ring-specimen tensi le strength was found. Effects of material type, water content, soil-p lacement conditions, rate of loading, and specimen size have been stud ied, and values of fracture toughness measured by bending tests are co mpared to ring-test results. Test results show that fracture toughness of cohesive soils is affected significantly by material type and wate r content at time of fracture. In contrast, effects of material-placem ent conditions, molding water content, and molding compactive effort a re relatively un important.