Determination of the Mode I Fracture Toughness and Tensile Strength of Compacted Clays

ABSTRACT: An understanding of tensile properties of geomaterials is important to control the formation and propagation of tensile cracks in geotechnical structures. Tensile strength σt and fracture toughness KIc are two parameters used to define the ability of resisting fracture under tensile stresses (mode I). In this study, KIc and σt of two clays were measured by straight notched disk bending (SNDB) method and uniaxial direct tensile test respectively. For Calgary till, KIc of specimens with same dry density increases with decreasing moisture content within the test range; for Regina clay, of which the samples were compacted with consistent compaction energy, the values show a peak when moisture content goes down. The changing trends of σt are very similar with KIc, hence there is a strong positive correlation between tensile strength and fracture toughness.