Occurrence of Extensile Cracks in Cohesive Soils due to Compression

Abstract

ABSTRACT It is a generally accepted fact that tensile failure takes precedence over shear failure when a material is transformed from a ductile state into a brittle one. In order to evaluate the growth of extensile cracks, two series of compression tests with samples from volcanic cohesive soil obtained from a low fill dam were performed. Results show that extensile cracks may generate prior to shear failure when the friction between the specimen and the pedestal was reduced. Under such circumstances, compressive strength does not decrease until the shearing cracks are generated. This is the same in the case when a confining pressure is acting. In a test using a composite specimen made of two samples of different water contents, extensile cracks occurred at the portion with a low water content. The compressive stress at the time when the extensile crack occurred was lower than that in the case of the low water content specimen. Moreover, finite element analysis was performed to calculate the stresses in the specimens at the generation of extensile crack. Results shows that the horizontal stresses that exerted on the crack surfaces were not tensile but compressive in the case when a confining pressure was acting.