Relation between fracture size and shear behavior of a single fracture in granite

This paper presents the results on the size effect of a tensile fracture in granite on the shear behavior determined by direct shear tests with a normal stress of 10MPa. Normal and shear stresseswere unloaded at designated shear displacements, and the change in the surface topographywas measured by using a non-contact surface profile measurement system with a laser profilometer, to determine the evolution of surface damage and aperture during shear. The standard deviation of the initial aperture of the sheared fracture significantly increases with both shear displacement and fracture size, resulting in an increase in the non-linearity of the closure curve with shear displacement. Furthermore, while the shear stiffness of the fracture in the initial stage decreases with fracture size, that in the residual stage increases with fracture size. In addition, itwas shown that the damage zones are enlarged and localized with shear displacement and tend to form perpendicular to the shear displacement.