Scale Effect on Closure of a Tensile Fracture under Normal Stress

Abstract

Tensile fractures with various sizes of from 37.5 mm to 260 mm were created in a sandstone block perpendicular to the bedding plane by indenting wedges, and scale effect on the closure of the fracture under normal stress was investigate. The surface topography of the fractures was measured to determine the initial aperture distribution, which showed that the standard deviation (SD) of the initial aperture increases with fracture size. The closure of the fracture was measured in cyclic loading for normal stresses up to 10 MPa. The experimental results have shown that the closure of the fracture significantly increases with an increase in fracture size. However, the closure curves become approximately identical by normalizing the closure by the SD of the initial aperture and are almost independent of fracture size. Thus, the scale effect on the closure of the fracture under normal stress is governed by that on the SD of the initial aperture.