This test series also reveal a linear transition from the Brazilian tensile
strength to the uniaxial compressive strength, which can be best demonstrated by
using Mohr’s circles, as shown in Figures 4.8 through 4.10.
Post-failure observations show that under low σz a single splitting
extension crack along the loading diameter is normally induced in the disk specimen.
Multiple extension cracks are developed as σz increase. When σz reaches the uniaxial
compressive strength of the rocks, the specimens fail without applying the diametral
line load. At this point the specimens are crushed, resulting in multiple shear
fractures and extension cracks (Figure 4.11)Introduction
The objectives of the laboratory experiments are to determine the effects of the
intermediate principal stress on the rock tensile strength and to measure of the elastic
parameters from the Brazilian tension test. This chapter describes the method and
results of the laboratory experiments. It is divided into two parts; Brazilian tension
tests under axial compression and measurements of elastic modulus and Poisson’s
ratio from the Brazilian test specimens.