Increasing-amplitude fatigue loading experiments to exam the effects of
dynamic frequency on rock bridge fracturing revealed by acoustic
emission and CT techniques
Abstract
Real-time acoustic emission (AE) monitoring combined with post-test 3D
computed tomography (CT) technique was employed to reveal the rock
bridge fracturing behaviors of pre-flawed granite. Results show that the
structural deterioration of rock bridge is strongly influenced by
dynamic loading frequency. The strength, deformation, and fatigue
lifetime of the pre-flawed granites are impacted by loading frequency.
AE activities in the form of counts and energy increase with increasing
loading frequency. In addition, AE spectral frequency analysis reveals
six kinds of crack type, and the proportion of high frequency-high
amplitude signal decreases, indicating that large-scaled cracks are
prone to forming under high dynamic frequency. Moreover, post-test CT
scanning visualizes fracturing pattern of rock bridge, a most striking
finding is that complex crack network forms under high loading
frequency. It is suggested that flaws are easy to be communicated for
rock that subjected to low dynamic loading frequency conditions.