Low Amplitude Fatigue Performance of Sandstone, Marble, and Granite
under High Static Stress
Abstract
Fatigue tests under high static pre-stress loads can provide meaningful
results to better understand the time-dependent failure characteristics
of rock and rock-like materials. However, fatigue tests under high
static pre-stress loads are rarely reported in precious literatures. In
this study, the rock specimens were loaded with a high static pre-stress
representing 70% and 80% of the UCS, and cyclic fatigue loads with a
low amplitude (i.e., 5%, 7.5% and 10% of the UCS) were applied. The
results demonstrate that the fatigue life decreased as the static
pre-stress level or amplitude of fatigue loads increased for all rock
types, and the high static pre-stress affected the fatigue life greatly
when the static pre-stress was larger than the damage stress of rocks in
uniaxial compression test. The accumulative fatigue damage exhibited
three stages during the fatigue failure process: crack initiation,
uniform velocity, and acceleration, and so the fatigue modulus showed an
“S-type” change trend. The lateral strain and volumetric strain had a
much higher sensitivity to the cyclic loading and could be used to
predict fatigue failure characteristics, and it was found that
volumetric strain “ε” _“v” = 0 is a threshold for microcracks
coalescence and is an important value for estimating the fatigue life.