To predict the long-term strength of granite, fatigue and creep tests were conducted under uniaxial compression. Fatigue and creep properties of granite were investigated and compared . The results showed that the strength properties are different for fatigue and creep. For lower applied stresses , the time to failure in the fatigue becomes shorter than that in the creep. This indicates that it is important to evaluate both the fatigue and creep strengths for the prediction of long-term strength of granite . The behaviour of dilatant strain in fatigue is similar to that in creep. The volume of dilatant strain , giving an indication of the degree of damage in rock, is larger in the fatigue than in the creep at lower stress levels. This implies that the damage in rock is influenced strongly under cyclic loading than under constant stress.Effect of stress amplitude on fatigue failure time was investigated and the mechanism of fatigue failure was discussed based on the Costin's model. It is concluded that fatigue failure can be explained by the two mechanism .One is stress corrosion cracking ruled by the mean stress level and the other is fatigue cracking influenced by the stress amplitude. The relative contribution of the latter becomes more when maximum stress is small and/or stress amplitude is large.
Cyclic loading tests on Inada Granite were carried out under 0,5 and 25 MPa of confining pressure to examine the next two effects: the effect of confining pressure on the characteristics of strength and deformation; and the effect of stress amplitude on fatigue life. The main results are as follows. 1) The fatigue strength rises as the confining pressure is increased. However, the rate of the increase of the fatigue life Nf to the decrease of the maximum differential stress 0-Dmax is almost identical despite of the different level of confining pressure. A same curve can represent the relationship between up,-D0-max(difference between static strength UDC and UDmax) and log Nf under the two levels of confining pressure (5, 25 MPa). That is, this curve can be used to predict the fatigue strength from the static strength. 2) Three stages, namely. transient, steady and tertiary stage, are observed in fatigue deformation. Under the 25 MPa of confining pressure, the transient stage is shorter and the steady stage is relatively longer. As the confining pressure is increased, dilatant strain is restrained and the rate of the increase of volumatric strain per one cycle decreases. 3) When the maximum differential stress is fixed at a constant value, the fatigue life increases as the stress amplitude decreases. This tendency becomes more evident as the value of the maximum differential stress becomes lower. 4) When the maximum differential stress in fatigue tests and creep tests are the same, time to failure in fatigue is shorter than that in creep in the range of the maximum differential stress lower than a certain point.
scite is a Brooklyn-based startup that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.