ABSTRACT
Fatigue life prediction of limestone is the basis of long-term stability analysis of surrounding rock in karst tunnel under train cycle loading. Through the low cycle fatigue tests of karst limestone under different upper limit stress, stress amplitude, loading frequency and saturated condition, the basic fatigue characteristics of the limestone are experimented. The fatigue test results show that the fatigue life of rock will be significantly reduced after saturation and increases linearly with the decrease of upper limit stress. There is also a fatigue threshold for the limestone and the fatigue threshold value increases with the loading rate increasing. The stress amplitude plays a key role in the fatigue life of the limestone. The fatigue life of the limestone increases with the loading frequency increasing. The linear relationship between the fatigue life and loading frequency satisfies the double logarithmic coordinate. By introducing a correction coefficient, a fatigue life evaluation model based on load frequency and stress level is established.
