The mechanical behavior of additional hard rock types under cyclic uniaxial compression and tension was studied, and a program of cyclic triaxial compression testing was initiated. All rocks (granite, sandstone, limestone, marble) exhibited cyclic fatigue characteristics in both tension and compression with fatigue strengths of 55-70% within 100,000 - 1,000,000 cycles. Prefailed granite exhibited substantial fatigue endurance. An inter-relationship between compression fatigue and the complete stress-strain curve has been demonstrated. For the same maximum stress cyclic stress amplitudes appear to affect fatigue life. In particular, indications are that compression-tension cyclic loading could be most damaging.
