Kaiser effect study on determining rock stress in triaxial loading

This paper introduces the experimental investigation on the Kaiser effect in sandstone, which was under different triaxial loading conditions, namely, the vertical stress greater than, equal to or less than the confining stress. The results show that both the vertical stress and the confining stress affect the Kaiser effect. When the previous applied vertical stress is given the stress determined in axial direction from the Kaiser effect take-off point decreases as the confining stress increases if the confining stress is less than the vertical stress. But if the confining stress is greater than the vertical stress the estimated stress increases with the increase of the confining stress. The estimated stress is more or less equal to the previous applied differential stress between the vertical stress and the confining stress if the vertical stress is greater than the confining stress.