a. Graduate School of Mining and Engineering, Akita University, Gakuen-machi, Akita 010-8502, Japan
b. Faculty of Engineering and Resources, Akita University

In order to clarify the fatigue failure process of shirahama sandstone, fatigue tests were done, and deformation characteristics and AE occurrence behavior were investigated. Then, the strength of specimens, which loading and unloading were repeatedly applied to for some times, and crack development in them were examined.
In the fatigue test, fatigue failure occurs in the comparatively short time (about 3.5 days), when upper limit stress corresponds to the stress at stage C of uniaxial compression failure process, where the volume of the rock specimen expands. The fatigue failure process are divided into three stage (I, II, III) from change in strain and AE activity. Lowering the strength of the rock specimen begins from stage II of fatigue failure process, and it is in a good correlation with the increase in lateral / axial strain ratio. The value of b obtained from the relationship between AE event frequency and AE energy of each event decreases when macroscopic cracks develop in the specimen.