a. Graduate School of Engineering, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan
b. National institute or Resources and Environment. Tsukuba, Ibaraki 305-8569, Japan

In the present study we have experimentally investigated DRA Method (Deformation Rate Analysis Method) to understand the effect of confining pressure and stress level on the estimation of previous stress. In addition, the DRA and AE Methods were applied on the estimation of the in-situ stress from the rock cores that were obtained from Ikeshima Colliery. The following main results were obtained.
(1) The previous stress can be obtained by the objective criterion that is settled for reading the laboratory data
(2) The confining pressure did not have any significant influence on the stress estimation in DRA Method.
(3) DRA using the strain data in the test under a confining pressure enabled us to accurately estimate the axial stress that was previously applied under a confining pressure, even if the previous stress was very close to the uniaxial compressive strength.
(4) DRA and AE Method that are carried out at a laboratory can be applied on the in-situ stress measurement method.