Kaiser effect is a widely investigated laboratory testing method combining Acoustic Emission technology with uniaxial compressive test to determine the pre-stress of a rock. This paper provides a quantitatively discussions on the influences of anisotropy on the accuracy of pre-stress determination with different stress levels. The results show that rock anisotropy has insignificant influences on the accuracy of pre-stress determination. In addition, a rock with high stress state has low error for the pre-stress assessment. However, more studies are required to investigate the applicability of AE method to estimate the low pre-stress for the samples having different dip angles of schistosity.
Underground space has the characters of containing natural resources, insignificant influences affected by the ground surface, and high resistance of the movement of toxic materials etc. Thus, developments of transportation network, mining natural resources, and activity spaces are involved underground. Building underground structures at a great depth, for example: Hsuehshan Tunnel in Taiwan, remain a task full of challenge and accidents although underground excavation experiences have been obtained from shallow tunnel constructions, mining, and obtaining natural resources in the past centuries. The researches on investigating the environments, which include temperature, stress and groundwater, and the behavior of rock mass are essential to enhance the underground construction to a higher safety status in the future. Huang (2003) mentioned that the discontinuities significantly control the behavior of a shallow rock mass, but the deep one is governed by the direction and level in-situ stress. Martino and Chandler (2004) found that the spread of excavation damage zone (EDZ) is remarkably influences by the magnitude and orientation of in-situ stress, as well as, the direction of tunnel. Eberhardt et al. (1997), Myrvang (1993) and Pariseau et al. (1995) proposed that the in-situ stress will affect the stability, support design, and the shape of an underground excavated chamber. Thus, in-situ stress is an essential parameter for analyzing and design to ensure the safety of an underground structure.
