Leelasukseree, Cheowchan (Chiang Mai University) | Pipatpongsa, Thirapong (Tokyo Institute of Technology) | Khosravi, Mohammad Hossein (Tokyo Institute of Technology) | Mavong, Narongsak (Tokyo Institute of Technology)
ABSTRACT The object of this study is to investigate the unloading failure mechanism of hard rocks in the unloading process. A commercial finite element program LS-DYNA was employed to simulate the rock unloading process. The implicit and explicit methods were performed in sequence to simulate the static initialization-dynamic unloading process of rocks. The numerical results indicated that the rock failure can be induced by releasing of the initial stress, and the previous result of the equivalent initial stress release rate (EISRR) theory based on the 1D stress state is not suitable for 3D stress state. In 3D stress state, a new definition of equivalent strain energy release rate (ESERR) was introduced. The further study indicated that the ESERR can characterize the effect of different confining stresses and different unloading path on rock unloading. A significant finding is that the ESERR can quantitatively describe the characteristics of the unloading process under 3D stress state. This finding indicated that in practical underground excavation engineering, dynamically controlling the ESERR can be used to increase excavation potential of rocks and minimize the needed external excavation energy by using the initial energy.’
Since the establishment of the International Society for Rock Mechanics (ISRM) in the 1960s, there have been important scientific developments and technological advances both in rock mechanics and rock engineering. Particularly, modeling of rock behaviour, design methodologies for rock structures and rock testing methods are the main issues in these developments and advances. The models developed depend considerably on the input parameters such as boundary conditions and material and rock mass properties. For this reason, establishing how to obtain these input parameters for a particular site, rock mass and project is important. Accordingly, since 1974, the ISRM Commission on Testing Methods has spent considerable effort in developing a succession of Suggested Methods (SMs) for different aspects of rock mechanics with the contribution of a number of working groups. The SMs are intended as guidance, explaining the recommended procedures to follow in the works associated with the various aspects of rock mechanics, such as rock characterisation, testing and monitoring. In this paper; the past, present and future of laboratory and in-situ rock testing and monitoring techniques and then the general principles followed in developing the ISRM SMs, stages in their evaluation and the recent developments related to the SMs are briefly given.
Mun, Hee-Sook (Chonnam National University) | Yang, Hyung-Sik (Chonnam National University) | Kim, Bo-Hyun (Itasca) | Kim, Won-Beom (Drilling Services International, INC.) | Kim, Jong-Gwan (Chonnam National University) | Kim, Jung-Gyu (Chonnam National University) | Kim, Seung-Jun (Chonnam National University)