A new methodology for block identification and its application in a large scale underground cavern complex

The occurrence of geologic planes is a major feature of rock mass. In underground excavation, the intersection of geologic planes and excavation surfaces generates blocks. A new methodology for block identification is presented. This methodology employs finite element (FE) modeling technique to identify blocks so it is different from the traditional topology-based block identification algorithms. As complex spatial excavation surfaces are precisely simulated by FE model, this methodology can identify blocks considering complex profile and layout of underground caverns. By considering the finiteness of geologic planes, convex and concave blocks can be both identified. As is defined on FE model, the identified block system can be visualized directly by employing FE graphic system. As a result, there is no need to specially develop graphic system for block visualization. A case study is done on a large scale hydropower underground cavern complex. The block identification results prove the effectiveness of the proposed methodology. The results are further compared with the observation data derived from in situ investigation. The comparison indicates that the proposed block identification methodology is reliable. Therefore, it provides a new approach for block analysis.