MBC model analysis for predicting the rock behavior in excavating the Mizunami Underground Research Laboratory

Mori, Takayuki*; Morikawa, Seiji*; Tabei, Kazuto*; Iwano, Keita*; Nakajima, Makoto*

As a first step of Mizunami Underground Research Laboratory Plan (MIU plan), through the laboratory and borehole in-situ tests, JNC Tono Geoscience Center plans to constitute the comprehensive geological model and predicts the rock behaviors in excavating the shaft and gallery. These model and results leads to be reflected by the next step research projects.So far, the first step of MIU plan is coming to final stage, and the second step will start at next year in which the in-situ researches are planned through the excavation. In this study, the comprehensive geometrical model was drawn out through the first step data, and MBC model analysis was carried out to predict the rock mass behavior around the shaft and gallery. The following results are obtained. (1) With MIZ-1 borehole core, artificial joints, which are assumed to be produced by rock blasting, were formed through the Brazilian test. And through the rock shear test for these joints, these mechanical properties were obtained. (2) By examining the MIZ-1 borehole research data, Mizunami site was classified by mechanical and joint properties and the Geomechanical model were made up. (3) Through the MBC model, the shaft and gallery cases were analyzed which depend on the rock mass classification, Excavation Damaged Zone, and the direction of the galleries. These results showed that in most cases, the joint opening were little because of the rock stiffness, but by the existence of high inclined joints, the side wall of the galleries were damaged by the excavation.