In Phase I, a variety of surface-based investigations have been carried out to obtain detailed information on the geological environment prior to the construction of research galleries at the MIU Construction Site. Surface-based investigations include geological investigations, geophysical surveying and surface hydrological investigations. Several shallow boreholes and a 1,300m long deep borehole have been drilled for core sampling, borehole geophysics, hydraulic and mechanical testing to obtain detailed information on the deep geological environment.

Based on the information obtained through these investigations, from knowledge of the local geological setting for Shobasama Site and for the more extensive area of the RHS(Regional Hydrogeological Study) Project, facility-scale models have been constructed to represent the current understanding of the geology, hydrogeology, hydrochemistry and rock mechanics. Furthermore, based on these models, the character of the geological environment have been predicted prior to the excavations.

Phase I goals

Construct models of the geological environment from all surface-based investigation results that describe the geological environment prior to excavation and predict the excavation response Formulate detailed design concepts and a construction plan for the underground facilities Establish detailed investigation plans for Phase II

The following investigations have been carried out at the MIU Construction Site or the surrounding area for surface-based investigations.

Geological mapping Ground geophysics such as seismic reflection/refraction Shallow borehole investigations Deep borehole investigations Cross hole tomography and hydraulic tests using the boreholes at and around the site Groundwater monitoring such as hydraulic pressure and hydrochemistry