Synthesis of the Shallow Borehole Investigations at the MIU Construction Site

Kumazaki, Naoki; Koki, Ikeda; Goto, Junichi; Mukai, Kei; Iwatsuki, Teruki  ; Furue, Ryoji

The Shallow Borehole Investigations were one of the first programmes to be conducted at the MIU Construction Site, together with the reflection seismic survey and the re-investigation of borehole DH-2. The Shallow Borehole Investigation targeted the shallow part of the site, from the sedimentary cover rocks to the upper part of the granite. The main aims are understanding of initial groundwater flow and the groundwater chemistry, long term monitoring and to identify structural discontinuities in the sedimentary rocks and the weathered granite. From April to October 2002 four boreholes were drilled through the sedimentary sequence and the weathered granite section at the MIU Construction Site. Planned geological, hydrogeological and hydrochemical investigations were carried out. MP systems were installed in all boreholes by December 2002 and continuous monitoring of hydraulic head begun. Information on geology, hydrogeology and hydrochemistry of the sedimentary formation and the weathered granite was acquired. JNC's quality control procedures for borehole investigation programmes were employed. In addition, recommendations for future borehole investigation programmes, especially in sedimentary rocks, were given.