Feasibility study on construction of Horonobe URL

Shirato, Nobuaki; Ouchi, Kazutoshi; Yamazaki, Shinichi

The Horonobe underground Research Laboratory (URL) programme hosted by sedimentary rocks is aimed to obtain deep geological characteristics of sedimentary rock mass and to confirm the applicability of the investigation methods for the geological environment and the engineering technology for the geological disposal described in the H12 report. In addition, the URL is aimed to have public people experience a deep geological environment in order to understand a deep geological disposal of HLW. The objective of this report is to make the ground of the site selection of the Horonobe URL Based on the results obtained from two deep investigation boreholes drilled in the B1 and B2 district two kinds of geological model were constructed. For each geological model four types of preliminary layout were prepared for the feasibility study. The types of the URL were as follows: (i)two shafts (ii)three shafts (iii)spiral drift and one shaft (iv)spiral drift and two shafts. For the combination of the geological model and the layout tbe construction schedule and the construction cost were estimated through the study of the construction method with the auxiliary method, the construction procedure and the cycle time. The analysis of vibration and noise during construction was also estimated. The results of the feasibility study indicated that mechanical excavation was employed for the whole construction. The shafts were suggested to be constructed by the short step sinking method and the drifts and the spiral drifts by NATM. The mucking system should be rail haulage for the drift for the case of shafts(i) and (ii)), and road haulage for the drift for the case of spiral drifts(iii) and (iv)). The estimation of construction time was around seventy months for the case of shafts(i) and (ii)) and around ninety months for the case of spiral drifts(iii) and (iv)). This work was re-edited from the results performed by Taisei Corporation under contract with JNC; "Feasibility study on ...