The Results of the investigation on rock mechanics in HDB-38 boreholes and study about the rock mechanical model around the Horonobe URL construction area

Niunoya, Sumio; Matsui, Hiroya 

This paper shows the result of the rock mechanical investigations on HDB-3 to HDB-8 which have been carried out from 2002 to 2003 as a part of the investigations of Horonobe URL(Underground Research Laboratory) project. The objectives of the investigation are as follows, to confirm the distribution of rock mechanical properties by laboratory and in-situ tests, and to obtain the rock mechanical data in order to understand the deference of state of stress between the west and east side area of Omagari fault. Omagari fault separated the URL construction area between west and east side. So that, we arranged the rock mechanical data which were obtained from each laboratory tests and in-situ measurements. According to the results of the investigations, we found that it is good agreement with the distribution and the state of rock mechanical properties in each borehole with regardless of east or west area of Omagari fault. So, we suppose that the rock mechanical model of sedimentary rock around the URL construction area is nearly continuum, because that the intact part of sedimentary rock around here is weak character, and that the scale of fracture confirmed by geological investigation is too small to influence rock mechanical properties. And according to the model which is constructed by the results of the physical and mechanical investigations, we can explain about the rock physical and mechanical properties in common through 3 zones with regardless of location.