Initial stress estimation of diatomaceous mudstone using hydraulic fracturing test

Nakamura, Takahiro; Kato, Harumi*; Sanada, Hiroyuki; Sugita, Yutaka 

This paper shows the results of initial stress obtained from stress relief method, hydraulic fracturing technique and breakout analysis which have been carried out at 140 m niche as a part of the investigation of Horonobe Underground Research Project. The results of investigations are summarized as follows. Initial stress measuring has been tried by stress relief method, but none of the gluing of the gage plugs was successful because clayish slime stuck over the end of the borehole. The direction and value of initial stress obtained from hydraulic fracturing technique and breakout analysis was closely similar.