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Aoyagi, Kazuhei; Ishii, Eiichi; Fujita, Tomoo; Motoshima, Takayuki*
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.313 - 318, 2016/01
The objective of this research is to investigate the extent and failure mechanism of an Excavation Damaged Zone (EDZ) induced around the East Access Shaft in the Horonobe Underground Research Laboratory. As a result of hydraulic tests, hydraulic conductivity within 2 m from the shaft wall was increased by 1 to 3 orders of magnitude. This result is consistent with the extent of the development of fractures detected by borehole televiewer surveys. Furthermore, the dominant failure mechanism of the fractures around the shaft wall was almost tensile; also these fractures were caused by the short-term excavation-induced unloading.
Hata, Koji*; Niunoya, Sumio*; Aoyagi, Kazuhei; Fujita, Tomoo
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.319 - 324, 2016/01
Long-term monitoring and EDZ (Excavated Damage Zone) evaluation is carried out by this multi-optical measurement probe in the depth of 350m vertical shaft of Horonobe Underground Research Center project of the Japan Atomic Energy Agency. We have developed a multi-optical measurement probe incorporating an optical AE sensor, an optical water pressure sensor and an optical temperature sensor. Result of the measurement of AE, water pressure and temperature, it was made clear the influence of the shaft excavation. And from the source location analysis, it was found EDZ was less than 1.5m from shaft wall.
Niunoya, Sumio*; Aoyagi, Kazuhei; Fujita, Tomoo; Shirase, Mitsuyasu*
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.336 - 341, 2016/01
In the Horonobe Underground Research Laboratory, rock mass classification and determination of mechanical properties of rock mass was conducted considering the effect of the density of fractures in the rock mass. In this paper, the authors report the mechanical properties of rock mass detected by plate loading tests and in situ shear tests in the 250 m and 350 m galleries. As a result, the failure criteria based on the result of in situ shear tests provides the most conservative value for the design of support pattern and assessment of stability of the gallery.
Tsuji, Masakuni*; Kobayashi, Shinji*; Sato, Toshinori; Mikake, Shinichiro
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.359 - 364, 2016/01
Pre-excavation grouting of shafts and galleries has been conducted during the construction of Mizunami Underground Research Laboratory in the aspect of safe works and reducing the discharge treatment of the water inflow. The grouting methodology has been simultaneously studied and developed as there is less experience of grouting in low conductive rock with high water pressure, especially in Japan. After excavating GL.-500m gallery on the ventilation shaft side, a post-excavation grouting campaign was performed on a 16-meter section of the pre-grouted area. Three new options for the grouting design were adopted and found to be effective with sufficiently decreasing the water inflow into the gallery.
Kamemura, Katsumi*; Fujita, Tomoo; Aoyagi, Kazuhei; Nago, Makito*; Shirase, Mitsuyasu*; Sugawara, Kentaro*
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.109 - 114, 2016/01
How to estimate the initial stress state as well as a mechanical characteristic of rock mass is important in the design of deep underground structures. Some stress measurement methods using borehole, which methodology and evaluation method have been discussed in detail, are carried out if necessary. However, obtained results are often varying widely, so the evaluation of initial stress is difficult. Here, the initial stress state corresponding to the rock mass behavior of about 120m
200m area is evaluated using the convergence measurement results during tunnel excavation in 350m depth. Analysed result corresponded to that of other method, so the validity of the proposed method was shown.