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Bruines, P.*; Tanaka, Tatsuya*; Koyama, Tomofumi*; Kishi, Hirokazu; Nakanishi, Tatsuro; Onishi, Yuzo*
Proceedings of 2012 ISRM International Symposium; Rock Engineering and Technology for Sustainable Underground Construction (EUROCK 2012) (USB Flash Drive), 15 Pages, 2012/05
To better understand the grouting process and the effect of grouting on the performance of a nuclear waste repository, the Japanese Atomic Energy Agency (JAEA) has initiated a grouting test carried out in the fractured granite of the Grimsel Test Site (GTS) located in the Swiss Alps. This paper describes the characterization of the rock mass, how the data obtained has been used to make a discrete fracture network (DFN) model and how an up-scaled equivalent continuous porous media (ECPM) model for the purpose of numerical simulation of the grout injection process is generated. The generated DFN model and the up-scaled ECPM model was able to reproduce the measured fracture characteristics (e.g. orientation, density) as well as the hydraulic behavior observed in the field (e.g. transmissivity distribution, anisotropy, heterogeneity) and has proven to be suitable for modeling grouting behavior.
Koyama, Tomofumi*; Onishi, Yuzo*; Bruines, P.*; Tanaka, Tatsuya*; Hasui, Akinori*; Katayama, Tatsuo*; Kishi, Hirokazu; Kuzuha, Yuji
Proceedings of 2012 ISRM International Symposium; Rock Engineering and Technology for Sustainable Underground Construction (EUROCK 2012) (USB Flash Drive), 10 Pages, 2012/05
Grouting, which involves injection of grout material, is commonly used to decrease the hydraulic conductivity of the fractured rock masses and control the groundwater inflow. However, the mechanism of grout injection process has not been clarified sufficiently yet due to complicated chemical and physical processes of grout. In this study, to simulate the grout injection process, the three-dimensional numerical model based on equivalent continuum approach was developed.
Kobayashi, Shinji*; Nobuto, Jun*; Sugiyama, Hirokazu*; Kusano, Takashi*; Tsuji, Masakuni*; Mikake, Shinichiro; Matsui, Hiroya
Proceedings of European Rock Mechanics Symposium (EUROCK 2012) (CD-ROM), 13 Pages, 2012/05
JAEA (Japan Atomic Energy Agency) has been conducting geoscientific research and development at underground research laboratory under construction, in crystalline rock at Mizunami, Gifu. Considering water treatment expense, the water inflow should be minimized. Although cement grout has been applied to reduce the inflow at 460 m depth at the MIU (Mizunami Underground Research Laboratory), water inflow through narrow fractures which cement grout cannot penetrate might be a problem at deeper underground. Colloidal silica grout, which is liquid-type grout, has high durability as well as good penetrability and is therefore tested at a depth of 300 m. The results indicated that liquid-type grout could sufficiently reduce the hydraulic conductivity of rock mass with less than 1 Lu. In the water pressure resistance test, the ultra-high-pressure packer was set in the pilot hole. The results indicated that liquid-type grout could keep sealing effect even under high water pressures over 9 MPa.
Niimi, Katsuyuki*; Kobayashi, Shinji*; Nobuto, Jun*; Matsui, Hiroya; Yamamoto, Masaru
Proceedings of European Rock Mechanics Symposium (EUROCK 2012) (CD-ROM), 13 Pages, 2012/05
JAEA has been conducting geoscientific research and development at underground research laboratories under construction in Japan. In this study, frequency and wave propagation characteristics were analyzed using seismic records for six earthquakes obtained with the seismometers in URL. It was found that seismic motions were amplified from the deep underground to the shallow surface and that the wave propagation characteristics were different in NS and EW directions. It was also assumed that the recorded data of the seismometer on the ground might be influenced by aboveground structures. Then, numerical simulations using SHAKE, which is commonly used for seismic response analysis in Japan and had been applied to the earthquake resistance design in Phase I, were carried out to compare analytical results and observed records. The results showed that the calculated results agreed well with those observed when epicenters are close.