Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Takayama, Yusuke; Kikuchi, Hirohito*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 77(3), p.302 - 313, 2021/09
Numerous swelling pressure tests have been conducted to understand the swelling properties of bentonite which is planned to be used as a buffer material in repositories for the geological disposal of radioactive waste. In this study, in order to clarify the cause of the decrease in swelling pressure during the swell-in pressure test period, the change in wet density distribution inside the specimen during the swelling pressure test was observed by X-ray CT measurement. It was supposed that this phenomenon was caused by the collapse inside the specimen. Furthermore, in order to confirm that collapse is generated by water absorption, the swelling deformation test was carried out under various load conditions. As a result, it was confirmed that collapse occurs even under the load conditions that are equal to or slightly smaller than the swelling pressure. These test data are expected to be used for validation of coupled analysis codes for evaluating the mechanical behavior of disposal facilities during re-saturation period.
Mikake, Shinichiro; Ikeda, Koki; Matsui, Hiroya; Tsuji, Masakuni*; Nishigaki, Makoto*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 74(1), p.76 - 91, 2018/03
Pre-grouting of shafts and galleries had been conducted during the construction of MIU in the aspect of reducing water inflow. After excavating GL.-500m gallery, a post-grouting was performed on section of the pre-excavation grouting area under high water pressure condition (max: 4MPa). The post-grouting experiment was performed outside of the pre-grouting zone with designs, applying colloidal silica grouting material and complex dynamic grouting. It was estimated that the inflow after post-grouting was reduced by 1/100 of the case that pre- and post-grouting were not performed. These results indicate that the applied combined pre- and post-grouting methodology is effective in reducing water inflow and it can be applicable under high water pressure condition. Then, this paper states the theoretical evaluation of relationship between reduction of hydraulic conductivity and the grouting zone is very convenient and useful for grouting design and estimate of water inflow.
Tada, Hiroyuki*; Kumasaka, Hiroo*; Saito, Akira*; Nakaya, Atsushi*; Ishii, Takashi*; Fujita, Tomoo; Sugita, Yutaka; Nakama, Shigeo; Sanada, Masanori*
Doboku Gakkai Rombunshu, F2 (Chika Kukan Kenkyu) (Internet), 73(1), p.11 - 28, 2017/03
This study examined the mechanical characteristics of rock segments and backfill materials and analyzed the stability of the drift that is supported by the rock segments and gravel backfill. The results confirmed the technical aspects of the formation of the rock segments and the effectiveness of the planned efforts to further reduce the amount of cement used.
Onoe, Hironori; Saegusa, Hiromitsu; Takeuchi, Ryuji
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 72(1), p.13 - 26, 2016/01
The Japan Atomic Energy Agency is conducting the Mizunami Underground Research Laboratory (URL) project in Mizunami, Gifu, in order to establish scientific and technical basis for geological disposal of high-level radioactive waste. This paper comprehensively describes the result of groundwater flow modeling using data of hydraulic responses and hydrochemical changes due to URL construction. Technical know-how and methodology of hydrogeological monitoring and groundwater flow modeling were presented for characterization of hydraulic heterogeneities in fractured crystalline rock. Furthermore, effectivity of data acquisition of hydrochemical changes in groundwater for validation of result of groundwater flow modeling was indicated.
Yamasaki, Masanao*; Tsusaka, Kimikazu*; Otani, Tatsuhiko*; Shinji, Masato*
Doboku Gakkai Rombunshu, F2 (Chika Kukan Kenkyu) (Internet), 71(1), p.1 - 10, 2015/04
Japan Atomic Energy Agency has been constructed the Underground Research Laboratory in Hokkaido. In the shaft excavation, length, direction and aperture of geological observation are measured and analyzed in order to estimate rock permeability around lining. In this report, correlation between frequency of cracks and rock permeability based on crack tensor and stereology was discussed. Prediction equation of rock permeability from the frequency of cracks on the shaft wall was also proposed.
Aoyagi, Kazuhei; Tsusaka, Kimikazu; Kubota, Kenji*; Tokiwa, Tetsuya; Kondo, Keiji; Inagaki, Daisuke
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 70(4), p.412 - 423, 2014/12
The authors have been conducting seismic and resistivity tomography surveys in a gallery of the Horonobe Underground Research Laboratory in order to investigate an extent of an excavation damaged zone (EDZ) along time. The objective of this paper is to discuss an influence of fracture distribution and water saturation of a rock mass on variations in seismic velocity and the value of apparent resistivity in an EDZ. Based on the result of seismic tomography survey, the extent of a layer which has low seismic velocity was about 1.0 m from the gallery wall after excavation of the tomography area. From the results of resistivity tomography survey, the value of apparent resistivity has not changed remarkably along time. To investigate a relationship between variations in seismic velocity and density of fracture in the survey area, the authors built a three dimensional fracture model around the tomography area. From the comparison of seismic velocity with density of fracture, seismic velocity decreased almost linearly as the density of fracture increased. Also, it was found that density of fracture in the layer of low seismic velocity could be estimated using a simple numeric model. From this result, seismic tomography survey and investigation of density of fracture are suitable method for evaluation of an EDZ.
Mikake, Shinichiro; Nishigaki, Makoto*; Sato, Toshinori
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 70(1), p.33 - 43, 2014/01
This paper states establishment of the theoretical evaluation of the grouting zone during excavation of tunnel deep underground tunnel under high water pressure condition. In this study, relationship between allowable pressure and active pressure in the grouting zone is examined by means of one dimensional theoretical solution of pressure due to seepage forces act on the cross-section of the tunnel. The results indicate that allowable pressure is lower than active pressure under conditions of low cohesion. Furthermore, relationship between reduction of hydraulic conductivity and active pressure in the grouting zone is examined and it is confirmed that active pressure increases as hydraulic conductivity decreases by grout injection. Therefore, an accurate evaluation of the grouting zone is very important for grouting design based on the results obtained.
Imai, Hisashi*; Amemiya, Kiyoshi*; Matsui, Hiroya; Sato, Toshinori; Saegusa, Hiromitsu; Watanabe, Kunio*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 69(3), p.285 - 296, 2013/07
The more accurate understanding and appropriate control of unsaturated area around tunnel excavated in deep rock-mass are required, for the geological isolation of radioactive waste project and also underground rock cavern storage project of liquefied petroleum gas. The numerical simulation of seepage flow is usually conducted to understand and evaluate the unsaturated zone around tunnel. The unsaturated parameters (such as moisture characteristic curve and relative permeability) and appropriate control of boundary condition are indispensable for the simulation. Authors developed methodology to measure unsaturated parameters utilizing the measuring method conventionally applied to soils and showed the efficiency of the method via a laboratory experiment. The idea of combining seepage face condition and flow rate fixed condition was derived, and the efficiency was shown in an model simulation. The two developments enabled the accurate estimation and understanding the evolution of unsaturated zone around tunnel.
Yabuuchi, Satoshi; Kunimaru, Takanori; Kishi, Atsuyasu*; Komatsu, Mitsuru*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 67(4), p.464 - 473, 2011/11
Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. Pore water pressure and water content around a horizontal drift in the URL have been monitored for over 18 months since before the drift excavation was started. During the drift excavation, both pore water pressure and water content were decreasing. Pore water pressure has been still positive though it continued to decrease with its gradient gradually smaller after excavation, while water content turned to increase about 6 months after the completion of the excavation. It turned to fall again about 5 months later. An unsaturated zone may have been in homogeneously formed around the horizontal drift considering a degassing.
Oda, Yoshihiro; Takasu, Tamio*; Sato, Hisashi; Sawada, Atsushi; Watahiki, Takanori*
Doboku Gakkai Rombunshu, C (Chiken Kogaku) (Internet), 67(2), p.186 - 197, 2011/04
Because of the density difference between fresh groundwater and saline groundwater, the groundwater behaves complicated flow. It is well known that the expected barrier functions such as candidate buffer materials and others for high level radioactive waste geological isolation are inhibited by the saline water. The simulations have been required to evaluate the groundwater flow, because the available data by in-situ investigation of the saline and fresh ground water flows is very limited. In the simulation, the complex coupled process of advection-dispersion, seepage flow and density drive flow should be implemented in the simulation codes. The extensive verification studies have been done for modeling and simulation codes until now, but those results were compared only with qualitative experimental data. For the quantitative evaluations, we developed the quantitative measurement technique by optical method for saltwater intrusion, especially for the saltwater concentration distribution in transition zone, on laboratory experiment. We have obtained the quantitative data of the shape of saltwater wedge and saltwater concentration distribution at both transient and steady states.
Honda, Makoto*; Yamamoto, Shinya*; Sakurai, Hideyuki*; Suzuki, Makoto*; Sanada, Hiroyuki; Sugita, Yutaka; Matsui, Hiroya
Doboku Gakkai Rombunshu, C, 66(3), p.609 - 624, 2010/08
This paper proposes a geostatistical system for modeling the groundwater properties which have a correlation with the ground resistivity data obtained from widespread and exhaustive electromagnetic survey. That is, the methodology for the integration of resistivity data measured by various methods and the methodology for modeling the groundwater properties using the integrated resistivity data has been developed. The proposed system has also been validated using the data obtained in the surface-based investigations of the Horonobe URL project. Additionally, the quantification of uncertainties in the estimated model has been tried by numerical simulations based on the data. As a result, the uncertainties of the proposal model have been estimated lower than other traditional model's.
Sato, Hisashi; Sawada, Atsushi
Doboku Gakkai Rombunshu, C, 66(3), p.487 - 497, 2010/07
The high resolution, 0.15 mm spacing, fracture aperture distribution data, tracer migration data with hydraulic test data under the same conditions were obtained by using optical measurement method of 100 mm 
100 m transparent replica specimen, making a duplicate copy of rock fracture. This series of experimental data is useful for verifying the previous studies conducted by using mainly numerical method that showed the characteristics of in-plane heterogeneity of a single fracture and the effect of one onto hydraulic phenomena. For example, it was reported that the two-dimensional numerical simulation with assuming that the local transmissivity might be calculated from measured aperture data by a cubic law is overestimated the flow rate larger than hydraulic test result. In this study the similar result was obtained.
Motoshima, Takayuki*; Onoe, Hironori*; Ijiri, Yuji*; Otsu, Hiroyasu*; Saegusa, Hiromitsu
Doboku Gakkai Rombunshu, C, 66(2), p.370 - 386, 2010/06
Since water inflow into a tunnel significantly impacts construction costs and schedules, it is important to estimate the impact on these factors quantitatively based on prior information about hydrogeological properties. A simplified formula is proposed in order to estimate water inflow volume into tunnel and is validated through comparing the results of DFN model. This formula is able to calculate water inflow risk more quickly than DFN model. Monte Carlo simulation and sensitivity analysis about water inflow risk are performed by using this formula. Then relationships between water inflow risk and amount of information about fracture properties are obtained based on the sensitivity analysis.
Nishiyama, Satoshi*; Onishi, Yuzo*; Sawada, Atsushi; Yano, Takao*
Doboku Gakkai Rombunshu, C, 65(4), p.776 - 788, 2009/10
This paper describes the simulation method to explain the mechanism of the permeability characteristics of specimens with single discontinuties under shear through shear-flow coupling tests, showing that on the shear stress-displacement curve obtained by the constant normal load testing, the water flowing through the discontinuties have different transmissibility-aperture width relation before or after the yield range. As a technique to serve this purpose, the lattice gas method, which is to substitute the fluid with particles and repeat letting them collide. With this technique, the factors of surface structure of discontinuties that determine the shear/permeability characteristics are identified.
Nobuto, Jun*; Mikake, Shinichiro; Nishigaki, Makoto*
Doboku Gakkai Rombunshu, C, 65(4), p.806 - 821, 2009/10
This paper describes a study on efficient pre-excavation grouting concept using cement grout for reducing water-inflow during excavation of crystalline rock in deep underground. Although thick grout mix is favorable for the efficiency of pre-excavation grouting, clogging phenomenon at the entrance of rock fractures in grout hole is concerned for thick grout mix. The influence of water-cement ratio on basic grout characteristics and clogging phenomenon is studied by laboratory experiment using cement grout with water-cement ratio of from 0.5 to 10.0. Finally, the efficient pre-excavation concept for the excavation of deep underground is proposed.
Kurikami, Hiroshi; Takeuchi, Ryuji; Yabuuchi, Satoshi; Seno, Shoji*; Tomura, Goji; Shibano, Kazunori; Hara, Minoru; Kunimaru, Takanori
Doboku Gakkai Rombunshu, C, 64(3), p.680 - 695, 2008/09
Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. This paper shows the results of hydrogeological investigations in the surface-based investigation phase of the project. Hydrological and meteorological investigations show that the infiltration rates of the drainage basins varies and that the infiltration rate depends on the flora and the topography. The hydraulic tests using the deep boreholes reveals that hydraulic conductivity of the scale of a few decameters to a hundred meter varies widely and decreases with depth in the same formation, while the laboratory hydraulic tests suggest that hydraulic conductivity of the intact rock is influenced by the stress history. The hydraulic tests and the long-term monitorings of hydraulic pressure clarify relatively high pressure in the deep underground. Furthermore, groundwater flow analysis shows that the groundwater in and around the URL area flows regionally from the east to the west and depends locally on the geography and geology.
