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JAEA Reports

Three-dimensional stress analysis of reflooding tunnel during submerging process using crack tensor model at Mizunami Underground Research Laboratory

Ozaki, Yusuke; Matsui, Hiroya; Kuwabara, Kazumichi; Tada, Hiroyuki*; Sakurai, Hideyuki*; Kumasaka, Hiroo*; Goke, Mitsuo*; Kobayashi, Shinji*

JAEA-Research 2016-007, 125 Pages, 2016/06

JAEA-Research-2016-007.pdf:34.66MB

In Mizunami Underground Research Laboratory (MIU), the stress analysis of fractured rock have been performed with crack tensor model. In MIU, a reflooding test is performed at 500m stage. In this study, stress analysis of rock during submerging process of the tunnel is performed by using crack tensor model. The deformation of the rock under different water levels in the tunnel is simulated. The stress condition by high pressure due to inflow of groundwater into tunnel is also estimated. These simulation are performed under assumption that groundwater does not permeate into rock for the estimation of maximum pressure acting on the rock. The stress analysis with consideration of permeation of groundwater into rock is also conducted for the estimation of stress condition after the diffusion of water pressure in tunnel. The results of these analyses lead the conclusion that the pressure of the rock reaches the groundwater pressure near the face of tunnel when the tunnel is submerged.

Journal Articles

Excavation analysis using crack tensor theory at the Mizunami Underground Research Laboratory, Japan

Sanada, Hiroyuki; Hikima, Ryoichi; Tanno, Takeo; Sato, Toshinori; Goke, Mitsuo*; Tada, Hiroyuki*; Kumasaka, Hiroo*

Proceedings of ITA-AITES World Tunnel Congress 2013 (WTC 2013)/39th General Assembly, p.855 - 860, 2013/05

Japan Atomic Energy Agency (JAEA) has been implementing the Mizunami Underground Research Laboratory (MIU) Project for the R&D of geological disposal of High-level Radioactive Waste (HLW) in granite. The MIU Project has been divided into three overlapping phases: Surface-based Investigation Phase (Phase I), Construction Phase (Phase II), and Operation Phase (Phase III). In this paper, FEM analysis using crack tensor theory at the MIU was carried out in order to estimate deformation around the horizontal tunnel for investigations and construction during Phase III, and to confirm the validity of FEM analysis results including parameter settings using fracture information from the vertical borehole drilled during Phase I. The relationship between statistical observations on tunnel walls and pilot boreholes was used to estimate the crack tensor for the investigated area. FEM analysis in this work described the increase of stress in concrete liners due to decrease of Young's Modulus compared to Phase I. Since investigations during Phase II could effectively detected high angle fractures, which couldn't be satisfactorily detected during Phase I, the crack tensor was improved using the Phase II results. Predictions and applicability of the analysis method are to be confirmed with in situ experiments during Phase III.

JAEA Reports

Study on equivalent continuum modeling with crack tensor on crystalline rock

Tanno, Takeo; Sato, Toshinori; Sanada, Hiroyuki; Hikima, Ryoichi; Matsui, Hiroya; Tada, Hiroyuki*; Goke, Mitsuo*; Kumasaka, Hiroo*; Ishii, Takashi*

JAEA-Research 2012-002, 86 Pages, 2012/03

JAEA-Research-2012-002.pdf:8.48MB

The Crack tensor model which is a kind of equivalent continuum model has been studied in rock mechanical investigation in the MIU. The fractured rock mass is modeled as the elastic continuum model with the crack tensor. In this study, crack tensor based on the geological observation in the MIU project was calculated, and REV (Representative Elementary Volume) in the shafts and research galleries was studied based on the relative error of the crack tensor. The correlation between the crack density, the trace length of crack and the trace of crack tensor and the rock mass classification was also studied.

JAEA Reports

A Study on the technology for reducing cement-type materials used for tunnel supports at high-level radioactive waste disposal sites (Joint research)

Hayashi, Katsuhiko; Noguchi, Akira; Kishi, Hirokazu; Kabayashi, Yasushi*; Nakama, Shigeo; Fujita, Tomo; Naito, Morimasa; Tada, Hiroyuki*; Kumasaka, Hiroo*; Goke, Mitsuo*; et al.

JAEA-Research 2010-057, 101 Pages, 2011/03

JAEA-Research-2010-057.pdf:7.47MB

Cement-type materials that are used for supports or grouting at high-level radioactive waste disposal facilities leach into the groundwater and create a highly alkaline environment. Of concern in highly alkaline environments are the alteration of bentonite used as buffers or backfill materials, and of surrounding rock mass, and the increased uncertainty regarding the provision of performance of the disposal system over a long period of time. In this study, to reduce the quantity of cement-type materials that cause highly alkaline environments, technical feasibility of the support structure including the materials which considered the long-term performance of the HLW disposal system are discussed by using knowledge and technology accumulated in JAEA and Shimizu Construction. Moreover, based on the results, the problems remained in the application to the future HLW disposal institution are summarized.

Journal Articles

Variation of hydraulic properties on sedimentary rock due to shear deformation

Goke, Mitsuo*; Ishii, Takashi*; Sanoki, Satoru*; Matsui, Hiroya; Sugita, Yutaka

Dai-40-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.282 - 287, 2011/01

In order to investigate the variation of hydraulic properties on soft rock due to shear deformation, permeability tests were performed on hard shale of the Wakkanai formation by axial flow and radial flow techniques under triaxial compression. The experimental results showed that the axial direction permeability increased to approximately 10 times lager than the initial one in residual strength zone. On the other hand, the radial direction permeability increased remarkably in strain softening zone. The results suggested that a permeability increase could be restrained, if the strain softening is not to be attained in the rock mass surrounding caverns by invention of construction methods.

JAEA Reports

Estimation of crack tensor for evaluating excavation disturbance of research gallery at the Mizunami Underground Research Laboratory

Matsui, Hiroya; Tanno, Takeo; Hirano, Toru*; Goke, Mitsuo*; Kumasaka, Hiroo*; Tada, Hiroyuki*; Ishii, Takashi*

JAEA-Research 2010-043, 87 Pages, 2010/12

JAEA-Research-2010-043.pdf:3.99MB

The results are as follows (1) For the ventilation shaft at GL-350m, the crack tensor deformation analysis based on FY2004 work's results showed the calculated displacement was smaller than the measured displacement. A geometrical parameters of fractures in FY2004 work's result was different from one based on geological observation in the shaft. Therefore, the crack tensor of FY2004 work's results seems to be underestimated. (2) Large discontinuities with NE strike and high dipping observed in a shaft were major reason for the difference of crack tensors determined by borehole investigation from surface and geological observations in a shaft. Therefore, the crack tensor for pilot borehole investigation in a shaft was calculated as well and compared with each results. It was found that the fabric tensor is similar with it of geological observation and the vale was medium. (3) The crack tensor around GL-500m was estimated by relation of statistical quantities for fractures between GL-300m and GL-500m. Consequently, the deformation analysis based on the estimated crack tensor showed an increase in convergence and stress in the support system compared to FY2004 work's results.

JAEA Reports

Excavation disturbance analysis based on Crack Tensor Model and Virtual Fracture Model for predicting the rock mass behavior during excavation of shafts and research galleries at the Mizunami Underground Research Laboratory

Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori*; Goke, Mitsuo*; Tada, Hiroyuki*; Sakurai, Hideyuki*

JAEA-Research 2007-081, 120 Pages, 2008/01

JAEA-Research-2007-081.pdf:13.48MB

A 3D Crack Tensor Model analysis was carried out to predict the rock mass behavior of the complex (articulated) section at -500 m. Properties were chosen based on the Rock Mechanics Model constructed in the Surface-based Investigation Phase (Phase I). The Virtual Fracture Model was applied to analyze the change the hydraulic conductivity.

Journal Articles

Excavation disturbance analysis in consideration of excavation damaged zone for research drift of Mizunami Underground Research Laboratory

Goke, Mitsuo*; Tada, Hiroyuki*; Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori

Tonneru Kogaku Rombunshu, 16, p.35 - 45, 2006/11

no abstracts in English

Journal Articles

Japanese underground research laboratory project and prediction of rock mass behavior around deep shafts and galleries using continuous and discontinuous models

Sato, Toshinori; Mikake, Shinichiro; Nakama, Shigeo; Seno, Yasuhiro; Mori, Takayuki*; Iwano, Keita*; Goke, Mitsuo*; Tada, Hiroyuki*

Proceedings of 7th International Conference on Analysis of Discontinuous Deformations (ICADD-7) (CD-ROM), p.245 - 256, 2005/12

Two one-thousand meter deep shafts and research galleries at several levels will be excavated in granite for the Mizunami Underground Research Laboratory (MIU) project. Research on the deep geological environment in this project will provide the basis for Research and Development on geological disposal of high-level radioactive waste. The site of MIU project is located in Mizunami, Gifu, in the central part of the main island of Japan. By July 2003, entrances to the shafts were constructed, and excavation of lower part of shaft entrance was started in March 2004. Current status (September 2005) of construction is excavation of the shafts to a depth of 150 m has been done. Mechanical investigations including hydraulic fracturing test and laboratory tests on core samples were performed, and numerical analysis using continuous model and discontinuous model; MBC (Micro-mechanics based continuum model), Crack tensor model and FRACOD (fracture propagation code), were also performed to predict mechanical stability of openings and support systems, and rock mass behavior around openings. In this analysis EDZ (Excavation Damaged Zone) due to blasting and excavation step were considered in same cases. This paper describes the current status of Mizunami Underground Research Laboratory for crystalline rock and the results of prediction for rock mass behavior around the deep underground openings using some analytical methods. Measurements during shaft sinking and future plan of investigations in the URL are also describes in this paper.

JAEA Reports

Excavation disturbance analysis based on crack tensor model and virtual fracture model for research drift of the Mizunami Underground Research Laboratory

Goke, Mitsuo*; Horita, Masakuni*; Wakabayashi, Naruki*; Nakaya, Atsushi*

JNC TJ7400 2005-058, 167 Pages, 2005/03

JNC-TJ7400-2005-058.pdf:7.49MB

The purposes of this study were to contribute to both the evaluation of mechanical stability of a research drift and the plan of future studies. The crack tensor model based on mechanical property on the Toki granite at the Mizunami Underground Research Laboratory construction site was applied to analyze the rock stress as a research drift and a shaft were excavated. The virtual fracture model was applied to the hydraulic conductivity change analysis.The results are as follows:1)In the reference case of a shaft, convergence showed 9.03mm at the GL-500m, and 21.78mm at the GL-1000m. The maximum increase rate of hydraulic conductivity showed about 14 times at the both depth. In the reference case of a drift, convergence of a splingline showed 3.36mm at the GL-500m, and 7.99mm at the GL-1000m. The maximum increase rate of hydraulic conductivity showed a range of about 28 times from about 19 times at the GL-500m, and a range of about 45 times from about 15 times at the GL-1000m.2)As rock class getting weaker, the convergence of a shaft and a drift increased, also the stress in support parts increased, while distributions of the safety factor and the hydraulic conductivity change were almost changeless.3)As the direction of a drift changed to 90 degrees form 0 degrees, the convergence of a shaft and a drift increased, also the stress in support parts increased, and distributions of the safety factor and the hydraulic conductivity change were affected.4)As compared with analytical result regardless of excavation damaged zone, analytical result in consideration of excavation damaged zone showed that the convergence and the stress in support parts increased. Especially, the maximum increase rate of hydraulic conductivity increased remarkably. For example, the maximum increase rate of hydraulic conductivity was 240 times to 400 times at the bottom of a drift

JAEA Reports

Drift excavation analysis based on crack tensor model and virtual fracture model in consideration of excavation damaged zone

Goke, Mitsuo*; Horita, Masakuni*; Tada, Hiroyuki*

JNC TJ7400 2004-007, 102 Pages, 2004/02

JNC-TJ7400-2004-007.pdf:4.85MB

Tono Geoscience Center (TGC), Japan Nuclear Cycle Development Institute (JNC) conducts the Mizunami Underground Research Laboratory (MIU) project in order to develop the comprehensive investigation techniques for the geological environment and the engineering techniques in the deep underground application. The purposes of this work were to contribute to the rock mechanical modeling for MIU project. We proposed an analytical method of modeling of excavation damaged zone. The crack tensor analytical model was applied to analyze the rock stress in consideration of the existence of excavation damaged zone as a research drift and a shaft were excavated. The virtual fracture model was applied to the hydraulic conductivity change analysis.The results are as follows:1) As compared with analytical result without excavation damaged zone, the crack tensor stress analysis in consideration of excavation damaged zone showed that the convergence of a shaft and a drift increased and the maximum value of principal stress decreased, while the safety factor distribution was almost changeless.2) As compared with analytical result without excavation damaged zone, the hydraulic conductivity change analysis in consideration of excavation damaged zone showed the maximum increase rate of hydraulic conductivity increased remarkably.3) As the stiffness decreased in excavation damaged zone, the convergence of a shaft and a drift increased, the maximum value of principal stress decreased, and the maximum increase rate of hydraulic conductivity increased. Especially, in analytical case supposed that new cracks parallel to perimeter of a drift broke out in excavation damaged zone, the maximum increase rate of hydraulic conductivity was up to 5000 times.4) As the stiffness of rock mass decreased by taking into the existence of excavation damaged zone, the convergence reduction effect increased, and the stress in support parts increased.

JAEA Reports

Hydraulic Conductivity Change Analysis of Surrounding Rock Mass in Excavating Research Drift

Goke, Mitsuo*; Tada, Hiroyuki*; Horita, Masakuni*; Wakabayashi, Naruki*

JNC TJ7400 2003-003, 93 Pages, 2003/02

JNC-TJ7400-2003-003.pdf:5.87MB

Tono Geoscience Center (TGC), Japan Nuclear Cycle Development Institute (JNC) conducts the Mizunami Undergroud Research Laboratory (MIU) project in order to develop the comprehensive investigation techniques for the geological environment and the engineering techniques in the deep underground application. The purposes of this study were to contribute to the construction of rock mechanical modeling for MIU project. The virtual fracture model based on mechanical property on the Toki granite was applied to the 2-D hydraulic conductivity change analysis in excavating a research drift and a shaft. The crack tensor analysis model was introduced to the stress analysis before the hydraulic conductivity change analysis. The results are as follows: (1) The crack tensor stress analysis showed very small displacement on the perimeter of a shaft and a drift in intact rock mass, while large displacement appeared in fault zone. (2) More than 10 times large hydraulic conductivity from the initial one appeared in the extent of 1m from the perimeter of a drift and a shaft, in the hydraulic conductivity change analysis with the virtual fracture model for the intact rock mass. The maximum increase of hydraulic conductivity was up to 100 times from initial one. The fault zone showed more than 10 times larger hydraulic conductivity in the extent of 4m from the perimeter. (3) The extent of hydraulic conductivity change was affected by the direction of a drift due to the direction of fractures and the initial stress condition. For example, the rate of hydraulic conductivity increased from initial one changed 110 times to 670 times with the direction of a drift, at the side wall of a drift at the depth of 945m. (4) There was no clear effect to reduce the displacement by supports in the drift in intact rock mass.

JAEA Reports

The Arrangement of the seismic design method of the underground facility

Tanai, Kenji; Horita, M.*; *; Goke, Mitsuo*

JNC TN8410 2001-026, 116 Pages, 2002/03

JNC-TN8410-2001-026.pdf:9.19MB

Earthquake resistance for the underground structure is higher than the ground structure. Therefore, the case of examining the earthquake resistance of underground structure was little. However, it carries out the research on the aseismic designing method of underground structure, since the tunnel was struck by Hyogo-ken Nanbu Earthquake, and it has obtained a much knowledge. However, an object of the most study was behavior at earthquake of the comparatively shallow underground structure in the alluvial plain board, and it not carry out the examination on behavior at earthquake of underground structure in the deep rock mass. In the meantime, underground disposal facility of the high level radioactive waste constructs in the deep underground, and it carries out the operation in these tunnels. In addition, it has made almost the general process of including from the construction start to the backfilling to be about 60 years (Japan Nuclear Fuel Cycle Development Institute, 1999). During these periods, it is necessary to also consider the earthquake resistance as underground structure from the viewpoint of the safety of facilities. Then, it extracted future problem as one of the improvement of the basis information for the decision of the safety standard and guideline of the country on earthquake-resistant design of the underground disposal facility, while it carried out investigation and arrangement of earthquake-resistant design cases, guidelines and analysis method on existing underground structure, etc.. And, the research item for the earthquake resistance assessment of underground structure as case study of the underground research laboratory.

JAEA Reports

Investigations on repository layouts

Tanai, Kenji; Iwasa, Kengo; Hasegawa, Hiroshi; Goke, Mitsuo*; Horita, Masakuni*; Noda, Masaru*

JNC TN8400 99-044, 140 Pages, 1999/11

JNC-TN8400-99-044.pdf:7.85MB

This report consists of three items: (1)Study of the repository configuration, (2)Study of the surface facilities configuration for construction, operation and buckfilling, (3)Planning schedule, In the repository configuration, the basic factors influencing the design of the repository configuration are presented, and the results of studies of various possible repository configurations are presented for both hard and soft rock systems. Here, the minimum conditions regarding geological environment required to guide design are assumed, because it is difficult to determine the repository configuration without considering specific conditions of a disposal site. In the surface facility configuration, it is illustrated based on the results of construction, operation, buckfilling studies for underground disposal facility and EIS report of CANADA. In the schedule, the overall schedule corresponding to the repository layout is outlined in link with the milestone of disposal schedule set forth in the government's basic policy. The assumptions and the basic conditions are summarized to examine the General Schedule from start of construction to closure of a repository. This summaly is based on the technologies to be used for construction, operation and closure of a repository. The basic national policies form the framework for this review of the general schedule.

Oral presentation

3D analysis for predicting the rock mass behavior of a research shaft and gallery considering excavation damaged zone

Seno, Yasuhiro; Mori, Takayuki*; Goke, Mitsuo*; Nakama, Shigeo; Sato, Toshinori*

no journal, , 

The Excavation Disturbed Zone is defined as the zone host rock around an underground excavation whose characteristics are altered by excavation. This includes the Excavation Damaged Zone, Stress Redistribution Zone and Unsaturated Zone. It is assumed that such zone will become a selective pathway for the migration of groundwater and/or radioactive materials. Therefore, for the design of geological repository where low permeability is required, it is important to establish an accurate method for evaluating and predicting the rock mass behavior due to excavation. This paper describes the results of 3D FEM analysis results using two type continuous models that consider the reduction of stiffness of the Excavation Damaged Zone due to blasting.

Oral presentation

Development of construction methods of a drift to be reduction of amount of cement use, 8; The Bending test of the rock segment using low alkaline mortar

Saito, Akira*; Goke, Mitsuo*; Nakaya, Atsushi*; Tada, Hiroyuki*; Hayashi, Katsuhiko; Noguchi, Akira; Kishi, Hirokazu; Nakama, Shigeo

no journal, , 

We are supposing a low cement use tunner support made for granite rock block connecting low alkaline cement applying to HLW repositories. Because of the bending moment of the segment by dead load and the variance of the earth pressure, We made a model segment bending experiment to get a mechanical properties. The maximum load of the positive bending moment is around 210kN, which is around twice of the dead load of 117kN. The other hand, the maximum load in the negative bending moment is around 44kN, as same as the dead load. As the result of observating the cracks of the model segment, We found three or four cracks along the surface of the boundary of the rock block and mortar in the positive bending experiment. The other hand, we found only one crack at the center avoiding rock block in the negative bending experiment. Next, we will improve the construction method, prevention of the crack in the segment and the exfoliation of mortar and the steel panel.

Oral presentation

Preliminary analysis of long-term evolution for geological environment around drift in the Horonobe Underground Research Laboratory

Goke, Mitsuo*; Okihara, Mitsunobu*; Maemura, Tsuneyuki*; Yasuda, Ryo*; Matsui, Hiroya; Ozaki, Yusuke; Mochizuki, Akihito

no journal, , 

We performed the numerical simulation to simulate the long term change in geological environment under open drift condition. We developed the conceptual model for the purpose and performed the geomechanical and hydrological simulation with the models considering the existence of excavation damaged zone and tunnel support. The geomechanical simulation results suggested that the deformation for long term is so slight that the excavation damaged zone does not enlarge. The hydrological simulation considering the degassing predicted the expansion of the unsaturated zone in the high pore pressure domain.

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