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Kuwabara, Kazumichi*; Aoyagi, Yoshiaki; Ozaki, Yusuke; Matsui, Hiroya
JAEA-Research 2017-002, 39 Pages, 2017/03
JAEA-Research-2017-002.pdf:3.58MB
Authors developed a displacement meter using optical fiber sensor. The displacement meter can be set at any locations in a borehole and guarantee the measurement accuracy up to 5MPa. Total twelve displacement meters were installed in three boreholes to measure the rock mass displacement during groundwater recovery test. The measurement of the rock mass displacement was stated on March, 27, FY 2014. During the first and second groundwater recovery experiments, compressive displacements were observed close to the closure test drift wall. Magnitude of the measured displacements, except vicinity of test drift wall, was smaller than that of calculated under the assumption of it is an isotropic elastic material.
Ichikawa, Yasuaki*; Kimoto, Kazushi*; Matsui, Hiroya; Kuwabara, Kazumichi; Ozaki, Yusuke
JAEA-Research 2016-018, 23 Pages, 2016/12
JAEA-Research-2016-018.pdf:4.41MB
It is important to evaluate the stability of a repository for high-level radioactive waste not only during the design, construction and operation phases, but also during the post-closure period, for time frames likely exceeding several millennia or longer. The rock mass around the tunnels could be deformed through time in response to time dependent behavior. On the other hand, it was revealed that the chemical reaction of groundwater in a rock had an influence on the long-term behavior. An evaluation of the microcracks to have an influence on this mechanical and chemical coupled phenomena should be worked on chiefly. In fiscal year 2015, using a laser Doppler vibrometer that extends a frequency band up to 20 MHz, and measuring the surface wave transmitted through the granite specimens were estimated group velocity. As a result, group velocity until 100 kHz 
500 kHz, revealed that tends to decrease while vibrating. The group speed estimate from a group delay was shown to be easier than the estimate by wave number - frequency spectrum. This is because in order to improve reliability, the estimated frequency band is by using a spatially averaged waveform. As a result obtained, in the case of the modeling by the viscoelastic theory of the granite and a microcrack nondestructiveness evaluation, it is thought that it is useful information in the future. In order to use the knowledge of this study, there is a need to clarify the correspondence between the microscopic properties of the medium such as a crack and crystal grain and the change of the group velocity.
Fukui, Katsunori*; Hashiba, Kimihiro*; Matsui, Hiroya; Kuwabara, Kazumichi; Ozaki, Yusuke
JAEA-Research 2016-014, 52 Pages, 2016/09
JAEA-Research-2016-014.pdf:7.19MB
With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock is required, not only during construction and operation but also over a period of thousands of years after closure. On the other hand, it is known that rock and the rock mass surrounding the disposal gallery shows time dependent behavior such as creep or the stress-relaxation. It becomes the issue in the stability evaluation of the disposal gallery to grasp the behavior. In order to solve this issue, we pushed forward research development. we pushed forward research development. In the fiscal year of 2015, the creep testing machine for Tage tuff was moved to the new building. The creep test was continuously conducted and the total testing time exceeded 17 years. The testing equipment and procedure were examined to investigate the deformation, failure and time-dependency of rock under wet conditions and between room temperature and 100
C. The long-term strength of rock under triaxle stress state was researched with the aid of laboratory testing results and in situ stress measurement.
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.
Ichikawa, Yasuaki*; Kimoto, Kazushi*; Sato, Toshinori; Kuwabara, Kazumichi; Takayama, Yusuke
JAEA-Research 2015-025, 31 Pages, 2016/03
JAEA-Research-2015-025.pdf:13.0MB
It is important to evaluate the stability of a repository for high-level radioactive waste not only during the design, construction and operation phases, but also during the post-closure period, for time frames likely exceeding several millennia or longer. The rock mass around the tunnels could be deformed through time in response to time dependent behavior. On the other hand, it was revealed that the chemical reaction of groundwater in a rock had an influence on the long-term behavior. An evaluation of the microcracks to have an influence on these mechanical and chemical coupled phenomena should be worked on chiefly. In fiscal year 2014, this study performed numerical analysis to examine the supersonic scattering attenuation decrement behavior in the crystalline rock and a measurement sequentially last year. The measurement of the head and surface waves were carried out. As a result, group speed was provided. On the other hand, the spread scattering analysis of the elastic wave by the FDTD (Finite Difference Time-Domain) method made a numerical analysis. However, a laboratory finding is different from expectation of the simulation, and crystal anisotropic influence of a microcrack and rock-forming minerals is thought about as a cause of this estrangement. Therefore it was revealed that it was necessary to examine these two points of influence more in future.
Hama, Katsuhiro; Mikake, Shinichiro; Ishibashi, Masayuki; Sasao, Eiji; Kuwabara, Kazumichi; Ueno, Tetsuro; Onuki, Kenji*; Beppu, Shinji; Onoe, Hironori; Takeuchi, Ryuji; et al.
JAEA-Review 2015-024, 122 Pages, 2015/11
JAEA-Review-2015-024.pdf:80.64MB
Japan Atomic Energy Agency (JAEA) at Tono Geoscience Center (TGC) is pursuing a geoscientific research and development project namely the Mizunami Underground Research Laboratory (MIU) Project in crystalline rock environment in order to construct scientific and technical basis for geological disposal of High-level Radioactive Waste (HLW). The MIU Project has three overlapping phases: Surface-based Investigation phase (Phase I), Construction phase (Phase II), and Operation phase (Phase III). The MIU Project has been ongoing the Phase III, as the Phase II was concluded for a moment with the completion of the excavation of horizontal tunnels at GL-500m level in February 2014. This report presents the results of the investigations, construction and collaboration studies in fiscal year 2014.
Fukui, Katsunori*; Hashiba, Kimihiro*; Sato, Toshinori; Kuwabara, Kazumichi; Takayama, Yusuke
JAEA-Research 2015-015, 61 Pages, 2015/11
JAEA-Research-2015-015.pdf:5.52MB
With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock is required, not only during construction and operation but also over a period of thousands of years after closure. On the other hand, it is known that rock and the rock mass surrounding the disposal gallery shows time dependent behavior such as creep or the stress-relaxation. It becomes the issue in the stability evaluation of the disposal gallery to grasp the behavior. About this issue, we pushed forward research development. In the fiscal year of 2014, the creep test was continuously conducted and the total testing time exceeded 17 years. The testing equipment and procedure were examined to investigate the deformation, failure and time-dependency of rock under wet conditions and between room temperature and 100C. The long-term strength of rock under triaxial stress state was researched with the aid of laboratory testing results and in situ stress measurement.
Kuwabara, Kazumichi; Sato, Toshinori; Sanada, Hiroyuki; Takayama, Yusuke
JAEA-Research 2015-005, 378 Pages, 2015/07
JAEA-Research-2015-005.pdf:125.5MB
JAEA-Research-2015-005.zip:0.53MB
This report presents the results of following rock mechanical investigations conducted at the -500m Stage. (1) Laboratory tests using cores and block samples obtained at the -500m Stage. (2) In-situ stress measurement using Compact Conical-ended Borehole Overcoring (CCBO) method at the -500m Stage. (3) In-situ stress measurements using Differential Strain Curve Analysis(DSCA) method at the -500m Stage. (4) Development of rock mechanical model.
Ichikawa, Yasuaki*; Kimoto, Kazushi*; Sato, Toshinori; Sanada, Hiroyuki; Kuwabara, Kazumichi
JAEA-Research 2014-027, 25 Pages, 2015/02
JAEA-Research-2014-027.pdf:16.92MB
The rock and the rock mass are known to show time-dependent behavior such as creep and the stress-relaxation. It is to evaluate long-term rock mechanics stability that the important theme understanding the property. From the research study until now, it is rock mechanics and chemical coupled phenomenon to have an influence on the long-term behavior. It is a theme to develop technique to model this coupled phenomenon, and to analyze. About an evaluation of the microcrack to have an influence on this coupled phenomenon, it is the theme that we should work on in a long-term rock mass behavior study chiefly. This study developed numerical analysis to check the ultrasonic scattering decrement behavior by the microcrack of the crystalline rock and the measurement technique. The FDTD method which modelled a crack was used for numerical analysis by split node. It depends on the simulation technique that it developed that useful knowledge was provided by elastic wave modeling. On the other hand, the ultrasonic measurement in a rock sample was measured by the water immersion method. As a result, we understood that we could acquire useful information to evaluate the scattering decrement of an elastic wave in a rock sample.
Fukui, Katsunori*; Hashiba, Kimihiro*; Sato, Toshinori; Sanada, Hiroyuki; Kuwabara, Kazumichi
JAEA-Research 2014-020, 50 Pages, 2014/11
JAEA-Research-2014-020.pdf:2.8MB
On the radioactive waste disposal, the long-term mechanical stability of shafts and galleries excavated in rock is required. Therefore, it is very important to understand the time-dependent behavior of rock mass for evaluating long-term mechanical stability. The purpose of this study is determining the mechanisms of time-dependent behavior of rock mass by precise testing, observation and measurement in order to develop methods for evaluating long-term mechanical stability of a rock mass. This report describes the results of the activities in fiscal year 2013. In Chapter 1, we described the overview and background of this study. In Chapter 2, the results of a long-term creep test on Tage tuff, started in fiscal year 1997 are described. In Chapter 3, the result of organization and analysis for time-dependent behavior of crystalline rock was described. In Chapter 4, for the drafting of in-situ test plan, examination of the numerical analysis technique of rock mass was carried out.
Kuwabara, Kazumichi; Takayama, Yusuke; Sanada, Hiroyuki; Sato, Toshinori; Tanno, Takeo*; Itamoto, Masaharu*; Kato, Harumi*
no journal, ,
In-situ stress measurements using CCBO (Compact Conical-ended Borehole Overcoring technique) were performem with two boreholes (13MI34, 13MI35) at depth of 500m in Mizunami Underground Research Laboratory. As a results, the Maximum stress in the horizontal plane was 15 MPa, and its azimuth were nearly N-S direction.
Takayama, Yusuke; Sato, Toshinori; Kuwabara, Kazumichi; Sanada, Hiroyuki
no journal, ,
no abstracts in English
Sato, Toshinori; Kuwabara, Kazumichi; Takayama, Yusuke; Tanno, Takeo*; Itamoto, Masaharu*; Kato, Harumi*
no journal, ,
This paper shows the results of in-situ stress measurement, uniaxial load and unload test, P-wave velocity measurement at the Mizunami Underground Research Laboratory. As the results of these measurements, microcrack distributed in Granite at deep depth influences physical and mechanical properties of rock and in-situ stress state.
Kuwabara, Kazumichi; Sato, Toshinori; Takayama, Yusuke; Tanno, Takeo*; Kato, Harumi*; Itamoto, Masaharu*
no journal, ,
It is very important to understand an initial stress state of the rock mass in doing a design, the construction of large-scale facilities under the ground. Groundwater recovery experiment will be conducted at the MIU GL.-500m closure test drift. This report described what stress measurement were performed by the CCBO (Compact Conical-ended Borehole Overcoring technique) to understand an initial stress state of intact rock and a stress state of the -500m gallery wall surface. As a result, the magnitude of principal stresses were 16.8 MPa, 10.2 MPa and 7.5 MPa. The maximum principal stress level was approximately same at the GL.-500m level. The direction of maximum principal stress is approximately 60 from a horizontal plane. The width of stress redistributed zone was about 2m from the wall of research galleries. Numerical analysis was carried out to examine an outbreak condition of core disking.
Kuwabara, Kazumichi; Ozaki, Yusuke; Matsui, Hiroya
no journal, ,
In the rock mechanical investigations at the Phase II, the research aims at "Characterization of geological environment in the Excavation Disturbed Zone (EDZ)" from the viewpoint of safety assessment. For the research, the specific information of the EDZ such as (1) size and structures, (2) petrophysical/geomechanical properties, and (3) stress state are required. The research also aims at "Characterization of geomechanical stability around tunnel" from the viewpoint of design and construction of underground facilities. For the research, the specific information such as (4) local stress regime, (5) spatial variability of petrophysical/geomechanical properties of rocks, and (6) distribution of discontinuities intersecting underground tunnels are required. The measurement system for rock mass behavior has been manufactured and set for groundwater recovery experiment in the Phase III. This report presents the results of following rock mechanical investigations conducted in FY 2014. In situ stress measurements using Compact Conical-ended Borehole Overcoring Technique were performed at the - 500m stage. Measurement system for rock massdisplacement using optical fiber was installed at the - 500m stage as part of the groundwater recovery experiment.
Kuwabara, Kazumichi; Matsui, Hiroya; Ozaki, Yusuke
no journal, ,
It has begun to groundwater recovery experiment, which measured to build a system to measure the rock behavior using the optical fiber-type rock displacement sensor as part of this experiment in the rock mechanical investigations at the Phase III. This report presents the results of following rock mechanical investigations conducted in FY 2015. Measurement system for rock mass displacement using optical fiber was installed at the - 500m stage as part of the groundwater recovery experiment.