Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 31

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

Strength and impermeability recovery of siliceous mudstone from complete failure

Sugita, Yutaka; Sanada, Masanori; Fujita, Tomoo; Hashiba, Kimihiro*; Fukui, Katsunori*; Okubo, Seisuke*

Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.207 - 212, 2013/01

Radionuclide migration can be undesirably increased by weakening the mechanical properties of a rock mass in the excavated disturbed zone (EDZ) around the tunnels of a geolical disposal facility for high level radioactive waste. Laboratory testing of loading stress and loading time on failed siliceous mudstone specimens has identified the potential for the long-term recovery of the strength and impermeability of the rock mass in the EDZ.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock, 5

Sanada, Masanori; Kishi, Hirokazu*; Sugita, Yutaka; Hayashi, Katsuhiko*; Takebe, Atsuji*; Okubo, Seisuke*

JAEA-Research 2012-025, 130 Pages, 2012/09

JAEA-Research-2012-025.pdf:4.12MB

In this study, strength recovery, generalized stress relaxation and two tensile strength tests were carried out using shale sampled in the Wakkanai-formation. As the results, by using the value of a suitable constant with the constitutive equation showing strength recovery, it was showed that change of the axial stress in a compacting test could be expressed. About the generalized relaxation, it examined by the air dried and the saturated condition. Visco-elastic behavior was more remarkable in saturated condition than the air dried. Moreover, when the loading rate up to the starting point of the generalized relaxation test was large, the influence on visco-elastic behavior was remarkable. About tensile characteristics, a splitting tensile strength test and a uniaxial tensile strength test were carried out. About splitting tensile strength, it turned out that the influence of the loading direction on a bedding plane is great.

JAEA Reports

Phenomenological study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Fukui, Katsunori*; Hashiba, Kimihiro*; Hikima, Ryoichi; Tanno, Takeo; Sanada, Hiroyuki; Matsui, Hiroya; Sato, Toshinori

JAEA-Research 2011-040, 54 Pages, 2012/02

JAEA-Research-2011-040.pdf:2.85MB

With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock are required, not only during construction and operation but also over a period of thousands of years after closure. Therefore, it is very important to understand the time-dependent behavior of rock for evaluating long-term mechanical stability. This report describes the results of the activities in FY2010. In Chapter 1, we provide an overview and the background to this study. In Chapter 2, the results of a long-term creep test on Tage tuff, started in FY1997 are described. In Chapter 3, the relation of loading-rate dependency of strength and stress dependency of creep life, the relationship of time dependency and probability distribution of strength or creep life and size effects are discussed to indicate more clearly the meaning of the value of "n" to express the degree of time dependency of the rock. In Chapter 4, failure criterions of a rock mass considering time dependency are discussed. In Chapter 5, the FEM analysis implemented with a generalized variable-compliance-type constitutive equation considering the change of "n" in confining pressure and strength distribution of rock mass carried out to clarify the long-term behavior of Toki granite is described. Finally, based on the numerical analysis, an in situ testing method is proposed.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock, 4

Sanada, Masanori; Hayashi, Katsuhiko*; Kishi, Hirokazu; Takebe, Atsuji*; Okubo, Seisuke*

JAEA-Research 2011-028, 102 Pages, 2011/11

JAEA-Research-2011-028.pdf:3.08MB

In this study, strength recovery, generalized stress relaxation and two tensile strength tests were carried out using shale sampled in the Wakkanai-formation. As the results, recovery of failed rocks in strength and hydraulic conductivity were observed under a certain condition. We believe this result is very important for the stability evaluation of underground space in the bedrock that needs good sealing up characteristic, isolation characteristic, safety and high reliability for long term. Generalized stress relaxation test was conducted submerging samples in water. Experimental results showed comparatively smaller scatter than those in air-dried condition. It was also found that testing results were affected by strain rate up to the starting point of generalized relaxation test. Indirect and uniaxial tensile strength tests were also conducted submerging samples in water and smaller tensile strength with smaller scatter were obtained than those in air-dried condition.

JAEA Reports

Phenomenological study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Hikima, Ryoichi; Hirano, Toru*; Matsui, Hiroya

JAEA-Research 2010-031, 45 Pages, 2010/10

JAEA-Research-2010-031.pdf:1.22MB

Rock shows time-dependent behavior such as creep/relaxation. With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock are required, not only during construction and operation but also over a period of thousands of years after closure. Therefore, it is very important to understand the time-dependent behavior of rock for evaluating long-term mechanical stability. The purpose of this study is determining the mechanisms of time-dependent behavior of rock by the precise test, observation and measurement, to develop methods for evaluating long-term mechanical stability. In previous work, testing techniques have been established and basic evaluation methods were developed. Recently, some parameters needed for simulation of time-dependent behavior were determined at the Mizunami underground research facilities. However, we did not have enough data to check on the reliability of the evaluation method for these parameters. This report describes the results of the activities in fiscal year 2009. In Chapter 1, we provide an overview and the background to this study. In Chapter 2, the results of the long-term creep test on Tage tuff, started in fiscal year, 1997 are described. In Chapter 3, methods for obtaining parameters of the constitutive equation for rock are reviewed and summarized. The time dependent behavior of Toki granite and Inada granite (40-80 $$^{circ}$$C) are also summarized based on data obtained prior to the previous fiscal year. In Chapter 4, the FEM analysis implemented with a generalized variable-compliance-type constitutive equation carried out to clarify the long-term behavior of Toki granite is described. Finally, based on the numerical analysis, an in situ testing method is proposed.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock, 3

Hayashi, Katsuhiko; Kishi, Hirokazu; Kabayashi, Yasushi*; Takebe, Atsuji*; Okubo, Seisuke*

JAEA-Research 2009-058, 106 Pages, 2010/02

JAEA-Research-2009-058.pdf:18.82MB

In this study, experimental studies on the strength recovery, the generalized stress relaxation behavior and the tensile strength were conducted using samples obtained from the Wakkanai-formation shale. As the results, the strength recovery has time-dependent characteristics. It was founded that the generalized stress relaxation behavior depends on the draining conditions. Furthermore, regarding the tensile strength, complete stress-strain curve under uniaxial tensile strength conditions was gotten and it was found that there is small residual strength. The results of uniaxial tensile strength in this year are almost same as the minimum value of splitting tensile strength test results.

JAEA Reports

Phenomenological study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Hirano, Toru; Matsui, Hiroya

JAEA-Research 2009-020, 36 Pages, 2009/08

JAEA-Research-2009-020.pdf:9.18MB

On the radioactive waste disposal, the long-term mechanical stability of tunnel was required. Therefore, we have been developing the method evaluating the stability. This report describes the works in the FY2008. Chapter 1 is the overview. Chapter 2 is the result of long-term creep test on Tage tuff. The strain was increasing at very low speed and the strain rate was decreasing following elapsed time to the powers of -0.9. This behavior is likely to short-term creep. In Chapter 3, the control program was extended to conduct the generalized relaxation test along any relaxation pattern. Then, that test of Toki granite was carried out successfully. The parameters in the variable-compliance-type constitutive equation for Toki granite were deduced. In Chapter 4, parameter-obtaining methods for the constitutive equation were reviewed and criticized. In the final part, an idea of new rock characterization where time-dependent behavior of rock is considered as the important factor was proposed.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock, 2 (Contract research)

Okubo, Seisuke*; Hayashi, Katsuhiko; Kobayashi, Yasushi; Hiramoto, Masayuki*

JAEA-Research 2008-106, 91 Pages, 2009/02

JAEA-Research-2008-106.pdf:6.08MB

It is generally known that the rock has the properties of strength recovery by elapse of time around the tunnel inside sedimentary rock with ground support due to inner pressure and ground pressure. The properties of strength recovery must be taken into account of the estimation about cavity shape stability or the long-term dynamical behavior of closed disposal ground. Our research study is focusing on the properties of strength recovery, generalized relaxation behavior and the characteristics of tensile strength by experiments using boring cores obtained from the Horonobe Underground Research Laboratory so as to improve the modeling for future stage.

JAEA Reports

Phenomenological study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Seno, Yasuhiro*; Hirano, Toru; Nakama, Shigeo; Matsui, Hiroya

JAEA-Research 2008-065, 51 Pages, 2008/08

JAEA-Research-2008-065.pdf:2.9MB

This report describes the results of the works in the fiscal year 2007. In Chapter 1, we described the overview and background of this study. In Chapter 2, the result of continuing creep test of Tage tuff which was started from the fiscal year 1997 was described. Although there was some annual variability, the precious data were obtained. In Chapter 3, the control program for the generalized relaxation test was developed. The generalized relaxation test of Toki granite was conducted in order to get basically data. In Chapter 4, the extended constitutive equation of variable compliance was analytically discussed. Using the data obtained in Chapter 3, the parameters of Toki granite of the constitutive equation were obtained and numerical simulation was conducted.

JAEA Reports

Studies about strength recovery and generalized relaxation behavior of rock (Contract research)

Hiramoto, Masayuki; Kobayashi, Yasushi; Okubo, Seisuke*

JAEA-Research 2008-002, 60 Pages, 2008/03

JAEA-Research-2008-002.pdf:2.52MB

Strength recovery and generalized relaxation behavior of rock were examined. The sample rock was Wakkanai-formation shale. In Chapter 2, strength recovery characteristic of rocks was examined. It was found that strength recovery increases with increase of testing time or load-holding time. It was interesting that the sample with relatively small unconfined compressive strength showed higher strength recovery. These results were obtained for only two sample rocks. Therefore, the accumulation of the data is needed in future to evaluate the influence of the boring places quantitatively. In Chapter 3, the generalized relaxation behavior of rock was examined. As a result, scatter in obtained data is considerably large, so the accumulation of the data is needed in future to understand rightly the complicated generalized relaxation behavior.

JAEA Reports

Phenomelogical study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Seno, Yasuhiro; Nakama, Shigeo; Sato, Toshinori*; Hirano, Toru

JAEA-Research 2007-088, 118 Pages, 2008/03

JAEA-Research-2007-088.pdf:27.7MB

This report describes the results of the works in the FY2005 and 2006. In Chapter 2, as the fundamental study on time-dependent behavior, followings were described; (1) The result of continuing creep test of Tage tuff which was started from the FY1997. (2) The results of multi-stage creep test of Inada granite at mid-range temperature. (3) The consideration of the generalized relaxation test. (4) The consideration of new testing method to determine the parameter in the constitutive equation supposed by Okubo. In Chapter 3, followings were described; (1) The results of rock mechanical tests of Toki granite. (2) The results of obtained parameters for the constitutive equation considering time-dependent behavior by mechanical tests and numerical simulations. Furthermore, in this report, following two related studies were attached in appendix; (1) Study on evaluating the effects of scatter in in-situ rock properties. (2) Study on new rock classification method considering long-term behavior of rock mass.

Journal Articles

Determinaion of parameters for a stress-strain constitutive equation considering time-dependent behavior of Toki granite

Hirano, Toru; Seno, Yasuhiro; Nakama, Shigeo; Okubo, Seisuke*

Dai-37-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.397 - 402, 2008/01

Toki granite was tested to obtain parameters for the constitutive equation and numerical simulations were carried out. The testing method was uniaxial compressive loading at the moderate a constant strain rate that is decreased after yielding to obtain the complete stress-strain curve. In addition, two kinds of the strain rate were alternately switched to obtain the parameter ${it n}$ from one specimen. The ${it n}$ represents the strength time-dependence in the constitutive equation. Based on ${it n}$ and the complete stress-strain curve, second parameter ${it m}$ can be calculated by numerical simulations. The ${it m}$ accounts for the behavior after yielding. According to the results, Toki granite has ${it n}$=52 and ${it m}$=60. Thus shows relatively low time-dependence.

JAEA Reports

Investigation on Evaluation Methods for Long-Term Stability of Near-Field Rock Mass

Okubo, Seisuke*

JNC TJ8400 2004-018, 94 Pages, 2005/02

JNC-TJ8400-2004-018.pdf:1.07MB

This study was conducted to increase the reliability of evaluation methods for assessing the long-term stability of near-field rock mass. In chapter 2, triaxial creep results were given. In chapter 3, strength recovery of Horonobe mudstone was researched.Evaluation methods by investigation of old underground structures and in-situ test were stated in chapter 4.

JAEA Reports

Phenomenological Study on Crystalline Rock Aiming at Evaluation of Long-Term Behaviour of Rock Mass

Okubo, Seisuke*

JNC TJ7400 2005-004, 107 Pages, 2005/02

JNC-TJ7400-2005-004.pdf:2.24MB

This study was based on the outcomes of the research conducted between the fiscal year of 1994 and 2003.In this year,creep test of Tage tuff was continuously conducted and the total testing time exceeded 7 years.The data is considered to be very scarce and valuable(chapter 2).Results of creep test at mid-range temperature were described(chapter 3).Creep test under relatively low stress was also conducted and the results were described(chapter 4).Mechanism of time-dependent behaviour of rock was discussed considering scatter of data as valuable information(chapter 5).Main results of the 10-years investigation were overviewed,and new research project was proposed(chapter 6).Chapter 7 is a conclusion.

JAEA Reports

Investigation on Evaluation Methods for Long-Term Stability of Near-Field Rock Mass

Okubo, Seisuke*

JNC TJ8400 2003-081, 107 Pages, 2004/02

JNC-TJ8400-2003-081.pdf:2.94MB

A concept for evaluation methods of long-term behavior of rock mass, based on natural analog approach, is proposed. For an example, long-term strength was estimated from the published data of in-situ rock stress. Data were plotted on sigma-1 vs. sigma-3 diagram (major vs. minor principal stress diagram). It was found that all data except one were plotted under the line sigma-1 = 4 sigma-3 . Data were measured in relatively stable rock mass, then, this line indicates the long-term strength, and the region below this line is considered to indicate stable region for quite long-term. Sample rock was obtained in Horonobe area. Experimental works were carried out in the triaxial compression stress, and the effects of the confining pressure on long-term deformation or stability of the sample rock were examined. At first, triaxial compression tests were carried out. In the test, loading rate (strain rate) was changed several times to obtain viscoelastic properties of the sample rock. Newly developed transparent platens made of acrylic acid resin were used together with a transparent triaxial cell recently developed by this author. By virtue of these transparent apparatuses, it was easy to observe gradual deformation of the sample, formation of faults and in/outflow of water from the sample during the tests. Multi-stage creep tests were also performed in triaxial compression stress. By the photographing system cooperated with the loading and measuring apparatuses, it was possible to observe deformation of the sample in the tertiary creep region. The Poisson's ratio under confining pressure was evaluated, and the parameter set of a constitutive equation of variable compliance type was obtained based on the testing results.

JAEA Reports

Fundamental study on long-term stability of rock from the macroscopic point of view

Okubo, Seisuke*

JNC TJ7400 2004-002, 115 Pages, 2004/02

JNC-TJ7400-2004-002.pdf:0.74MB

In the fiscal year of 1994, this project was started. In this year, creep testing of Tage tuff was continuously conducted and the total testing time exceeded 6 years. The data is considered to be very scarce and valuable (chapter 2). Short-term creep testing was also conducted in the multi-cylinder hydraulic creep-testing machine and the results were described (chapter 3). Applicability of a non-linear constitutive equation to various loading conditions was discussed(chapter 4). The results of triaxial compression test by the transparent triaxial cell were also described (chapter 5). Results of creep testing at mid-range temperature were described (chapter 6). Finally, the sequences and results of the 10-years investigation were overviewed in chapter 7. In the fiscal year of 1994, this project was started. In this year, creep testing of Tage tuff was continuously conducted and the total testing time exceeded 6 years. The data is considered to be very scarce and valuable (chapter 2). Short-term creep testing was also conducted in the multi-cylinder hydraulic creep-testing machine and the results were described (chapter 3). Applicability of a non-linear constitutive equation to various loading conditions was discussed(chapter 4). The results of triaxial compression test by the transparent triaxial cell were also described (chapter 5). Results of creep testing at mid-range temperature were described (chapter 6). Finally, the sequences and results of the 10-years investigation were overviewed in chapter 7.

JAEA Reports

Study on long-term beghavior of weak rock

Okubo, Seisuke*

JNC TJ8400 2002-062, 57 Pages, 2003/03

JNC-TJ8400-2002-062.pdf:1.14MB

Using the boring core obtained in the Horonobe region, the data in triaxial compression stress state was acquired, and the examination was carried out on the effect of the confining pressure on long-term deformation or stability of the sample rock. At first, triaxial compression tests were carried out. In the test, loading rate (strain rate) was changed several times to obtain viscoelastic properties of the sample rock. Multi-stage creep tests were also performed in triaxial compression stress. The parameter set of a constitutive equation of variable compliance type was obtained based on the testing results. In this study, a transparent triaxial cell recently developed by this author was used. The external cylinder of this vessel was made of the transparent acrylic resin. Therefore, gradual deformation of the sample under testing was easily and clearly observed.

JAEA Reports

Fundamental study on long-term stability of rock from the macroscopic point of view

Okubo, Seisuke*

JNC TJ7400 2002-011, 86 Pages, 2003/03

JNC-TJ7400-2002-011.pdf:2.99MB

In the fiscal year of l994 when this project was started, a pneumatic creep testing machine was modified. At the end of the fiscal year of l994, Inada granite was purchased, and the preliminary tests such as P-wave velocity measurement and Schmidt hammer testing were carried out. Through the fiscal year of l995, a specimen of Tage tuff under water-saturated condition had been loaded in uniaxial condition in the pneumatic creep testing machine. In the fiscal year of 1995, the uniaxial compression and tension tests, and the short-term creep test of Inada granite were also carried out in the servo-controlled testing machines to obtain the complete stress-strain curves. A hydraulic creep testing machine which was planned to use in the next year was modified for long-term creep testing. Finally, a constitutive equation of variable compliance type was examined based on the experimental results. In the fiscal year of 1996, creep, compression and tension tests were carried out. Two types of pressure maintenance equipment (hydraulic and pneumatic types) were developed and examined. In the fiscal year of 1997, creep, compression and tension tests etc. were again carried out on the basis of the results heretofore. The experimental results of long-term creep testing of Tage tuff, middle-term creep testing of Inada granite were described. In both creep tests, samples were submerged in water. In the fiscal year of 1998, creep testing of Tage tuff was conducted. Results of relatively short-term (middle-term) creep conducted on a servo-controlled testing machine were also described. Sample rock was Sirahama sandstone that showed a considerably large creep strain in low stress level such as 17 % of the uniaxial compression strength. Results of triaxial compression test and uniaxial tension test including unloading-reloading tests were described. In the fiscal years of 1999, 2000 and 2001, creep testing of Tage tuff was continuously conducted. A multi-cylinder hydraulic creep ...

JAEA Reports

Fundamental study on long-term stability of rock from the macroscopic point of view

Okubo, Seisuke*

JNC TJ7400 2001-010, 100 Pages, 2002/03

JNC-TJ7400-2001-010.pdf:23.8MB

no abstracts in English

JAEA Reports

Fundamental study on long-term stability of rock from the macroscopic point of view

Okubo, Seisuke*

JNC TJ7400 2001-003, 134 Pages, 2001/03

JNC-TJ7400-2001-003.pdf:2.57MB

no abstracts in English

31 (Records 1-20 displayed on this page)