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Journal Articles

Current status of geological disposal by "all-Japan" activities, 4; Repository design and engineering technology (2)

Motoshima, Takayuki*; Matsui, Hiroya; Kawakubo, Masahiro*; Kobayashi, Masato*; Ichimura, Tetsuhiro*; Sugita, Yutaka

Nihon Genshiryoku Gakkai-Shi ATOMO$$Sigma$$, 64(3), p.163 - 167, 2022/03

no abstracts in English

Journal Articles

A Study on support design for deep shaft sinking in rock masses of low strength and anisotropic initial stress

Motoshima, Takayuki*; Koike, Masashi*; Hagihara, Takeshi*; Aoyagi, Kazuhei

Dai-46-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.208 - 213, 2019/01

The short step construction method is the standard construction method for deep shaft excavation. However, considering the shaft construction in the sedimentary rock widely distributed in Japan, the support concrete stress can become excessive especially when there are bad conditions such as low rock strength, anisotropic initial stress, or high ground pressure. In this research, we introduced the dual support design to the short step construction method in order to reduce the support stress, and confirmed the validity by three dimensional numerical analysis. Validation analysis was conducted using the in-situ data in the Horonobe Underground Research Project conducted by Japan Atomic Energy Agency.

Journal Articles

Three-dimensional visualization of methane concentration distribution in tunnels to increase underground safety

Nago, Makito*; Motoshima, Takayuki*; Miyakawa, Kazuya; Kanie, Shunji*; Sanoki, Satoru*

Proceedings of ITA-AITES World Tunnel Congress 2017 (WTC 2017) (USB Flash Drive), 10 Pages, 2017/06

This study presents a new approach to increase construction safety under methane inflow conditions by providing the three-dimensional concentration distribution of methane in underground structures. The study was conducted at the Horonobe Underground Research Laboratory, which is located in Neogene sedimentary rock where groundwater contains dissolved methane. As conventional gas sensors are confined to measurement at a single point in time and space, a new system was developed combining a laser methane detector and a laser range finder to effectively obtain the spatial concentration distribution of methane. This system was tested in tunnel galleries located at a depth of 350 m. The results show that this system is effective for identifying unpredicted methane emissions as well as predicted emission hotspots and for examining the validity of the ventilation scheme, which ensures construction safety.

Journal Articles

Design and verification of support system for underground excavations under anisotropic stress conditions

Motoshima, Takayuki*; Fujita, Tomo; Aoyagi, Kazuhei; Shirase, Mitsuyasu*; Nago, Makito*

Proceedings of 7th International Symposium on In-situ Rock Stress (RS 2016) (Internet), 9 Pages, 2016/05

JAEA Reports

Measurement of the deformation behavior of the rock mass in the 350 m gallery in the Horonobe Underground Research Laboratory

Sakurai, Akitaka; Aoyagi, Kazuhei; Fujita, Tomo; Motoshima, Takayuki*

JAEA-Data/Code 2015-023, 46 Pages, 2016/02

JAEA-Data-Code-2015-023.pdf:48.03MB
JAEA-Data-Code-2015-023-appendix(CD-ROM).zip:48.51MB

In a high level radioactive waste (HLW) disposal project, it is necessary to investigate the long-term behavior of thermos-hydro-mechanical-chemical of the rock mass around the engineered barrier system of the HLW waste for the safety assessment of the disposal system. In addition, long-term stability of the rock mass around the galleries are required for the disposal facility. Considering these backgrounds, the authors measure the deformation behavior of the vertical pit drilled on the floor of the 350 m gallery in the Horonobe Underground Research Laboratory. In situ measurements of the deformation of the pit and rock mass around the pit was conducted to apply to the assessment of the long-term deformation behavior. The authors describe the drilling of the vertical pit, geological observation, specification of the measurement instrument, measurement method, and result of the measurement in this report.

Journal Articles

Investigation of an excavation damaged zone in the east access shaft at the Horonobe Underground Research Laboratory

Aoyagi, Kazuhei; Ishii, Eiichi; Fujita, Tomo; Motoshima, Takayuki*

Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.313 - 318, 2016/01

The objective of this research is to investigate the extent and failure mechanism of an Excavation Damaged Zone (EDZ) induced around the East Access Shaft in the Horonobe Underground Research Laboratory. As a result of hydraulic tests, hydraulic conductivity within 2 m from the shaft wall was increased by 1 to 3 orders of magnitude. This result is consistent with the extent of the development of fractures detected by borehole televiewer surveys. Furthermore, the dominant failure mechanism of the fractures around the shaft wall was almost tensile; also these fractures were caused by the short-term excavation-induced unloading.

Journal Articles

Tunnel support design for anisotropic stress state and comparison between in-situ convergence results and calculated results

Motoshima, Takayuki*; Yabuki, Yoshio*; Minamide, Masashi*; Nago, Makito*; Aoyagi, Kazuhei

Tonneru Kogaku Hokokushu (CD-ROM), 24, p.I_10_1 - I_10_5, 2014/12

Economic tunnel support design for Horonobe underground research laboratory was obtained according to the relationship in the direction of the initial stress and the direction of excavation. The authors compared between the in situ convergence results and calculated results in order to investigate the validity of initial stress measurements. As a result, a positive correlation was observed between the in situ convergence results and calculated results, and the difference between the two was able to be explained by the difference between the assumed deformation coefficient and the measured coefficient. From these results, the measurement results of the initial stress performed in the surface based investigation has been confirmed almost reasonable.

JAEA Reports

Study on development of evaluation technique of in-situ tracer test in Horonobe Underground Research Laboratory Project (Contract research)

Yokota, Hideharu; Amano, Kenji; Maekawa, Keisuke; Kunimaru, Takanori; Naemura, Yumi*; Ijiri, Yuji*; Motoshima, Takayuki*; Suzuki, Shunichi*; Teshima, Kazufumi*

JAEA-Research 2013-002, 281 Pages, 2013/06

JAEA-Research-2013-002.pdf:13.03MB

To evaluate permeable heterogeneity in a fracture and scale effects which are problems to be solved based on the ${it in-situ}$ mass transportation data of fractures in hostrock, a number of tracer tests are simulated in a fictitious single plate fracture generated on computer in this study. And the transport parameters, e.g. longitudinal dispersion length, true velocity and dilution rate, are identified by fitting one- and two-dimensional models to the breakthrough curves obtained from the simulations in order to investigate the applicability of these models to the evaluation of ${it in-situ}$ tracer test. As a result, one-dimensional model yields larger longitudinal dispersion length than two-dimensional model in the both cases of homogeneous and heterogeneous hydraulic conductivity fields of the fictitious fracture. And, the longitudinal dispersion length identified from a tracer test is smaller and/or larger than the macroscopic longitudinal dispersion length identified from whole fracture. It is clarified that these are occurred by shorter or longer distance between boreholes compare to the correlation length of geostatistical heterogeneity of fictitious fracture.

Journal Articles

Gas control measures taken during deep shaft excavation

Nago, Makito*; Hagihara, Takeshi*; Minamide, Masashi*; Motoshima, Takayuki*; Jin, Kazumi; Kudo, Hajime; Sugita, Yutaka; Miura, Yoichi*

Dai-49-Kai Zenkoku Kensetsugyo Rodo Saigai Boshi Taikai Kenkyu Rombunshu (CD-ROM), p.77 - 80, 2012/10

This paper presents measures against gas emission during deep shaft excavation in the Horonobe Underground Research Laboratory Project (Horonobe URL Project). The gas control measures taken in the Horonobe URL Project include the following: (1) determination of the amount of methane contained in surrounding strata and groundwater, and gas concentration based on preliminary investigations, (2) determination of the specifications of fans, dust collectors, and ducts through ventilation network analysis (simulation), (3) reduction of methane gas emission through the use of waterproofing grout, (4) prohibition on the use of internal-combustion engine and the adoption of explosion-proof equipment, (5) development of methane gas control system, and (6) monitoring of methane gas emission. (3) to (6) described above are performed daily in the safety management activities and described in detail in this paper. The ventilation and eastern access shafts have currently reached a depth of 290 m and 250 m, respectively. The emission of methane gas has been observed to rise 0.3 % to 1.3 % in the fault zone, and it is controlled appropriately according to the gas control measures described above. As the measure to reduce the methane gas concentration, monitoring is confirmed to be effective.

JAEA Reports

Mizunami Underground Research Laboratory project (Study on hydrogeology in crystalline fractured rock); Geo-risk management focused on water inrush using discrete fracture network model

Onoe, Hironori; Saegusa, Hiromitsu; Motoshima, Takayuki*; Ijiri, Yuji*; Otsu, Hiroyasu*

JAEA-Research 2010-021, 73 Pages, 2010/10

JAEA-Research-2010-021.pdf:6.1MB

It is important to evaluate the influence of water inrush into underground facility on costs and schedules for construction of deep underground facility based on prior information. In this study, risk assessment method using a combination of discrete fracture network model with financial engineering theory has been developed taking into account unexpected water inrush into the underground facility constructed in crystalline fractured rock. The risk assessment method has been applied to the construction of the Mizunami Underground Research Laboratory. The relationship between the amount of information due to the progress of investigations and the risk regarding cost variation for the countermeasure against water inrush has been evaluated. As a result, site characterization procedure for decreasing the water inrush risk efficiently was suggested. The applicability of the risk assessment method for the ex-post-facto assessment of construction of the underground facility was also confirmed.

Journal Articles

A Study on risk assessement approach of water inflow into a shaft in fractured rock mass

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.

Oral presentation

Development of risk management approach for underground facility construction in granite

Shimono, Masato*; Motoshima, Takayuki*; Ijiri, Yuji*; Otsu, Hiroyasu*; Sakai, Ryosuke*; Sakai, Kazuo*; Sato, Toshinori; Mikake, Shinichiro

no journal, , 

It is considered that the uncertainty of construction cost due to geological heterogeneity is quite large. Therefore, it is crucial to make a long-term consistent budget plan for a construction period of tens years and to have engineering strategies for reducing a total budget. In this study, a risk management approach for construction in a heterogeneous fractured rock is developed. In this approach, methodologies of calculating construction costs for excavating drifts and taking countermeasures at high-hydrostatic pressured fracture zones in a heterogeneous rock are established. The cost for excavating drift is calculated from the heterogeneity of rock strength estimated from a geostatistical modeling approach. The cost for taking countermeasures is calculated from the heterogeneity of large fracture zone estimated from a probabilistic discrete fracture network modeling approach. In addition, a risk for a construction is assessed by a risk cost curve commonly used in the financial business.

Oral presentation

Risk evaluation and management method for high-pressure inflow, 1; Hydrogeological investigations of faults with high-pressure inflow risk during the shaft construction

Onoe, Hironori; Saegusa, Hiromitsu; Watanabe, Tadashi; Motoshima, Takayuki*; Ijiri, Yuji*; Otsu, Hiroyasu*

no journal, , 

no abstracts in English

Oral presentation

Risk evaluation and management method for high-pressure inflow, 2; Management of high-pressure inflow risk during the shaft construction using the groundwater level in the boreholes

Motoshima, Takayuki*; Ijiri, Yuji*; Onoe, Hironori; Saegusa, Hiromitsu; Watanabe, Tadashi; Otsu, Hiroyasu*

no journal, , 

no abstracts in English

Oral presentation

Analysis of stable chlorine isotopic ratios and saline water diffusion model in sedimentary formation

Tokunaga, Tomochika*; Kimura, Yuki*; Ijiri, Yuji*; Motoshima, Takayuki*; Kunimaru, Takanori; Takamoto, Naohiko*; Shimada, Jun*; Hosono, Kenichi*

no journal, , 

no abstracts in English

Oral presentation

Application of risk evaluation method for high-pressure inflow to evaluation after the fact in clystalline rock

Hotta, Yohei*; Otsu, Hiroyasu*; Motoshima, Takayuki*; Onoe, Hironori

no journal, , 

no abstracts in English

Oral presentation

A Study of risk assessment of rapid inrush of water into the underground facility at the Mizunami Underground Research Laboratory project, 2; Relationship between progress of investigations and cost variation related to water inrush

Onoe, Hironori; Saegusa, Hiromitsu; Motoshima, Takayuki*; Ijiri, Yuji*; Otsu, Hiroyasu*

no journal, , 

In the construction of deep underground facilities in a fractured rock mass, it is important to evaluate the influence of hydraulic and rock mechanical heterogeneities due to faults and joints, based on prior investigations. Risk assessment methodology using a combination of discrete fracture network model with financial engineering theory was developed considering unexpected water inrush, which is assumed to be one, if not the most significant issue for construction in fractured rock. In this study, the relationship between the amount of information due to the progress of investigations and cost variation regarding water inrush was evaluated, and a management method based on the risk assessment is discussed. The project that serves as the basis for the study is the construction of the underground facility in the Mizunami Underground Research Laboratory (MIU), which is now under construction by the Japan Atomic Energy Agency (JAEA).

Oral presentation

A Study of risk assessment of rapid inrush of water into the underground facility at the Mizunami Underground Research Laboratory project, 1; Development of risk assessment methodology of water inrush using discrete fracture network model

Motoshima, Takayuki*; Ijiri, Yuji*; Onoe, Hironori; Saegusa, Hiromitsu; Otsu, Hiroyasu*

no journal, , 

Since the groundwater inflow into a tunnel has a large impact on a construction cost and a schedule. It is important to estimate the influences of groundwater inflow on the cost and schedule quantitatively based on prior information about hydrogeological properties. In this study, the hydrogeological structure of fractured granite distributed at the Mizunami Underground Research Laboratory was modeled by a stochastic Discrete Fracture Network, and the risk of water inrush is evaluated probabilistically based on the model. The effects of parameter value uncertainties derived from field data on the risk of water inrush were also discussed.

Oral presentation

Risk management methodology for construction of underground structures

Ijiri, Yuji*; Motoshima, Takayuki*; Kamemura, Katsumi*; Mikake, Shinichiro; Matsui, Hiroya; Sugihara, Kozo

no journal, , 

no abstracts in English

36 (Records 1-20 displayed on this page)