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Aoyagi, Kazuhei; Sugawara, Kentaro*; Kamemura, Katsumi*; Nago, Makito*
International Journal of Rock Mechanics and Mining Sciences, 178, p.105776_1 - 105776_11, 2024/06
Times Cited Count：0 Percentile：0.00(Engineering, Geological)A method for estimating the stress state during the construction of underground facilities such as deep geological disposal repositories is necessary to enhance the reliability of their design, construction, and long-term performance. For this purpose, numerous in situ measurements of variables such as hydraulic fracturing or the stress relief method have been typically performed to estimate the stress state. However, it is difficult in some cases to validate the stress state, particularly in sedimentary rock, because of the variation related to heterogeneous rock masses and topography. This study developed a new method for reliably estimating the in situ stress state of rocks using the measured initial elastic displacement of the loop gallery at 350 m depth in the Horonobe Underground Research Laboratory (URL), Japan. The estimated magnitudes of the maximum and minimum horizontal stresses are 11.25 and 6.25 MPa, respectively, which are similar to the stresses measured using the hydraulic fracturing method performed before excavating the facility. Although the proposed method could only be applied after excavation of the gallery in the studied case, it yielded an estimate of the stress state over a region of hundreds of square meters with high accuracy, as assessed by comparison with measured results. We conclude that the method can be applied to optimizing the design, construction, and performance of large underground facilities, such as deep geological repositories.
Kamemura, Katsumi*; Aoyagi, Kazuhei; Nago, Makito*; Sugawara, Kentaro*
Dai-45-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.43 - 48, 2018/01
In situ stress state is very important for the design of deep underground facility of high-level radioactive waste disposal repository. This study establishes a practical and effective method for estimating in situ stress state based on the measured convergence and detailed geological observations during gallery excavation. The convergence was measured in various directions of the loop gallery at 350m depth of the Horonobe URL; this allows determination of the stress state corresponding to the rock mass behavior in 120m 
200m area. In situ stress state estimated by the back analysis considering existing faults and fractures showed a good agreement with that of estimated from hydraulic fracturing method.
Shirase, Mitsuyasu*; Abe, Akimasa*; Nago, Makito*; Ishii, Eiichi; Aoyagi, Kazuhei; Wakasugi, Shinichi*
Doboku Gakkai Heisei-29-Nendo Zenkoku Taikai Dai-72-Kai Nenji Gakujutsu Koenkai Koen Gaiyoshu (DVD-ROM), p.1795 - 1796, 2017/09
JAEA has executed the underground facility construction operation from February 2011 to June 2014, while carrying out the maintenance and research project until 2018. This report is about the extra high head pump which was able to drain the high specific gravity grout drainage, which develops during grouting operation at this facility, directly from 250m underground to the surface.
Aoyagi, Kazuhei; Nago, Makito*
Jiban Kogakkai-Shi, 65(8), p.12 - 15, 2017/08
In this paper, we described the development of the supporting tool of observational construction of the underground research laboratory, and the monitoring result of hydro-mechanical properties around the gallery wall. As an observational construction tool, we developed a "3D geological structure/construction data visualization system". The geological data, measurement data, construction data, and prediction analysis results are visualized and integrated comprehensively as the construction proceeds. The planned support pattern was examined according to the visualized data. In addition, the Excavation Damaged Zone (EDZ) was extended within 1.0 m from the gallery wall. In this area, hydraulic conductivity was enhanced. However, the extent of the EDZ was not enlarged along with time; the stability of the support was also confirmed on the basis of the measurement of stress in the shotcrete. Integrating these results the observational construction considering the development of an EDZ can be established. This technology will have an important role in geological disposal of high-level radioactive waste.
Aoyagi, Kazuhei; Kamemura, Katsumi*; Nago, Makito*; Sugawara, Kentaro*; Matsubara, Makoto*
Proceedings of ITA-AITES World Tunnel Congress 2017 (WTC 2017) (USB Flash Drive), 10 Pages, 2017/06
An in situ stress state is one of the important factors in the design of deep underground facility of high-level radioactive waste disposal repository. This study establishes a practical and effective method for estimating in situ stress state on the basis of the measured convergence during gallery excavation. The convergence was measured in various directions of the loop gallery at 350m depth of the Horonobe Underground Research Laboratory; this allows determination of the stress state corresponding to the rock mass deformation behavior in an approximately 120 m* 200 m area. To estimate in situ stress state around that area, a back analysis method considering the existence of faults and fractures around the gallery was developed. The analyzed results showed a good agreement with the trend of in situ stress state estimated from hydraulic fracturing method.
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.
Kamemura, Katsumi*; Aoyagi, Kazuhei; Nago, Makito*; Sugawara, Kentaro*; Matsubara, Makoto*
Dai-14-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), 6 Pages, 2017/01
In the design of deep underground structures such as high-level radioactive waste disposal repositories, the estimation of rock mass stress state is important as well as the estimation of mechanical characteristics of rock mass. This study establishes a practical and effective method for estimating in situ stress based on the convergence measurement results obtained during gallery construction of URL. The convergence was measured in various directions of the URL loop gallery at 350 m depth, and this will allow determination of the stress state over a large area using a back analysis method. In order to improve the accuracy of initial stress estimation, the relationship between convergence measurement results and geological situation of existing fractures were studied. The analysis results show good agreement with the in situ stress state results reported in previous studies and confirm the applicability of the proposed method.
Aoyagi, Kazuhei; Nago, Makito*; Kamemura, Katsumi*; Sugawara, Kentaro*
Proceedings of 9th Asian Rock Mechanics Symposium (ARMS-9) (USB Flash Drive), 10 Pages, 2016/10
Motoshima, Takayuki*; Fujita, Tomoo; Aoyagi, Kazuhei; Shirase, Mitsuyasu*; Nago, Makito*
Proceedings of 7th International Symposium on In-situ Rock Stress (RS 2016) (Internet), 9 Pages, 2016/05
Kamemura, Katsumi*; Fujita, Tomoo; Aoyagi, Kazuhei; Nago, Makito*; Shirase, Mitsuyasu*; Sugawara, Kentaro*
Dai-44-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.109 - 114, 2016/01
How to estimate the initial stress state as well as a mechanical characteristic of rock mass is important in the design of deep underground structures. Some stress measurement methods using borehole, which methodology and evaluation method have been discussed in detail, are carried out if necessary. However, obtained results are often varying widely, so the evaluation of initial stress is difficult. Here, the initial stress state corresponding to the rock mass behavior of about 120m200m area is evaluated using the convergence measurement results during tunnel excavation in 350m depth. Analysed result corresponded to that of other method, so the validity of the proposed method was shown.
Fujita, Tomoo; Aoyagi, Kazuhei; Nago, Makito*
Tonneru To Chika, 46(7), p.481 - 489, 2015/07
The Japan Atomic Energy Agency (a National Research and Development Agency) is constructing shafts and research tunnels in Horonobe-cho, Teshio-gun, Hokkaido as part of the Horonobe Underground Research Project. This report summarizes investigations into computerized construction while excavating the shaft for the Horonobe Underground Research Centre. Cracking in the lining concrete occurred due to the development of rock spalling near the wall surface while excavating the ventilation shaft. To that end, we created a flowchart to select kinds of shaft supports for use in subsequent works that took steps appropriate for the bedrock collapse phenomenon during excavating, countermeasures for this and extent of spalling. In addition, this report contains information on pre-grouting works on the fault zone and its results which were conducted as a measure against groundwater inflow which can be a problem during excavating works and also the results of these works.
Inagaki, Daisuke*; Tsusaka, Kimikazu*; Aoyagi, Kazuhei; Nago, Makito*; Ijiri, Yuji*; Shigehiro, Michiko*
Proceedings of ITA-AITES World Tunnel Congress 2015 (WTC 2015)/41st General Assembly, 10 Pages, 2015/05
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.
Tsusaka, Kimikazu*; Inagaki, Daisuke*; Nago, Makito*; Ijiri, Yuji*
Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 9 Pages, 2014/10
Jin, Kazumi; Nago, Makito*
Soritsu 50-Shunen Kinen Zenkoku Kensetsugyo Rodo Saigai Boshi Taikai Shiryoshu, p.123 - 127, 2014/09
no abstracts in English
Kato, Nobuyoshi*; Tsusaka, Kimikazu; Nago, Makito*; Yamagami, Masahito*; Matsubara, Makoto*; Shigehiro, Michiko*; Aizawa, Takao*; Kamemura, Katsumi*
Chishitsu To Chosa, (139), p.17 - 22, 2014/04
no abstracts in English
Nago, Makito*; Jin, Kazumi; Miura, Yoichi*
Dai-50-Kai Zenkoku Kensetsugyo Rodo Saigai Boshi Taikai Kenkyu Rombunshu (CD-ROM), p.68 - 72, 2013/10
no abstracts in English
Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Aoki, Tomoyuki*; Shigehiro, Michiko*
Proceedings of 6th International Symposium on In-situ Rock Stress (RS 2013) (CD-ROM), p.339 - 346, 2013/08
The Horonobe Underground Research Laboratory is planned to consist of the Ventilation Shaft (4.5 m in diameter), the East and West Access Shafts (6.5 m in diameter). The host rock of the URL site comprises Neogene sedimentary rocks. The unconfined compressive strength of the rocks is less than 20 MPa on average. Anisotropic stress distribution around the URL is also confirmed. Because several highly permeable fractures (hydraulic transmissivity: approximately 10
m
/s) with the size greater than the shaft diameter develop under the condition of around 2 in competence factor (i.e., the ratio of the unconfined compressive strength of rock to the initial stress) below a depth of 250 m, shaft sinking is a challenging issue from the viewpoint of tunnel engineering in the Horonobe URL Project. In this paper, the construction of the Ventilation Shaft below a depth of 250 m at the Horonobe URL is reported. During shaft sinking, fracture mapping of the shaft wall was performed. The geometry of the shaft wall was also measured using a three-dimensional laser scanner in order to investigate the shape and volume of rock spalling in the shaft wall resulting from the excavation work. Rock spalling was predominantly observed on the south and north wall rock corresponding to the direction of the minimum horizontal initial stress. A large amount of rock spalling also developed along a large-scale fault. With respect to the lining span and the layout of rockbolts, several support patterns were designed and installed as the countermeasures to prevent the development of excessive rock spalling. A flowchart for selecting the optimum support design was then developed.
Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Kamemura, Katsumi*; Matsubara, Makoto*; Shigehiro, Michiko*
Proceedings of ITA-AITES World Tunnel Congress 2013 (WTC 2013)/39th General Assembly, p.2014 - 2021, 2013/05
Japan Atomic Energy Agency (JAEA) has been constructing three shafts to a depth of 500 m in the Horonobe Underground Research Laboratory Project. In this study, in consideration of support patterns installed, a relationship between the rock mass properties and mechanical response to excavation was investigated in detail during the construction of the East Access Shaft below a depth of 250 m. Since the shaft has intersected several faults with the size greater than the shaft diameter, some amounts of rock spalling have occurred and cracks have severely developed in a concrete lining in highly fractured zones. The results of pre-excavation grouting were compared with the results of fracture mapping in the shaft wall obtained during the shaft sinking. Applicability of several support patterns installed to control massive spalling during the shaft sinking was also analysed using the results of geometry profiling of shaft wall using a three-dimensional laser scanner and convergence measurements. As a result, based the empirical relationships among the characteristics of rocks, dimension of spalling, damage of a concrete lining and support patterns, a flow chart for selection of span of a concrete lining was proposed to control its severe damage prior to shaft excavation.
Tsusaka, Kimikazu; Inagaki, Daisuke; Nago, Makito*; Koike, Masashi*; Matsubara, Makoto*; Sugawara, Kentaro*
Dai-13-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (CD-ROM), p.911 - 916, 2013/01
A repository for high-level radioactive waste in deep underground consists of several underground structures such as access and disposal drifts and shafts. In deep geological disposal project, a shaft is the first underground structure to be constructed and the last one to be backfilled. Therefore, the stability of shaft is one of key factors to steadily manage the project in the construction and operation phases. In this paper, the authors discuss influence of rock spalling on concrete lining in shaft sinking. Japan Atomic Energy Agency has been constructing three shafts (one is for ventilation and the others are for access use) up to a depth of 500 m in the Horonobe Underground Research Laboratory. During the construction of the Ventilation Shaft (4.5 m in diameter) below a depth of 250 m, rock spalling occurred at several depths and an open crack has developed in a concrete lining installed just above rock spalling. The authors have measured geometry of shaft wall by using three-dimensional laser scanner. They also conducted numerical analysis in order to calculate change in stress distribution and deformation induced by rock spalling in a concrete lining and the surrounding rock. As a result, it was clarified that rock spalling induced tensile stress in the vertical direction in a concrete lining. Especially, the tensile stress in a concrete lining was likely to exceed tensile strength of a concrete lining in the case that it developed more than 100 cm in depth.
