Influence of a fault system on rock mass response to shaft excavation in soft sedimentary rock, Horonobe area, northern Japan

Tokiwa, Tetsuya; Tsusaka, Kimikazu; Ishii, Eiichi; Sanada, Hiroyuki; Tominaga, Eiji; Hatsuyama, Yoshihiro; Funaki, Hironori

doi:10.1016/j.ijrmms.2011.04.007

Cited by 17 publications

(8 citation statements)

References 17 publications

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“…Such tensile/hybrid fractures are less common in the deep DI > 2 domain than in the shallow DI < 2 domain (Figures b–d; Ishii, ). In the Koetoi Formation, fault zones and tensile/hybrid fractures are less common, but shear fractures without fault rock and fracture mineralization are prevalent (Figure a; Funaki et al, ; Ishii, ; Ishii et al, ; Tokiwa et al, ).…”

Section: Geological Settingmentioning

confidence: 99%

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

Ishii

2018

Water Resources Research

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Assessing the hydraulic connectivity of fractures by single-borehole investigations is crucial to radioactive waste disposal but is still a challenge as such connectivity is difficult to measure directly. This study presents geological, hydrological, hydrochemical, and rock-mechanical data for three faulted/ fractured mudstones (the Koetoi, Wakkanai, and Palfris Formations) and proposes a new methodology for assessing the hydraulic connectivity of fractures. The methodology consists of three steps: (a) dividing the formation into two domains with a ductility index (DI) of >2 and <2 (DI is defined as the effective mean stress normalized to the tensile strength of intact rock), (b) estimating the hydraulic connectivity of fractures by analyzing pressure change obtained by packer tests and geological interpretation, and (c) verifying the estimation using pore pressure and water chemistry/geochemistry. The first step is necessary because the failure mode of damage-zone fractures in fault zones can differ between the DI > 2 and DI < 2 domains, which may lead to significant differences in the hydraulic connectivity of fractures. During the second step, potential domains in which the hydraulic connectivity of fractures is limited are identified where upward trends, characterized by slopes of 0.5-1.0, are observed during the middle to late period of elapsed time on log-log plots of pressure derivatives. Although the third step can be performed in various ways, this study employs the observation of pressure anomalies and the detection of young external water. Analyses of the three formations demonstrate the applicability and reliability of the proposed methodology.

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Section: Geological Settingmentioning

confidence: 99%

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

Ishii

2018

Water Resources Research

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“…1). Because of the region's deep down cutting river valleys, active tectonic environment, and weathering processes, rock slope stability has been one of the key engineering problems not only in the studied area, but in several areas worldwide (Qi et al, 2004;Yao et al, 2006;Xu et al, 2011;Song et al, 2011;Tokiwa et al, 2011;Chen et al, 2012;Mineo et al, 2015;Stead and Wolter, 2015). In the studied area, the height of natural slopes can reach over 1000 m, and cut slopes measuring 300-500 m in height are common.…”

Section: Introductionmentioning

confidence: 99%

Stability investigation and stabilization of a heavily fractured and loosened rock slope during construction of a strategic hydropower station in China

Chen

Deng

Sitar

et al. 2017

Engineering Geology

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This paper presents a case history of the 205 m high intake slope at the Huangjinping (HJP) hydropower station on the Dadu River. Deformation and cracks developed on the cut slope during excavation, and the deformation extended onto the natural slope above the cut, giving rise to serious safety concerns. Research was conducted to study the engineering geological conditions and the deformation characteristics of the slope during excavation. In situ monitoring data and possible causes of cracking were analyzed. The results show that the zone of loosened rock mass extended much deeper into the rock mass than it did at other sites in the region because of the tectonic history of the site and cutting. The empirically designed cable anchors with lengths of 40 m or 45 m were insufficient to stabilize the slope, while the remedial cable anchors as long as 100 m successfully stabilized the slope. The analytic method and procedure used in this paper could be useful to similar projects.

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“…These conditions occur especially close to important tectonic structures, such as fault segments controlling the slope deformation (Tokiwa et al, 2011) and stability. Willenberg et al (2008) describe a crystalline rock mass in Switzerland, where the main instability area laid in a high density of faults and fracture zone.…”

Section: Introductionmentioning

confidence: 99%

Integrated geostructural, seismic and infrared thermography surveys for the study of an unstable rock slope in the Peloritani Chain (NE Sicily)

Mineo

Pappalardo

Rapisarda³

et al. 2015

Engineering Geology

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Influence of a fault system on rock mass response to shaft excavation in soft sedimentary rock, Horonobe area, northern Japan

Cited by 17 publications

References 17 publications

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

Assessment of Hydraulic Connectivity of Fractures in Mudstones by Single‐Borehole Investigations

Stability investigation and stabilization of a heavily fractured and loosened rock slope during construction of a strategic hydropower station in China

Integrated geostructural, seismic and infrared thermography surveys for the study of an unstable rock slope in the Peloritani Chain (NE Sicily)

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