Mechanical strength of the transition zone at the boundary between opal-A and opal-CT zones in siliceous rocks

Ishii, Eiichi; Sanada, Hiroyuki; Iwatsuki, Teruki; Sugita, Y.; Kurikami, Hiroshi

doi:10.1016/j.enggeo.2011.05.007

Cited by 53 publications

(33 citation statements)

References 26 publications

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“…Wakkanai siliceous mudstone is widely found around the Horonobe Underground Research Laboratory of the Japan Atomic Energy Agency. A large number of laboratory tests (but not uniaxial tension tests) have been conducted on this mudstone (Sanada et al 2009;Ishii et al 2011). As the in situ rock for water-saturated conditions, mudstone was adopted for the uniaxial tension test in this study.…”

Section: Sample Rockmentioning

confidence: 99%

Effect of Water on the Deformation and Failure of Rock in Uniaxial Tension

2014

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To design and construct underground structures, it is essential to understand the mechanical properties of rock in not only compression but also tension. It is well known that water is one of the important factors affecting the deformation and failure of rock. In this study, laboratory tests and numerical simulations were conducted to understand the effect of water on rock properties in uniaxial tension. In the experiments, a testing machine previously used for uniaxial tension tests in dry conditions was modified for tests in wet conditions. Using this machine, complete stress-strain curves from the pre-to postpeak regions of water-saturated specimens in uniaxial tension were obtained. The results for granite, tuff, and two types of andesite showed that the stress-strain curves in wet conditions have a lower initial slope and lower strength than those in dry conditions, and they are strongly nonlinear in the prepeak region. Comparing the changes in the results for uniaxial tension versus compression due to water, it was found that the reduction rate of uniaxial tensile strength was greater than that of uniaxial compressive strength, while the ratio between the reduction rates was almost constant for various rocks. In numerical simulations, the stress-strain curves in the prepeak region under dry and wet conditions could be reproduced by crack extension models under uniaxial tensile stress. Numerical analyses indicated that the nonlinearity of the stress-strain curves is probably due to the longer crack extension in wet compared with dry conditions.

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Section: Sample Rockmentioning

confidence: 99%

Effect of Water on the Deformation and Failure of Rock in Uniaxial Tension

2014

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“…The Koetoi, Wakkanai, and Masuporo (upper part) formations, which are composed mainly of homogeneous siliceous rocks, were deposited successively in a marine environment with a thickness of ∼2 km as indicated in Figures 1 and 2 [22,26]. The burial and subsidence of these formations occurred throughout the Neogene and Quaternary.…”

Section: Generalmentioning

confidence: 99%

“…The age of the studied section is based on FT ages of intercalated tuff beds reported by Ishii et al [27]. Porosity and bulk chemistry data are from Ishii et al [22] and Tsuji and Yokoi [26].…”

Section: Generalmentioning

confidence: 99%

“…The hydraulic conductivity of the formations from packer tests (interval: meters to decameters) range 9 × 10 −10 to 5 × 10 −6 m s −1 for the Koetoi formation and 1 × 10 −12 to 5 × 10 −5 m s −1 for the Wakkanai formations [22]. The hydraulic conductivity of rocks (matrices) from laboratory hydraulic tests is 2 × 10 −11 to 5 × 10 −10 m/s and 5 × 10 −13 to 3 × 10 −11 m s −1 for the Koetoi and Wakkanai formations, respectively [22].…”

Section: Generalmentioning

confidence: 99%

“…The study area is in the Tempoku basin located in northwestern Hokkaido, on the eastern margin of a Neogene to Quaternary sedimentary basin ( [22,23], Figure 1). This basin is part of an active foreland fold-and-thrust belt, developed near the boundary of the Okhotsk and Amurian plates (Figure 1).…”

Section: Generalmentioning

confidence: 99%

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An Evaluation of the Long-Term Stagnancy of Porewater in the Neogene Sedimentary Rocks in Northern Japan

et al. 2018

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A groundwater dating for very old porewater using 36 Cl and 4 He was applied to the Koetoi and Wakkanai formations distributed in the northernmost part in Japan. Measured 36 Cl/Cl in the Koetoi Formation was 2.6 ± 2.0 × 10 −15 and that in the Wakkanai Formation was 8.1 ± 2.5 × 10 −15 . These values are similar to 36 Cl/Cl in situ secular equilibrium calculated from chemical compositions of core suggesting that Cl − ions and porewater have remained in the formations for much longer than half-life of 36 Cl . He concentration in porewater ranged from 1.1 × 10 −6 to 2.6 × 10 −5 (cc STP g w −1 ) and it is much higher than water saturated with air indicating that both formations contain very old porewater. However, the possibility of mixing of young water was indicated because He concentration was lower than that calculated by multiplication of in situ He production and time after the uplift. This possibility was also supported by Cl − , D, and 18 O data. After combining information on 36 Cl/Cl, 4 He, and D and 18 O, it was inferred that the porewater in the deep part of the Wakkanai Formation might have been stagnant since the uplift. The porewater in the Koetoi Formation and the shallow part of the Wakkanai Formation were found to be affected by young surface water.

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Predictions of the highest potential transmissivity of fractures in fault zones from rock rheology: Preliminary results

Ishii

2015

JGR Solid Earth

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Fracture transmissivity in a fault zone is a significant parameter when solving certain geoscientific and geotechnical problems. However, the transmissivities are difficult to predict quantitatively owing to the complexity of in situ conditions such as the apertures of fractures. This study analyzes extensive data sets on flow anomalies (transmissive zones) detected from fluid/flow logs of boreholes in fault zones in the light of rock rheology, fracture mineralization/dissolution, and fracture orientation at six sites, namely Horonobe (Japan; siliceous mudstone), Wellenberg (Switzerland; argillaceous marl), Forsmark (Sweden; granite/granodiorite), Olkiluoto (Finland; gneiss), Northern Switzerland (granite/gneiss), and Sellafield (UK; volcaniclastic rocks and sandstone). The flow anomalies are correlated to fractures in fault zones. The data sets show that the transmissivities of the flow anomalies are strongly controlled by the ductility index, defined as the effective mean stress normalized to the tensile strength of the intact rock. An empirically derived power law relationship exists between the transmissivity and the ductility index, allowing predictions of the highest potential transmissivities of fractures in possible fault zones with maximum errors of about 2 orders of magnitude, due to the inevitable heterogeneity of a fault zone. The actual transmissivities may be further reduced by mineral precipitation in the fractures, or increased by mineral dissolution. Fracture orientation has no discernable influence on the transmissivity. The results may prove helpful for understanding and predicting the long-term transport properties of fault zones in the upper crust.

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Mechanical strength of the transition zone at the boundary between opal-A and opal-CT zones in siliceous rocks

Cited by 53 publications

References 26 publications

Effect of Water on the Deformation and Failure of Rock in Uniaxial Tension

Effect of Water on the Deformation and Failure of Rock in Uniaxial Tension

An Evaluation of the Long-Term Stagnancy of Porewater in the Neogene Sedimentary Rocks in Northern Japan

Predictions of the highest potential transmissivity of fractures in fault zones from rock rheology: Preliminary results

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