Permeability of Granite Including Macro-Fracture Naturally Filled with Fine-Grained Minerals

Nara, Yoshitaka; Kato, Masaji; Niri, Ryuhei; Kohno, Masanori; Sato, Toshinori; Fukuda, Daisuke; Satō, Tsutomu; Takahashi, M.

doi:10.1007/s00024-017-1704-x

Cited by 20 publications

(9 citation statements)

References 58 publications

(1 reference statement)

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“…Figure 7 shows the hydraulic conductivities of granite as well as those of HSULPC. The hydraulic conductivities of granite are those previously reported for an intact sample of Toki granite by Nara et al 21) The hydraulic conductivity for HSULPC is similar or less than that for intact Toki granite, indicating that HSULPC is a dense and low permeability material, which can effectively confine radionuclides.…”

Section: Discussionsupporting

confidence: 77%

Precise Permeability Measurement for High Strength and Ultra Low Permeability Concrete under Controlled Temperature

Kato

Nara

Shibuya³

2020

Mater. Trans.

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High strength and ultra low permeability concrete (HSULPC) is being considered as a material used to package transuranic (TRU) waste for disposal in geological repositories. Therefore, information on the permeability of HSULPC is essential. Permeability tests need to be highly accurate to determine the hydraulic conductivity of HSULPC because of its ultralow permeability. In our study, we measured the permeability of HSULPC samples using the transient pulse method. The temperature of the concrete was finely controlled and held constant. The hydraulic conductivities were determined from the measurements to be around 10 ¹13 to 10 ¹12 m/s for confining pressures between 2 and 10 MPa. The pore pressure was a constant 1 MPa. The results further showed that the permeability of HSULPC had a hysteretic dependence on the effective confining pressure. We found that the hydraulic conductivity of HSULPC is comparable to or less than that of intact Toki granite obtained from Gifu Prefecture in central Japan. It was also considered that the hydraulic conductivity of HSULPC stabilized at around 10 ¹13 m/s after being buried and stressed. The high density and impermeability of HSULPC would enable it to effectively confine 14 C radionuclides found in TRU waste.

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Section: Discussionsupporting

confidence: 77%

Precise Permeability Measurement for High Strength and Ultra Low Permeability Concrete under Controlled Temperature

Kato

Nara

Shibuya³

2020

Mater. Trans.

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“…Mitchell and Faulkner 18) suggested that the permeability of a rock can decrease if its fractures are filled with fine-grained particles such as clays. According to Nara et al, 19,20) Wang et al, 21) and Pérez-Flores et al, 22) the permeability of dense rocks such as igneous rocks is significantly affected by finegrained rock fracture fillings. If the rock includes an open macroscopic fracture, its permeability is high.…”

Section: Discussionmentioning

confidence: 99%

Application of the Transient Pulse Method to Measure Clay Permeability

et al. 2018

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To ensure the safe geological disposal of radioactive waste, it is important to determine the permeability (hydraulic conductivity) of clays. The transient pulse method is suitable for low-permeability materials because it requires a relatively short time to determine their permeability. Upstream pore pressure typically increases in the measurement conducted via the transient pulse method. However, this procedure cannot be used to determine the permeability of clays due to the increase in pore pressure. Therefore, the transient pulse method has never been applied to determine clay permeability. In this study, we applied the transient pulse method to a clay sample obtained in the Mizunami Underground Research Laboratory to determine its permeability while decreasing the downstream pore pressure. We found that this method was also appropriate for conducting measurements on granite. The hydraulic conductivity of the clay measured by the proposed method was higher by only one order of magnitude than that determined using the falling head method, indicating that hydraulic conductivity can be determined using the transient pulse method with reasonably small error. The measurement time of the transient pulse method was much shorter than that of the falling head method. We concluded that the transient pulse method is appropriate for determining clay permeability.

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“…Pérez-Flores et al 2017showed that the permeability of fractured rock was decreased by filling even though the fracture was unmated. Nara et al (2018) reported that the permeability of macro-fractured granite decreased significantly when the macro-fracture was filled naturally by fine-grained minerals. Therefore, it is desirable to produce filling powders to decrease the permeability of fractured rock.…”

Section: Discussionmentioning

confidence: 99%

Precipitation of calcium compounds onto rock surfaces in water with cementitious material

Nara

Kashiwaya

Nakao

et al. 2018

Carbonates Evaporites

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In this study, the precipitation of minerals onto rock surfaces was investigated to consider whether sealing of pores and cracks in rock can be accelerated. Cylindrical specimens were prepared and then kept in purified water with powders of high-strength and ultra-low-permeability concrete (HSULPC), which will be used to confine transuranic (TRU) wastes in Japan. Then, the rock specimens were weighed and the surfaces of rock specimens were inspected under a microscope. It was recognized that precipitation occurred on the surface of the rock specimens. It was also shown that precipitation did not occur on rock specimens kept in water without HSULPC. The weight of all specimens stored in HSULPC increased, and the observed weight change was larger for rocks with higher porosities. It is concluded that precipitation of minerals occurs on the rock surface when the rock is kept in water with HSULPC powders. From the results obtained in this study, it is suggested that the sealing of pores and cracks in rock can be accelerated by the precipitation of calcium compounds using HSULPC. It is concluded that HSULPC is useful for underground radioactive waste disposal.

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Permeability of Granite Including Macro-Fracture Naturally Filled with Fine-Grained Minerals

Cited by 20 publications

References 58 publications

Precise Permeability Measurement for High Strength and Ultra Low Permeability Concrete under Controlled Temperature

Precise Permeability Measurement for High Strength and Ultra Low Permeability Concrete under Controlled Temperature

Application of the Transient Pulse Method to Measure Clay Permeability

Precipitation of calcium compounds onto rock surfaces in water with cementitious material

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