材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
67 巻 , 3 号
選択された号の論文の19件中1~19を表示しています
巻頭言
論文
  • 緒方 奨, 安原 英明, 岸田 潔
    2018 年 67 巻 3 号 p. 310-317
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    We improved our coupled thermo-hydro-mechanical-chemical (THMC) simulator by adopting the dual porosity model to predict the long-term permeability change of the fractured rocks. The model evaluates influence of the geochemical reaction on the evolution of the permeability in fractured rock. Pressure solution that may occur both at grain contacts and the contacting asperities within fractures was incorporated in the model. By using the developed THMC numerical model, long-term prediction of rock permeability under simulated subsurface environments near the radioactive waste repository was conducted. As a result of analysis, the permeability decreased by two orders of magnitude smaller than the initial value due to the pressure solution contacting asperities within fractures in the excavation distributed zone (EDZ). When carrying out radioactive waste disposal, the pressure solution within the fractures may have the effect on minimizing the increasing of the permeability in EDZ area.

  • 加藤 昌治, 奈良 禎太, 岡崎 勇樹, 河野 勝宣, 佐藤 稔紀, 佐藤 努, 高橋 学
    2018 年 67 巻 3 号 p. 318-323
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    To ensure the safe geological disposal of radioactive wastes, it is important to determine the permeability of clays. The transient pulse test is suitable to apply to the low permeability materials, because it takes relatively short term to determine the permeability. Usually we increase the upstream pore pressure in the measurement with the transient pulse test. However, it is impossible to determine the permeability of clay in this procedure because of the increase of pore pressure. Therefore, the transient pulse test has never been applied to the determination of permeability of clays. In this study, we tried to apply the transient pulse test to a clay obtained in Mizunami Underground Research Laboratory to determine the permeability with decreasing the downstream pore pressure. It was clarified that the transient pulse test with decreasing downstream pore pressure is appropriate from the measurement of granite. It was shown that the permeability of a clay was determined by the transient pulse test with decreasing the downstream pore pressure, which agreed with the permeability determined from the falling head test. The measurement time of the transient pulse test is much shorter than that of the falling head test. It is concluded that the transient pulse test is appropriate for the determination of the permeability of clays.

  • 河野 勝宣, 竹原 裕太, 西村 強
    2018 年 67 巻 3 号 p. 324-329
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    It is generally known that physical and mechanical properties of rock materials significantly change by clay mineral content. Therefore, it is considered that clay mineral content or type is one of the factors that greatly affect the rock strength. In order to clarify that effect of only clay mineral content, a series of experiments has been carried out on artificial rock by the use of gypsum specimen mixed with clay minerals. The value of P-wave velocity, uniaxial compressive strength and degree of strength reduction differ with the clay mineral content and type. Comparative tests revealed that the difference of clay mineral content or type in the clay mineral-bearing rock material specimens influences the physical and mechanical properties of rock materials. Furthermore, the results suggested that uniaxial compressive strength of clay mineral-bearing rock materials under dry condition can be evaluated on the basis of interlayer bonding force (i.e. chemical bonds type) in the clay minerals. Our results can be useful and contribution as basis data when evaluating physical and mechanical properties of clay mineral-bearing rock materials.

  • 鴨志田 直人, 大河原 正文, 齊藤 剛
    2018 年 67 巻 3 号 p. 330-337
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    It is commonly known that water-saturated rock increases in strength due to freezing of pore water when cooled. This increase in strength due to freezing obviously appears in rock with relatively high porosity. It is also known that water-saturated rock increases in thermal diffusivity due to freezing of pore water when cooled. Despite its relatively high porosity, however, frozen tuff does not increase in thermal diffusivity. In this study, we considered the presence of clay minerals and investigated the influence of pore water on the mechanical properties of water-saturated rock under low temperatures. Specifically, we put a specimen of Ogino tuff and that of Berea sandstone through a uniaxial compression test and an indirect tensile test in a temperature range of -170°C to room temperature. Our findings are as follows. The influence of pore water on the strengthening mechanism of water-saturated rock under low temperatures needs to be investigated separately on bulk water and interlayer water. The strength of water-saturated sandstone is presumed to result from the interaction between a load distribution effect due to freezing of bulk water and an increase in the strength of ice due to cooling after the freezing of bulk water. In water-saturated tuff, since interlayer water does not freeze, the load sharing effect due to freezing is not expected to contribute to the strength of the rock. Therefore, it is necessary to design a new model.

  • 富樫 陽太, 菊本 統, 谷 和夫, 細田 光一, 小川 浩司
    2018 年 67 巻 3 号 p. 338-345
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    To confirm applicability of a method of determining anisotropy of transversely isotropic elasticity via a single triaxial test for a sedimentary soft rock specimen in which bedding plane were not clearly observed, anisotropic deformation behavior of soft sedimentary mudstones, which were sampled in Sagamihara and were not sufficiently studied yet, was experimentally investigated by proposed triaxial test in this study. Non-coaxial anisotropic relationships of stresses and strains were evaluated by full three dimensional strain tensor of mudstone measured by nine strain gauges set on the lateral plane of cylindrical specimen. Orientations of principal strains during isotropic consolidation were agreed with that of bedding orientations observed in the outcrop. Anisotropic stiffness of the mudstone was finally determined by a method of determining anisotropy of transversely isotropic elasticity via a single triaxial test.

  • 大津 宏康, Pipatpongsa Thirapong, 北岡 貴文, 伊東 俊一郎, 矢部 満, Suttisak Soralump
    2018 年 67 巻 3 号 p. 346-353
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    In this study, fine particle distribution in artificial slopes comprising weathered granite, which may affect rainfall-triggered landslide, was investigated comprehensively, based on electrical resistivity, soil composition and unsaturated soil properties. The results showed that while degree of saturation plays a key factor on electrical resistivity in unsaturated soil, it has close correlation to pore-size distribution. Therefore, it can be considered that electrical prospecting is an effective method to investigate distribution of both coarse particle and fine particle. In addition, it was also pointed out that there is possibility that fine particle fraction involved in soil poorly compacted in artificial slopes may be eroded due to rainfall infiltration.

  • 長谷川 信介, 長谷川 真吾, 北岡 貴文, 大津 宏康
    2018 年 67 巻 3 号 p. 354-359
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    In construction projects of mountain tunnels, with a purpose of improving accuracies of rock classifications in preliminary survey, we have studied applicability of Artificial Neural Network (ANN). One characteristics of ANN is that it does not require defining clear formula correlating data input and output, by using its learning function. Leveraging the characteristics, accuracy of rock classification improved by using geophysical datasets (seismic velocity and resistivity) at a tunnel face and surrounding. Also, ANN has a problem of reduced applicability caused by over learning to training data. It is possible to avoid the over learning problem by increasing training dataset, but it is not easy to accumulate complete dataset of geophysical properties and actual rock classification obtained in construction stage. We found that it is important to collect various tunnel data without much deviation, for accumulating training datasets effectively in the future.

論文
  • 田中 和人, 冨澤 舞, 片山 傳生, 森田 有亮
    2018 年 67 巻 3 号 p. 361-366
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    Replacement of an aneurysm with a vascular graft and treatment using a stent graft - a covered stent: combining a covering material with a metal stent - is conducted for aneurysm. A vascular graft is used as covering material of the current stent graft. A large-diameter stent graft has good stent patency. In the case of the stent graft that has less than 6 mm of caliber, covering material that promotes endothelialization is necessary in order to prevent thrombus formation. For the covering material, nanofibers, which have been applied to regenerative medicine due to the similarity to extracellular matrix of a native vessel, is expected to be used. In previous studies, when the fiber diameter of the scaffold was more than 1 μm, cells were reported to infiltrate more into the scaffold, and the porous scaffold was clarified to offer better surfaces to anchor and culture endothelial cells as compared to a nonporous scaffold. Thus, fibers with nano-order dimples are expected to promote endothelialization, and the fabrication process of these fibers has to be developed. In this study, in order to develop the fabrication process of PET fiber with dimples, PET fibers were fabricated under various processing parameters. Dimples were successfully formed on PET fiber surface under high humidity condition by using Hexafuoro-2-propanol(HFIP) which can dissolve PET and has rapid volatilization speed, and Ethylene glycol(EG) which cannot dissolve PET and has slow volatilization speed for solvent in electrospinning.

  • 田中 和人, 中塚 潤, 片山 傳生, 桑原 秀行
    2018 年 67 巻 3 号 p. 367-374
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    In the automotive industry, it is necessary to reduce the cost of molding process for an application of CFRTP in car component parts. Recently, a heating method of the mold by using the high frequency direct resistance heating is attracting a great deal of attention. With this method, electric current passes near the mold surface intensively by skin effect and heats the mold by Joule heating. By applying direct resistance heating to the flat mold for CFRTP molding, simplification of the equipment and facilities as well as high-speed molding can be expected. However, the uniform temperature distribution is one of the important issues to be solved for flat plate because of a current concentration at the corners. In this study, in order to apply the direct resistance heating to the flat mold for CFRTP molding, FEM analysis of the electromagnetic field and heat transfer was conducted and analyzed results were compared with the experimental results. Target part of the mold was efficiently heated by positioning the electrodes close to the molding surfaces, and the temperature rise in the corner part was remarkable under the higher frequency. For preventing a current concentration at the corner parts, a new feeding model, in which copper plates were positioned at the both sides of the mold, was proposed.

  • 安川 昇一, 大谷 眞一, 熊谷 正芳, 菊地 拓哉
    2018 年 67 巻 3 号 p. 375-382
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    Shot peening, which imparts compressive residual stress, is a very effective means for improving the fatigue strength and is widely used for manufacturing process such as automobile industry and aircraft industry. In this study, with the aim of clarifying experimentally the microscopic residual stress distribution of a single dent by projecting a fine ceramic ball with a diameter of 3 mm onto an aluminum alloy material, and the existence of shear stress is clarified by triaxial stress analysis. Furthermore, the change of the residual stress distribution when multiple shots are given to the same position of single dent is also clarified. Obtained results are summarized as follows: (1) The central portion of the dent has a tensile residual stress in both radial and circumferential directions of the dent. A residual stress in the radial direction of the dent has a peak of compressive residual stress outside the dent mark, and a compressive residual stress is given up to an area up to about four times the dent diameter. On the other hand, a tensile residual stress is generated in the circumferential direction of the dent to the region of four times the dent diameter, and the peaks of the tensile residual stress are present on the central part of the dent and outer of the dent. (2) The macroscopic residual stress in the radial direction gradually changes to compressive stress in accordance with the number of shot projections, but does not change substantially in the circumferential direction. (3) As a result of triaxial stress analysis on a single dent, shear stress components σ12 and σ23 does not exist, but it became clear that shear stress σ13 is generated at the dent boundary.

  • 髙木 節雄, 赤間 大地, Jiang Fulin, 土山 聡宏
    2018 年 67 巻 3 号 p. 383-388
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    Williamson-Hall (WH) plots in polycrystalline metals are characterized by the irregular arrangement of data due to the elastic anisotropy in each crystal plane. In this study, direct correction of the elastic anisotropy was attempted in WH plots for 30% cold rolled pure iron, pure nickel and an austenitic stainless steel (SUS316L). The results obtained are as follows: 1) Good linearity is realized in the relation between the orientation function H2 and the inverse of Young’s modulus for single crystal and poly crystal (the diffraction Young’s modulus). It was found that both lines intersect at H2≒0.25 which corresponds to the {110} crystal plane. 2) Using the diffraction Young’s modulus ratio which was standardized against that of {110}, the elastic anisotropy in the WH plots was precisely corrected and good linearity was obtained in the corrected WH plots (Diffraction Young’s modulus correction method). 3) In the direct fitting method which evaluates the linearity of WH plots with varying Young’s modulus ratio, almost same results were obtained as the diffraction Young’s modulus correction method.

  • 各務 周, 宮川 進, 宮本 宣幸
    2018 年 67 巻 3 号 p. 389-395
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    In this paper, delayed fracture strength of SUJ2 bearing steel in biodiesel fuel with water is investigated. In order to evaluate the delayed fracture strength in fuel environment, a newly constant load test procedure was established. When specimens were immersed in biodiesel fuel with water applying a constant load, fracture stress was measured at about 1400 MPa at the test time of 200 hours, which highlights a clear decrease compared to the tensile strength of 1893 MPa found in air. After the test, intergranular fracture was observed at the fracture origin, and corrosion traces were observed on the surface near the origin. Intergranular fracture and corrosion traces tended to increase with test time. From these observations, the cause of strength reduction can be considered as follows: (i) intergranular embrittlement by hydrogen absorbing, or (ii) stress concentration due to surface roughness. Influence of intergranular embrittlement on strength reduction was investigated by slow strain rate test (SSRT). On the other hand, influence of surface roughness on strength reduction was undertaken by tensile test using corroded specimen. According to experimental results, strength reduction in this condition was mainly induced by intergranular embrittlement due to hydrogen absorbing. Finally, the relationship between the square root of the intergranular area (√areag) and the diffusible hydrogen content as well as between the fracture stress and √areag were investigated. As a result, √areag increased with increasing the diffusible hydrogen content. Furthermore, the fracture stress decreased with increasing √areag. Therefore, the strength reduction due to intergranular embrittlement in biodiesel fuel with water should be the consequence of the hydrogen diffusion in grain boundaries, which makes grain boundaries brittle.

  • Hiroshi YAMADA, Hiroshi KATAHIRA, Hiroshi WATANABE
    2018 年 67 巻 3 号 p. 396-400
    発行日: 2018/03/15
    公開日: 2018/03/20
    ジャーナル フリー

    The factors which affect drying shrinkage of concrete are material properties and environmental conditions, and so on. It is said that the type of coarse aggregate is one of the most dominant factors which affect concrete drying shrinkage. Therefore, it is important that the length-change properties of coarse aggregate particle are grasped when concrete drying shrinkage strain is estimated. Moreover, it is a practical benefit that concrete drying shrinkage strain is estimated by using coarse aggregate properties to be obtained the result early, regardless of the mix proportion of concrete. From the above backgrounds, in this research, we tried to estimate concrete drying shrinkage strain by composite model which has been proposed by KISHITANI & BABA, and investigated applicability of the model by using the initial tangent modulus or the secant modulus for coarse aggregate. For this study we used 19 types of crushed stone from different regions and of different qualities. As a result, the estimation of concrete drying shrinkage strain by KISHITANI & BABA equation was made different results of accuracy due to types of modulus of elasticity to be used for calculation. The calculated value against the experimental value was a range of -30 to +10% when using the initial tangent modulus, and was a range of -30 to +30% when using the secant modulus.

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