著者

木下 尚樹 安原 英明

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.133, no.3, pp.53-57, 2017-03-01 (Released:2017-03-31)

参考文献数

16

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It is of significant importance to safely isolate the radioactive wastes from the human environments. Entombment of the wastes in deep subsurface may be a plausible solution on this issue, and will be adopted in the countries where the nuclear power plants are in operation. Before burying them in the targeted rocks, the longterm evolution of the mechanical and the hydraulic properties of the targeted rocks should be predicted with a certain precision. To this end, in this study we examined the change of the apparent secant elastic modulus and the permeability of a single fracture in the Berea sandstone and the Horonobe mudstone samples under the relatively high temperature and confining pressure conditions. The apparent secant elastic modulus of the mudstone increased with the increase of the holding time and specifically, the values at 90 ºC were greater than those at 25 ºC, while that of the sandstone little increased with time. In contrast, the permeability of both the mudstone and sandstone samples monotonically decreased with time, and the rates of the permeability reduction were close among all the samples. The increase of the elastic modulus and the decrease of the permeability may be attributed to the chemomechanical processes such as pressure solution and the mechanisms explaining the changes should be clarified. Although the mechanisms are still ambiguous, the increase of the elastic modulus and the permeability reduction with time may improve the integrity of the targeted rocks.

著者

木下 尚樹 安原 英明 矢田部 龍一 加賀山 肇

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.133, no.3, pp.45-52, 2017-03-01 (Released:2017-03-31)

参考文献数

17

被引用文献数

1

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Rockfall is an important geo-hazard of mountainous area in Japan and has gained greater attention and recognition due primarily to the severe accidents and mortalities happening in roadways and railways. Rock fall countermeasures are classified into preventive works and protectors. In rock protectors that have high rigidity, there are rock protecting fence, rock protecting wall and rock shed, etc. On the other hand, there is a pocket type rock net which excels in the application condition of the topography and absorbs energy by deforming itself. The standard absorbable energy of the pocket type rock net is 100 kJ. Then, the rock net is designed so that the absorbed energy exceeds the falling rock energy. However, in recently, many types of rock net such as high energy type and long span type have been developed, and there are cases where conventional design methods cannot be applied. In this study, the performance of a long span pocket type rock net was evaluated by dynamic analysis. Firstly, the physical properties of the rock net members were identified by comparing the results of the real scale field experiments with the dynamic analyses. Then, the relationships between the displacement of the net and the net width, the maximum tensional force of a horizontal rope and the rope position, etc. were evaluated by the dynamic analyses. Typically, these evaluations by conventional design methods are laborious and are carried out using the results of real scale field experiments. However, the current study revealed that the predictions by the dynamic, numerical analyses showed the validity of the performance evaluation by this means.

著者

木下 尚樹 安原 英明

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.138, no.6, pp.84-94, 2022-06-30 (Released:2022-06-30)

参考文献数

25

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The purpose of this study is to expand the application of wastepaper sludge ash (WPSA) as a construction material. The strength and thermal conductivity of WPSA solidified by hydration reaction were investigated for use as a ground improvement solidifier and civil engineering material. The mixture of fly ash, silica fume, gypsum, and ordinary Portland cement was also investigated. The effect of the mix proportion and the amount of the powder mixture on the strength was investigated, and the strength development was discussed based on the XRD and SEM-EDX results. The experimental results showed that the uniaxial compressive strength of mortar specimens with a water-powder ratio of 1.0 was 5 MPa to 9 MPa at 28 days of age. The strength of the mortar specimens decreased with the addition of fly ash but increased with the addition of by-products such as silica fume. The strength of the solidified material using WPSA was lower than that of the existing solidified materials. The strength of the solidified material made of WPSA was developed due to the formation of albite by hydration reaction, recrystallization of WPSA, and pozzolanic reaction with fly ash and silica fume. Then, the reflectance and thermal conductivity of the solidified material were measured, and the thermal conductivity was examined by the heat transfer experiments. The thermal diffusivity of the solidified material was also estimated by analyzing the experimental results. It was confirmed that the reflectance of WPSA was higher than that of ordinary Portland cement. In addition, the re-incineration of WPSA showed higher reflectivity. The thermal conductivity of the WPSA paste specimens was smaller than that of cement mortar and larger than that of gypsum. The results of the heat transfer experiments suggest that the thermal insulation property of the re-incinerated WPSA is improved.

著者

木下 尚樹 安原 英明 矢田部 龍一 加賀山 肇

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.138, no.6, pp.70-83, 2022-06-30 (Released:2022-06-30)

参考文献数

19

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It is obligatory to verify the performance of high-energy-absorbing pocket-type rockfall protection nets by full-scale experiments. While the performance verification by full-scale experiments can provide a practical evaluation, it requires a lot of cost and time because it is necessary to conduct the experiments under several conditions depending on the structure of the rockfall protection net. Therefore, the performance verification by combining full-scale experiments and numerical analysis may be a useful tool. In this study, a full-scale experiment of a high-energy-absorbing pocket-type rockfall protection net was conducted to evaluate the net performance with respect to the required capability, and reusability and repairability of the components by understanding the behavior of the net under the action of heavy weights. Throughout the experiment, the deformation of the net, the change of the wire rope tension with time, and the displacement of the top of the net and the top of the pillar were measured in detail. Moreover, it was confirmed that it is possible to evaluate the performance verification based on the performance requirements. Then, the full-scale experiment was replicated by numerical simulations to examine the effects of the rock shape on the behavior and performance of the simulated net. Through the thorough investigations on the deformation of the net, the relation between the maximum tension of the wire rope and the slip length of the shock absorber, the temporal change of the tension of each wire rope, and the absorbed energy of each structural member, it was judged that the reproducibility of the model predictions is adequately high. Specifically, when the impact energy is constant, the effect of the rock shape on the behavior and performance is considered to be small.

著者

安原 英明 木下 尚樹 操上 広志 中島 伸一郎 岸田 潔

出版者

公益社団法人 土木学会

雑誌

土木学会論文集C

巻号頁・発行日

vol.63, no.4, pp.1091-1100, 2007

被引用文献数

3

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高レベル放射性廃棄物処分坑道近傍では,廃棄体からの発熱により化学作用が活発化し,岩盤の力学 · 水理学特性に大きな影響を及ぼすことが考えられる.本論文では,圧力溶解現象を考慮した概念モデルを用いて,熱 · 水 · 応力下における化学作用を定量化し,珪質岩石の透水性評価を行った.特に,珪質岩石の構成主鉱物である石英,クリストバライト,アモルファスシリカの溶解 · 沈殿特性に着目し,深地層下における圧力,廃棄体からの発熱作用を考慮し,透水特性の変化を定量的に評価した.その結果,90 °Cの温度条件下で時間と共に透水性が低下する傾向が得られた.また,クリストバライト,アモルファスシリカを多く有する珪質岩石は,石英系岩石よりも透水性の変化がより顕著となることが確認された.

著者

木下 尚樹 氏家 勲 河合 慶有 川口 隆 安原 英明 長江 俊勝

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.133, no.6, pp.132-139, 2017-06-01 (Released:2017-06-23)

参考文献数

13

被引用文献数

12

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Industrial waste generated in the domestic paper industry in Japan was 5.1 million tons in 2015, and after reduction and recycling, 152 thousand tons of the waste was consequently disposed. Organic sludge (paper sludge), which occupies two-thirds of the industrial waste generated in the paper industry, is incinerated for the purpose of volume reduction and thermal recycling, and then it becomes paper sludge ash (PS ash). PS ash is recycled as aggregate, roadbed material in the civil engineering field and cement raw material, but it is necessary to further expand the application and reduce the final disposal amount. From the above background, in this research, the strength characteristics, the durability performance and the environmental impact of low carbon concrete produced by reducing cement usage to 45% by using PS ash as admixture in addition to fly ash and blast furnace slag fine powder, were investigated. Experimental results show that the low carbon concrete produced in this research has long term strength development, and that PS ash does not contribute to long term strength. Moreover, the clay mineral contained in the PS ash has an effect of reducing drying shrinkage by water retention and expansion. With respect to durability performance, neutralization is promoted by decreasing the total cement amount, while salt tolerance resistance is improved. Frost damage resistance tends to decrease. The elution amount of toxic substances is less than the soil environmental standard value.