著者

福井 勝則 辻本 知範 大久保 誠介 松永 昌太

出版者

公益社団法人 土木学会

雑誌

土木学会論文集C (ISSN:1880604X)

巻号頁・発行日

vol.65, no.1, pp.19-28, 2009 (Released:2009-01-20)

参考文献数

13

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地震の前後に観測される電磁波の発生は興味深いことと考えられており,古くから研究されてきた.しかしながら,その現象は極めて複雑であり,電磁波の発生原因を明快に説明することは現状では難しいとされている.本研究では従来あまり検討されていない,AM波に混在する電磁ノイズに着目することとし,日本各地に設置されているAM波帯の電磁ノイズ観測装置による,過去の観測データを調べ,地震前後の電磁ノイズ発生状況の検討を行った.その結果,地震の2週間から5週間前より電磁ノイズは通常より多くなり始め,地震の1,2週間前に最大値を迎えた後,減少し,地震を迎える事例が多いことを示した.

著者

高 秀君 大久保 誠介 福井 勝則 金田 博彰

出版者

一般社団法人 資源・素材学会

雑誌

資源と素材 (ISSN:09161740)

巻号頁・発行日

vol.122, no.1, pp.26-34, 2006 (Released:2007-02-24)

参考文献数

20

被引用文献数

1 1

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For flood prevention, power generation and conveyance, the world's largest Three Gorges Dam was begun to construct in 1993. However, the problem of landslide around the Three Gorges reservoir has not been solved completely so far. Although a lot of geological investigations have been carried out in the field, the role of rock mechanical characteristics in the failure of rock slope has not been cleared thoroughly.In order to study the geological setting and the mechanical characteristic of the landslide area around the Three Gorges reservoir, field investigation and laboratory work including microscope observation, X-ray powder diffraction analysis and uniaxial compressive tests have been carried out. Rock specimens such as two muddy sandstones, a red mudstone, a limestone and a sandstone were collected and examined.The main mineral composition of examined rock specimens except for limestone is quartz. Under the air-dried condition, sandstone is the strongest and weathered muddy sandstone is the weakest. It is interesting to note that calcium contents (carbonate observed) in unweathered muddy sandstone are significantly decreased in weathered one. The decrease in strength for the weathered rock may arise from the dissolution of calcium. For all sample rocks, uniaxial compressive strength shows remarkable decrease under the water-saturated condition. It may be attributed to high content of clay minerals.Complete stress-strain curves were obtained. For all sample rocks, stress increased almost linearly with strain up to the peak strength and then dropped rapidly indicating brittle feature. Weakening under water-saturated condition and high degree of brittleness indicate that very careful and sophisticated measure is necessary to prevent landslide in the area.

著者

福井 勝則 大久保 誠介 羽柴 公博

出版者

東京大学

雑誌

基盤研究(B)

巻号頁・発行日

2007

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AM帯域に混在する電磁波の観測を行い, 地震発生の1ヶ月前から電磁ノイズが増加し始め, 10日前にピークに達し, その後低下し(空白期間といえる部分が存在), 地震に至るという例が多数見られることを示した. 岩石破壊試験を実施した結果, 電磁ノイズなどの予兆現象が地震のかなり前にピークを迎えることは解釈が難しく, 破壊の集中あるいは水の移動により, 空白期間が発生した可能性が高いことを示した.

著者

福井 勝則 大久保 誠介 森山 守 青木 智幸 小塚 孝 松原 誠

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan (ISSN:18816118)

巻号頁・発行日

vol.123, no.9, pp.467-474, 2007-10-25

参考文献数

14

被引用文献数

2

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The main drive of Hida Tunnel for Tokai-Hokuriku Highway was excavated by a world-largest-class TBM with the diameter of 12.84 m. The TBM have bored over 3.0 km of the tunnel through Nouhi Rhyolite, Granite Porphyry and Hida Gneiss. The uniaxial compressive strength of these rocks was found to be extremely high. Such high strength accompanied by high content of silicon dioxide resulted in significantly high wear rate of the disc cutters mounted on the TBM.<BR>In this study, cutter wear was carefully measured together with the operation conditions such as thrust force, penetration rate, cutter-head rotation rate and the rock properties such as uniaxial compressive strength, rock strength estimated from TBM cutting force, abrasivity obtained from turning operation test, chemical composition determined by X-ray analytical microscope.<BR>It was found that the extent of cutter wear largely depends on position of the disc cutter; cutter wear per unit rolling distance near the fringe of cutter head was extremely larger than that near the center of cutter head. A combination of rock strength estimated by TBM cutting force and length of wear flat in turning-operation test was found to be an excellent index to predict cutter wear rate.

著者

福井 勝則 大久保 誠介 寺嶋 卓文

出版者

一般社団法人 資源・素材学会

雑誌

資源と素材 (ISSN:09161740)

巻号頁・発行日

vol.117, no.9, pp.703-710, 2001 (Released:2006-01-08)

参考文献数

21

被引用文献数

1 2

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A number of studies on electromagnetic wave emission from fractured rocks have been heretofore carried out. By many authors it was pointed out that rock fracturing or acoustic emission could be concerned with electromagnetic wave emission. However, the origin of electromagnetic wave emission is still not well understood.In this study electromagnetic wave from rocks was measured with a radio interference measuring apparatus during uniaxial compression testing under several kinds of loading conditions.Firstly, the uniaxial compression testing under constant strain rate of 10-4 s-1 was conducted for seven rocks. It was found that Inada granite, Honkomatsu andesite and Kuzuu dolomite emit electromagnetic wave. However electromagnetic wave cannot be detected for Sanjome andesite, Akiyoshi marble, Kimachi sandstone and mortar.Secondly, electromagnetic wave emission was investigated under several experimental conditions. It was found that Inada granite emits electromagnetic wave during uniaxial compression testing under a constant strain rate of 10-5 s-1 and under a constant rate of (stress-strain / Young's modulus).In most cases, electromagnetic wave emission was accompanied with sudden decrease of stress. By analysis on results of the uniaxial compression testing under constant strain rate, it was found that electromagnetic wave emission is closely related to cracking or crack extension.The main results in this study can be summarized as follows;1) Amplitude of electromagnetic wave is relatively large for strong rock.2) For Inada granite, the larger the stress drop occurred in uniaxial compression test is, the larger the amplitude of electromagnetic wave.

著者

福井 勝則 大久保 誠介 本間 直樹

出版者

一般社団法人 資源・素材学会

雑誌

資源と素材

巻号頁・発行日

vol.112, no.5, pp.303-308, 1996

被引用文献数

7

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A method to estimate rock strength with TBM cutting force is proposed. It is assumed that thrust force for a disc cutter increases linearly with product of rock strength and cutting depth. This assumption leads to the following equations:<BR>(Rock strength)&prop;(Resultant thrust force)/(Penetration rate)<BR>(Rock strength)&prop;(Resultant torque)/(Penetration rate) <SUP>1.5</SUP><BR>By the method, rock strength along Niken-goya tunnel was estimated. The tunnel mainly consists of sandstone and slate. Estimated rock strength well agreed with the results of geological investigation; extremely small strength in fragmented slate, on the other hand, very large while boring through massive sandstone. The estimated rock strength was compared with the results of Schmidt hammer test, and it was found that the correlation between the two was excellent. Correlation between estimated rock strength and rock classification was also examined. It was found that the correlation existed, however, the classification used was too rough to evaluate the proposed method precisely.<BR>The proposed method is relatively simple and requires only three values: thrust force, torque and penetration rate. It can be said that the proposed method is promising for real-time estimation of rock strength on the face.