著者

高橋 良尭 山口 耕太郎 笹岡 孝司 濱中 晃弘 島田 英樹 一ノ瀬 政友 久保田 士郎 佐分利 禎

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.135, no.10, pp.94-100, 2019-10-31 (Released:2019-10-31)

参考文献数

19

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Rock blasting is one of the most common techniques for rock breakage in the open-pit mining excavation. On the other hand, the application of the technique has been restricted by law since it may cause a serious impact on surrounding environment, such as flyrock, ground vibration and noise. According to the statistics, more than 70% of accidents relating to the usage of explosives is flyrock. This accident may cause serious damage to buildings, human beings, and objects in the surrounding area. However, a detailed guideline for prevention of flyrock has not been developed yet. From these points of views, a series of field experiments was conducted and initial velocity and flying direction of fragmented rock were discussed by considering blasting standard and rock mass conditions such as strength, fractures/cracks and joints. The result shows that powder factor and burden have strong influence on the initial velocity of fragmented rock. Not only blasting designs but also rock mass conditions, cracks/joints strongly effect on the initial velocity. In addition, it was also made clear that the existence of fractures/cracks/joints in the blasting face have an obvious impact on the direction of fragmented rock.

著者

児玉 淳一 立川 多久登 中 良介 濱中 晃弘 板倉 賢一 出口 剛太 福田 大祐 藤井 義明

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.134, no.7, pp.91-98, 2018-07-31 (Released:2018-07-31)

参考文献数

24

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Small-scale underground coal gasification (UCG) model tests with a linking hole were carried out using two types of specimens made of either block coal or crushed coal to clarify their characteristics of combustion and gasification. Many similar characteristics were found between both specimens in terms of temperature change and its spatial distribution as well as concentration and heating value of each gas product as long as the crushed coal specimen was sufficiently consolidated. The shape and dimension of the cavity formed in the both specimens were also similar. Texture of the both specimens was changed after the combustion and gasification. Initiation of radial cracks from the linking hole was found in the both specimens. Within the zone with the radial cracks initiation, grains in the crushed coal were bonded whereas cleats in the block coal were healed. The grain bonding and the cleavage healing can be explained by melting and expansion of coal due to temperature increase. The radial cracks are likely initiated after the grain bonding or the cleavage healing due to tensile thermal stress induced by temperature gradient in the coal specimens. It can be concluded that the characteristics of combustion and gasification of the crushed coal and the block coal are similar because both types of coals become similar in texture through combustion and gasification. These results indicate that characteristics of combustion and gasification of coal seam can be mostly estimated from a model test with artificial coal seam made of crushed coal.