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Volume 51 (2010 - 201･･･
- Issue 6 Pages 257-
- Issue 5 Pages 220-
- Issue 4 Pages 170-
- Issue 3 Pages 112-
- Issue 2 Pages 62-
- Issue 1 Pages 2-
Volume 51, Issue 2
Displaying 1-4 of 4 articles from this issue
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Original Article
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Akira JOHMORI, Yuji MITSUHATA, Susumu NISHIMURA, Nobuhide JOHMORI, Tak ...2010 Volume 51 Issue 2 Pages 62-72
Published: 2010
Released on J-STAGE: March 31, 2013
JOURNAL FREE ACCESSThe CSMT (controlled-source magnetotellurics) and TDEM (time-domain electromagnetics) methods adopting an artificial electromagnetic source have been used, as electromagnetic exploration methods for relatively deep geological targets. These methods transmit an electromagnetic signal from the source which is placed away from signal measurement sites. By measuring weak electromagnetic fields induced in ground at various frequencies, we can evaluate a subsurface resistivity distribution from the surface to several kilometers.
Even though these methods use the artificial and controllable source, periodic electromagnetic noises generated by power lines or electrical appliances become fatal obstacles for receiving the weak electromagnetic fields, especially near urban areas. In order to overcome this periodic noise problem, we have examined some efficient wave-analysis schemes. Consequently, we arrived at the conclusion that it is a key factor to improve the resolution of frequency spectrum because it can avoid diffusion of the periodic noises in the process of frequency-spectrum analysis. To improve the resolution, it is required to extend the sampling length of time-series data for the frequency-spectrum analysis. For dealing with long sampling time-series data, accurate time synchronization is crucial. In this study, we have developed a deep electromagnetic exploration instrument with high frequency spectrum resolution by using GPS synchronization. A field test of the instrument has been carried out in the Nanki Sirahama Hot Spring area, in the central western part of Japan. As a result, we obtained better quality data in comparison with the data evaluated by a conventional stacking process, even if there are many noises in a town.View full abstractDownload PDF (3481K) -
Study on the Sinkhole Phenomena at Abandoned Coal Mine and Its Investigation and Preventive MeasuresRyugo MAKINO, Ibrahim DJAMALUDDIN, Tetsuro ESAKI2010 Volume 51 Issue 2 Pages 73-84
Published: 2010
Released on J-STAGE: March 31, 2013
JOURNAL FREE ACCESSIn Chikuho-KitaKyushu district, the phenomena of sinkhole have occurred in the abandoned coal mined area. Those sinkholes are caused by old working at shallow depth.
In this paper, the sinkhole databases from 1965 to 2009 have been developed such as time occurrences, places, scales and the related coal mine information. By conducting GIS (geographic information system) analysis, the characteristic of sinkholes have been clarified where the shape and type of sinkholes are frequently rounded type and the diameters of ground sinking are mostly generated about 3 meter or less.
The sinkhole number generations have high correlation to the amounts of rainfall. This correlation results shows that when the amount of rainfall is also high, so the generation of sinkhole becomes large. These generated sinkholes are mainly resulting from underground coal at shallow depth by small and medium scale of mining activities.
Furthermore, the GIS analysis shows the sinkhole might be not occurred if the minimum thickness of rock support is cover by about 30m of extraction height. By studying the correlation between the extraction times, the generated sinkhole locations and the mining opening times, it can be concluded that the sinkhole phenomena is potentially to be possible to occur even 100 year after mining opening.
With regard to the investigation on the underground cavity, an extraction mining technology and the history of social-economic background in that era is very important to recognize. In order to perform measure of cavity for preventing sinkhole to the construction plan, the advantage and disadvantage of method measurement, the existence effect of old cavity, the extraction map and sinkhole record, and also preventive measures method including adjustment plan related to sinkhole are very important to study.View full abstractDownload PDF (4663K)
Report
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Ryo TAKAHASHI, Yuuji ENDOU, Kaoru MARUTANI2010 Volume 51 Issue 2 Pages 85-91
Published: 2010
Released on J-STAGE: March 31, 2013
JOURNAL FREE ACCESSWe summarized hydrogeological features around 533 landfill sites for industrial wastes in Hokkaido based on the existing data and geological survey around them. In this study, the hydrogeological features around the landfill sites were classified into four types, impermeable layer type, permeable layer type, surface permeable-subsurface impermeable type and heterogeneous permeability type. Since most of the landfill sites locate on permeable deposits, such as Alluvium and pyroclastic deposit, 56.3% of the landfill sites were classified to the permeable layer type. Infiltration water from the landfill sites situated on the permeable layer type would be easy to permeate vertically. If toxic substances are contained in the infiltration water, the widespread pollution would occur. In this case, the observations of the groundwater quality play an important role to recognize the pollution immediately. On the other hand, 26.5% of the landfill sites locate on the impermeable layer type which is hard to cause the widespread pollution. These hydrogeological data about each landfill site would provide useful information to perform the prompt circumstantial judgments for prevention of the widespread pollution.View full abstractDownload PDF (1736K)
Short Report
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Takato TAKEMURA, Masahiko OSADA, Yukiyasu FUJII, Tatsuo KANAMARU, Mana ...2010 Volume 51 Issue 2 Pages 92-96
Published: 2010
Released on J-STAGE: March 31, 2013
JOURNAL FREE ACCESSIn order to estimate long-term hydraulic properties of rocks, we carried out the comparison between a permeable fracture and a low-permeable fracture filled by calcite, and evaluated three-dimensional structure of both fractures by means of X-ray computed tomography. As a result, the low-permeable fracture function as permeable fracture because the joint is connected to each other as channel. Furthermore, the permeability of fracture filled by calcite is the potentially same permeability of permeable fracture since the calcite dissolve in the longer term.View full abstractDownload PDF (3623K)
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