• Journal of the Korean GEO-environmental Society
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• v.8 no.6
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• pp.85-95
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• 2007

It is difficult for seismic survey to get hold of characteristic of coal shale fractured zone and if coal shale zone did not come into contact with underground water, coal shale zone has characteristic of good strength. But in case coal shale zone is exposed by excavation or blasting to the air, strength of coal shale zone decreases in short term and weathering of coal shale zone progresses rapidly. Therefore, the prediction of tunnel collapse is not easy in the coal shale zone and the great portion of tunnel collapse takes place in a moment. From a view point of strength, after twelve hours form result of point load test strength of coal shale decreases by fifty six percent when coal shale zone come into contact with ground water. The standard reinforcement design of coal shale fractured zone was presented in the paper.