• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.241-250
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• 2007

During enlarging an existing tunnel under operation, unexpected excessive overbreaks and large cavities around the tunnel were found. It was an issue that they might influence the stability the new tunnel. The overbreaks and cavities are assumed that they were attributed to excessive blasting under the condition of insufficient ground investigation. To enlarge the existing tunnel safely, therefore, a remedy measure for the overbreaks and cavities is suggested.

• Journal of Conservation Science
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• v.20
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• pp.89-103
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• 2007

The bedrock beneath the Chokseongnu pavilion consists of sandstone with alternate dark-gray to light-brown siltstone and dark-gray shale of the Jinju Formation, where bedding is well developed toward the Chokseongmun gate. Large to small joints and overbreak from the erosion weathering have been developed in the bedrock. Besides, water leakage from development of discontinuity planes, fragmentation of shale, crack and joint by tree roots are observed on the bedrock. While shale and siltstone showed high sensitivity in physical and chemical weathering, respectively, sandstone indicated the highest weathering sensitivity in both. As the results of structural stability analysis, the whole bedrock has high instability in wedge failures, and especially section No. II slope is more instable than section No. I. Therefore, it is necessary for the bedrock to be strengthened by improvement method for soft foundations and the surface reinforcement. The trees causing mechanical collapse of the bedrock should be also removed and a water flow prevention measure or a water exhaust are required.