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| | Abstract | | Tunnel construction costs depend on the type of bedrock in tunnel face. When high-strength rock exists between layers of rock that are not hard, drilling excavation must be combined with blasting, which raises the construction cost. In this study, rock in cores from horizontal boring was classified into typical types, and the relationship between the unconfined compressive strength and magnetic susceptibility of each rock type was examined. High-strength rock tended to have low magnetic susceptibility, whereas Low-strength rock tended to have high magnetic susceptibility. The magnetic susceptibility changes at about 1 or 2 meters from the boundary between the rock types. This suggests that immediately beyond locations where the magnetic susceptibility decreases, hard rock probably exists. |
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