When the blasting is executed at the face adjacent to existing lining for widening of existing tunnel, serious damage on the existing tunnel lining due to blast will cause less safety during construction. Then, to confirm the safety, the blasting vibration velocity of existing lining was ing was measured at the tunnel con-struction site, and the relationships between the measured data and the site conditions were examined by regression method. As a result, it is made clear that the generated vibration is small and the crack appears in the range of 3 ～ 5 m from the face at most.
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