METHOD FOR WIDENING EXISTING MOUNTAIN TUNNEL

摘要

PROBLEM TO BE SOLVED: To reduce a time and labor required for widening an existing mountain tunnel. SOLUTION: In a method for widening an existing mountain tunnel, a path 14 is constructed under an existing tunnel 10 and then a ground 28 around the existing tunnel 10 is drilled to form part of a new tunnel 44. Further, the ground is drilled and part of the path 14 is broken to form the remaining part of the new tunnel 44.