UNDERGROUND EXCAVATOR AND METHOD FOR CONSTRUCTING TUNNEL

摘要

PROBLEM TO BE SOLVED: To provide an underground excavator capable of varying a cross section in a number of ways and minimizing separated portions when a large- cross-section tunnel is changed into a small-cross-section tunnel, and a method for constructing tunnels. SOLUTION: A first cutter head 37 for excavating the natural ground is disposed in such a way as to be capable of parallel link movement on eccentric multiple axes and a second cutter head 59 for excavating the natural ground is disposed on the outside of the first cutter head 37 in such a way as to be capable of parallel link movement on eccentric multiple axes. A tandem circular cross section serving as a first excavation range excavated by the first cutter head 37 continues with a cross section corresponding to a dent serving as a second excavation range excavated by the second cutter head 59, and the latter cross section is provided on a portion of the periphery of the tandem circular cross section. The second cutter head 59 is separable from the first cutter head 37.