PURPOSE: To increase the thickness of an underground wall at a place having large external force of the ground and to make it possible to construct an advantageous underground structure constructionally by providing side cutters to drum cutters of a horizontal multi-shaft excavator, and advancing and retracting in the drum shaft direction to carry out a partial width widening excavation.
CONSTITUTION: Side cutter 3 are mounted to both sides of a pair of drum cutters 2A and 2B, an expansion pressure cylinder 7 having a tension spring 8 to the inside thereof is liquid-tightly loaded between the cutter 3 and the ends of the drum cutters 2, and it is connected together with a hydraulic port 6 provided to he inside of a rotary shaft 5. When oil pressure is applied from the hydraulic port 6, the expansion pressure cylinder 7 expands against the spring 8, and the drum cutters 3 are pushed outward. In addition, the side cutters 3 are excavated vertically to a specific depth H1 with an excavation width C1 by a variable width excavator while supplying stabilized liquid 15, and the oil pressure is applied from the hydraulic port 6 at a place necessary for a widening width. Then, the side cutters 3 of the ends of both sides of the drum cutters 2 are pushed outward for an excavated width C2 only through the expansion pressure cylinder 7 to carry out the width widening excavation.
KISHI YASUHIRO
SAKATE MASAAKI
