Abstract
When a steel pipe in installed into a ground in the pipe roof auciliary tunneling method, an overbreak excavation by expanding bits and friction cutters is carried out since friction and drag around the steel pipe's surface and on joints between the steel pipes must be reduced. Consequently, spaces around the steel pipe are generated and settlement might be caused in a small overburden condition. In order to clarfy the charactertics of the surface settlement by overburden and to propose the control method of surface settlement, in this paper, the modeling apparatus of overbreal excavation has been developed and the several cases of modeling expereiments have been also performed. With considering two factors, namely, overburden and overbreak ratio, in the experiments, the surface settlement has been discussed. Based on the experimental results, the contsraction method of the pipe roof which controls the surface settlement as much as possible has been proposed.
