Abstract
Shaft method applied for aggregate production at the Miyagase-dam quarry site was the third experience in dam construction projects. In the Miyagase-dam case, its scale was the largest (total volume of dam; about 2 million m3) and shafts were used for removing topsoil and disposal rock at first as well as rock materials. Shafts consist of one vertical shaft (D6m×L110m) and two inclined shafts (D6m×L113m, D6m×L132m). Excavation was carried out through pilot-drilling and downward expansion method, excellent both in safety and in workability. Slight troubles by choking happened two times, but rock production was completed practically almost as for the planned program by taking adequate countermesures. Finally, the shaft method is efficient and safe, if in a large-scale with steep shafts, and also is effective for preservation of surrounding environment.
