Gas Control in a Vertical Boring Machine Advanced Shaft in Shale

摘要

Gas inflows into Cleveland, Ohio tunnels are well-documented and historically addressed with ventilation. Until recently, shafts were thought open and accessible enough to avoid gas buildup. Dugway Storage Tunnel (DST) shaft DST-7 was completed using a vertical boring machine (VBM). During shaft excavation, gas inflow rates exceeded the volume controllable with the VBM ventilation system and the VBM could not be advanced. Nearly thirty working days of delay occurred before gas levels dissipated enough to allow safe shaft entry and completion of the excavation. A case history of the shaft excavation with recommendations regarding dealing with gas impacts on future VBM-advanced shafts is provided.