Trenchless Installation of 60 inch sanitary sewer using a 72 inch Robbins Rockhead hard rock TBM

摘要

This paper describes the use of a 72 inch Rock TBM to excavate 13,000 psi limestone for jacking540 LF of a 72 inch casing liner and 60 inch carrier pipe for a flat 0.05% sanitary sewer installation in blockyground with high levels of petroleum contamination in Louisville KY.Louisville MSD's Southeastern Interceptor Part B Project’s called for a 25 foot deep tunnel using 7 gage 84 inchdiameter liner plate initial lining with 60 inch Class IV RCP as the carrier pipe installed in a drill and shoot tunnel.Midwest Mole, Inc a subcontractor for MAC Construction & Excavating, Inc. determined that the project could beconstructed more efficiently by jacking 72 inch steel casing behind a Robbins TBM and installing 60 inch HOBASflush reline fiberglass pipe as the carrier.With 7.1 inches of clearance between initial lining and carrier pipe, accurate tunnel excavation was required.Encountering blocky and seamy ground made tunneling challenging.Another complication was high levels of petroleum contamination in the tunnel atmosphere while excavating thelimestone rock. Investigation of the contamination was performed and workers completed the tunnel excavationusing both suction and supply ventilation and supplied breathing air systems for the TBM and haul unit operator.This paper discusses the benefits, risks and considerations of small diameter rock TBM installation of jacked steelcasing with tight clearances between the casing and carrier pipe. The process for tunneling the initial casing liner inthe difficult ground and the carrier pipe installation along with grouting will be described. The efforts required tocontend with the contaminated atmosphere within the tunnel will be described and will include a discussion of howthe hazards were quantified, monitored and mitigated so that the workers could complete the project safely.