Valley Line West LRT: Drainage Relocation—Microtunneling Construction Impact on Existing Infrastructure Using Finite Element Analysis

Design and construction on the new Valley Line West LRT which connects downtown to the west side of Edmonton are currently underway. EPCOR owns and operates a number of sanitary sewers along the new LRT alignment. Due to the location, depth, length, and other utility conflicts, the primary sewer was designed to be replaced primarily by microtunneling methods as it will conflict with the new LRT alignment. Shanghai Construction Group was awarded the project and began planning for the work. Due to the tight construction timeline, two drives were planned to occur simultaneously from both sides of an existing 1,500 mm diameter trunk at installation lengths between 400 m and 990 m. The anticipated jacking loads for the installations were identified as a concern as the existing deep trunk was not designed to take the laterally imposed 500 and 1,000 t. A finite element analysis of the proposed shaft design system and the loading imposed by the microtunneling was completed to determine if the potential impacts to the existing tunnel were in excess of what could be resisted. This paper discusses the steps taken to assess the structural impact of the construction loads on the existing deep sewer trunk.