Replacement of a Timber Trestle with an MSE Retaining Wall SystemCN Rail, Yale Mile 118.93 Trestle Replacement

摘要

This timber trestle caught fire in the early 1990's. The structure required replacement due tornsubsequent deterioration over time, coupled with ever increasing rail demands. CanadianrnNational (CN) had to ensure minimal rail disruptions during replacement of this section ofrnmainline, with upwards of 40 trains per day.rnThis paper will discuss the innovative approach adopted by CN using Mechanically StabilisedrnEarth (MSE) to replace the ageing structure, and support the overhead rail. The project wasrnchallenging from the construction and staging perspectives. Canadian Pacific (CP) and FrontrnStreet were located immediately parallel to each side of the trestle. Construction was furtherrncomplicated by limited headroom as MSE panel placement proceeded directly below the existingrntrestle deck.rnThe MSE system selected was Reinforced Earth ? , designed and supplied by the Reinforced EarthrnCompany Ltd., and consisted of precast facing panels, inextensible steel reinforcement, andrnprecast coping. Precast MSE panels were placed around the timber bent structure. MSE panelrnplacement then proceeded upward, and as close to underside of deck as practical. CN opted tornfinish panel placement/backfill at the top of wall during two separate track closures work blocks.rnThe first was for 12 hours and the second was for 18 hours. The timber pile cap, deck, and railrnwere removed by crane. The removal of the deck enabled CN to complete the top of wallrnplacement, and resume backfilling by more conventional backfill techniques. The rail was re-installedrnby use of jointed rail sections. The precast coping was placed atop the wall andrnhandrails completed. The mainline was back in service being fully supported atop the MSE wall.rnConstruction commenced in January of 2004, and was substantially completed in May of 2004.rnMSE provided a successful staged construction solution, while allowing CN to maintain safe railrntraffic throughout the construction corridor, during the entire course of structure replacement.rnThis paper will illustrate the technical considerations of using MSE, along with the variousrnconstruction stages, and safety considerations associated with this project.