PROJECT DETAILS

/ CONTEXT Delsan AIM was awarded a contract to demolish a section of the Autoroute Bonaventure that passes through an industrial area of Montreal and is part of the north-east approach to the Champlain Bridge.  The project involved the complete replacement of an elevated section of roadway as well as the restoration of the associated piers.The structure consisted of four spans constructed of pre-stressed concrete “AASHTO” girders bearing on piers and carrying a cast-in-place, reinforced concrete deck.  The girders were tied laterally with post-tensioned, reinforced concrete, transversal diaphragms.
/ DEMOLITION Delsan AIM was required to execute the demolition work in four phases with the construction of the new deck closely following each phase.  All the major demolition work was completed using machinery operated from below the highway on ground level.  A temporary gravel pad was installed below the work area to protect existing infrastructure.  In addition, environmental control measures were implemented in order to prevent not only sediment from entering existing sewer systems, but also debris and dust from impacting live roadways and neighboring facilities.
/ EXTENSIVE ENGINEERING The structures were demolished in accordance with engineered guidelines using a combination of high-capacity lifting jacks, and 45 to 65 ton excavators equipped with shear, hammer, and pulverizer attachments.  Temporary bracing was installed to maintain the lateral stability of the live roadway prior to the deactivation of the existing diaphragms.  A separation was created, furthermore, between each phase to ensure the integrity of adjacent structures, using concrete saws and small demolition equipment operated on the deck.
/ SOLUTIONS With sufficient room adjacent to the highway, the first phase was executed by demolishing the deck and girders in-situ.  However, due to the proximity of the new and existing highway structures, the remaining phases had to be completed by lowering each span onto concrete-blocking using high-capacity lifting jacks and beams.  The lowered deck sections, which weighed up to 250 tons, were safely demolished near ground level using excavators.
/ As the demolition work was completed, front-end loaders were used to transfer the debris to a staging area adjacent to the work site, where the concrete was crushed to remove the rebar.  Both the rubble and scrap metals were shipped off site for recycling.