Innovative Approach to Establish Transitions Between Two Materials of Different Frost Susceptibilities Under Rigid Concrete Pavement at Montreal-Pierre Elliott Trudeau International Airport

Natural soils at the site of Montreal-Pierre Elliot Trudeau International Airport are not easily reusable as trench backfill for laying underground infrastructure (sewers, fuel pipeline) since they generally have a high proportion of fine particles (< 80 micrometres) along with a high water content, making them difficult to compact. Previously, it was common practice to fill trenches with a stone screening containing more than 15 percent fine particles (< 80 micrometres) so as to mimic as much as possible the frost behaviour of the existing natural soil. However, this process raised another issue, as during the rainy season, these materials (stone screening) became easily saturated and thus unstable, leading to subgrade's instability. Given this recurring problem, especially in the fall, ADM decided in 2012 to fill these infrastructure trenches with crushed stone close to a 0-20 mm calibre or 0-56 mm calibre so as to ensure the stability of the materials laid. As a result, the frost susceptibility of the crushed stones in these trenches was completely different from that of the surrounding natural soils. This lecture will present the innovative approach put forward by the authors to design an appropriate transition between these two materials, for a rigid concrete pavement, using the SSR model for frost heave calculation used by Quebec's Department of Transportation (MTQ) in its "CHAUSSEE 2" software. (A) For the covering abstract of this conference see ITRD record number 201310RT334E.