A recent warehouse expansion off Route 116 revealed saturated silty clay just 0.8 meters below the proposed parking area grade. Without a proper pavement design, the first winter freeze-thaw cycle would have cracked the asphalt within 18 months. The solution required a layered structural section tailored to Saint-Hyacinthe's high water table and agricultural belt soil conditions. Our team models the granular base, subbase, and asphalt concrete thicknesses based on projected traffic loads using AASHTO 1993 and mechanistic-empirical methods. For heavy truck yards, we often integrate CBR road testing to calibrate the subgrade strength index directly from field samples before finalizing the structural number.
Saint-Hyacinthe's 1.8-meter frost depth and silty subgrades demand pavement sections designed for drainage first, structural capacity second.
Local geotechnical context
Saint-Hyacinthe sees 55 freeze-thaw cycles per year on average, which is among the highest in southern Quebec. This thermal stress, combined with the silty soils of the Saint Lawrence Lowlands, creates a pavement failure mechanism driven by differential heave. The risk is not just cracking. It is structural fatigue propagating from the subgrade upward. An underdesigned flexible pavement here can lose 30 percent of its service life within the first five years. Moisture trapped in the granular base during November rains freezes in December, expands, and lifts the asphalt in isolated patches. Come April, those patches collapse into potholes. Our design mitigates this with a minimum 450 mm combined base and subbase thickness, positive crossfall of 2 percent, and edge drains for commercial lots adjacent to agricultural drainage ditches common east of the city center.
