Design of through-grade culverts to mitigate road roughness (case study: PTH-68)

Roadways over culverts experience severe roughness due to the differential frost heave and thaw settlement in cold regions. Five instrumented culvert sites with different designs to mitigate road roughness were constructed and monitored for two years in Manitoba, Canada. The sites were different in the culvert diameter, type of backfill material, depth of cover, geosynthetics, and thermal insulation. The objectives of the study was to provide design of culverts in cold regions to mitigate road roughness, and develop a numerical model for geotechnical engineering applications in cold regions. A 2-D thermal numerical model was established, validated, and applied on geotechnical engineering applications in cold regions. The study concluded that thermal insulation and geosynthetics had noticeable effect on mitigating road roughness over culverts, and different placements of thermal insulation at the vicinity of culverts could be used to reduce the severity of several geotechnical problems in cold regions.