A Case Study of Roadway Embankment Construction Over Existing Sewers in Montreal, Canada

Abstract

This paper presents a case study of the influence of a roadway embankment on existing sewers with diameter or width of approximately 3.3 to 4.3 m. The proposed embankment would be constructed directly above the existing sewers, which would induce an additional load. Traditional analysis methods cannot account for the structural/soil interaction and the benefit of the lateral supporting characteristics of the soils. In order to evaluate the loading of the proposed embankment on the existing sewers, a structural/soil interaction analysis using a two-dimensional finite element computer program was performed for various loading cases. The sensitivity of soil parameters was also considered in the analysis. From the analysis, the loadings on the sewers including axial force, bending moment and shear force were obtained and then the structural capacity of the existing sewers was checked. Light-weight sand fill or expanded polystyrene (EPS) geofoam was considered to reduce the additional vertical and horizontal loads on the sewers. The EPS geofoam or a structural protection system consisting of a concrete slab supported by concrete piles was considered to eliminate any incremental vertical and horizontal loads on the sewers. These mitigation methods were compared. It is found that the light-weight sand fill is most economic material to reduce the additional loads on the sewers, the EPS geofoam is most suitable material to eliminate incremental loads on the sewers for a lower embankment, and the structural protection system is only option to eliminate incremental loads on the sewers for a higher embankment.