Design of Culvert Considering Soil-Structure Interaction

Culverts are buried structures used to carry vertical loads through a combination of internal capacity and soil arching around the structure, which is called soil-structure interaction. The culverts carry vertical loads vary significantly between different structure types due to their relative stiffnesses. Concrete culverts are categorized as rigid culverts and are assumed to carry the design loads internally with limited requirements or benefits from the soil. However, flexible culverts, such as corrugated steel culverts carry loads through soil-structure interaction, which is substantially different from rigid culverts. This is complicated for flexible culverts subjected to considerable induced earth pressures from high embankment fill. In addition, the material and installation requirements of the culverts and founding conditions should be sufficiently defined to ensure that the assumed soil-structure capacity can be achieved, and the settlements are not too excessive. Due to the complexity of soil-structure interaction, current design empirical methods may not be able to provide sufficient and accurate information for culvert design, particularly for soil-culvert interaction. Readily available software packages can provide good predictions of the culvert’s behavior, as well as the loads transfer mechanism of soil-structure interaction. In this paper, case studies were carried out to investigate the soil-structure interaction influence on the culvert behaviors. High embankment induced complex soil-culvert interaction as well as the footings put uncertainty on the loads sustained by the culverts and footings. The soil-culvert interaction analysis involves methods of construction and the type and placement of the backfill. Design implications and product optimization were developed based on the numerical modelling results. The culvert design considered loads and founding conditions in both longitudinal and transverse directions.