Stresses induced in a buried corrugated metal arch culvert due to backfilling compaction efforts

The use of flexible buried corrugated metal culverts (CMCs) for traffic and watercourses has recently expanded as a promising technique for shallow underground tunnelling. However, in the design of such structures it is challenging to mimic the performance of the mobilized soil-structure interaction. The backfilling process, with the use of compaction forces, can be considered the major loading mode that develops the predominant deformations and internal forces in the culvert body. Therefore, a thorough understanding of the backfilling process and its effects can contribute to improving CMC design methodology. In this study, a laboratory experiment was used to investigate a flexible buried corrugated metal open-bottom arch culvert, where the compaction impact was monitored during each backfill stage. Following the installation of the culvert in a rigid steel tank, seven sequenced backfill layers were added and compacted, until the target cover depth was reached. Culvert deformations and internal forces were recorded during each backfilling stage. Moreover, the variations in vertical soil stresses developed due to backfilling were measured at two locations: the surface of the bedding soil, and just above the culvert crown. In addition, the lateral perpendicular stresses induced at the exterior circumference of the culvert body near the midpoint of each side backfill layer were measured during backfilling. Finally, a numerical analysis using 3D finite element modelling was performed to simulate the construction sequence of the laboratory test during the backfilling process. The numerical modelling results for the culvert deformations and internal forces were then validated against the recorded measurements obtained in the laboratory experiment and a numerical procedure to simulate the induced backfilling efforts was recommended.