Collapsing Peak Up of a Large Highway Steel Pipe-Arch

This case history reports the collapse of a large highway steel pipe-arch (8.12 m rise - 10.95 m span), occurring just when backfilling reached the top of the arch. No fill was placed on top as backfilling proceeded; the arch raised, thereby flattening side radius. It shows that stability in a soil-structure interaction system requires not only adequate design of the structure barrel, it also presumes a well engineered backfill. Performance of the flexible steel pipe-arch in retaining its shape and structural integrity depends greatly on placement and compaction of the envelope of earth surrounding the structure and distributing its pressures to the abutting soil masses.