Case Study of Settlement of Gravelly Sand Backfill

A case study of the settlement of gravelly sand backfill is presented. Flatwork, which had been constructed on top of the backfill, was damaged due to the settlement. It is likely that the cause of the settlement was improper compaction methods and/or too low of a compaction standard. Laboratory tests were performed to investigate the settlement behavior of the gravelly sand. If the gravelly sand had 0–20% oversize particles, there were not enough oversize particles to interfere with compaction and the settlement behavior depends on the matrix dry density. For 20–40% oversize particles, they begin to interfere with compaction, but the settlement behavior still depends on the matrix dry density. For 40–70% oversize particles, they continue to interfere with compaction, and the settlement behavior is very complex and depends on the proportion of vertical stress carried by the oversize particles. For 70–100% oversize particles, the compaction energy is absorbed by the oversize particles and the settlement behavior depends on the compression behavior of the oversize particles.