Compaction of dune sand backfill by concrete shaft vibrators

Abstract

Backfilling is a time-consuming operation at any construction project. Because of construction constraints and to minimize excavation and backfilling costs, utility trenches are made as narrow as practicable, which precludes the use of large compactors. The backfill is therefore placed in thin layers and compacted with hand compactors, making backfilling a slow operation. This paper presents the details of development of a fast, effective, and reliable backfill compaction procedure. This method is based on the concept that the sand being a cohesionless material can be easily densified under its own weight by mere vibrations if the intergranular friction between the sand particles is reduced. The method allows placement of saturated dune sand backfill in lifts up to 1 m in thickness, and the compaction is achieved by vibrating the mass by inserting concrete shaft vibrators on a regular grid pattern. The results and analysis of numerous laboratory experiments and 13 full-scale field test trials which form the basis of this compaction technique are also included in this paper. Key words : backfilling, dune sand, intergranular friction, vibrations, concrete shaft vibrators.