ABSTRACT
In the Pannerdensch Canal railway tunnel project the twin-bored tunnel passes a formerly excavated sandpit. Because the tunnel passes above the – at that moment existing – bottom level of the pit, this pit had to be partially backfilled with 500,000 m3 of sand. In order to support the lining, and to prevent blow out the backfill had to fulfil a whole set of criteria which required the compaction of sand with a well-defined grading by vibroflotation. The definition of these criteria and the translation into measurable parameters led to an elaborate process. As the particle-size distribution curve of the used sand needed to fit into a tight band and the sand spraying process was advancing in a higher speed than the prescribed testing methods could give results, some correlations with quicker testing methods were investigated.
