Placing and compaction of the select backfill

The backfill is placed and compacted in layers on both sides of the arch. Both sides must be brought up evenly to ensure uniform distribution of loads. Detailed construction requirements can be found in RECO’s TechSpan® construction manual.The degree of compaction required depends on the function of the structure and is stated in the project specification, but in any case should not be less than 95 percent of the maximum dry density (Standard Compaction). The backfill should never be placed with a moisture content higher than Optimum Moisture Content.

Choice of select backfill

A granular engineered fill material as specified by RECO is required in a 2m zone around the back of the arch. Generally a minimum of 1m cover of backfill is required over the crown of the arch. Select, non-plastic, granular backfill material for dry land structures should be used. Three backfill zones (refer to diagram below) are generally required. The material properties for each zone can be found in RECO’s TechSpan® Technical Specification.