The introduction of flexibility into a road ironwork installation

This paper describes research undertaken to examine the option of replacing the upper portion of a rigid traditional brick access chamber with a flexible material, so that the system is more compatible with the surrounding flexible (asphalt) pavement construction, and is therefore less likely to exhibit premature failure. It focuses on one example of a suitable material, the influence of the confinement of this material within the surrounding pavement, and the importance of using a compatible backfill that acts as a bridge between the pavement and the ironwork. Full-scale experiments have been undertaken using a laboratory-based rolling-wheel test facility. Results show that flexibility incorporated into a road ironwork chamber can smooth out the step change in stiffness between a flexible pavement and a rigid chamber. Replacement of the upper portion of a chamber with a suitable flexible section results in the structure being more compatible with an asphalt pavement. It was also confirmed that the backfill around the chamber should be well compacted to provide good confinement, and the reinstatement material around the frame is a key element in the overall performance of a flexible chamber installation.