Use of Infrared Technology to Detect Backfill Voids Behind Steel Lining in Tunnels

Author(s) A. MacKinnon, B. Harland
RETC 2017 - Rapid Excavation & Tunnelling Conference - June 4-7, 2017, San Diego, CA


The traditional method for discovering voids in the backfill behind a steel liner is by systematic tapping the liner interior with a hammer.

This method was specified for the Seymour Capilano Twin Tunnels Project, but issues were recognized and alternative methods were sought.

The hammer test was deemed to be subjective in determining ‘pass or fail’ criteria. Also hammer blows could potentially damage the pipe polyurethane lining. The paper explains how infra-red technology was employed successfully as an innovation and an improvement on the hammer test for detecting voids.