The objective of this research program was to determine the effect of various backfill types on ductile fracture behavior by a relative comparison of fracture behaviors in model pipes. Model pipes of 6.0-inch outside diameter were selected because they could be tested at the West Jefferson facility using an all gas pressuring medium and remain within the noise and environmental protection limitations.
The types of backfill studied were air, sand or soil, water, frozen annulus of sand, and simulated permafrost.