Centrifuge Modeling of Buried Pipelines

Abstract

Fault crossing, lateral spreads and other types of permanent ground deformation (PGD) are arguably the most severe seismic hazards for continuous buried pipelines. Current analysis and design procedures, to a great extent, are based upon Finite Element (FE) modeling. There are, unfortunately, relatively few full- scale case histories which could be used to benchmark or confirm the applicability of FE assumptions. That is, full scale field verification of the predicted behavior of buried pipes is, at best, sparse. In this paper, a new centrifuge based method for determining the response of continuous buried pipeline to PGD is presented. Laboratory equipment, experimental procedures, similitude relations as well as sample results are presented. Specifically, physical characteristics of the Rensselaer centrifuge are described, as well as those for our current lifeline experiment split-box. The split-box contains the model pipeline and surrounding soil and is manufactured such that half can be offset in flight, simulating PGD. Governing similitude relations which allow one to determine the physical characteristics (diameter, wall thickness, material modulus of elasticity) of the model pipeline are presented. Finally the recorded strains induced in a prototype 0.64 m (25 in.) diameter, 0.013 m (0.5 in) wall thickness, steel pipe by 0.80 m (2.6 feet) and 2.0 m (6.6 feet) of full scale fault offset for a prototype steel pipe 0.95 m (37 in.) diameter, 1.9 cm (.75 in.) wall thickness are presented and compared to corresponding FE results.