Centrifuge model tests of buried pipes installed in sloping-sided ditches

Abstract

Earth pressures acting on, and deformation of, buried pipes installed in sloping-sided ditches were investigated through 24 centrifuge model tests using 1/30-scale 2-D models. The models were placed in a centrifugal acceleration field of 30 G, and a load equivalent to a design load due to several 25-ton vehicles was applied at the center of the ground surface by means of a strip loading plate. The test results fully quantified the effects of the following investigated factors, on the mechanical behavior of the buried pipes: inclination of ditch wall, roughness of ditch wall, cover height, type of backfill soil, and flexibility of pipe. The test results, measured before the surface loading and during the surface loading, were compared with results predicted in accordance with current design standards. The comparison revealed that the current design standards do not reflect the actual behavior of the buried pipes and tend to underestimate the safety of the pipes in most cases, leading to a conclusion that a new design method for the buried pipes is needed instead of the problematical current design standards.