Study of Nonuniform Bedding Support Because of Erosion under Cast Iron Water Distribution Pipes

Several recent studies have investigated failure mechanisms for cast iron water pipes. These studies have primarily focused on the adverse effects of corrosion, frost, reactive backfill, and earthquakes. It appears that leaking pressure pipes can produce erosion voids under the buried structure. In this paper, a parametric study employing three-dimensional finite-element analyses is used to examine buried, continuous, cast iron water pipes. The objective is to understand the effect of such erosion voids on the stability of buried cast iron pipes and the longitudinal soil-pipe interaction. The results of the finite-element analyses demonstrate that the radial (sigma(R)) and the axial stresses (sigma(A)) are low compared with the hoop stresses (sigma(theta)), and the peak tension is always in the hoop direction. As a result of the high hoop stresses induced by the nonuniform bedding support, longitudinal fractures are likely to occur in the pipe, which may consequently cause pipe failure. DOI: 10.1061/(ASCE)GT.1943-5606.0000689. (C) 2012 American Society of Civil Engineers.