Soil-Structure Interaction of Very Flexible Pipes: Centrifuge and Numerical Investigations

The unprecedented increasing cost of steel coupled with the superior mechanical and anticorrosion properties of fiber-reinforced plastic (FRP) creates a huge opportunity for FRP pipes to take the market share of steel and be the pipe of choice for geotechnical engineers for a variety of applications ranging from potable-water systems to feed lines and penstock for hydroelectric power plants. Recently, very flexible large-diameter FRP pipes have been installed in eastern Canada and the United States to replace old wood-stave pipes to convey water to drive the turbines of small hydroelectric plants. The behavior of buried very flexible pipes is one of the complex soil-structure interaction (SSI) problems in geotechnical engineering and has not been studied thoroughly until now. The flexibility classification of pipes is determined based on their effective stiffness. Accordingly, flexible pipes will have an effective flexibility of 10 kPa/m or less. In this paper, the results of centrifuge modeling of fully buried very flexible pipes with shallow soil cover with and without surface loading are presented to supplement the very limited data that exist for such very flexible pipes. In addition, a three-dimensional finite-element (FE) model was created as part of this study to simulate the centrifuge results obtained and to investigate the effect of surface loading on the buried pipes. In addition, the results from the model testing and the FE model were compared with the predictions of two analytical solutions to assess their suitability for such an application. Finally, the positive arching predicted by the analytical methods and its practical significance were examined. (C) 2014 American Society of Civil Engineers.