Development of a Model for Estimation of Buried Large-Diameter Thin-Walled Steel Pipe Deflection due to External Loads

Abstract

Diameters and wall thicknesses of flexible pipes are usually designed as per hydraulic requirements, such as flow capacity, internal fluid pressure, and pipe material properties. Proper embedment is then designed to protect the pipe integrity against external loads. This paper considered engineering properties of embedment soils in analysis of flexible pipe–soil system for external load conditions and a new model was developed for the prediction of deflection of flexible steel pipe. Full-scale laboratory tests were performed to develop the new model and finite-element models were analyzed to validate the test results. In this research, the finite-element method was effectively used to model the soil–pipe interaction for five full-scale laboratory tests conducted on a steel pipe. Such models can be used for analysis of flexible pipe embedment design for layered embedment conditions. The results of finite-element analysis showed that the squaring of the pipe occurs when the haunch soil is weak compared to the side column. Another critical observation made during the tests was that the stresses at the bottom of the pipe and the bedding angle are highly dependent on haunch soil strength. It is desirable that the stress due to surcharge load on top of the pipe, weight of the pipe, and water inside the pipe be distributed uniformly across the width of the bedding.