Design Equations for Large Diameter Buried Steel Pipes Inspired by the Modified Iowa Formula

The performance of large diameter pipes under construction loads is inherently coupled with knowledge of the complex soil–pipe system. Current methods do not cover all the different combinations for material, trench width, and native soil properties, and were developed based on limited experimental studies. In this work, a comprehensive parametric study using nonlinear finite-element analysis was conducted to predict the deformation and forces of buried large diameter steel pipes during construction. Different parameters, including pipe diameter, diameter-to-thickness ratio, soil properties, trench width, and burial depth, were considered. Results were used to develop equations inspired by the modified Iowa formula to estimate changes in pipe diameter and internal forces during construction that directly include the mechanical properties of the pipe, embedment, trench, and backfill material, as well as the pipe and trench dimensions and the applied loads. They were further validated by estimating the available data from previous studies with acceptable accuracy. These equations can act as a tool for engineers to calculate the desired outputs, without the need for a sophisticated finite-element analysis program.