Field Validation of Installation Loads on Horizontal Directionally Drilled Fusible PVC Pipe

Engineers and contractors are continually challenged with evaluating alternative pipe material and construction options for best meeting their project needs. Traditional open-cut construction methods have proven design and installation specifications; however, the increase in utilization of trenchless construction methods has facilitated the development of pipe materials suited for such installation methods. Today, technologies such as Horizontal Directional Drilling (HDD) have increased significantly as an alternative installation method in the municipal sector. Installation of potable water, force mains, reclaimed water, and gravity projects employing directional drilling have grown as demand for installations in difficult areas, like under rivers or major highways, or highly urbanized and congested utility corridors has increased. The nature of the HDD process necessitates the use of continuously joined pipe products capable of being pulled in, as opposed to pushed in by segmental installations. Fusible PVC pipe is one such material for installation of water and wastewater, pressure and non-pressure infrastructure using HDD. While maximum safe pull load criteria have been developed for this material, the present pull load predictive tools for the HDD process are highly variable and, in some cases, overly conservative in evaluating safe pull loads. This paper describes the field validation of a predictive model for HDD installations using Fusible PVC from data captured during commercial installations using an in-line measuring device attached between the backreamer and the product pipe. The results of eight projects are presented in this paper to demonstrate the model validity.