Development of a numerical model for predicting pulling loads on fusible PVC pipe

Design engineers are continually evaluating alternative pipe and construction options for addressing their municipal infrastructure needs. Today, the use of trenchless technologies such as Horizontal Directional Drilling (HDD) in the municipal sector has increased significantly as an alternative construction method. 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™ (FPVC™) 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 results of research to develop a predictive model for HDD installations specific to FPVC™. A three step process was used to define the methodology of predicting safe pull load. The first step was the development of empirical equations based on existing methodologies, experience, and PVC-specific material properties. The second step involved field measurement of pipe pull loads during HDD installations. Finally, the field data was compared to the calculated data and the predictive equations were modified accordingly. This design model, calibrated by field verified data, enables a more accurate determination of required safe pull load for any given HDD installation. Copyright ASCE 2009.