Soil Structure Interaction Effects in Thrust Restraint Systems of Buried Pipelines

Abstract

Current design guidelines for the design of thrust restraint system for the pipelines are primarily based on the geotechnical characteristics of the soil surrounding the pipeline and upon the ability of the soil to resist the unbalanced forces in the bends through a combination of frictional and passive resistances. The fact that the pipeline has to sufficiently deform in order to mobilize such resistance is often ignored in the design guidelines, including those published by AWWA. Consequently, most designers do not consider the additional axial and bending stresses induced on the pipeline from the Soil-Structure Interaction (SSI) effects near the bends, resulting in a potentially unsafe design. This paper presents finite element analysis models of a number of steel pipe bends that were analyzed, designed, and constructed in the field using thrust restraint joints. A typical project that was completed recently, consisting of horizontal and vertical bends, will illustrate the benefits of including soil-structure interaction effects in the thrust restraint system design for pipelines.