An Energy-Based Pipe-Soil Interaction Model

This paper describes a research project into pipe-soil interaction conducted by SINTEF on behalf of the American Gas Association (A.G.A). An empirical model has been developed which predicts soil resistance to lateral motion of untrenched pipelines. Full scale pipe-soil interaction tests were conducted for three soils providing data for the empirical relationships in the model. The tests confirm previously reported results; that soil resistance is strongly dependent on pipe embedment and soil condition (shear strength of clay and relative density of sand). Pipe embedment is estimated empirically from the energy dissipated in the soil and soil resistance is split into two components; a sliding component and a penetration dependent component. In this manner the soil model accounts for the effects of cyclic pipe movements on soil resistance. The new model represents a significant improvement compared to the Coulomb friction estimation traditionally used in pipeline stability calculations. Especially on soft clay and loose sand and in general at high lift forces, the predicted soil resistance is larger than that predicted using friction coefficients typical in design.