An experimental and numerical investigation of pullout behavior of ductile iron water pipes buried in sand

Abstract

Buried pipelines, used for transporting liquid and gas, are often subjected to axial pulling forces due to seasonal temperature changes and (or) relative ground movements. The axial pullout force is exerted through soil–pipe interaction, which depends on the pipe material, surrounding soil and pipe–soil interface properties. In this research, axial pullout force on ductile iron pipe buried in sand is first experimentally investigated through development of a new laboratory facility. Based on the test results, simplified methods for predicting the axial forces are discussed. Finite element modelling is then used to investigate the mechanism of soil–pipe interaction and identify the key parameters contributing to the axial pullout force, which could not be measured during the laboratory tests. The constrained dilation of sand near the pipe–soil interface and arching effects due to a different stiffness of the pipe with respect to the soil are found to influence the mobilized axial forces on pipes.