Numerical investigation on failure modes and TDA-based mitigation measure of jointed rigid pipes under ground subsidence

Abstract

Jointed rigid pipes are vulnerable to permanent ground deformation (PGD). Compressible and lightweight materials, such as tire-derived aggregate (TDA), geofoams and straws, can be placed around buried pipes to reduce the loads from PGD and minimize the risk of pipe failures. In this study, a calibrated three-dimensional finite element model incorporating a modified Mohr-Coulomb model for simulating the strain softening behavior of surrounding soils is employed to analyze the failure modes of jointed rigid pipes under ground subsidence with various crossing scenarios, where the fault plane intersects different positions of the pipeline. Then, the efficiency of TDA mitigation in reducing the risk of pipe failure is evaluated, considering variations in geometry, size and density of TDA zone. It is found that the most detrimental fault-pipe crossing position locates at 3/4L of the pipe barrel, where excessive bending moment can lead to longitudinal cracking. TDA mitigation mainly prevents structural failure of pipelines, while its influence on the kinematics of joints is negligible. The most pronounced loading reduction for pipelines is achieved by employing TDA with a lower degree of compaction, combined with the burial configuration of full-surrounded layout pattern of TDA.