Numerical Investigation on Buried Pipelines Subjected to Permanent Ground Deformations Due to Shallow Slope Failure

Abstract

Permanent ground deformations (PGDs) induced by slope failures cause catastrophic damage to buried pipelines. This paper presents a 2D plane-strain numerical analysis of the behavior of a 800 mm water transport pipeline buried in the Aine-Tine slope (Mila, Algeria) subjected to shallow PGD, as it could be triggered by the recent earthquake of August 07th, 2020 (M= 4.9). The analysis is carried out through the application of an incremental displacement to simulate the soil-pipeline interaction while focusing on the effect of (1) the magnitude of the PGD and (2) the rigidity of the pipeline on the structural response of the pipeline. The elasticperfectly Mohr-Coulomb model was used to simulate the soil behavior and the elastic model was used to simulate that of the steel pipe. Pipeline deformations (i.e., translation and ovalization) and radial internal forces’ (i.e., axial forces F୅, shear forces Fୗ and bending moments M୆) results highlighted that shallow PGD can exert additional loads on pipelines that are proportional to the magnitude of the PGD. It has been found that the soil deformations as well as the internal forces induced on the pipeline ring are higher for rigid pipelines. Moreover, the results indicated that rigid pipelines are more effective than flexible ones as far as ovalization-serviceability limit state is concerned. In effect, for PGD magnitudes of 0.5, 1 and 2 m, the ovalization values of the flexible pipeline are, respectively, higher by 23%, 21% and 18% than those calculated for the rigid pipeline. Through a simplified linear numerical simulation such as that presented in this study, engineers and planners could be guided to foresee the possible causes of pipeline leaks and the mechanisms of ruptures that lead very often to severe disruption of pipelines’ normal operation. KEYWORDS: Soil-structure interaction, Slope failure, Permanent ground deformation, Pipelines, Radial internal forces, Ovalization