Performance assessment of buried steel pipelines reinforced with carbon fibre-reinforced polymer under reverse fault movement

Buried oil and gas pipelines are often affected by the active zones across faults, and the failure of pipeline functions owing to relative fault movements has attracted widespread attention. Carbon fibre-reinforced polymer (CFRP) was proposed as a reinforcement measure for buried continuous pipelines crossing faults to mitigate the structural damage to pipelines subjected to large permanent ground deformations. In this study, the lamina model and Hashin failure criterion were used to simulate the CFRP material in a three-dimensional nonlinear finite element model of the pipeline-soil interaction. The peak strain and cross-sectional ovalization of the pipeline were used to quantify the nonlinear response of the steel pipeline subjected to reverse fault movement. Parametric studies in terms of the CFRP wrapping angle, thickness, length, as well as internal pressure were conducted to comprehensively assess overall performance of CFRP-wrapped steel pipelines. Results indicated that the CFRP wrapping in direction of 0°/90° with respect to the axial direction of the pipeline exhibit the optimum effects in improving the performance of pipelines. For steel pipelines subjected to reverse fault, increase of the CFRP wrapping thickness effectively reduces the development of compressive strain on the pipeline wall, thereby delay the local buckling failure of the pipeline. Besides, CFRP is effective in increasing the bending curvature radius and preventing the local buckling of the pipeline, but insufficient wrapping length of CFRP can lead to local buckling of steel pipelines under same fault displacement. For pipelines with internal pressures internal pressure can enhance the overall performance of CFRP wrapped pipelines against reverse fault movement.