Numerical Analysis of Underground Pipelines with CFRP Against Surface and Subsurface Blasts

The contribution of underground pipelines in the present time is imperative. However, in recent years, they have become a target to explosives and terrorist attacks. So, its assessment against blast loading has become very crucial. The present work is focused on the blast resistant design of pipelines. In this study, CEL (Combined Eulerian–Lagrangian) approach is used to assess the response of X70 grade steel pipelines against blast loading. Underground steel pipelines subjected to TNT (Trinitrotoluene) charges placed at or below the ground surface are investigated. The CFRP (Carbon Fiber Reinforced Polymer) sheets have been used to strengthen the pipeline against these types of incidents. Different material models, Equation of State (EoS) are utilized to replicate the actual response of different components under blast loading. X70 grade steel pipelines of two different thickness are studied with and without protective barriers to determine the mitigation provided by protective covering. The results of this study are validated with empirical formulas and are in good agreement. Effect of application of CFRP on maximum equivalent plastic strain of pipes and damage length of pipes are studied. A parametric study has been carried out by considering different thickness, internal pressure in pipelines, varying the position, amount of explosive and CFRP thickness to analyze the response of buried pipelines to such dynamic events. It is observed that the CFRP shield reduces the damage, strain induced due to explosion substantially and can be effectively utilized as an additional measure to improve the resistance of pipelines against blast. Consequently, this study contributes towards the safety and blast resistant design of underground steel pipelines.