Evaluation of the Mechanical Strength of Bund Walls under the Catastrophic Failure of Storage Tanks via Fluid Structure Interaction

Abstract

The catastrophic failure of storage tanks is a serious problem that can have disastrous effects on the environment, local community and the economy. Bund walls are structures used around storage tanks where hazardous substances are stored and handled for the purpose of retaining the losses in materials. This study investigates the performance of bund wall structures under the impact loading caused by the collapse of storage tanks. Research on this subject has taken place at Liverpool John Moores University over two decades. Studies have included investigating the dynamic pressures exerted on the bund wall, the overtopping fractions of the material representing the ratio of the quantity of fluid that escapes the bunded area to the quantity of fluid that was initially in the tank, and mitigation measures to reduce the incurred losses. These previous studies along with other publications indicate clearly that bund walls are not designed to withstand dynamic loading that arises in the wake of sudden collapse of storage tanks. The novelty of this research lies in studying the performance of bund walls under the impact loading exerted by the sudden release of the stored material and proposing a new design of bund walls using Ultra-High Performance Fibre Reinforced Concrete (UHP-FRC). The investigation was carried out using the Fluid Structure Interaction (FSI) approach. InterFOAM solver in OpenFOAM software was used to model the multiphase flow of the sudden release of the fluid. The available experimental data sets were used to validate the performance of the solver in terms of the prediction of dynamic pressures and overtopping fractions. The solver gives good results for many of the simulations investigated. An optimisation study on the optimum configuration of mitigation technique was conducted. FSI modelling was used to study the behaviour of the bund wall by coupling the explicit solver of Abaqus 2017 to InterFOAM via the MpCCI coupling environment. Bund walls with different shapes and under different loading conditions were simulated. Results show that bund walls made of plain concrete fail with the exception of circular bund walls. The use of UHP-FRC with the incorporation of Catastrophic Overtopping Alleviation of Storage Tanks (COAST) mitigation technique allows the reduction of the overtopping fractions and minimises the damage to the bund wall. Results of the research allow the operators and site managers to gain an insight into the behaviour of bund walls under impact loading and perform more meaningful risk assessments.