Rigid Barrier with a Gabion Cushion Subjected to Boulder Impact

© 2019 Jude Shalitha Perera Pethati Mudiyanselage DonProtection against rockfalls occurring alongside landslides contribute to the major part of the disaster management budget in many counties like Switzerland, Japan and Hongkong. Protective structures are usually built over disaster trajectories to safeguard lives and properties. Reinforced concrete barriers that are fitted with gabions are one common form of installations to provide the protection. Few experimental investigations involving impact testings of a rigid reinforced concrete barrier which was fitted with a gabion cushion cover have been reported in the literature. But these investigations were limited to studying the localised actions of impact. The change of structural response behaviour of the barrier as a whole by the presence of a cushion layer is typically not within the scope of the reported investigations. Design methodologies that have been developed are typically limited to overly simplified calculations based on applying an equivalent static force to the barrier. To fill this knowledge gap full-scale pendulum tests have been conducted by the authors on a barrier that was fitted with a gabion cushion layer. The structural response behaviour of the barrier, contact force and tensile strains in the longitudinal reinforcement were of interests. Results recorded from the tests were compared with results from control experiments which were without the protection of any cushion materials. The introduction of a layer of cushion is shown to be able to have the deflection demand on the structure reduced by more than 70% when the amount of energy delivered by the impact is kept constant. An analytical procedure employing the Hunt and Crossley contact model, Swiss code model and two-degrees-of-freedom (2DOF) system modelling technique is presented for evaluating the flexural response demand behaviour of the cushioned barrier. The proposed analytical procedure is shown to be able to predict the reduced deflection demand with a reasonable degree of conservatism. At the end of the thesis, a simple hand calculation procedure featuring the use of design charts is presented for engineering applications. The procedure is illustrated by a worked example which is based on a realistic rockfall scenario