Dynamic behaviour of geogrid reinforced segmental block walls under earthquake loads

Abstract

This study investigates the seismic performance of geogrid reinforced segmental block walls. For this purpose, shaking table tests were performed on four ½ reduced-scale geogrid reinforced segmental block walls at Bogazici University Kandilli Observatory and Earthquake Research Institute. The walls were instrumented by installing 9 accelerometers to measure the accelerations within the soil and facing blocks, 6 linear laser displacement sensors to measure the displacement of facing blocks. Additionally, the strain gages were installed on the three geogrid reinforcement layers to measure the reinforcement strains. The heights of the models were 1.9 m and each wall was excited with El Centro, Izmit and Sakarya earthquake motions. The effect of increasing horizontal base acceleration, reinforcement length and stiffness, backfill material type, facing batter (inclination) on measured parameters under seismic excitation are analyzed and presented. The experimental work in this study helps to develop a better understanding of the tensile stress-strains generated in geogrid reinforcement and facing displacements of geogrid reinforced soil walls during construction and extreme seismic excitations. Additionally, whether the experimental results are in accordance with the current NCMA and FHWA design methodologies for reinforced soil retaining walls are investigated and conclusions are drawn. The results obtained from experiments, permanent displacements and geogrid reinforcement tensile loads obtained from experiments are compared with Newmark’s displacement method and NCMA and FHWA design methodologies respectively. The geogrid reinforced segmental block walls designed according to current specifications showed a very good resistance to earthquake loading conditions. They remained stable even under extreme lateral accelerations (peak lateral acceleration values up to 0.97 g). All four wall configurations designed in this study showed very successful behavior. No stability problem occurred even under extreme lateral accelerations. The Geogrid Reinforced Segmental Block Walls showed minimal residual deformations and acceptable maximum deformations under extreme lateral earthquake accelerations.