Experimental investigation of back-to-back MSE walls with different reinforcement configurations under footing loading

Back-to-back mechanically stabilized earth (BBMSE) walls have been used for bridge abutments, highway and railway embankments. FHWA guidance for BBMSE walls emphasizes the effects of reinforcement configuration on wall interaction and external stability. However, their behavior under footing loading has received less attention. In this study, five BBMSE wall models with separated, meeting, overlapped, continuous, and mixed configurations were tested under static footing loading to investigate the effects of reinforcement configuration on pressure-settlement response, lateral earth pressure distribution along the wall facing, reinforcement strain, and facing deformation. Continuous or overlapped configurations exhibited higher bearing capacities, whereas the separated configuration showed 80% reduction in ultimate bearing capacity compared to the continuous configuration. Separated or meeting configurations developed localized peak lateral pressures at intermediate elevations while the overlapped and mixed configurations shifted the pressure concentration to lower elevations. In all tests, peak tensile strains developed at a horizontal distance of approximately 0.3 times the wall height from the wall facing, reaching up to 0.45%, although their magnitudes and distributions varied among reinforcement layers and configurations. Reinforcement continuity strongly influenced deformation and failure mechanisms: separated configurations exhibited pronounced bulging and localized failure, while overlapped and mixed configurations promoted more distributed deformation and integrated behavior.