Behavior of Geogrid Reinforced Foundation Systems Supported on Clay Subgrades of Different Strengths

This paper presents an experimental study investigating the behaviour of geogrid reinforced sand-clay foundation systems with clay subgrades of different strengths. Model tests were carried out on a circular footing of 150 mm diameter ( D ) resting on 1 × 1 × 1 m foundation bed having clay subgrades of different undrained shear strengths ( c u ), ranging from 7 to 60 kPa. Different series of laboratory model tests were performed on homogeneous and layered foundation systems. The layered systems were comprised of dense sand of varying layer thicknesses ( H = 0.63–2.19 D ) overlying the clay subgrades. Pressure-settlement responses obtained indicated that the foundation performances were largely influenced by footing settlement ( s/D %), layer thickness ( H ), and subgrade strengths ( c u ). The results indicated that the planar geogrid reinforcement, placed at the sand-clay interface, can substantially improve the performance of the foundation beds depending on layer thickness and subgrade strength. A maximum of about 5.6-fold improvement in bearing capacity was observed in the study, for very soft clay subgrade of 7 kPa.