Shell folded footings using different angles and EPS cavity filling: experimental study

Abstract

Shell folded footings have drawn the interest of researchers for decades as an alternative to typical flat isolated footings because folded footings can reduce the needed amount of reinforced concrete in addition to enhancing the overall geotechnical performance of the supporting soil medium. The main setback of utilizing such folded footings is the relatively complex geometry of the bottom cavity, which requires proper compaction of the soil used to fill that cavity. Current geosynthetic materials such as geofoam or expanded polystyrene (EPS) proved efficiency in many geotechnical applications, where EPS was adopted herein as a cavity-filling material for folded footings. EPS and footing concrete properties were determined using the ultrasonic test device, such as modulus of elasticity and damping coefficient. The main aim of this study was to experimentally assess the behavior of folded footings with and without EPS filling using seven fully instrumented footing models with folding angles ranging from 0° to 45°. Reinforcement was placed in the footing models and limited along the perimeter to act as a hidden ring beam. The models were load tested inside a sandbox to measure internal stresses induced in the soil and the overall settlement. Results showed a significant enhancement in the soil behavior after using EPS. Modification factors were developed for the standard bearing capacity and settlement equations to account for the folding angle and EPS filling effects.