Behavior of Pyramidal Shell Foundations on Reinforced Sandy Soil

Shell foundation has been considered as the best shallow foundation for transferring heavy load to weak soils because of the high bearing capacity values, where a conventional shallow foundation submit to excessive settlement. An experimental work has been conducted to investigate the behavior of pyramidal shell foundations as compared with flat counterpart on loose sandy soils. Four types of aluminum rigid foundation were casted for this purpose; flat footing and shell footing of dimension (20 × 20 cm) and different angles (20°, 30°, and 45°). Twenty eight loading tests were carried out on these types of footings which were settled on the surface of loose sand layer with and without geogrid reinforcement. The geogrid sheet was inserted within the sand layer (single and double layers) under the footing base. The shell foundation on reinforced and unreinforced sand showed higher ultimate load capacity than those on unreinforced sand for flat foundation and the load- settlement curves were clearly modified. The shell foundations over reinforced soil can be considered as a good method to increase the effective depth of the foundation and decrease the resulting settlement. The bearing capacity ratio (BCR) reaches to 88.5% and settlement reduction factor (SRF) reaches to 37.3%, where the BCR is the ratio of bearing capacity for a foundation resting on reinforced (q_R) to that resting on unreinforced soil (q) while the SRF is the ratio of settlement for a foundation resting on reinforced soil (S_R) to that resting on unreinforced soil. The experimental work were also verified and analyzed numerically using ABAQUS software taking into a consideration the effect of different relative densities (15%, 20%, 30%) on settlement and bearing capacity of soil. The improvement range was greater at relative density (15%), compared with the others which reflects the improvement in loose condition due to shell effect. This confirms the premise that shells are reputably better performers in weaker soils that necessitate a large load transferred to them.