Spread footings bearing on circular and square cement-stabilized sand layers above weakly bonded residual soil

Abstract

The practice of soil-cement reinforced layers to bear shallow foundations is a feasible option in low bearing capacity soils. This paper addresses the interpretation of plate load tests bearing on compacted artificially cemented sand layers of distinct sizes and shapes (cylindrical and prismatic) overlaying a weakly bonded residual soil stratum. Static load tests were carried out on a rigid circular steel plate (diameter of 300-mm) resting on sand-cement reinforced layers with distinct areas (diameters/widths of 450, 600, and 900-mm) and constant thickness of 300-mm. The results have shown two distinct failure modes that rely on the cemented layer’s diameter/width: (a) the steel plate and the artificially cemented layer punch together into the weakly bonded residual soil, without the failure of the cemented layer, and (b) the artificially cemented layer fails. The combination of two traditional methods for predicting bearing capacity in soils was successfully applied considering the shape (and geometry) of the improved layer and the existence (or not) of interaction of the lateral of the cemented layers and the residual soil. Finally, this study highlights the importance of considering the shapes and sizes of soil-cement layers in the bearing capacity estimation (combining analytical solutions) of spread footings resting on treated layers above weakly bonded residual soils.