Enhancing bearing capacity of shallow foundations through cement-stabilised sand layer over weakly bonded residual soil

The addition of a soil–cement reinforcement layer is an alternative to improve the bearing capacity of shallow foundations on weak soils. Recent research with small-scale tests highlighted the influence of the soil–cement layer's geometry and tensile strength in bearing capacity prediction of footings resting on treated layers. This work presents the evaluation of field static load tests of circular steel footings resting on soil–cement layers above a weak residual soil. Results showed on the one hand that traditional methods for predicting bearing capacity in homogeneous soils could be applied when the foundation and reinforcement layer are expected to punch together into the weakly bonded residual soil, without the failure of the reinforcement layer until some prescribed load. On the other hand, methods for continuous double-layer systems could be used where the reinforcement layer is expected to fail before reaching the prescribed load. The failure mode could be predicted by calculating the maximum tensile stress at the bottom of the reinforcement layer at the prescribed foundation load. An equation for this purpose was suggested and successfully tested against real-size field test results. Finally, analytical solutions for determining the bearing capacity were effective in foreseeing the field values.