Effect of non-liquefiable layer on bearing capacity and settlement of shallow foundations

Liquefaction during earthquake excitations is one of the most important causes of damage imposed on structures. This phenomenon in saturated loose sand deposits increases water pressure and reduces stiffness. An increase in pore-water pressure during excitations can reduce soil shear strength, and consequently, lead to a decrease of the soil bearing capacity and an increase of settlement. In this study, using physical modelling, the effect of the presence of a non-liquefiable layer with different thicknesses on the improvement of the bearing capacity and settlement of shallow foundations has been investigated for both full and partial liquefaction cases. In these experiments, various constant excess pore-water pressure ratios are generated using the steady-state seepage. The tests are carried out in two different groups. The first group is designed for determining the effect of excess pore-water pressure generation on the bearing capacity; the second group is designed for assessing the effect of design safety factor on the settlement of shallow foundations located on non-liquefiable layers with different thicknesses. The presence of non-liquefiable layers causes considerable improvement in the bearing capacity and settlement of shallow foundations, and this issue may be considered in the engineering problems.