Bearing Capacity of a Footing on an Expansive Unsaturated Bentonite Sand Mixture

Shallow foundations are usually built above the groundwater table. In such cases, this soil is considered dry in analysis and design, while it is actually an unsaturated soil. This unsaturated soil can lead to many geotechnical issues, such as swelling when wet and collapsing when dry. It can also change the soil?s shear strength, which in turn affects the bearing capacity of the soil. The classical principles of saturated soil are often not suitable for explaining these phenomena. Limited studies dealt with a large scale model close to the field conditions for such soil and therefore, there is much more room for improvement. The study reveals that compacting the expansive soil on the wet side of optimum is capable of reducing swelling pressure and the expansion index for both the bentonite?sand mixture and kaolin soil. The bearing capacity of a footing resting on both swelling and non-swelling soils decreases noticeably with the increase in the soil degree of saturation due to the effect of matric suction which increases the soil stiffness. The results show that the measured bearing capacity is (1.1?3.3) higher than that estimated by Terzaghi equations.