EFFECT OF FOOTINGS SHAPE AND SIZE ON ULTIMATE BEARING CAPACITY OF COHESIONLESS SOIL

The supporting power of a soil or rock is referred to as its bearing capacity. The settlement and ultimate bearing capacity of footings resting on cohesionless soil depend on the properties of the soil as well as the shape, the size and the embedment depth of the footings. The bearing capacity of soil depends significantly on the friction angle (Φ) and the depth of foundation (D). However, the bearing capacity goes up significantly as the depth of the footing below the surface increases. Settlement of the soil is usually the most important consideration in assessing the allowable bearing pressure. In the present study, the ultimate bearing capacity of footings on cohesionless soil at surface with and without surcharge has been determined in field for graded sand samples. The tests have been conducted in field by using the plate load test. In the present study nine steel rigid plates were used in testing. The plates have a finished thickness of 32 mm. The first three rigid circular plates have been used with diameter B = 305 mm, 455 mm and 610 mm. The second three other are rigid square plates and have equivalent areas to the above mention plates. The last three are rigid rectangular plates having the same equivalent areas as the first and second group .The settlement has been measured under different stress levels at the surface along the center line of the plate as well as the edge of the plate. Also, the settlement has been measured under different applied stresses. The effect of plate shape and size on the ultimate bearing capacity of cohesionless soil has been determined for different relative densities of the tested soil.