Experimental Study on Bearing Capacity of Shallow Footings Based on Sand in Saturated and Unsaturated conditions

Shallow footings are usually located above the ground water table and the soil under footings is in unsaturated condition. Therefore, the bearing capacity of Shallow footings should be influenced by the capillary stresses due to unsaturated soil conditions. In this research, the effect of soil unsaturation has been investigated on the bearing capacity of square and rectangular surface footings located on dense sand with different ground water table, in laboratory scale. The results of the experiments show that by lowering the ground water table and consequently by increasing the soil suction due to capillarity, by changing the matric suction from 0.5 to 4.5 kPa, the ultimate bearing capacity in unsaturated conditions increase nonlinearly 2.3 to 4.3 times the ultimate bearing capacity of the saturated condition. furthermore, at matric suction close to the residual suction and passing through the desaturation zone, the increasing rate of bearing capacity decreases and By increasing the length to width ratio of the footing, the increasing rate of bearing capacity increases.