To evaluate the enhancement mechanism of ultimate bearing capacity and the bearing capacity properties

considering the loading process of tapered pile

two stages were adopted in the proposed approach: the elastic stage and the soil-squeezing plastic stage. Based on these two stages

a simplified analytical expression for the ultimate carrying capacity was deduced. The bearing capacity augmentation factor was introduced to calculate the enhancement of the ultimate bearing capacity for the tapered pile. Then the effects of the friction coefficient on the pile-soil surface

the taper angle and the coefficient of earth pressure at rest on the bearing capacity were analyzed. Finally

the bearing capacity predicted by the proposed expression was compared with the data from the available model test. The results demonstrate the validity of the augmentation factor adopted in the prediction. The bearing capacity augmentation factors increase with the increase of the coefficient of earth pressure at rest and friction coefficient between pile and soil

while decrease with the increase of the soil friction angle. The augmentation factors reach the maximum values with a specific taper angle.