Calculation of the axial bearing capacity of tapered bored piles

Fourteen calibration chamber tests were performed on one cylindrical pile and two tapered piles with different taper angles to investigate how the bearing capacity of tapered piles varies in relation to the soil state and the taper angle of the piles. The results show that the ultimate unit base resistance of a tapered pile increases when there is an increase in the mean stress, relative density and taper angle of the pile. The ultimate unit shaft resistance of the pile also increases as the vertical and horizontal stresses, relative density and taper angle increase. The results of the model pile load tests form the basis of a new design method for estimating the bearing capacity of tapered piles in sandy soil. The proposal is based on consideration of how the soil state and taper angle affect the bearing capacity of tapered piles. Field pile load tests were conducted on cylindrical and tapered bored piles in clayey sand to check the accuracy of predictions calculated with the new design method. A comparison of calculated and measured values shows that the new design method produces satisfactory predictions for tapered piles in sandy soil.