Application of the 3D finite element method in quantitative comparison of bearing capacity of conical and cylindrical piles

Abstract: Piles are structural members made of wood, concrete, steel, or other materials that are used to transfer surface loads to lower levels in the soil. This transfer is done by distributing the load along the length of the pile body or by directly transferring the load to the lower layer through the pile tip, the first case being called a friction pile and the second being called a support pile. Usually, all piles transfer the load as a combination of body friction and tip resistance, except in cases where, for example, the pile penetrates very soft soil to reach a hard bed. By having data on the bearing capacity and settlement of the pile group as well as the individual piles used in each group, the following results can be obtained: in sandy soils, as the angle of internal friction of the soil increases, the bearing capacity of single tapered piles increases to a certain extent with increasing cone angle. For single cone piles placed in sand, with increasing the angle of internal friction of sandy soil, the frictional load of the piles has always increased and the bearing load has decreased, while at the optimal angle for the total load of cone piles, the percentage of increase in the body friction load is greater than the percentage of decrease in the bearing load. For single piles placed in sand, the optimal angle of taper is in the range. For the group of piles placed in sand, with increasing the angle of internal friction of the soil, the group with the highest taper angle performs the maximum load. The efficiency of a group of tapered piles placed in sand always decreases with increasing the angle of taper. The rate of decrease in the efficiency of a group of tapered piles in sand decreases with increasing the angle of internal friction of the sand. The settlement rate of the conical and cylindrical pile group in the sand is less than the rate considered by Vesic, which is evidence of the more conservative results of this study regarding the bearing capacity of the piles.