Static interaction in soil – pile - cap system using three-dimensional analysis

Abstract

A value of interaction load along the pile shift in the pile foundations design is an important factor in calculation of the bearing capacity and consequently, not taking the interaction load into consideration cased an increase in the piles lengthy and then cost increased. In this paper, was studying the effect of skin friction on behavior of soil- raft foundation, (soil -single pile – cap) system and (soil – 2 piles group- cap) system is investigated and analyses using Abaqus software (is a 3D finite element). Parameters studied were raft footing thickness, length of square concert pile in the (soil-single piles –cap) system, the spacing ratio in the (soil-2 piles –cap) system. It was intended to investigated the skin friction distribution around the pile shaft for the (soil-single piles –cap) and (soil-2 piles –cap) system. The results showed that the mobilized interaction among raft footing and clay soil caused increases in raft capacity and reduce the value of vertical settlement compared with frictionless soil raft model and the interaction load value (skin friction) increased with increasing in raft thickness. The percentage of the increases in load capacity due to interaction mobilized was 43% compared with frictionless case. There was a clear difference in capacity load for mobilized interaction case compared to the absence of interaction between single pile and cap with soil. This increase was clear when the length of pile is more than 10 m, and this increased reaches about 67%. The distribution of interaction load along the pile shaft is linear where the interaction load is equal to zero at the head of the pile. The interaction load begins to increase when the length of pile increases.  Highest value for interaction load was at the end of pile.