Effect of Stress Level of Surrounding Soil on Bored Pile Capacity in Sand

This study deals with assessing the effect of stress level on bearing capacity factor , distribution of shear stresses at soil-pile interface along pile shaft, and presence of critical depth concept for bored piles axially loaded in compression and embedded in dense sand. These investigations are made using finite element method with the employment of a wide range of stresses by using piles with dimensions starting from laboratory dimensions and goes towards field dimensions with embedment ratio range from (15-40). The soil and the interface behavior is modeled using Duncan-Chang hyperbolic soil model with empirical equations account for reduction of angle of internal friction ø with increasing in stress level. Bored pile is modeled as a linear elastic material. The results showed a dramatic decrease in bearing capacity factor as length of pile increase. It was also found that the embedment ratio has a significant effect in increasing bearing capacity factor , and the distribution of shear stresses at soil-pile interface is not linear and does not tend to take a constant value beyond a certain depth of pile nor decreases after a certain depth along pile shaft. The fallacy of critical depth also noticed and discussed in this paper

Effect of Stress Level on Behavior of Bored Piles Embedded in Medium Sandy Soil

In this paper investigation in the end bearing and shaft resistance of bored piles embedded in medium sand and subjected to axial load for wide rang of stress levels starting from laboratory dimensions and go toward field dimensions were made by utilizing the finite element method. The soil is modeled using hyperbolic soil model with empirical equation account for reduction of angle of internal friction Ø with increase in stress level while the bored pile assumed as a linear elastic material. It was found that the stress level has a significant effect on pile’s behavior and the small scale model in laboratory dimension not represent the real behavior of pile in field dimensions and if the results from such dimensions are adopted, it will lead to overestimate of bearing capacity factor Nq. Also, the effect of embedment ratio (L/D) on pile’s behavior is examined in this study and the results showed that the embedment ratio (L/D) increases the bearing capacity factor Nq up to a certain length beyond it the effect of embedment ratio (L/D) diminished