ASSESSING THE INCREASE IN BEARING CAPACITY OF BORED PILES IN SANDY SOIL USING EXPANSIVE ADDITIVES

The pile foundation is usually designed to exceed the weak soil to the strong stratum. There is very close relation between the pile capacity and surrounding soil conditions. In cohesionless soil, the bored pile is effecting surround soil by loosening deposits through a combination of pile volume replacement and exist of pile case used for installation of bored pile. In this study, the improvement of the weak soil that surrounds the pile and observing the effect of improvement on pile increase the skin friction of the bored pile capacity for bored pile carried out. This study conducts research into the use of expansive additives in concrete bored piles. The aim of this project was to investigate how Na2Co3 as an additive in concrete can increase the shaft resistance of a bored pile. Several tests were conducted on concrete single piles with a variation of length to the diameter ratios and different percentages of soda ash additives. All tests were made in dry, sandy soil at loosening state. All tests showed that the shaft capacity could be increased using expansive additives due to increase the volume of the pile or enlargement of pile volume during concrete setting ;it was also concluded that the shorter expansive piles could be able to achieve the same pile capacity as a longer conventional pile. This would lead to reductions on the volume of concrete poured, the amount of steel reinforcement used and the amount of soil excavated. Therefore, construction costs can be decreased and construction times can be shortened