Effect of Particle Size Distribution of Cohesionless Soil and Pile Diameter on the Behavior of Open Ended Pipe Piles

Abstract

Pipe piles are normally used in deep foundations to transfer the structure load to stronger layer beneath the ground or to rock formations. More popular applications of pipe piles are marine construction (offshore structures), bridge piers construction and building construction. This research is conducted to study the effect of grain size distribution of cohesionless soil (i.e. fine, medium and coarse sand) on the ultimate load capacity of pipe piles with different diameters under dry and fully saturated state through an experimental model. Also, Degree of soil plugging behaviors for different pipe pile diameters and saturation conditions (i.e. dry, fully saturated conditions) for different particle size distribution was studied. Karbala sand, were used as a natural soil in the present study, it is poorly graded clean sand of rounded particles. The sandy soil is sieved to obtain a fine, medium and coarse graded according to (ASTM D 422-02). The experimental model tests conducted on four open-ended steel pipe piles models with diameters of (25, 30, 35 and 41mm) embedded within different grain size distribution of sand prepared under dry and fully saturated conditions with relative density of 65%. The results shows that, the ultimate load capacity of open-ended pipe piles embedded within medium grain size exerted higher bearing capacity than the other grain size distribution and increased with increasing piles diameters. The increasing values of the ultimate load carrying capacity for different pipe pile diameters under dry conditions are almost greater than that of saturated conditions by about (1.95-2.4) times for fine sand, (2.36-3.04) times for medium sand and (1.62-1.97) times for coarse sand. Furthermore, Plug Length Ratio PLR (which is the proportion of a soil plug length to the pile penetration depth) was measured for different pile diameters, and it was found that the length of soil column increases gradually with the increasing of a piles diameter