الفهرس 
CONSTRUCTION OF UNDER-REAMED PILES
QUATIONS TO ESTIMATE UPLIFT CAPACITY OF UNDER-REAMED PILESOnly 14 pages are availabe for public view
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Abstract
Many modern engineering structures necessitate a foundation system designed to resist pull-out loads. Under-reamed piles have been developed to maximize uplift capability in comparison to conventional piles. Under-reamed piles are cast-in-situ concrete piles which have one or many enlargements around their stem. In the recent years, a limited number of studies have experimented with deep individual and groups under-reamed piles subjected to uplift forces in sand. Hence, this research aims to experimentally investigate the uplift response of individual under-reamed piles embedded in dry sand with different relative densities while varying the piles’ geometrical characteristics. Furthermore, the behaviour of groups of double under-reamed piles with varied numbers of piles in varying layouts is studied. The tests are conducted in loose (Dr=30%), medium (Dr=50%), and dense sand (Dr=80%). The under-reamed pile was found to be an effective solution for increasing uplift capacity, with the pull-out capacity increased as more bulbs were added. And the optimum efficiency is achieved in the multi under-reamed pile when the spacing between the under-reams is approximately 1.5 the diameter of the under-ream. Further, the efficiency of the group increased with increasing the spacing between the piles. In contrast, it decreased with increasing the relative density and number of piles. In all cases the optimum spacing between the double under-reamed piles was not reached. Eventually, the failure mechanism of the group double under-reamed piles was discussed.