EXPERIMENTAL OBSERVATIONS ON THE BEHAVIOR OF A PILED RAFT FOUNDATION

الملخص

The piled raft is a geotechnical composite construction consisting of three elements: piles, raft and soil.
In the design of piled rafts, the load shared between the piles and the raft, and the piles are used up to a
load level that can be of the same order of magnitude as the bearing capacity of a comparable single
pile or even greater. Therefore, the piled raft foundation allows reduction of settlements in a very
economic way as compared to traditional foundation concepts.
This paper presents experimental study to investigate the behavior of piled raft system in sandy
soil. A small scale “prototype” model was tested in a sand box with load applied to the system through
a compression machine. The settlement was measured at the center of the raft, strain gages were used
to measure the strains and calculate the total load carried by piles. Four configurations of piles (2x1,
3x1, 2x2 and 3x2) were tested in the laboratory, in addition to rafts with different sizes. The effects of
pile length, pile diameter, and raft thickness on the load carrying capacity of the piled raft system are
included in the load-settlement presentation.
It was found that the percentage of the load carried by piles to the total applied load of the
groups (2x1, 3x1, 2x2, 3x2) with raft thickness of 5 mm, pile diameter of 9 mm, and pile length of 200
mm was 28% , 38% , 56% , 79% , respectively. The percent of the load carried by piles increases with
the increase of number of piles.