Piled foundations are used in the cases where the structural loads cannot be carried safely
with the shallow foundations. Piled raft foundation has become a prominent foundation
system in recent years due to that it combines load bearing capacities of piles and raft.
Therefore, comprehensive analytical and experimental studies have been carried out for
reliable and economic design of piled raft foundations. In this study, the effects of design
parameters of piled raft foundations in sand (pile spacing, pile diameter, pile length and
relative density etc.) have been investigated experimentally. In the laboratory tests, model
composite (steel and concrete) piles with diameters of 20, 30 mm and lengths of 200, 300
mm were used.The raft was made of steel plate with plan dimensions of 160x160, 240x240
mm and a thickness of 6 mm. The model piled raft foundations with different design
parameters were tested. From the tests results, as the pile spacing getting larger, the bearing
capacities of the model pile raft foundation increased up to a limit value and the optimum
distance between the piles was determined to be 4D. Some design parameters are suggested
for use in foundation engineering applications.