Abstract
This paper introduces an experimental research on the behavior of the piled raft foundation (PRF) in sand of two states (loose and medium sand). A small model has been tested in a soil container and the vertical load was applied to the foundation through a pneumatic jack. The settlement of the foundation was measured using a displacement transducer; three sensors were attached to the pile heads to measure the axial load borne in a group by each pile by the Arduino data logger. The laboratory experiments were carried out on models of (1 pile), (1x2), (1x3), (2x3), (3 x3), (3 piles triangular), (4 piles diamond), (5 piles), and (9 pile circle), as well as to tests on an unpiled raft. Test variables were pile length, number of piles, and sand density. It is noticed that when the piles increased to nine piles in the group, the bearing capacity increased by 40%. The effect starts to increase when one pile is just placed under the raft as the bearing capacity of the piled raft increased by 3% and 7% when the pile length is 15D and, 20D, respectively. The reduction in the settlement is also observed to be smaller and no economic advantage is achieved with more increase in the number of piles. If the number of piles reaches (6) piles, the influence of the piled raft on settlement reduction disappears.
Highlights
In foundation engineering, raft foundations or pile foundations are usually the most common kinds of foundations performed in large buildings or structures
It was noticed that the stiffness of theP-R was as much as 30 percent higher than that of the “freestanding pile's group”, while the "piled raft" load-carrying capacity was higher than that of the "freestand pile group" the results identified the influence of piles length on the behavior of the piled raft foundation (PRF), andnoted that piles must be tall enough in proportion to the dimensions of the raft
1) The load displacement curve is seen to be non-linear for each model test. It appears that the local shear failure controls the piled raft failure in all model's tests
Summary
Raft foundations or pile foundations are usually the most common kinds of foundations performed in large buildings or structures. Such systems can meet the design criteria when implemented alone; they are in most situations over-safe and inefficient economically. They can cause some serious problems in some cases when used alone. The piled raft foundation (PRF) is one such combined system. This system of foundations consists of three elements: raft, soil, and piles. The mechanism of interaction between these elements is very complex, containing the interaction of PileSoil, Pile-Soil-Pile interaction, Raft-Soil interaction and the interaction of Pile-Raft
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