Abstract
This paper deals with testing defected model piles in the soil in order to study their behavior. In this respect, the results of model pile tests are discussed either geotechnically or structurally according to the type of failure.
 
 Two parameters were studied in order to evaluate the general behavior of defective piles. These parameters include the defect location and the defect type for floating and end bearing pile. The results of the experimental work indicated that the critical case for floating pile is seen to be when the defect of (5%) at the first third of the pile length at which the decrease in the bearing capacity is about (21%), while the decrease in the bearing capacity is found to be (14%) and (10%), when the defect is at the middle and the lower third of the pile length, respectively. The decrease in the bearing capacity for floating pile is found to be (31%) and (21%) for void and neck defect, respectively, while the decrease in the bearing capacity for end bearing pile is found to be (43%) and (52%) for void and neck defect, respectively.
Highlights
The defects in the cast-in-situ piles are often the consequence of faulty concreting. use of deleterious concrete materials, improper mix design, faulty concrete placement, and subsequent ground disturbances due to the construction of adjoining piles may combine to produce a poor quality pile (Mohan, 1981)
The critical case is seen to be when the defect is at the first third of the pile length at which the bearing capacity decreased to about (21%) while the decrease in bearing capacity is found to be (14%) and (10%) when the defect is at (L/2) and (2L/3), respectively
The critical case for (5%) neck defect, at which the minimum bearing capacity is obtained, is seen to be when the defect is at the one third of the pile length, the bearing capacity is decreased to about (21%) while the decrease in bearing capacity is found to be (14%) and (10%) when the defect is at (L/2) and (2L/3), respectively
Summary
The defects in the cast-in-situ piles are often the consequence of faulty concreting. use of deleterious concrete materials, improper mix design, faulty concrete placement, and subsequent ground disturbances due to the construction of adjoining piles may combine to produce a poor quality pile (Mohan, 1981). The common defects of piles are cold joints, zone of segregated or contaminated concrete, trapping of bentonite mud necking, and cavities (Johnson and Kavanagh, 1968 ; Winterkorn and Fang, 1975; Thorburn and Thorburn, 1977; Fleming et al, 1985; Tomlinson, 1994). The first two types of defects result from interruptions in the concrete placement or premature extracting of the tremie pipe either partially or completely above the concrete-slurry interface. Mud trappings are caused by concrete of low workability and impediment to the flow of concrete due to closely spaced bars. Discontinuities or partial separation in the piles at the bottom edge of temporary casing can be caused by accidental lifting of low workability concrete or concrete without controlled setting during casing extraction. If the concrete in the casing is too stiff and has considerable frictional resistance against the casing, a column of concrete can be pulled up with casing
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