EFFECT OF BED SCOUR AND PILE REFUSAL ON THE BEHAVIOR OF PILES IN WATER COURSES IN EGYPT | ||
| ERJ. Engineering Research Journal | ||
| Article 10, Volume 33, Issue 4, October 2010, Pages 419-430 PDF (1.15 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/erjm.2010.67342 | ||
| Author | ||
| Y. B. M. Heza | ||
| Construction Research Institute, National Water Research Center, Cairo, Egypt | ||
| Abstract | ||
| For construction of bridges in water courses, vertical or nearly vertical driven piles are usually used as the foundation element, because they could be constructed in the presence of water which means quick and cheap construction. Recently, many problems have arisen in several bridge sites using driven piles in water courses. Three such sites have been investigated by the author. A full assessment of those sites was required to avoid the risk of failure. In this paper, the assessment of a case study at the first site is presented and discussed. A comprehensive geotechnical investigation was carried out. Examining the results of the field and laboratory tests showed the presence of a soil layer at the design pile toe level which is very dense and explains the refusal happening while driving the piles. The field investigation also showed that a platform of steel beams and wooden logs built on wooden piles was used for the pile driving machine in the presence of water. The presence of the platform lead to the contraction of the water course cross section and the contraction gets worse by driving the reinforced concrete piles which in turn lead to a higher water velocity causing scour around the driven piles. Therefore, the stability of the piles became questionable, because of the shorter embedment length due to the refusal of the piles and the scour around them. The stability of the piles under the new conditions in the field was investigated using three criteria; the pile capacity, the buckling length, and the bending moment on the piles. It was shown that pile refusal and the scour reduced the allowable pile capacity. It was also shown that the slender ratio of the piles in 3 supports exceeded the limit defined in the Egyptian code and is unsafe in buckling. | ||
| Keywords | ||
| Pile foundations; Drag forces; Break forces; Scour; Offshore; Buckling length; Slender ratio; Bending moment; stresses and Bridges | ||
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