Experimental Study of Eccentrically Loaded Raft with Connected and Unconnected Short Piles
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 136, Issue 10
Abstract
Piled raft foundations are often used when the supporting soil has adequate bearing capacity but the raft settlements exceed allowable values. In traditional practice, long piles with high load capacity are usually used that may lead to two structural problems: the structural collapse of the pile and large strains mobilized in the raft leading to an uneconomic design. This paper presents an experimental study of the effectiveness of using short piles either connected or unconnected to the raft (instead of long piles) on the behavior of an eccentrically loaded raft. The load configuration was designed to simulate rafts under vertical loads and overturning moment. Several arrangements of piles with different lengths and numbers along with the effect of the relative density of the soil and the load eccentricity were studied. Test results indicate that the inclusion of short piles adjacent to the raft edges not only significantly improves the raft bearing pressures but also leads to a reduction in raft settlements and tilts leading to an economical design of the raft. However, the efficiency of the short piles-raft system is dependent on the load eccentricity ratio and pile arrangement. Also, connecting short piles to the raft gives greater improvement in the raft behavior than unconnected piles. Based on test results, the effects of different parameters are presented and discussed.
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Acknowledgments
The tests were performed in the Soil Mechanics Laboratory of Structural Engineering Department, University of Tanta which is acknowledged.
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© 2010 ASCE.
History
Received: Jun 17, 2009
Accepted: Feb 18, 2010
Published online: Feb 20, 2010
Published in print: Oct 2010
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