Analysis of Footing Load Tests on Aggregate Pier Reinforced Clay
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 138, Issue 9
Abstract
Despite the increased use of aggregate piers for soil reinforcement, the role of typical construction variables on footing performance remains uncertain. This paper describes a series of full-scale footing load tests conducted to evaluate the effect of aggregate gradation, pier length, and compaction method. Tests were conducted on small (0.76 m) and large (2.74 m) instrumented spread footings supported on single aggregate piers and groups of aggregate piers, respectively. The bearing pressure-displacement response of these tests is presented and the statistical significance of the construction variables is quantified for single piers using a factorial analysis within an ANOVA framework. The statistical significance of the effect of pier length, gradation, and compaction was determined by controlling for the spatial variability in matrix soil strength and stiffness across the test site, which indicated that these variables were largely insignificant at the treatment levels evaluated. Additionally, no appreciable difference in the bearing pressure-displacement performance of the footings on groups of piers constructed with various levels of treatment was observed. Small variations in the observed displacement performance are attributed to sources of variability other than construction variables. The similarity in the performance of the uniformly constructed pier groups, representing production conditions, suggests that variations in the inherently variable matrix soil stiffness and strength control the aggregate pier performance.
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Acknowledgments
The writers thank Hayward Baker, Inc., for construction of the aggregate piers and for funding the test program. Additional support provided by the Valle and ARCS Fellowship Programs through the University of Washington is gratefully acknowledged. The writers thank Fugro Southwest for the donation of X-ray photographs of undisturbed samples, and Hart Crowser, Inc., for the use of its laboratories for testing the site soils. The writers also thank Dave Yonemitsu and the Port of Seattle for the use of geotechnical instruments.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 138 • Issue 9 • September 2012
Pages: 1091 - 1103
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Apr 2, 2011
Accepted: Nov 29, 2011
Published online: Dec 1, 2011
Published in print: Sep 1, 2012
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