Analysis of Footing Load Tests on Aggregate Pier Reinforced Clay

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 23 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. DOI: 10.1061/(ASCE)GT.1943-5606.0000677. (C) 2012 American Society of Civil Engineers.