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144When analyzing the obtained bearing capacity results in terms of the calculated or designbearing capacity values, the conclusion can be made that the calculated results had atendency to underestimate the actual measured values (Figure 71). On average, the ratiobetween design and calculated bearing capacity values was 80 percent. The correlationbetween measured and calculated values shown in Figure 72 did not show a particularly goodlinear agreement between the values. Therefore, the design approach would need to berevised and modified.Groups of PiersAggregate Piers - Stress-SettlementAs outlined in Figure 88, the plotted stress-settlement results were found to behave in apredictable manner, where least performance was attributed with single aggregate pier andthe greatest load bearing capacity was obtained for the group of six piers. As a general trend,the shorter 305 mm groups of aggregate piers were observed to support less load than longpiers at the same amount of settlement. The calculated stiffness and stiffness ratio resultsobtained for unreinforced matrix soil and soil reinforced with aggregate piers are summarizedin Table 37. Stiffness ratio, n between the reinforced and unreinforced matrix soil wascalculated on the basis of difference in stress and is outlined in Equation 20.The collected stress data for reinforced and unreinforced soil conditions have shown verysporadic results (Table 37). While no definitive conclusion can be made regarding thedependence of number of piers within the group and stiffness ratio parameter, the overallresults have shown a minimum value of 1.3 for most cases. However a useful observationcan be attributed with the length of the pier criteria, where the stiffness ratio provided by thelong piers was approximately twice the amount of improvement provided by short piers formost groups.