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120Aggregate Piers - Group EfficiencyThe group efficiency parameter was calculated for all the groups of aggregate piers and thecomparison between stiffness values of a single pier and multiple piers was made. The stress,stiffness and settlement results were summarized in Table 27 and calculated per Equation 15.Sample calculations can be found in the appendix. Table 27 shows group efficiency values interms of a single pier and Table 29 in terms of unit cell.Table 27: Stress, stiffness and deflection comparison measurements for aggregate piergroup load test results and group efficiency in comparison to a single pierService loadPier type 1Aggregate PierSingle PierLength(mm)k at δ top =2 mm(kPa/mm)σ at δ top= 2 mm(kPa)σ at δ top= 5 mm(kPa)σ at δ top= 10mm(kPa)δ tell-tale atδ top = 10mm(mm)Ratioδ tell-tale /δ top atδ top = 10(mm)GroupEfficiencyat 2mmGroupEfficiencyat 5mmUltimateGroupEfficiencyat 10mm305 64 129 247 406 0.44 0.04 1.0 1.0 1.0610 176 352 704 949 3.80 0.4 1.0 1.0 1.0Loess - 22 67 158 285 - - - - -Aggregate PierUnit Cell305 174 348 588 908 1.30 0.13 2.7 2.4 2.2610 441 894 1,330 1,533 2.80 0.3 2.5 1.9 1.6Loess - 139 278 685 1101 - - - - -Aggregate PierGroup of 2305 241 483 1,345 2,146 3.90 0.4 1.9 2.7 2.6610 630 1,260 2,521 3,017 0.40 0.04 1.8 1.8 1.6Loess - 321 642 1055 1609 - - - - -Aggregate PierGroup of 4305 433 867 2,254 3,406 4.80 0.5 1.7 2.3 2.1610 798 1,596 3,105 3,947 1.5 0.2 1.1 1.1 1.0Loess - 514 1028 1891 2719 - - - - -Aggregate PierGroup of 5305 765 1,529 3,233 4,150 3.50 0.4 2.4 2.6 2.0610 1,755 3,511 4,375 4,825 1.00 0.1 2.0 1.2 1.0Loess - 514 1028 1891 2719 - - - - -Aggregate PierGroup of 6305 1,537 3,073 4,100 4,898 7.00 0.7 4.0 2.8 2.0610 1,567 3,134 5,361 7,068 0.10 0.01 1.5 1.3 1.2Loess - 509 1018 1486 1886 - - - - -Legend:1 all scaled piers were constructed using cone beveledtamper headk – stiffness modulus (kPa/mm)δ top - deflection at the top of the pier (kPa)δ tell-tale - deflection at the bottom of the pier (mm)σ – stiffness of the pier (kPa)Ratio δ tell-tale / δ top = δ tell-tale /10mmConversions:1 m = 3.3 ft1 mm = 0.0394 in1 kPa = 0.145 psi1 kg/m 3 = 0.0624 pcf