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112Groups of PiersAggregate Piers - Stress-SettlementGroups of aggregate piers were further constructed and tested in order for the groupefficiency of unit cell, and groups of two, four, five and six piers to be evaluated. The stresssettlementresults are provided in Figure 73 through Figure 80. The results are grouped bypier length and the summary of all stress-settlement plots is outlined in Figure 80. The stressdisplacementtesting was performed in a similar manner as the tests completed for singlepiers of different composition. However, in order to evenly distribute the load from hydraulicjack to every pier in the group several steel cover plates of various dimensions were designedand built. Unreinforced matrix soil was also loaded up to 12 mm of displacement for all theplates and an additional ―Loess‖ curve is provided in figures. A single tell-tale plate wasinstalled for each group of piers and the obtained amount of tip movement was considered tobe representative for the entire pier group being tested.Applied stress at bottom of the footing (kPa)00 2000 4000 6000 800024Settlement (mm)68101214Top16Figure 73: Stress-settlement test results for matrix soil used for placement of aggregatepier groups