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27Article#7ReferenceHughes andWithers,1974Type of piersStone columnswere composed ofLeighton BuzzardsandTable 4: Case 7 for reduced scale columnsDepth of pierinstallationØ12.5mm and Ø38mm, H=150 mmH/D ~ 4-12Soil materialConsolidatedkaolin clayLab scale andSignificant findings, results andapparatusobservations*A significant amount of lateral stressfound within the matrix soil at distanceof 1.5 times the column Ø.1/10th scale,*Ultimate column Q was governed bycolumns placed inlateral reaction in bulging zone.consolidometer*No movement was found at the225 mm wide anddistance of 4 times the column Ø.160 mm long*Columns failed by bulging, degree ofbulging was dependent on the c ofmatrix soil.*A lot of lateral of expansion found inthe top portion of the columns.Legend:C u – undrained shear strength PWP – pore water pressure Ø – diameter PI – plasticity indexq ult – compressive strength c – cohesion k 0 – initial stiffness H – length or depthw% - moisture content C c – compression index k – stiffness d 10 – effective sizeR a – area replacement σ p – consolidation pressure LL – liquid limit d 60 – Ø at 60% finerS e – elastic settlement e – void ratio PL – plastic limitCase StudiesCase 1 – Black et al., 2007b - Performance of Clay Samples Reinforced with VerticalGranular Columns (Queen’s University of Belfast, United Kingdom)This research study featured installation of single and groups of three vertical frozen granularcolumns in soft kaolin clay. The material was classified to have 60 percent clay fraction withliquid limit of 70 percent, and 36 percent plastic limit. Consolidation of clay was performedup to total pressure of 200 kPa. Sand material was characterized as medium sand withmoisture content of 18 percent. Single columns were constructed at 32 mm in diameter, whilethe groups of three piers were built at 20 mm in diameter (Figure 13). Columns were placedto a depth of 120 mm and 200 mm.The frozen columns were constructed in plastic Polyvinyl Chloride (PVC) tubes and placedinto a premade soil cavity after the freezing and extraction of the column from the PVC tube.The columns were allowed to thaw out within the kaolin clay matrix soil prior to performing