G MS THESIS_final version_Maxim Prokudin.pdf - Digital Repository ...

78Table 18: Average C u , w% and γ dry for 305 mm and 610 mm loess samplesPier typeVarious Bev. Single Pier Aggregate Pier C(I) + C(K)Head Pier Tests Mix Tests Groups Pier Tests Groups Pier Testsγ dry top (kg/m 3 ) 1,456 1,572 1,610 1,568w% top (%) 14.7 23.3 25.5 23.2γ dry bottom (kg/m 3 ) N/A 1,600 1,626 1,605w% bottom (%) N/A 23.4 24.6 24.6C u top (kPa) 120 40 33 32C u bottom (kPa) N/A 37 35 41Another effect of having dry and stiff soil conditions, is that there was limited amount of pierbulging. Knowing that the strength of the aggregate pier has a great dependence on the lateralstress developed between the pier aggregate and the matrix soil (Handy, 2001) had lead to aconclusion of the initial test bed soil conditions being undesirable for the model pier testing,After the first pier placement phase was completed, the new test bed was prepared at targetedmoisture content of 30 percent and undrained shear strength in the range of 30 kPa. The testbed at this stage was to be used for the placement and testing of single 305 mm and 610 mmlong piers of various compound mixes as outlined in Figure 41. Two density and moisturecontent evaluation methods were performed where nuclear gauge device and UC sampleswere used. The average value for density, moisture content and undrained shear strengthparameters in the upper 305 mm pier layer of soil were evaluated to be 1,572 kg/m 3 , 23.3percent, and 40 kPa respectively (Table 18). These values were significantly different fromthe values obtained in the first phase of testing and much closer to the soil conditions wherefull-scale aggregate piers are of the best performance. On the other hand, the deeper layer ofsoil to which the 610 mm piers were extended to, featured slightly higher density andcomparatively unchanged moisture content and undrained shear strength.Afterwards, the tests for the short and long groups of aggregate pier and cement type I and Kcomposition piers were conducted in the soil conditions very similar to the once produced at