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

140level of service load. On the other hand, the addition of cement type K component to thecement type I and NS7 mixture has shown reduction in pier stiffness at the service load andopposite effect at ultimate load.Tell-tale plate movement has shown a significant amount of pier plunging for all the cementtype I and type K composition piers. As one would expect, a greater amount of plunging wasobserved in case with short 305 mm piers. As per Table 24, the ratio δ tell-tale / δ top wasobserved to be relatively large for all cement type I, K and NS7 composition piers, where nointernal pier deformation was detected and, therefore, resulted in plunging type of settlement.While most cast-in-place composition piers have shown a greater capacity for stiffness andload bearing, some of the extraordinary behavior of loess and cement composition piers canbe attributed to the ramming and curing effects that contributed to bulging and hardening ofthe piers. Therefore, while much of the findings at this stage of the research have coincidedwith the expectations, the findings obtained for loess and cement composition piers haveshows a lot of potential for the future investigation where if no cracking is achieved, thecomposition can be beneficial due to potential for greater performance, simplicity,constructability and affordability.Additionally to the conclusions drawn from stress-settlement curves, as well as tabulatedresults provided in Table 24, another table was constructed in order to better understand theoverall improvement in stress and stiffness provided by the pier elements in comparison tothe unreinforced matrix soil. The stiffness ratio, n was calculated as per Equation 21. Thestiffness ratio was defined as the ratio between the total stress on the pier and theunreinforced footing. The results were summarized in Table 36.Equation 21: Stiffness ratio for pier supported versus unreinforced footingn = k pier / k unreinforced footing (Equation 21)