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

9Normal Stress, kPaShear Stress. kPa250200150100500 20 40 60 80 100 120 140 160=AASHTO No.57, lose (Jian and Park, 2007)1=AASHTO No.57 dense (White and Suleiman., 2004)2=AASHTO No.57 dense (Fox et al., 1998)3= 56.0 degrees=AASHTO No.57, dense (Jian and Park, 2007) 4= 52.2 degrees5 =AASHTO No.21A dense (Fox et al., 1998) 5= 48.8 degrees= 48.5 degrees2= 44.0 degrees10Figure 4: Friction angle for AASHTO No. 57 and No. 21A limestone aggregate(reproduced per Fox et al., 1998, Jian and Park, 2007 and White and Suleiman, 2004)Another unique feature of aggregate pier is associated with the potential of the aggregate togain strength with time. While concrete or cementitious grout composition piles and columnsundergo strength gain with time due to curing, the intermediate foundation elements feature aprocess of strengthening through dissipation of pore water pressure in matrix soil (Lechnerand Hanagan, 2009). As the pore water pressure of matrix soil is at its peak immediately aftercompletion of the pier, the process of dissipation of pore water pressure over time leads to anincrease in pier modulus (FitzPatrick et al., 2003). However, the dissipation of pore waterpressure is highly dependent on the permeability of the matrix soil, as well as, moisturecontent, presence of drainage and overall level of soil consolidation.Another material involved in the design of aggregate pier foundation systems is representedby the matrix soil. The most favorable soil conditions for aggregate pier applications are peat,weak soils and expansive clays. The peat type soils are typically associated with highmoisture content and feature high compressibility. Using aggregate pier elements in peatsoils has proven successful, while many other conventional methods have been costprohibitive in reinforcing peat.