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

13savings provided by the system (Allgood et al., 2003). Another example, where ability toreach bedrock was restricted, is the construction of an aboveground storage tank in Houston,TX (Wissmann et al., 2001b). By using aggregate pier intermediate foundations thisparticular project was finished 40 days ahead of schedule and yielded significant amount ofcost savings.Other types of soils such as silty and sandy soils are typically reinforced by a method ofdynamic compaction. Being often successful in densifying soil, the dynamic compactionapproach often introduces major vibrations to the ground surface and possible disturbance tothe structures within a close vicinity of the project. The process of ramming aggregate pieraggregate produces a significantly reduced level of frequency vibration at 300 to 600 cyclesper minute, thus, enabling construction of the pier at low level of noise and vibration (Foxand Cowell, 1998). A good representative example, where the reduction of vibration andnoise level was of the essence, is outlined in the construction of the Baptist MemorialHospital in Columbus, Mississippi (FitzPatrick and Wissmann, 2006). Installation of theaggregate piers provided acceptable level of noise and significantly reduced amount ofvibration.Bearing CapacityWhen evaluating design bearing capacity of the bulging piers, the calculations are performedby incorporating limiting radial stress and using Rankine passive earth pressure theory(Wissmann, 1999). Having this approach only to be valid for piers placed in cohesive soils,Western Iowa loess was deemed to be suitable (98% fraction of silt and clay). Ultimatebearing capacity of bulging piers can, therefore, be estimated as following:Equation 1: Ultimate bearing capacity due to bulgingq ult aggregate pier = σ' r.lim tan 2 (45+ φ p aggregate pier /2) (Equation 1)Equations 1-7 were taken from Wissmann, 1999.