Helical Piers with Grouted Shafts -A Case History

"A grouted helical pile was used to support new buildings in the reconstruction of a large residential development. Foundation options were complicated by urban fill underlain with variable alluvial soil. A driven timber pile and grade beam system was recommended to support the new buildings. Other foundation options are also discussed. The grouted helical pile was quoted as an alternate and ultimately won the bid based on the economics and performance of the system. Data from 8 load tests was used to develop an empirical site specific relationship for determining pile capacity based on both installing torque and installation depth. Design to incorporate tolerance on installed pile location is presented. With the three phases completed, 554 residential dwelling units supported by 3645 grouted helical piles had been constructed covering 18 city blocks on the 44 acre site. IntroductionThe Philadelphia Housing Authority reconstructed the Tasker Homes housing complex located in southern Philadelphia, Pennsylvania, adjacent to the Schuylkill Expressway in the Grays Ferry area. Keating Building Corp. and Pennoni Associates were the general contractor and the structural engineer respectively. The original Tasker Homes development was constructed from 1940 to 1941 and consisted of 44 acres of primarily two and three-story residential brick buildings. These buildings were supported by a timber pile foundation system. The structural condition of the buildings supported on the timber piles was generally good in comparison to areas outside the buildings. These areas had settled possibly up to 2-feet in places due to the heterogeneous nature of the urban fill."