500 Walnut Street: High-Capacity Auger Pressure-Grouted Piles Used to Support a 26-Story, Multi-Family Tower behind Independence Hall

The purpose of this case history is to showcase the viability of high-capacity auger pressure-grouted (APG) piles as an alternative to the traditional deep foundation systems commonly used within the Philadelphia region (e.g. drilled shafts or caissons; driven piles; micro-piles). This case history demonstrates that relatively high capacities can be developed using APG piles when installed in similar geologic settings as the subject site and highlights the circumstances where APG piles may be a favorable alternative. Included is a brief summary of the 500 Walnut Street multi-family residential development, geologic setting, and process of how APG piles were selected and implemented for support of the proposed tower. Explanations are included demonstrating how the designers of the APG piles arrived at the theoretical pile capacities. Finally, this paper summarizes the results of a pile load test program used to confirm the recommended pile capacities, as well as experiences during the installation of production piles.