Project Highlights

ACEC/TN Engineering Excellence Honor Award

S&ME used an innovative combination of traditional geotechnical drilling and Pile Integrity Testing techniques to evaluate a 90-year old Raymond concrete step taper pile foundation system’s capacity to support new Streetscape sidewalks in downtown Knoxville, Tennessee.  The complexity of the exploration and Pile Integrity Testing was compounded because the existing foundations were located in catacombs beneath the sidewalks.

Our initial services included providing drilling and laboratory testing, and providing geotechnical recommendations for subgrade improvements and retaining wall design.  During the Streetscapes construction, the existing columns supporting the sidewalk were to be replaced, and a new sidewalk was to be constructed.  Because of the poor soil conditions encountered at the planned foundation levels, we were asked to provide recommendations for alternative foundation systems.  In order to evaluate the subsurface conditions beneath the original ground surface and to evaluate the condition of the existing pile foundations, we had to set the boring casings either through former coal chutes or by coring through the existing sidewalk.  The core samples we obtained from the existing piles were tested in our laboratory.  We then conducted Pile Integrity Testing to evaluate the continuity of the pile and estimate the pile tip elevations.  After evaluating the options, we concluded that the existing foundations were capable of supporting the new loads where the alignment of the new columns matched the locations of existing foundations.  S&ME recommended new micro-pile foundations in the two locations where the alignment of new columns and existing foundations did not coincide.

S&ME’s outstanding investigative work and creative employment of engineering skills was vital to the successful conclusion of this project.  The existing Raymond cast-in-place pile foundation was an innovative method when constructed in 1919, and has proven to be a sustainable design, still useable in 2010. By reusing the existing pile foundations instead of installing new deep foundations to support the project’s structural loads, the City of Knoxville realized a savings of $1 million.