RUTGERS SOLAR ENERGY PROJECT – LIVINGSTON CAMPUS
CME Associates provided geotechnical consultation relative to foundation stability analyses for ground-mounted PV arrays comprising an area of approximately 4.5 acres within the Rutgers University Livingston Campus in Edison, New Jersey. The subsurface conditions generally consisted of two to seven feet of fills underlain by weathered/fractured shale bedrock. CME conducted geotechnical analyses to assess the minimum penetration depth of the driven poles and/or drilled piers required to resist the anticipated axial, lateral and uplift loads. In the event that the pole/drilled pier foundation would require pre-drilling into the underlying bedrock, the evaluation of the socket value of the concrete grout/soil interaction was also performed.
CME's participation included the following scope of work:
• Reviewed the structure designer's load takedown summary for the reactions for the typical solar panel support frame.
• Performed uplift analyses using published procedures for analyses of socketed gravity filled mini piles for supports installed in concrete filled sockets.
• Performed uplift analyses for driven steel piles.
• Performed lateral load analyses using computer analysis software.
The calculations considered two types of foundation installation.
• Alternate 1 considered driven pipe supports inserted in under-reamed or tight predrilled holes in the shale bedrock;
• Alternate 2 considered installation of the pipe supports in a predrilled socket measuring 8 inches in diameter and backfilled with plain concrete fill.
Loading criteria provided by the support designer indicate that the controlling loadings at grade for the supports would be a wind induced uplift ranging from 600 to 2800 pounds, lateral loads of approximately 1000 pounds, and moments ranging from 15 to 500 foot -pounds.
The installation alternate selected by our client, consisted of the 8 inch diameter socketed post which developed adequate resistance for the approximately 1,000 pound lateral load at the design depth required for uplift resistance. The selected alternate precluded the need for pre-drilling into the disintegrated rock and provided the required loading resistance at shallower depths than the driven pole alternate