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Solving geotechnical challenges with efficient and cost-effective ground improvement solutions

The Hartford Yard Goats (the AA affiliate of MLB’s Colorado Rockies) selected a site for a new ballpark that is located in the downtown area of North Hartford, CT.  The design consisted of a multi-level structure with a footprint area of approximately 200,000 square feet.  Soil conditions consisted of about 20 feet of granular urban fill, 35 feet of soft varved silt and clay, overlying dense glacial till and bedrock. These subsurface conditions, combined with column and retaining wall loads exceeding 500 kips and 50 kips per linear foot, presented several challenges. Supporting footings on these weak soils would have resulted in settlements exceeding the specified tolerance of 1-inch.  Geopier GeoConcrete® Column (GCC) system and spread footings were ultimately selected as the most economical foundation support approach. The GCCs were designed to limit total and differential post-construction footing settlement to less than 1-inch and ¾-inch, at an allowable footing bearing pressure of 4 kips per square foot (ksf).

Helical Drilling, Inc. installed more than 1,400 GCCs using a patented displacement mandrel that did not generate spoils or require dewatering.  A full-scale modulus test was performed to 200% of the GCC element design stress.  The testing results showed deflections of less than 1/4 -inch at the design stress levels indicating superior performance of the Geopier GCC ground improvement system.