Driving a casing through Fresno's subsurface often reveals what the San Joaquin Valley is known for: deep sequences of interbedded silts, clays, and loose sands deposited over millennia by the Kings and San Joaquin River systems. When the standard penetration test from an SPT drilling program comes back with N-values consistently under eight in the upper twenty feet, traditional spread footings become impractical. Stone column design offers a ground improvement alternative that densifies the surrounding soil and creates stiff, load-bearing elements through the soft zone. The design process for Fresno County requires careful consideration of the basin's variable groundwater, typically encountered between ten and twenty feet below grade, and the potential for liquefaction in the loose granular layers that are common across the 36.7° latitude line. Our approach integrates seismic settlement analysis from the start, recognizing that a stone column array must perform during a design event as well as under static building loads.
A properly designed stone column grid can reduce settlement by fifty to seventy percent compared to untreated ground, transforming a marginal site into buildable land.
