A common mistake we see on Nashville projects is selecting foundation parameters based on unconfined compression tests alone, then watching settlements appear within the first wet season. The Ordovician limestone beneath Davidson County weathers into a stiff, overconsolidated clay that loses significant strength when saturated. Without a proper triaxial test program that replicates in-situ confining pressure and drainage conditions, the effective stress parameters used in bearing capacity equations are little more than guesses. We run consolidated-undrained triaxial tests with pore pressure measurement on Shelby tube samples from the Hermitage and Bigby-Cannon formations so the design team gets real c-phi values, not textbook assumptions. Before mobilizing the drill rig for undisturbed sampling, the SPT drilling crew logs refusal depth on the bedrock surface, which in Nashville typically sits between 15 and 40 feet below grade depending on how close you are to the Cumberland River terrace.
A single CU triaxial test on Nashville clay residuum gives you three Mohr circles and a pore pressure coefficient — data that a pocket penetrometer can't provide.
