Austin sits on a mix of expansive clay over limestone bedrock, a combination that demands rigorous slope stability analysis. We follow FHWA-NHI-05 methods and ASCE 7 seismic provisions to assess both short-term and long-term failure risk. The team runs limit equilibrium models using Spencer and Bishop routines, calibrated with local soil parameters from test pits and SPT logs. For fills along the Colorado River terraces, we also check undrained shear strength via a veleta de campo to get real-time field data. Every analysis includes pore-pressure assumptions tied to Austin's wet-dry seasonal cycle.
Austin's seasonal wet-dry cycle can reduce clay shear strength by up to 40 percent between summer and winter months.