A twelve-story mixed-use tower on South Congress Avenue required a foundation that could transfer 1,200 kips per column through 30 feet of expansive clay into the underlying Austin Chalk. Conventional drilled shafts were ruled out due to overhead clearance and vibration limits near historic buildings. We designed a micropile system using 9 5/8-inch casing, single-bar 60-ksi steel, and neat cement grout with a water-cement ratio of 0.45. Each pile was proof-tested to 200% of design load per ASTM D1143. Before finalizing the micropile design, we cross-checked the soil profile with a trial pit excavation to verify the top-of-rock elevation. The project was completed on schedule with zero adjacent settlement.
A proper micropile design in Austin requires checking lateral load resistance, especially when used for seismic restraint under ASCE 7-22.