Parking in a Land Down Under: A Paradigm to Constructing Basements Next to a River with Shallow Rock-Video

Video Transcription

Video Summary

The presentation covered Zilker Point, a five-level underground parking project in downtown Austin, where diaphragm (slurry) walls served as both temporary excavation support and permanent basement walls. River-terrace sands and gravels overlie Austin Chalk and Georgetown Limestone; groundwater averages about 30 feet below grade. The design included 60 wall panels, five levels of tiebacks and corner bracing, plus a soil-nail wall for the access ramp.<br /><br />Construction involved guide walls, bentonite-supported panel excavation, rebar-cage placement, tremie concrete pours, and subsequent tieback installation and wall preparation. Key challenges included developing a reliable concrete mix, managing bentonite loss into porous gravel, addressing utilities, and coordinating equipment, deliveries, excavation, and tieback work on a constrained site. Early contractor involvement helped identify and resolve issues before construction. Despite the challenges, the team maintained watertightness while excavating below the water table and finished two weeks ahead of schedule.

Keywords

Zilker Point

diaphragm walls

underground parking

bentonite slurry

tieback excavation support

watertight basement walls