Abstract
The City Creek Block 75 Project encompasses a large city block in Salt Lake City, involving excavations to 90 feet below street grade and over 40 feet below groundwater. Earth retention, in combination with dewatering systems, was installed to support five adjacent high rise structures and three major streets abutting the site. Ground conditions are comprised of dense cobbles and gravels overlying interlayered lakebed deposits with incised stream deposits which provide conduits for groundwater recharge from the ancestral City Creek. The design and construction scheme provided the flexibility required and often emphasized by Terzaghi to adjust in response to actual underground conditions using the available means and methods. This case history traces the innovative modifications to dewatering and shoring systems implemented in response to subsurface conditions identified during Block 75 shoring and dewatering construction. Initial subsurface projections allowed for a dewatered approach using a complex multi-stage wellpoint system combined with soil nail and shotcrete shoring, supplemented by soldier or secant piles and post-tensioned elements for added stiffness at critical sections. In general, the wellpoint systems reduced pore pressures within the upper aquifer, but groundwater remained perched in an intermittent zone of interlayered silts and clays along the east wall. Modified shoring design, dewatering systems and changes to construction procedures were required to complete this wall. Consequently, the north perimeter of the project was redesigned as a composite shoring and groundwater cut-off system combining secant piling, jet grouting and soil nailing. The revised shoring and dewatering configurations from the east and north walls are presented with performance data for these unique earth retention systems.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call