Abstract:
The U.S. Army Corps of Engineers is replacing the lock at Chickamauga Lock and Dam on the Tennessee River approximately 7 miles upstream from Chattanooga, Tennessee. The local geology is complex, including karst limestone, which posed significant anticipated challenges to drilled shaft foundation construction. This presentation provides and overview of the value engineering (VE) drilled shaft foundation design for the new lock’s upstream guide walls. By increasing the diameter of the drilled shafts, the total number of drilled shafts was reduced by half and the lengths of the shafts were also reduced. The VE design reduced construction complexity and risk. The foundation VE design also allowed for structural VE design of the pier cap reinforcement, resulting in a more constructible and cost-effective cap design. A case history of the VE design and anticipated construction challenges is presented including project background, an overview of the geology and subsurface conditions, the results of a bi-directional load test, and comparison of the VE design to the base design. An overview of the actual conditions encountered during construction is also presented.