Circular Land Cofferdam for Deep Excavation

Site conditions, dewatering, design, construction procedures and observations and stress measurements made during construction of a circular land cofferdam for a 79-ft (24.0-m) deep excavation for construction of a car dumper structure for Oak Creek Power Plant in Oak Creek, Wis., are described. The cofferdam consisted of wood lagging, soldier posts, four levels of concrete ring beams, and a lower caisson section. The concrete ring beams were instrumented with mechanical strain gages. Apparent earth pressure diagram computed from the results of the instrumentation is presented. Design and construction of the caisson section and the dewatering system are also examined.