Nuclear Safety-Related Drilled Shaft Retaining Walls

Wolf Creek Generating Station, a nuclear power plant located in central Kansas, recently completed a project to improve the essential service water (ESW) piping system that supplies water to cool the reactor. Part of the project involved the construction of retaining walls in the cooling water reservoir adjacent to the existing ESW pumphouse to retain new earth embankments. Site conditions and operational restrictions dictated the use of a wall system that would not interfere with the pumphouse or encroach on the reservoir, that could be constructed without temporary cofferdams or dewatering, and that could meet the design and construction quality assurance requirements for nuclear safety-related structures. To meet these requirements, a cantilever retaining wall system consisting of nearly-tangent large-diameter rock-socketed drilled shafts was designed to resist conventional earth retention and bulkhead wall loads as well as forces associated with tornado-generated missiles. The steel-cased reinforced concrete shafts were installed from a barge, a cast-in-place concrete cap beam was built to tie the shafts together, and rock fill was placed behind the walls to form the new embankments.