The Devils in the Detail at Devils Kitchen Dam

Devils Kitchen Dam is an 83-foot-high concrete gravity dam located at the Crab Orchard National Wildlife Refuge in Marion, Illinois. Devils Kitchen Dam has provided recreation, wildlife habitat, and flood control for the refuge since it was constructed in 1959. A Phase I Investigation of Devils Kitchen Dam, performed in 1994, identified several potential deficiencies at the dam including inadequate sliding stability under normal and extreme loading conditions along a weak horizontal rock joint in the dam foundation.
This paper describes the state-of-the-art investigations and analyses used to evaluate potential sliding failure modes at the dam. The geotechnical investigations included two subsurface geotechnical drilling programs, rock core sample collection, direct shear testing, and standard geologic mapping of exposed rock at the abutments and along the stream channel. Several new technologies were incorporated into the investigations including digital photogrammetry for recording and analyzing primary joint and bedding orientations of the exposed abutment rock mass, and borehole imaging used to record and determine the rock type, condition, as well as fracture joint and bedding orientations of the foundation rock. A comprehensive automated instrumentation system consisting of several vibrating wire pressure transducers, weir monitors, and a barometer was also installed. The automated instrumentation system was used to evaluate the effectiveness of the rehabilitated foundation drains and to monitor the on-going foundation pressures, reservoir level, and gallery drainage flows at the dam. The methods and technologies used at Devils Kitchen Dam can be used in the evaluations of other similar dams and aging infrastructure so that risk can be adequately defined and proper allocation of funding can be applied where it is most needed.