Abstract:
The Department of Energy, Strategic Petroleum Reserve Choctaw Bayou facility is located in Plaquemine, LA adjacent to Cavern Lake. Ground surface cracking was observed in a plant roadway area immediately next the lake. Upon discovery of the ground movement, a geotechnical exploration program was developed to evaluate the cause and several inclinometers were installed to monitor the on-going movement. Global stability analyses showed a factor of safety against global stability failure as low as 0.93, indicating the need for immediate improvements to prevent failure. This paper will present the results of slope monitoring before, during and after Deep Soil Mixing (DSM) slope stabilization illustrating the effectiveness of this technique. Due to the low factor of safety of the existing slope, there was a particular concern with any improvements that could result in more slope de-stabilization. DSM columns were selected to due to the low vibrations associated with the DSM process and the high area replacement ratio, which would provide added subgrade stability for the roadway once re-constructed. The slope improvement was complicated by right of way restrictions, limiting improvements to a 25 foot wide zone, and the presence of utilities within the improvement area. Prior to the starting work, site grade was lowered to improve the factor of safety to allow construction to proceed safely. During the course of the DSM installation, the lake water level was monitored, and inclinometers were checked hourly to verify the safety of the slope during construction and verify that the DSM installation did not create temporary instability of the slope. Long-term monitoring of the slope is planned to verify the effectiveness of the slope improvements. Over the course of the DSM design and installation, collaboration between the geotechnical consultant, DSM design-builder, prime contractor, and owner were essential to the successful delivery of the project. Soil mixing, deep soil mixing, slope stability, ground improvement, soil stabilization