Design and Construction of Deep Mixing at Orleans Avenue Canal, New Orleans

摘要

The Orleans Avenue Outfall Canal is one of several canals that collect and transmit surface drainage from the northern portions of New Orleans. The earthen levees/floodwalls that flank the east and west banks of the canal were designed to provide parallel protection from tidal intrusion from Lake Pontchartrain. In response to the observed failures along portions of the flood protection system during hurricane Katrina, new design methodologies and criteria were adopted by the U. S. Army Corps of Engineers (USACE), and the entire New Orleans hurricane protection system was evaluated in terms of these new criteria. Portions of the flood protection system along Orleans Avenue Canal were found to be deficient. Ground improvement by the deep mixing method was selected to improve stability in two reaches due to right-of-way constraints and environmental concerns. This paper provides detailed descriptions of the design, specifications, and construction of the deep mixing at Orleans Avenue Canal, including results of the coring and strength testing in comparison to the specification requirements. The design process included site characterization, determination of the design strength of the deep-mixed ground with consideration of variability, limit equilibrium analyses of multiple failure modes, numerical analyses including a water-filled gap behind the floodwalls, and development of plans and specifications. Given the difficult access constraints and the close proximity to existing structures, the Contractor chose to install the deep mixing using the dry method. The use of real time data acquisition systems on the installation equipment allowed the Contractor to expedite QC/QA and site calibration of the mixing process. The project specifications required core drilling in the deep-mixed ground, logging of the recovered core, and strength testing on selected specimens. The process control documentation and the test results demonstrated satisfaction of the project specification requirements.