Abstract:
The establishment of the Nation’ s Capital by our Founding Fathers and subsequent population explosion in the 1800’ s resulted in massive reclamation of low-lying marsh and swamp areas. The urban development of these areas often resulted in the use of traditional deep foundation systems to support structures placed in these infill areas. These foundation systems traditionally consisted of piles driven to rock or the heavily over consolidated soils of the Potomac Formation. The advent of drilled systems in the mid 1960’ s led to the introduction of drilled shafts and auger cast piles. As population continued to grow through the 1990’ s and commercial development expanded into what was previously residential areas, ground improvement made its introduction into the local market through wick drains, lime and cement stabilization, grouting and stone column applications. Rigid inclusions were introduced in the mid 2000’ s into the commercial market, and the US Government, particularly the USACE, NAVFAC, and DOD, began accepting rigid inclusions under their structures shortly thereafter. Jet grouting applications also were introduced at this time. Ground improvement applications flourished through the last ten years, particularly during the construction of the DCWater Clean Rivers program and the necessity to support and protect fragile critical infrastructure during excavations and the construction of new structures.
The focus of the presentation will be on the evolution of the ground improvement applications in the Washington Metropolitan area. Case studies will be presented for different ground improvement applications. The case studies will focus on the practical applications of the ground improvement techniques, general approaches used to design the systems, efforts undertaken to gain acceptance of the systems, their measured performance, limitations, and potential evolution to meet new project demands. An instrumented case study will also be presented to provide quantification of the actual ground improvement away from the ground improvement elements.