Landfill Construction through Peat and Organic Silt: Fid-Bau Portal

Landfill Construction through Peat and Organic Silt

Tinjum, James M. / Schittone, Joel V.

This paper addresses design principles and construction practices used to combat soft ground conditions based on an extensive case history covering 3 years of landfill construction. It includes the characterization of the soft ground at the site using a variety of methods, including cone penetrometer testing (CPT), borings, laboratory testing, and landfill history. Conceptual designs evaluated to improve and/or mitigate the soft ground problems are reviewed. And finally, this paper addresses some of the many difficulties encountered in the field and how problems were resolved. Due to the severity of the soft ground problem, the potential impact to neighboring rail lines, and the available construction time frames, various technologies were implemented. For a 250-linear meter (m) section along the rail line where 85,000 cubic meters (m³) of soft soil required excavation and replacement at an accelerated schedule, an internally braced, dual-wall sheetpile system was selected. Two sheetpile walls were driven through the soft soil and embedded in underlying stiff clay till. Staged excavation of soft soil between sheetpile walls then commenced, internal bracing was placed, and replacement clay was compacted in place. Remaining soft soil on the landfill side was `mudwaved' out during placement of a soil buttress. For another section adjacent to the railroad, a soil preload application was employed. This economical approach was selected because the soft soil thickness was less than 4 m and there would be a 2-year construction schedule. The two case histories demonstrate a wide variety of techniques that may be employed to combat soft ground problems.