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Abstract

Considerable experience was gained with the development of sites underlain with peat and highly organic soils at Walt Disney World in central Florida. The most straightforward approach was to totally excavate the organics and replace them with sand fill. The excavation techniques and equipment used depended on the total depth of organics, the size of the area to be excavated, and the seasonal groundwater conditions. Various surcharging techniques were used to stabilize the peat before construction. Several specialized approaches were used successfully: (a) A portion of a major lagoon was developed by compressing a thick organic profile by surcharging. Vertical compressions of up to 15 ft (3.0 to 4.6 m) were achieved, thus avoiding the need for significant excavation and disposal. (b) A controlled surcharge program was used to develop over 3,000 linear ft (0.9 km) of a major four-lane access road over an organic profile extending to depths of 10 to 14 ft (3.0 to 12.2 m). Surcharging was found to stabilize the peat by removing primary consolidation and reducing the rate of secondary compression. (c) A section of an elevated monorail system in a deep organic area was developed in a phased sequence of surcharging, partial removal of surcharge, driving piles, and additional surcharge removal. (d) A finite-element program was used to assess the general vertical and horizontal displacement pattern within a sand fill extending partly over highly compressible organic soils. The purpose of this study was to evaluate the distance from the edge of the soft ground area where a structure could be safely supported in the sand fill.