The benewah county airport runway and apron pavements, reconstructed in 1977 over an unknown thickness of peaty, silty, and clayey flood plain deposits, settled more than 2 ft at some locations duringthe subsequent 10-year period. In 1987, the runway was reconstructed and the original grades reestablished following the removal of up to 3.5 Ft of a crushed rock ballast and up to 8 ft of the highly organic subgrade soil. These materials were replaced with a compacted lightweight wood fiber fill. The engineering properties of the wood fiber material--including its shear strength, compression, and creep properties--were determined. An analysis was performed in the designof a fill prism that imposed no net stress increase on the highly compressible subgrade soils. The objective of the design was to limitpost-construction settlements to creep of the wood fiber fill and secondary compression of the subsoils. Pavement elevation changes measured 15 to 32 months after the completion of the 1987 construction indicate that although settlements are larger than predicted, the objective of preventing a new cycle of subgrade consolidation settlement was achieved and that settlements were within acceptable limits. This paper appears in transportation research record no. 1310, Construction innovations 1991.
Abstract