Design and Construction of a Lightweight Material Embankment Supported on Timber Piles through a Load Transfer Platform

The paper presents design and construction aspects of a lightweight material embankment supported on timber piles through a geogrid reinforced load transfer platform in Orland Park, Cook County, Illinois. The pile supported embankment represented a feasible, durable and cost-effective solution for constructing the embankment on the low bearing capacity, high compressibility foundation soils encountered at the project site. The pile supported embankment technology uses conventional practice for all aspects of design, specification, and construction such that it can be readily implemented. Because of the very weak nature of the soils encountered at the project site, a stiff geogrid reinforced load platform was required between embankment and supporting piles. In order to reduce the loads on timber piles, expanded shale lightweight aggregate was used in the embankment and load transfer platform. Based on the estimated pile loads along the embankment and the available pile bearing capacity at various locations, the length of 10-inch tip timber pile with natural taper, spaced at a 7 feet center-to-center grid pattern varied from 40 feet to 60 feet. A pile concrete mini-cap, 3 feet by 3 feet, was placed on the top of the piles, which provided a clear spacing between individual supports of 4 feet. In addition to embankment design, the paper discusses PDA monitoring of piles during driving, settlement monitoring results and other challenges associated with the embankment construction.