The paper presents design and construction aspects of a lightweight materialembankment supported on timber piles through a geogrid reinforced load transferplatform in Orland Park, Cook County, Illinois. The pile supported embankmentrepresented a feasible, durable and cost-effective solution for constructing theembankment on the low bearing capacity, high compressibility foundation soilsencountered at the project site.The pile supported embankment technology uses conventional practice for allaspects of design, specification, and construction such that it can be readilyimplemented. Because of the very weak nature of the soils encountered at the projectsite, a stiff geogrid reinforced load platform was required between embankment andsupporting piles. In order to reduce the loads on timber piles, expanded shalelightweight aggregate was used in the embankment and load transfer platform.Based on the estimated pile loads along the embankment and the availablepile bearing capacity at various locations, the length of 10-inch tip timber pile withnatural taper, spaced at a 7 feet center-to-center grid pattern varied from 40 feet to 60feet. 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 ofpiles during driving, settlement monitoring results and other challenges associatedwith the embankment construction.
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