Construction of roadway embankments on soft foundation soils, such as peats or soft clays, has long been problematic. Two main strategies for coping with the problem are (1) to improve the engineering properties, e.g., shear strength and compressibility, of the foundation soils or (2) reduce the weight of the embankment and thus the load applied to the soft foundation soils. Less prevalent is the second alternative that consists of reducing the load of the embankment by replacing the soil fill material within the embankment with a lighter material, i.e., lightweight fill, and accepting the natural resistance (strength and compressibility) of the existing soft foundation soil.; Lightweight fills are currently underutilized in U.S. practice because a comprehensive design guideline and a material and construction standard specification for their use in roadway embankments has been unavailable. In an effort to address this need, a study was performed to develop a comprehensive document that provides both state-of-the-art knowledge and state-of-practice design guidance to engineers for the use of expanded polystyrene (EPS)-block geofoam for the function of lightweight fill in road embankments over soft ground. The research consisted of the following four tasks: (1) summarize relevant engineering properties, (2) develop a comprehensive design procedure, (3) develop a provisional material, product, and construction standard specification, and (4) perform an economic analysis.; This dissertation presents a design guideline or procedure as well as an appropriate material and construction standard. It is anticipated that the results of this study will encourage greater and more consistent use of EPS-block geofoam as an alternative for construction of embankments over soft ground. The ultimate benefit of this is an optimization of both the technical performance as well as cost of EPS-block geofoam embankments. The research has confirmed that EPS-block geofoam can provide a safe and economical solution to problems with construction of roadway embankments on soft soils. Although this study addresses only EPS-block geofoam, the completed design manual can serve as a blueprint for development of design guidelines for other types of lightweight fills.
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