Geofoam Applications in the Design and Construction of Highway Embankments (2004) / Chapter Skim
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From page 17... ...
CHAPTER 1 INTRODUCTION Contents General..........................................................................................................................................1-1 Soft Ground Treatment Methods ..................................................................................................1-3 Types of Lightweight Fills............................................................................................................1-7 EPS-Block Geofoam.....................................................................................................................1-8 Functions.....................................................................................................................................1-10 History of Geofoam ....................................................................................................................1-11 Current State of Practice .............................................................................................................1-12 Objectives of the Report .............................................................................................................1-14 Report Organization....................................................................................................................1-15 References...................................................................................................................................1-17 Tables..........................................................................................................................................1-20 ______________________________________________________________________________ GENERAL Although there are many lightweight fill materials than can be and have been used for embankments, geofoam has experienced an increase in usage over the last decade. It is estimated by the geofoam industry that approximately 10 percent of annual U
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1-2 objective of this report is to present the necessary technical information to facilitate usage of EPS-block geofoam in roadway embankments. Geofoam is any material or product that has a closed-cell structure that was created either in a fixed plant or in situ by an expansion process (1)
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1-3 EPS-block geofoam is unique as a lightweight fill material, with a density that is only about 1 percent of the density of traditional earth fill materials yet sufficiently strong to support motor vehicles, trains, airplanes, lightly loaded buildings, and the abutments of small bridges. The extraordinarily low density of EPS-block geofoam results in significantly reduced gravity stresses on underlying soil foundations as well as reduced inertial forces during seismic shaking.
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1-4 Table 1.1 (terminology has been updated in some cases)
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1-6 addition, the change in engineering properties should be verified prior to embankment construction to ensure satisfactory performance. Conversely, the properties and geometry of manmade lightweight fills, e.g., geofoam, are well defined which provides more confidence and less uncertainty in its use than foundation improvement techniques.
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1-7 As indicated in the above factors, the type of soft ground treatment that is selected will depend on the tolerable settlement of the embankment or bridge approach system. Postconstruction settlements as much as 0.3 to 0.6 m (1 to 2 ft)
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1-8 boiler slag, expanded clay or shale, shredded tires)
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1-9 geosynthetics. For example, when specifying a geotextile it is necessary to state the polymer, manufacturing technique (woven or non-woven)
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1-10 this record, the predominant geofoam material used successfully from a technical and cost perspective as lightweight fill in road construction is EPS. There are two additional terminology issues that need to be clarified before proceeding.
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1-11 functions do not duplicate those provided by other types of geosynthetics. A complete discussion of geofoam functions and applications is given in (1)
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1-12 In the early 1970s, XPS was used for a bridge approach fill in Pickford, Michigan.
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1-13 uncertain when lightweight fills are used rather than a foundation soil or ground improvement method. The shorter construction time results from the simplicity of placing the blocks and the ability to place the blocks in adverse conditions.
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1-14 considerations, if any, and value engineering of lightweight fill material. However, neither reference recommends or presents a detailed and comprehensive design procedure or a combined material and construction standard.
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1-15 The purpose of this report is to provide a comprehensive document that provides both state-of-the-art knowledge and state-of-practice design guidance for engineers. It is anticipated that designers will be more willing to consider EPS-block geofoam as an alternative for construction of embankments over soft ground using the design methodology and standard presented herein.
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1-16 wind, load bearing capacity of the blocks, and durability, that should be considered. Chapter 7 presents design examples that demonstrate the design methodology outlined in Chapter 3 and implemented in Chapters 4, 5, and 6 for a roadway embankment that can be used by design engineers to facilitate design of their projects.
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1-17 geofoam. The geofoam manufacturing industry typically uses the quantity of density with the SI units of kg/m3 but with the I-P quantity of unit weight with units of lbf/ft3.
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1-18 17. "Processed Blast Furnace slag, The All-Purpose Construction Aggregate." Bulletin No.
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1-19 38. Sanders, R
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Table1.1 Project 24-11.doc Category Alternative Variations of Method Reducing the load Reduced-stress method Lightweight Fill: bark, sawdust, peat, fuel ash, slag, cinders, scrap cellular concrete, low-density cellular concrete geofoam, expanded clay or shale (lightweight aggregate) , expanded polystyrene geofoam, shells, shredded tires.
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Table1.2 Project 24-11.doc Lightweight Fill Type Range in Unit Weight, kN/m3 (lbf/ft3) Range in Specific Gravity Approximate Cost, $/m3 ($/yd3)
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