Geofoam Applications in the Design and Construction of Highway Embankments (2004)

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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. S. sales of block-molded EPS is for the geofoam market, i.e., civil engineering applications, while ten years ago the U. S. geofoam market was non-existent. Another indication of increased geofoam usage is that geofoam usage in Japan started in 1985 and by 1995 the Japanese usage accounted for one-half of all geofoam usage worldwide. The Japanese usage suggests that provided proper technical support of EPS geofoam is available, the potential for significant growth is high. The main 1-1

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). Although most geofoam materials are polymeric (plastic) in composition, other materials such as Portland cement concrete (PCC) or glass have been and are used. Geofoam is now recognized as a type or category of geosynthetic in the same way as geogrids, geomembranes and geotextiles. Despite the fact that there are numerous geofoam materials and products, decades of worldwide use have demonstrated that block-molded expanded polystyrene (EPS) is the geofoam material of choice in lightweight fill applications. Therefore, this report focuses on EPS-block geofoam. Benefits of utilizing an EPS-block geofoam embankment include: (1) ease and speed of construction, (2) placement in adverse weather conditions, (3) possible elimination of the need for preloading, surcharging, and staged construction, (4) decreased maintenance costs as a result of less settlement from the low density of EPS-block geofoam, (5) alleviation of the need to acquire additional right-of-way to construct flatter slopes because of the low density of EPS-block and/or the use of a vertical embankment because of the block shape of EPS, (6) reduction of lateral stress on bridge approach abutments, (7) use over existing utilities which reduces or eliminates utility relocation, and (8) excellent durability. In a soil removal and replacement situation without the use of surcharging, the use of EPS-block geofoam may result in cost savings compared to other types of lightweight fill materials and conventional fill materials because the density of geofoam is 1/10th to 1/30th of the density of foamed concrete, 1/55th to 1/145th of the in-place density of boiler slag, and 1/100th of the density of conventional granular fill material. Thus, the lower density of EPS-block geofoam may alleviate the costs of soft soil removal (which include the attendant disposal problems and costs) and the possible need for an excavation support system, excavation widening, and temporary dewatering.

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. In addition, geofoam is extremely easy and quick to place in all types of weather. On many projects, the overall immediate and long-term benefits and lower construction cost of using EPS-block geofoam more than compensate for the fact that its material unit cost is greater than that of traditional earth fill materials. This chapter provides an overview of soft ground treatment methods and lightweight fills, which includes a history of geofoam development and a summary of the current state of practice of designing with geofoam. SOFT GROUND TREATMENT METHODS If either the allowable bearing capacity of the underlying soft foundation soil is too low and/or the estimated settlement of the proposed embankment is too large, the geotechnical engineer traditionally must either select a suitable ground treatment or improvement procedure or recommend use of an elevated structure supported on deep foundations if an alternative route is not possible. Roadway construction techniques over soft ground have a long history. The earliest known roads built over organic soils are found in England. These roads consist of planks and are estimated to be between 4000 and 4800 years old (2,3). Roads supported on wood piles have been discovered in roads constructed over the entire Roman territory during the period of 300 BC to AD 400 (3). A summary of various soft ground treatment alternatives that have been used for highway embankments in the United States can be found in (4). These alternatives are also summarized in

1-4 Table 1.1 (terminology has been updated in some cases). As indicated in Table 1.1, these treatment alternatives can be categorized into the following treatment approaches (4,5): • Reducing the applied load, • Replacing the problematic materials with more competent materials, • Increasing the shear strength and reducing compressibility of the problematic materials, • Transferring the loads to more competent layers via a deep foundation system, • Reinforcing the soft soil and/or the embankment, and • Providing lateral stability. The deep foundation alternative is typically the most expensive alternative so most efforts to date have focused on the other alternatives. The strategies for designing with the various soft ground treatment methods, except for the use of deep foundations, can be divided into two methods, each representing a different philosophical approach. The first method is to utilize conventional soil for the embankment and to increase the shear strength and compressibility of the soft foundation soil. The second method is to utilize a lightweight fill embankment to reduce the load applied by the embankment to the soft ground to prevent overstressing of the soft ground, which could lead to a bearing capacity failure or to unacceptable settlement. The basis for each method is to satisfy the following equations for the ultimate limit state (ULS) and serviceability limit state (SLS) respectively: ULS: resistance of embankment to failure > embankment loads producing failure (1.1a) SLS: estimated deformation of embankment ≤ maximum acceptable deformation (1.1b) The first soft ground treatment design method is based on increasing the resistance and stiffness of the overall embankment system (embankment material and natural foundation soil) to resist the applied loads and limit deformations to an acceptable level as required by Equations

1-5 (1.1a) and (1.1b). This is traditionally accomplished by employing a ground improvement technique that collectively increases the shear strength and reduces the compressibility of the overall system but primarily the soft foundation soil. As noted in Table 1.1, improvement techniques include preloading, surcharging, staged construction, accelerated consolidation through installation of prefabricated vertical (wick) drains, electroosmosis, excavation and replacement, use of stone or lime columns or other replacement techniques, and the placement of geosynthetic reinforcement within the base of the embankment soil. Geometric methods that result in overall improvement of the embankment system, e.g. flattening side slopes of the embankment and/or adding toe berms, are also included in this group. The overall use of ground improvement techniques is addressed in (4). Because ground improvement has been a popular geotechnical design tool for decades, there has been significant research into existing and new methods. The subject of ground improvement is the topic of a current (as of early 2000) U.S. Federal Highway Administration (FHWA) technology transfer initiative titled Demonstration Project 116. The current state of ground-improvement technology is well summarized in the manuals (6) prepared for and distributed to participants in the workshops held as part of Demonstration Project 116. Less prevalent is the alternative soft ground treatment design approach to satisfying Equations. (1.1a) and (1.1b) which involves reducing the load applied by the embankment. This involves replacing the soil fill material within the embankment with a lighter material and accepting the natural resistance (strength and compressibility) of the existing soft foundation soil. The use of this concept may yield a more technically effective and more cost efficient embankment because expensive ground improvement techniques do not have to be employed for the foundation soil. This is important because there is uncertainty involved in using ground improvement techniques. For example, the level of uncertainty involved in increasing the foundation shear resistance is high relative to the use of lightweight fill because strengthening of the foundation can be difficult to control and the soil strata may not be known accurately. In

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 man- made lightweight fills, e.g., geofoam, are well defined which provides more confidence and less uncertainty in its use than foundation improvement techniques. The reduced uncertainty is mainly caused by the fill being so light that it does not stress the foundation and thus the need to accurately know the soil strata is eliminated. By design, lightweight fill materials have unit weights (0.1 to 17 kN/m³ (0.8 to 109 lbf/ft3) less than that of soil and rock (20.4 kN/m³ (130 lbf/ft3)) so the resulting gravity or seismic forces from the lightweight fill materials are significantly less than those from normal earth materials. Table 1.1. Soft Ground Treatment Methods (modified from (4)). The following factors should be considered in evaluating the different types of soft ground foundation treatment alternatives (4,7): • The operating criteria for the embankment, e.g., stability requirements, allowable total and rate of settlement, level of maintenance, etc. This will establish the level of improvement required in terms of soil properties such as strength, modulus, compressibility, etc.; • The area, depth, and total volume of soil to be treated or improved; • Soil type and its initial properties; • Availability of construction materials; • Availability of equipment and required skills; • Environmental factors such as waste disposal, erosion, water pollution, and effects on adjacent facilities and structures; • Local experience and preference; • Time available; and • Cost.

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. Post- construction settlements as much as 0.3 to 0.6 m (1 to 2 ft) during the economic life of a roadway are generally considered tolerable provided that the settlements are uniform, occur slowly over a period of time, and do not occur next to a pile-supported structure (8). If post-construction settlement occurs over a long period of time, any pavement distress caused by settlement can be repaired when the pavement is resurfaced. Although rigid pavements have under gone 0.3 to 0.6 m (1 to 2 ft) of uniform settlement without distress or objectionable riding roughness, flexible pavements are usually selected where doubt exists about the uniformity of post-construction settlements and some states utilize a flexible pavement when predicted settlements exceed 150 mm (6 in.) (8). Tolerable settlements of bridge approach embankments depend on the type of structure, location, foundation conditions, operational criteria, etc (4). The following references are recommended for information on tolerable abutment movements: (9-12). TYPES OF LIGHTWEIGHT FILLS As summarized in (4) and also discussed in (13), there are a large number of potential lightweight fill materials available. The most significant aspect of lightweight fill materials is their range in density which can vary from as little as 1 percent to as much as 70 percent of the density of soil or rock. There is also a significant range in material costs, engineering properties, and construction costs so the technical and economic benefit of using lightweight materials can vary widely. Of course, lightweight fill materials can be used in combination with ground improvement techniques for the foundation soil. However, experience indicates that on most projects it is most cost effective to use either one technology or the other. Various categories have been used to classify lightweight fill materials. Categories used in (13) include lightweight fill materials with inherent compressive strength (EPS-block geofoam, foamed concrete geofoam) and granular lightweight fills (wood fiber, blast furnace slag, fly ash,

1-8 boiler slag, expanded clay or shale, shredded tires). Lightweight fill categories used in (14) include artificial fills (foam plastics and foamed concrete geofoams) and waste materials (shredded tires and wood chips). Lightweight fills are categorized in (15) as traditional light material (wastes from the timber industry such as sawdust and bark, wastes from the production of building blocks of cellular concrete, and expanded clay aggregate) and super-light fill (EPS- block geofoam). Table 1.2 provides a summary of the common types of lightweight fills. As indicated in Table 1.2, there is a significant range in density/unit weight, specific gravity, and costs, so the technical and economic benefit of using lightweight fill materials can vary widely. Chapters 11 and 12 herein present additional cost information for EPS-block geofoam. Factors that influence cost of the various types of lightweight fills include quantity required for the project, transportation costs, availability of materials, contractor’s experience with the product, placement or compaction costs, and specialty items, e.g., anchor plates for EPS- blocks or separator geosynthetics for wood fibers, that may be required (13,16). Additionally, the cost of using some waste materials will be dependent on the availability of federal or state government incentive or rebate programs. The lightweight fill types indicated in Table 1.2 are arranged by density/unit weight and it can be seen that EPS-block geofoam clearly has the lowest density/unit weight and specific gravity. Table 1.2. Summary of Various Lightweight Fill Materials (13). EPS-BLOCK GEOFOAM Geofoam is any manufactured material created by an internal expansion process that results in a material with a texture of numerous, closed, gas-filled cells using either a fixed plant or an in situ expansion process (1). Geofoam materials include polymeric (plastic), glass (cellular glass), and cementitious foams (19). Because geofoam encompasses a variety of materials and products, it is necessary in practice to state the specific geofoam material and product being discussed. This is also consistent with what is required for other types of

1-9 geosynthetics. For example, when specifying a geotextile it is necessary to state the polymer, manufacturing technique (woven or non-woven), and desired weight or mass per unit area of the geotextile, and possibly whether it is calendered. Most geofoam materials are polymeric with polystyrene foams being the most common. The two types of polystyrene foam are expanded polystyrene (EPS) and extruded polystyrene (XPS). They are collectively referred to by the American Society for Testing and Materials (ASTM) D 578 (20) as "rigid cellular polystyrene" (RCPS). EPS is a polymeric foam that is inherently white in color and can be found in some familiar consumer products such as coffee cups and cushion packaging. EPS and XPS are differentiated based on the manufacturing process. EPS is manufactured by a two-stage process. The first stage consists of pre-expansion of the polystyrene solid resin beads into a cellular sphere with numerous closed cells by heating with steam. The expanded polystyrene beads are referred to as pre-puff. The second stage consists of further expansion of the pre-puff by heating with steam within a fixed-wall mold. The pre-puff fuses during this additional expansion process. On the other hand, XPS is manufactured by expanding the polystyrene solid resin beads and shaping the cellular product in a continuous process using an extruder. The final XPS has the appearance of a uniform texture of closed cells whereas the EPS product has the appearance of individual, fused particles. XPS is typically molded as thin planks or panels whereas EPS is typically molded as prismatic blocks. Thus, the preferred or more representative name for an EPS product is EPS-block geofoam. Further discussion on the manufacturing processes is included in Chapter 2 herein and in (1). Although the generic use of the term geofoam is relatively new (it was used for a proprietary EPS product in Alaska starting in the late 1970s but has been in generic use worldwide only since the early 1990s), foam materials have been used in geotechnical applications, including in the U.S.A., since the early 1960s. Thus, there is a published historical record of use of the term geofoam that exceeds almost all other type of geosynthetics. Based on

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. First, because EPS-block geofoam is and has been the predominant geofoam material and product for many years, there is a tendency in current U.S. practice to simply use the term "geofoam" as a synonym for "EPS-block geofoam". Because there are so many recognized different geofoam materials and products (e.g., there is a brand of foamed portland-cement concrete that uses "geofoam" in its registered tradename), this synonymous relationship does not, in fact, exist and should be avoided to prevent potential errors, problems, or claims relative to supplying the appropriate geofoam material and product on a project. Second, it is common in colloquial speech in the U.S.A. to refer to all polymeric foams as styrofoam. This is incorrect because Styrofoam is the registered trademark and tradename of a line of XPS foam products manufactured by The Dow Chemical Company. Therefore, indiscriminate and incorrect use of the word styrofoam should be avoided in practice to prevent potential errors, problems, or claims relative to supplying the correct geofoam material and product for a project. A simple yet useful rule is to note that Styrofoam is always colored blue. Thus, the use of the word styrofoam must be restricted to those times when the blue-colored XPS product manufactured by The Dow Chemical Company is specifically intended. This would not likely occur when geofoam is used as lightweight fill for a road but might occur when geofoam is used as thermal insulation for a road pavement. Thus, Styrofoam usage might occur in road construction so diligent use of correct geofoam terminology is important in road construction. FUNCTIONS Geofoam is a type or category of geosynthetic. Depending on the particular geofoam material and product, geofoams can provide a wide variety of geosynthetic functions. Each of these functions may have numerous potential applications. With one exception, geofoam

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). As with most types of geosynthetics, geofoams can provide a wide variety of functions including thermal insulation, lightweight fill, compressible inclusion, fluid transmission (drainage), damping, and structural. Also, as with other geosynthetics, the design by function approach is the most effective means of designing with geofoam. Design by function is based on initially selecting the function(s) required in a project and then selecting the geofoam product that will satisfy the function(s) most cost effectively (19,21). Although the focus of the present study is on the geofoam function of lightweight fill and the specific application of this function is roadway embankments, the fact that geofoams provide other functions, even if not intended or not necessarily desired in a particular project, should be considered in design of lightweight fills for roads. These other functions include structural and thermal insulation. HISTORY OF GEOFOAM A comprehensive history of the various applications of geofoam is provided in (1). However, a general overview is presented here. Foam materials have been used in geotechnical applications since the early 1960s initially for the function of thermal insulation (19). The date and location of the first use of geofoam as lightweight fill is not known. EPS-block geofoam has been used as lightweight fill worldwide since at least 1972, which corresponds to a road project in Norway. The use of EPS-block geofoam in the U.S.A. for lightweight fill dates back to at least the 1980s although at least two conceptual patents for the use of plastic foams as lightweight fill in earthworks are known to have been issued in the U.S.A. in the early 1970s. Dr. Edward J. Monahan, P.E. indicates that he invented the geofoam function of lightweight fill circa 1970 (1,22) as part of his weight-credit concept (1,23,24) and through his U.S. patents in 1971 and 1973 (1,25,26).

1-12 In the early 1970s, XPS was used for a bridge approach fill in Pickford, Michigan. In (1) it is suggested that the Norwegian Road Research Laboratory (NRRL) developed the concept of using geofoam in general circa 1960 including use as lightweight fill circa 1970. Since a road project in 1972, the NRRL has utilized EPS blocks on hundreds of projects (27,28). The first lightweight fill project in Japan occurred in 1985. Approximately ten years later, an independent assessment found that geofoam usage in Japan comprised approximately 50 percent of the worldwide usage. Geofoam usage in Japan has largely been limited to the use of EPS-block geofoam. Significant research and development of the use of EPS-block geofoam has been performed in Japan for lightweight fill and seismic loading applications (19). Although XPS has been used to a limited extent as lightweight fill in the U.S.A., Japan, and the United Kingdom, geofoam applications worldwide have shown that XPS is not cost effective for use in lightweight fill applications (1), and consequently, the predominant geofoam material used as lightweight fill in road construction is EPS-block geofoam. EPS-block geofoam is mentioned in (4) (although not identified as a geofoam material as the term was not in generic use at that time) and is included in the FHWA Demonstration Project 116 manuals (13). However, its use for roads in the U.S.A. increased dramatically during the 1990s, largely as a result of technology transfer initiatives by Prof. John S. Horvath, Ph.D., P.E. of Manhattan College in New York City (his first of many publications on the subject appeared in 1990) as well as marketing and geotechnical-engineering conference displays by EPS molders beginning in 1993. To date, EPS-block geofoam has been successfully used as a lightweight embankment fill material for roads ranging from Interstate highways to two-lane residential streets. It has also been successfully used as a lightweight fill for landslide repairs. CURRENT STATE OF PRACTICE The use of lightweight fill materials including EPS-block geofoam for roadway embankments as an alternative to ground improvement increased during the 1990s due to four significant reasons. First, the overall time for construction is typically much shorter and less

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. Second, lightweight fills produce relatively small undrained (initial) and consolidation settlements whereas traditional ground improvement methodologies, such as preloading, typically produce relatively large undrained and consolidation settlements. While these settlements may not affect the final road, they can negatively affect adjacent property, roads, bridges, buildings, utilities, etc. However, it is important to note that the use of lightweight fill materials will not reduce the magnitude of secondary (creep) compression settlement that will occur without an embankment. The magnitude of secondary consolidation settlement is a function of the properties of the underlying soft foundation soil only, and is thus independent of the external stresses applied to the foundation soil. Third, lightweight fills decrease maintenance costs because of less settlement. Fourth, the durability of EPS-block geofoam has been proven by projects completed in the 1970s. In consideration of these benefits, the typically higher unit cost of lightweight fill materials (a "negative" cited in (4) which was prepared in the late 1980s) is usually more than offset by savings when overall project costs are considered. An increase in use of lightweight fill materials for road construction is reflected in the fact that they have been emphasized by various governmental transportation agencies. The U.S. Federal Highway Administration (FHWA) has developed Demonstration Project 116, Ground Improvement Methods, to enhance the acceptance and implementation of ground improvement methods by the transportation community. Lightweight fills have been incorporated in this FHWA project as a method of ground improvement by reducing the applied load (13). This project consists of workshops and seminars. On the international level, the Permanent International Association of Road Congresses (PIARC) has issued a document (29) describing the use of various lightweight fill materials for different applications in road construction. Both the FHWA and PIARC references address material properties, design considerations, general standards related to the construction, environmental

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. Various countries have developed general design guidelines and manuals to aid in the design of an embankment on soft soil incorporating EPS-block geofoam. These countries include France (30), Germany (31,32), Japan (33), Norway (34-37), and the United Kingdom (38). Other national efforts are currently known to be under development, e.g., NNI (the Dutch standards organization) through CROW (the Dutch standards organization dealing specifically with civil engineering) is currently preparing a document titled "Guideline for Design and Installation of EPS as Geofoam". The first monograph dedicated to geofoam discusses the concepts for analyzing and designing EPS-block geofoam fills (1). An outline-type manual with a general guideline specification has even appeared in the United States (13). However, these design guidelines and manuals do not provide a comprehensive design procedure that makes selection of a cost-effective design practical and reliable. OBJECTIVES OF THE REPORT Despite the extensive and continuing worldwide use of EPS-block geofoam, including in the U.S.A., specific design guidelines for its use as lightweight fill in roadway embankments is currently unavailable. Therefore, there was a need in the U.S.A. since the mid 1990s to develop formal and detailed design documents for use of EPS-block geofoam in routine practice. These documents would include both design guidelines as well as appropriate material and construction standard, both in the American Association of State Highway and Transportation Officials (AASHTO) format. The purpose of these design documents would be to encourage wider as well as more consistent use of EPS-block geofoam in roadway embankments. The ultimate benefit of these guidelines would be an optimization of both the technical performance as well as cost of EPS-block geofoam embankments.

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. REPORT ORGANIZATION The purpose of this report is to provide those who have primary involvement with roadway embankment projects, including the following four groups: end users, manufacturers, contractors, and owners, with both state-of-art knowledge and state-of-practice design guidance for use of EPS-block geofoam. The end users include engineers who perform the design and develop specifications; EPS block molders who manufacture the product; and construction contractors who install the product. To understand the technical basis for the design methodology and standard presented in the report, knowledge of the geotechnically relevant properties of block-molded EPS, e.g., modulus, compressive strength, Poisson’s ratio, and interface shear resistance, is required (Chapter 2). Chapter 3 provides an overview of the design methodology developed herein for embankments on soft foundation soil incorporating EPS-block geofoam. The design methodology consists of the following three main parts: pavement system design (Chapter 4), external stability evaluation (Chapter 5), and internal stability evaluation (Chapter 6). All three of these considerations are interconnected and must be considered for each geofoam embankment. Chapter 3 also includes the background for the “Provisional Design Guideline” that is included in Appendix B. Chapter 4 presents the pavement system design module that yields typical flexible or rigid pavement systems that can be constructed over EPS-block geofoam. Chapter 5 presents the external stability considerations, e.g., bearing capacity, settlement, static and seismic slope stability, hydrostatic uplift, translation due to water and wind, that should be evaluated when utilizing an EPS-block geofoam embankment. Finally, Chapter 6 presents the internal stability issues, e.g., seismic sliding between the EPS blocks, sliding due to water and

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. The key feature in Chapters 4, 5, and 6 are the inclusion of design charts that can be used to obtain a technically optimal design for a geofoam embankment on soft foundation soil. Chapters 8, 9, and 10 discuss geofoam construction practices, MQC/MQA testing, and design details, respectively. These chapters provide the background for understanding the basis of the “Provisional Standard” included in Appendix C. Chapter 11 provides a summary of several case histories that have successfully incorporated EPS-block geofoam into roadway embankments and slope stabilization applications. Chapter 12 provides cost information to allow a cost estimate to be prepared during the design phase so that an optimal geofoam design can be selected. The designer can then use this optimal cost-based design to perform a cost comparison with other soft ground construction techniques. Finally, Chapter 13 presents recommended areas of future research. Both the Système International d’Unités (SI) and inch-pound (I-P) units have been used in this report. SI units are shown first and I-P units are shown in parentheses within text. Numerous figures are included for use in design. Therefore, only SI units are provided in some of the figures to avoid duplication of figures. Additionally, in some cases figures have been reproduced that use either all SI or all I-P Units. These figures have not been revised to show both sets of units. However, Appendix F presents factors that can be used to convert between SI and I- P units. The one exception to the dual SI and I-P unit usage involves the quantities of density and unit weight. Density is the mass per unit volume and has units of kg/m3 (slugs/ft3) and unit weight is the weight per unit volume and has units of kN/m3 (lbf/ft3). Although density is the preferred quantity in SI, unit weight is still the common quantity in geotechnical engineering practice (39). Therefore, the quantity of unit weight will be used herein except when referring to EPS-block

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. Therefore, the same dual unit system of density in SI/unit weight in I-P units will be used when referring to EPS-block geofoam. REFERENCES 1. Horvath, J. S., Geofoam Geosynthetic, , Horvath Engineering, P.C., Scarsdale, NY (1995) 229 pp. 2. MacFarlane, I. C., ed., Muskeg Engineering Handbook, University of Toronto Press, Toronto, Canada (1969) pp. 3. Sasaki, H., “A historical review of foundation treatment techniques for embankments over peat deposits.” Symposium on Recent Developments in Ground Improvement Techniques,29 Nov.-3 Dec. 1982, Asian Institute of Technology, Bangkok, (1985) pp. 533-542. 4. Holtz, R. D., “Treatment of Problem Foundations for Highway Embankments.” NCHRP Synthesis 147, Transportation Research Board, Washington, D.C. (1989) 72 pp. 5. Broms, B. B., “Problems and Solutions to Construction in Soft Clay.” Proceedings of the Sixth Asian Regional Conference on Soil Mechanics and Foundation EngineeringSingapore, Vol. II (1979) pp. 3-38. 6. Elias, V., Welsh, J., Warren, J., and Lukas, R., “Ground Improvement Technical Summaries.” Publication No. FHWA-SA-98-086, 2 Vols, U.S. Department of Tranportation, Federal Highway Administration, Washington, D.C. (1999) . 7. Mitchell, J. K., “Soil Improvement - State-the-Art Report.” Proceedings of the Tenth International Conference on Soil Mechanics and Foundation EngineeringStockholm, Vol. 4 (1981) pp. 506-565. 8. “Treatment of Soft Foundations for Highway Embankments.” NCHRP Synthesis 29, Transportation Research Board, Washington, D.C. (1975) 25 pp. 9. “Bridge Approach Design and Construction Practices.” NCHRP Synthesis of Highway Practice 2, Transportation Research Board, Washington, D.C. (1969) 30 pp. 10. Wahls, H. E., “Shallow Foundations for Highway Structures.” NCHRP Synthesis of Highway Practice 107, Transportation Research Board, Washington, D.C. (1983) 38 pp. 11. Moulton, L. K., GangaRao, H. V. S., and Halvorsen, G. T., “Tolerable Movement Criteria for Highway Bridges.” FHWA/RS-85/107, Federal Highway Administration, Washington D.C. (1985) . 12. Moulton, L. K., “Tolerable Movement Criteria for Highway Bridges.” FHWA-TS-85-228, Federal Highway Administration, Washington, D.C. (1986) 93 pp. 13. Elias, V., Welsh, J., Warren, J., and Lukas, R., “Ground Improvement Technical Summaries.” FHWA-SA-98-086, Vol. 2, 2 Vols, U.S. Department of Transportation, Federal Highway Adminstration, Washington, D.C. (1999) . 14. Monahan, E. J., Construction of Fills, 2nd ed., John Wiley & Sons, Inc., New York, N.Y. (1994) 265 pp. 15. Flaate, K., “The (Geo) Technique of Superlight Materials.” The Art and Science of Geotechnical Engineering At the Dawn of the Twenty-First Century: A Volume Honoring Ralph B. Peck, E. J. Cording, W. J. Hall, J. D. Haltiwanger, J. A.J. Hendron, and G. Mesri, eds., Prentice Hall, Englewood Cliffs, N.J. (1989) pp. 193-205. 16. Harbuck, D. I., “Lightweight Foamed Concrete Fill.” Transportation Research Record 1422, Transportation Research Board, Washington, D.C. (1993) pp. 21-28.

1-18 17. “Processed Blast Furnace slag, The All-Purpose Construction Aggregate.” Bulletin No. 188-1, National Slag Association (1988) . 18. Upton, R. J., and Machan, G., “Use of Shredded Tires for Lightweight Fill.” Transportation Research Record 1422, Transportation Research Board, Washington, D.C. (1993) pp. 36-45. 19. Horvath, J. S., “Geofoam and Geocomb: Lessons from the Second Millennium A.D. as Insight for the Future.” Research Report No. CE/GE-99-2, Manhattan College, Bronx, NY (1999) 24 pp. 20. ASTM D 578-95, “Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation.” Vol. 04.06, American Society for Testing and Materials, West Conshohocken, PA (1999) . 21. Koerner, R. M., Designing with Geosynthetics, 4th, Prentice Hall, Upper Saddle River, N.J. (1998) . 22. Monahan, E. J., “editorial letter.” Geotechnical Fabrics Report, Vol. 11, No. 3 (April 1993) p. 4. 23. Monahan, E. J., Construction of and on Compacted Fills, , John Wiley & Sons, New York, N.Y. (1986) . 24. Monahan, E. J., “Weight-Credit Foundation Construction Using Artifical Fills.” Transportation Research Record No. 1422, Transportation Research Board, Washington, D.C. (1993) pp. 1-4. 25. Monahan, E. J., “Floating Foundation and Process Therefor.” U.S. Patent No. 3,626,702 (1971). 26. Monahan, E. J., “Novel Low Pressure Back-Fill and Process Therefor.” U.S. Patent No. 3,747,353 (1973). 27. Aabøe, R., “Long-term performance and durability of EPS as a lightweight fill.” Nordic Road & Transport Research, Vol. 12, No. 1 (2000) pp. 4-7. 28. Aabøe, R., “Evidence of EPS long term performance and durability as a light weight fill.” Preprint Paper, Transportation Research Record No. 1736, Transportation Research Board, Washington, D.C. (2000) . 29. “Matériaux Légers pour Remblais/Lightweight Filling Materials.” Document No. 12.02.B, PIARC-World Road Association, La Defense, France (1997) 287 pp. 30. “Utilisation de Polystyrene Expanse en Remblai Routier; Guide Technique.” Laboratoire Central Ponts et Chaussées/SETRA, France (1990) 18 pp. 31. “Merkblatt für die Verwendung von EPS-Hartschaumstoffen beim Bau von Straßendämmen.” Forschungsgesellschaft für Straßen- und Verkehrswesen, Arbeitsgruppe Erd- und Grundbau, Köln, Deutschland (1995) 27 pp. 32. “Code of Practice; Using Expanded Polystyrene for the Construction of Road Embankments.” BASF AG, Ludwigshafen, Germany (1995) 14 pp. 33. “Design and Construction Manual for Lightweight Fill with EPS.” The Public Works Research Institute of Ministry of Construction and Construction Project Consultants, Inc., Japan (1992) Ch. 3 and 5. 34. “Guidelines on the Use of Plastic Foam in Road Embankment.” Public Roads Administration, Road Research Laboratory, Oslo, Norway (1980) 2 pp. 35. “Expanded Polystyrene Used in Road Embankments - Design, Construction and Quality Assurance.” Form 482E, Public Roads Administration, Road Research Laboratory, Oslo, Norway (1992) 4 pp. 36. “Material Requirements for Expanded Polystyrene Used in Road Embankments.” Form 483E, Public Roads Administration, Road Research Laboratory, Oslo, Norway (1992) 2 pp. 37. “Quality Control of Expanded Polystyrene Used in Road Embankments.” Form 484E, Public Roads Administration, Road Research Laboratory, Oslo, Norway (1992) 4 pp.

1-19 38. Sanders, R. L., and Seedhouse, R. L., “The Use of Polystyrene for Embankment Construction.” Contractor Report 356, Transport Research Laboratory, Crowthorne, Berkshire, U.K. (1994) 55 pp. 39. Holtz, R. D., and Kovacs, W. D., An Introduction to Geotechnical Engineering, , Prentice Hall, Englewood Cliffs,NJ (1981) 733 pp.

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. Replacing the problem materials by more competent materials Removal of problem materials and replacement by suitable fill Complete excavation, partial excavation, displacement of soft materials by embankment weight assisted by controlled excavation, displacement by blasting. Increasing the shear strength and reducing compressibility of the problem materials Stabilization of soft foundation materials by consolidation By surcharge only, by surcharge combined with vertical drains, by surcharge combined with pressure relief wells or vertical drains along toe of fill. Consolidation with paving delayed (stage construction) Before paving, permit consolidation to occur under normal embankment loading without surcharge, accept post- construction settlements. Chemical alteration and stabilization Lime and cement columns, grouting and injections, soil mixing, electro- osmosis, thermal, freezing, organic. Physical alteration and stabilization; densification Dynamic compaction, blasting, vibrocompaction and vibro- replacement, sand compaction piles, stone columns, water. Transferring the loads to more competent layers Supported on deep foundations Drilled shafts, driven piles Reinforcing the embankment and/or its foundation Reinforcement Mechanically stabilized earth walls, reinforced soil slopes, soil nailing, geotextiles and geogrids, fascines, Wager short-sheet piles, anchors, root piles (minipiles). Providing lateral stability Berms; flatter slopes 1-20

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) Source of Costs EPS (expanded polystyrene)- block geofoam 0.12 to 0.31 (0.75 to 2.0) 0.01 to 0.03 35.00 - 65.00 (26.76 - 49.70)(2) Supplier Foamed portland-cement concrete geofoam 3.3 to 7.6 (21 to 48) 0.3 to 0.8 65.00 - 95.00 (49.70 - 72.63)(3) Supplier, (16) Wood Fiber 5.4 to 9.4 (34 to 60) 0.6 to 1.0 12.00 - 20.00 (9.17 - 15.29)(1) (17) Shredded tires 5.9 to 8.8 (38 to 56) 0.6 to 0.9 20.00 - 30.00 (15.29 - 22.94)(1) (18) Expanded shales and clays 5.9 to 10.2 (38 to 65) 0.6 to 1.0 40.00 - 55.00 (30.58 - 42.05)(2) Supplier, (16) Boiler slag 9.8 to 17.2 (62 to 109) 1.0 to 1.8 3.00 - 4.00 (2.29 - 3.06)(2) Supplier Air cooled blast furnace slag 10.8 to 14.7 (69 to 94) 1.1 to 1.5 7.50 - 9.00 (5.73 - 6.88)(2) Supplier Expanded blast furnace slag Not provided Not provided 15.00 - 20.00 (11.47 - 15.29)(2) Supplier Fly ash 11 to 14.1 (70 to 90) 1.1 to 1.4 15.00 - 21.00 (11.47 - 16.06)(2) Supplier Notes: These prices correspond to projects completed in 1993 - 1994. Current costs may differ due to inflation. (1) Price includes transportation cost. (2) FOB (freight on board) at the manufacturing site. Transportation costs should be added to this price. (3) Mixed at job site using pumps to inject foaming agents into concrete grout mix. 1-21