Geofoam Applications in the Design and Construction of Highway Embankments (2004) / Chapter Skim
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4-1 CHAPTER 4 PAVEMENT SYSTEM DESIGN Contents Introduction ................................................................................................................................................. 4-1 Benefits of a Thicker Pavement System......................................................................................................
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4-2 polystyrene (EPS) blocks.
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4-3 preliminary pavement system thickness and material unit weights to utilize for preliminary external and internal stability analysis are provided. Table 4.1.
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4-4 underlying layers is primarily accomplished by increasing the thickness of selected upper layer(s)
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4-5 thickness depends on the unit weights of the pavement materials and the pressure magnitude and footprint area of the vehicle tire. Differential Icing Lightweight fill materials, especially non-earth type of materials, have thermal properties that differ from earth materials.
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4-6 Because using base and/or subbase materials with fines affects the structural quality of the base and/or subbase and due to the lack of standardized tests to determine thermal properties of nonearth materials as well as the lack of a thermal design procedure that considers pavement material thickness and composition, it is recommended that a sufficient thickness of soil between the top of the EPS mass and the top of the pavement surface be used. Based on the minimum recommended pavement system thickness from the Norwegian design guidelines (5,8)
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4-7 anticipated that the greater the distance between the top of the pavement and top of the EPS mass, the less of an increase in pavement surface temperature. Accommodation of Utilities and Road Hardware Shallow utilities and road hardware (barriers and dividers, light poles, signage)
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4-8 pavement system thickness. However, the predominant practice in the U.S.A.
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4-9 • To enhance the overall performance and life of the pavement system by providing reinforcement, separation, and/or filtration. A separation layer used for these purposes is, technically, part of the pavement system.
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4-10 system thickness. In later designs, the PCC slab was also used for the function of a barrier against potential petroleum spills.
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4-11 The following is an assessment of the various separation layer alternatives that have either been used or proposed for use over the approximately 30 years that EPS-block geofoam has been used as lightweight fill for road embankments. They are listed in an approximate order of increasing complexity of construction (and, therefore, probable increasing cost)
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4-12 potential for geomembrane holes. However, the geomembrane surface should not be horizontal because liquid (including surface water infiltrating through the pavement system)
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4-13 geomembrane)
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4-14 the long-term development of cracks in PCC slabs is not uncommon. Additional problems with using a PCC slab include sliding of the slab during an earthquake (the Japanese require L-shaped reinforcing bar dowels cast into the slab and penetrating down into the EPS blocks)
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4-15 settlement of the pavement system. A separation layer to prevent migration and filtration of the finer soil particles from the unbound layer(s)
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4-16 a risk analysis by obtaining petroleum spill occurrence data from a transportation agency or the Environmental Protection Agency (EPA)
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4-17 Results of field studies of flexible pavement systems over EPS-block geofoam are available in (9,16-20)
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4-18 recommended that the modulus of elasticity of unbound materials placed directly over EPS blocks be reduced by up to 50 percent in design.
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4-19 However, it is anticipated that the revised AASHTO 1993 design procedure will include mechanistic-empirical procedures. The Dutch pavement design procedure is based on the Shell Pavement design procedure (22)
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4-20 performance data of pavements over geofoam in the U.S. becomes available, the typical design methods used in the U.S.
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4-21 Highway Officials) road test was 4.2 for flexible pavements.
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4-22 1993 flexible pavement design procedure by determining a suitable layer coefficient to represent the PCC slab.
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4-23 Table 4.4. Standard Set of Inputs for Sensitivity Analysis.
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4-24 for an asphalt concrete thickness of 102 mm (4 in.)
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4-25 • The procedure is based on the use of dowels at transverse joints. • The range of traffic loads for the performance period is limited to between 50,000 and 1,000,000 applications of 80 kN (18 kip)
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4-26 • Low 50,000 to 300,000 • A factor termed the "loss of support" factor is included in the AASHTO rigid pavement design procedure to account for the potential loss of support resulting from base and subbase erosion and/or differential vertical soil movements. Loss of support factors for typical base and subbase materials range between 0 and 3.
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4-27 histories for which pavement thickness data is available, the total pavement system thicknesses range from 508 to 864 mm (20 to 34 in.) and average 660 mm (26 in.)
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4-28 dry unit weights based on the ASTM D 698 laboratory procedure indicated in (26) and a compaction effort of 97 percent of the maximum dry unit weight.
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4-29 recommended pavement system thickness of 610 mm (24 in.) was maintained.
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4-30 average unit weights are based on a 610 mm (24 in.) overall pavement system thickness and lowvolume traffic, which is defined in (23)
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4-31 Regardless of the design process used, the goal of the pavement design should be to use the most economical arrangement and thickness of each material to protect the pavement from distress caused by both traffic loads and the environment (1)
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4-32 5. Horvath, J
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4-33 23. American Association of State Highway and Transportation Officials, AASHTO Guide for Design of Pavement Structures, 1993, , American Association of State Highway and Transportation Officials, Washington, D.C.
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FIGURE 4.1 PROJ 24-11.doc Resilient Modulus (MPa)
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FIGURE 4.2 PROJ 24-11.doc EPS Density (kg/m3)
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TABLE 4.1 PROJ 24-11.doc Design Values of Engineering Parameters Proposed AASHTO Material Designation Minimum Allowable Full Block Density, kg/m3(lbf/ft3)
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TABLE 4.2 PROJ 24-11.doc R EPS Type Traffic Level (%) Low Medium High 50,000 300,000 400,000 600,000 700,000 1,000,000 50 EPS50 4*
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TABLE 4.3 PROJ 24-11.doc Minimum Thickness , mm (in.) Traffic, ESALs Asphalt Concrete Aggregate Base Less than 50,000 25 (1.0)
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TABLE 4.4 PROJ 24-11.doc Variable Initial or Constant Input Value (18-kip) ESALs Over Initial Performance Period 1,000,000 Initial Serviceability 4.2 Terminal Serviceability 2.5 Reliability Level (%)
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TABLE 4.5 PROJ 24-11.doc EPS Type Total Crushed Stone Thickness mm (in.)
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TABLE 4.6 PROJ 24-11.doc LOAD TRANSFER DEVICES No Yes EDGE SUPPORT No Yes No Yes S'c MPa (lbs/in2)
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TABLE 4.7 PROJ 24-11.doc LOAD TRANSFER DEVICES No Yes EDGE SUPPORT No Yes No Yes S'c MPa (lbs/in2)
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TABLE 4.8 PROJ 24-11.doc New York: State Route 23A, Town of Jewett, Greene County: 230 mm (9 in.) asphalt pavement 381 mm (15 in.)
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TABLE 4.9 PROJ 24-11.doc Material Layer Coefficient (1) Unit Weight kN/m3 (lbf/ft3)
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TABLE 4.10 PROJ 24-11.doc Crushed Sandy No PCC Slab Separation Layer 4-In PCC Slab Separation Layer 6-In PCC Slab Separation Layer Asphalt Stone Gravel Avg.
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TABLE 4.11 PROJ 24-11.doc PCC Crushed Slab Stone Avg. Thickness Subbase Stress Density mm (in.)
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