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Pages 6-19

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From page 6...
... 6 Early literature on road building offers some clues about when and how people became aware that excessive moisture in pavement structures is detrimental to pavement performance.
From page 7...
... Literature Review 7   The Industrial Revolution of the late 18th and early 19th centuries, which began in Great Britain, brought, among its many technological innovations, powerful new ways of moving people and goods, including the steam locomotive and gasoline-powered automobiles and trucks. The Industrial Revolution also brought about unprecedented population growth and an explosive growth in trade, both of which resulted in enormously increased volumes of traffic on roads.
From page 8...
... 8 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance Source: Adapted from Cedergren et al.
From page 9...
... Literature Review 9   • Longitudinal edge drains, if present (i.e., if the permeable base layer is not daylighted to a side ditch) , placed in backfilled trenches along the pavement edge on one or both sides, depending on the geometry of the pavement cross section; • Outlet pipes that drain the longitudinal edge drains to the ditches; and • Headwalls to protect the ends of the outlet pipes.
From page 10...
... 10 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance full-scale field tests. The comparisons showed that the proposed formulas were satisfactory for use in the design of base drainage.
From page 11...
... Literature Review 11   1974) and the crack inltration approach (Ridgeway 1976)
From page 12...
... 12 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance and the emergence of new types of edge drains and lter materials, as reected by the development of prefabricated underdrains (e.g., Healy and Long 1971) and criteria for the use of lter fabrics (Bell and Hicks 1980)
From page 13...
... Literature Review 13   effects that moisture can have on asphalt, concrete, granular base, and subgrade layers; described case studies of drainable systems constructed as experimental pavements; and offered recommendations for the design of aggregate mixtures to achieve a balance between stability and drainability. In 1992, the FHWA published the results of a study titled Drainable Pavement Systems, commonly referred to as Demonstration Project 87, or more briefly as Demo 87, to provide guidance for the design of subsurface drainage systems to remove infiltrated water from pavement structures.
From page 14...
... 14 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance of subsurface drainage, the preponderance of data show a direct relationship between improved performance and extended pavement life." NCHRP Synthesis 239 does, however, acknowledge that the degree to which subsurface drainage systems may benefit pavement performance and be cost-effective also depends on whether their use is warranted, given decision factors that include climate conditions, subgrade permeability, and traffic levels. Cited research suggests that pavement subsurface drainage systems may not be beneficial at locations with subgrade permeabilities of more than about 10 ft/day (Grogan 1992)
From page 15...
... Literature Review 15   Video inspection prior to acceptance was identified as the only effective means of detecting construction-related problems with edge drains, such as crushing of pipes. Among the recommended post-acceptance inspection and maintenance practices were the following: • Regularly scheduled visual inspection of outlets and headwalls; • Periodic video inspection of longitudinal pipes and outlets; • Observation of water flow from outlets after storm events or during flow testing (e.g., pouring water on the pavement surface using a water truck)
From page 16...
... 16 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance province, as well as additional data on about 300 AC and PCC pavement sections in the FHWA's Rigid Pavement Performance and Rehabilitation database and the SHRP's LTPP database. However, pavement sections from the LTPP Specific Pavement Studies (SPS)
From page 17...
... Literature Review 17   Source: Hall and Crove 2007. ll Figure 5.
From page 18...
... 18 Subsurface Drainage Practices in Pavement Design, Construction, and Maintenance pavements -- namely, deflection response, roughness, rutting, faulting, and cracking -- were found to be influenced by the stiffness, not the drainability, of the base layers. Overall, the best- performing AC pavements in the SPS-1 experiment were those with the stiffest bases (densegraded asphalt-treated base layers)
From page 19...
... Literature Review 19   less than 20 percent of the edge drain outlets of the concrete pavements surveyed were damaged, approximately 65 percent were blocked to some degree; and (b) while less than 10 percent of the edge drains of the asphalt pavements surveyed were damaged, approximately 45 percent were blocked to some degree.

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