The functions of an all-weather bituminous or concrete surface for an engineered construction are varied and must be clearly understood by the design and maintenance engineer. These surfacings are impervious to surface water and protect a base and subgrade against its vertical infiltration. Conversely, such surfaces present an impervious membrane which entraps horizontal or upward moving groundwater and can easily be lifted by nominal hydrostatic forces. These surfacings provide added strength to a base course and distribute applied loads proportionately to their membrane strength as well as furnishing horizontal shearing and frictional strength to the medium they are covering (i.e., the base course). When not properly and permanently bonded to the lower medium, they serve as a high-strength, brittle membrane which, when broken, loses all of its inherent strength and thereafter acts merely as a discontinuous, strengthless, added thickness of the upper surface. Furthermore, the rupture of the upper covering provides passages for the introduction of surface water into the hitherto protected subgrade and base course. When the wearing surface is eroded, the frictional properties of the surface to resist vehicle skid become a function of the newly disclosed base course.
KeywordsRain Forest Surface Failure Public Work Traffic Control Frictional Strength
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