The Shell pavement design method was used in many

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for the design of new

pavements Pavement may refer to: * Pavement (architecture), an outdoor floor or superficial surface covering * Road surface, the durable surfacing of roads and walkways ** Asphalt concrete, a common form of road surface * Sidewalk or pavement, a walkway al ...

made of

asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...

. First published in 1963, it was the first mechanistic design method, providing a procedure that was no longer based on codification of historic experience but instead that permitted computation of strain levels at key positions in the pavement. By analyzing different proposed constructions (layer materials and thicknesses), the procedure allowed a designer to keep the tensile strain at the bottom of the asphalt at a level less than a critical value and to keep the vertical strain at the top of the subgrade less than another critical value. With these two strains kept, respectively, within the design limits, premature fatigue failure in the asphalt and rutting of the pavement would be precluded. Relationships linking strain values to fatigue and rutting permitted a user to design a pavement able to carry almost any desired number of transits of standard wheel loads. In such structural road design, the main inputs consist of

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s, parameters (thickness and stiffness) for the other road

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materials, and the expected number of times a standard load will pass over. The output of the calculation is the thickness of the asphalt layer. Originally published for highway design, it was expanded to include a procedure for airfields in the early 1970s. New criteria were added in 1978. The approach put forward in the Shell pavement design method formed the basis for most early mechanistic structural road design methods, while the AASHTO Mechanistic Empirical Design Guide (the 'MEPDG'),AASHTO, 2008, Mechanistic-empirical pavement design guide: A manual of practice first published in 2004, is, in effect, a modern successor.

References

Pavements Pavement engineering {{road-stub

See also

References