The Shell pavement design method was used in many

countries A country is a distinct part of the Earth, world, such as a state (polity), state, nation, or other polity, political entity. When referring to a specific polity, the term "country" may refer to a sovereign state, List of states with limited r ...

for the design of new pavements made of

asphalt Asphalt most often refers to: * Bitumen, also known as "liquid asphalt cement" or simply "asphalt", a viscous form of petroleum mainly used as a binder in asphalt concrete * Asphalt concrete, a mixture of bitumen with coarse and fine aggregates, u ...

. 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

soil Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...

parameter A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when ...

s, parameters (thickness and stiffness) for the other road foundation 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 The American Association of State Highway and Transportation Officials (AASHTO) is a standards setting body which publishes specifications, test quality control, protocols, and guidelines that are used in highway design and construction through ...

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