Principles Of Pavement Design

The purpose of this review will be to identify and discuss what are the effects, reasons and benefits for each use of the three main design principles in pavement designs.

Due to thorough research and intense reviews, the standards and principles are controlled in the designing of pavements. Methodologies and skills have been founded and created by many research faculties and organisations to achieve good road designs. Taking into account that there are many important factors that are valuable at improving the designs.

The design ideology for pavements at present are the empirical, mechanistic and the mechanistic-empirical design method and are fairly common. These principles have been devised to provide a basis and guideline to designing

The first study is the environmental deliberations where the climatic region (Draft TRH4, 1996) is ascertained and used to conclude the conditions the road will operate within as well as the subgrade conditions. The environmental effects are usually more visible on lower traffic volume roads because of the weaker pavement structure.

The second study is the assessment of the sub-grade conditions. The strength of the subgrade should be established to assess if it can endure the loading as well as to assess the design of the subsequent structural layers. The subgrade strength can be assessed by doing soil analysis, DCP tests, CBR tests, deflection tests, coring, etc. These tests will help assess the subgrade and verify its resilient modulus.

The third study is the focussed on traffic loading. The number of wheel loads and its collective illustration is translated into a single number which is the equivalent single axle load (ESAL). The ESAL is hence thought to be an illustration of what traffic loading should be in extreme traffic conditions. The degree of traffic loading on a road will establish the class of pavement to be constructed. Roads with low traffic volumes normally have approximately between 0 – 220 vehicles per lane, per day, per direction, (Draft TRH4, 1996). Hence the pavement class will be designed for light traffic. From then on the growth of traffic can also be established

The choice of the pavement type is decided by the amount of traffic loading which is applied to the road. Roads with low traffic volumes do not have high traffic loading and hence do not need a pavement with a high bearing capacity.

As the subgrade material has been investigated, a corrective measure can be decided. In cases where the subgrade is very weak and has a low bearing capacity, the material is required to be treated, to be strengthened or superior material must be brought in. In the case of roads with low traffic volumes, it is assumed that the structural layers should be supported by G9/G10 (TRH4, 1996) quality