The study of pavement design of Nairobi-Thika highway

Abstract

Highways (Roads) perform a very useful role in meeting the strategic and developmental requirements, accelerating all round development. Technological progress in road construction technology has kept pace with rapid changes in the field of infrastructural development. In Kenya, the projected (20 year design) traffic loads on most sections of Nairobi-Thika Road (A2) surpass the highest traffic classes stipulated in the Ministry of Roads (MoR) Road Design Manual (RDM) Part III, Materials and Pavement Design for New Roads. Over the years, there has been a significant change in vehicle volumes and designs. Current heavy and medium goods vehicles are designed to carry more axle loads as compared to 40 years ago. There is also a significant change in the spectrum of loads carried by these vehicles. This has effectively changed the repetitions of axle loads and magnitude of damage caused by the vehicles on the roads. A lot of research has previously been carried out on the Nairobi-Thika Road and documented. Based on this research and the fact that this road is currently undergoing improvement, this provides a good case for study as current vehicle volumes, axle loads and design could be used to compare with the scenario that existed 40 years ago. This research involved a study of both alignment soils and axle load data of the Nairobi-Thika (A2) Road. The objectives of the study were to establish the variation of engineering properties of soils with depth particularly at the deep cut sections, to establish axle load data for the Nairobi-Thika Road and to compare year 2011 axle loading with the 1971 axle load.