EFFECTS OF CENTRIPETAL FORCE AND HIGHWAY DETERIORATION ON VALLEY CURVES OF NATIONAL HIGHWAYS (A CASE STUDY OF ENUGU – AWKA EXPRESSWAY)

Adinna B.O, Umenwaliri S.N. and Aginam C.H.

Department of Civil Engineering; Nnamdi Azikiwe University, Awka

E-mail adinnaboniface@yahoo.com

ABSTRACT

This paper investigated the reasons for the ever presence of many potholes and alligator cracks at valley curves in most national highways, using Enugu – Awka express way as a case study. From the ensuing studies carried out on the case – study highway, it was discovered that centripetal force increases the axle load of vehicles by about 20% – 30% for pavements on valley curves, thereby causing serious damage to pavements at valley curves. A visual contrast which was discovered during the investigation seriously underscores the findings: where a summit curve and a valley curve occurs at same location on the two-lane-dual carriage way, the lanes going uphill are often totally free from potholes, while those going downhill a rife with ever widening potholes. Based on the above findings, it was recommended that road designers should provide sufficient thickness of road surfacing and base courses to counter the effect of centripetal force at valley curves. This thickness should be minimum at the beginning of the curve and maximum at the center of the curve, i.e should increase with increasing centripetal force along the length of transition curve. This should be done without compromise to high quality of construction materials and workmanship.

Keywords: highway vertical curves, centripetal force , road pavement, potholes.