Abstract:
Pavement design is a vital part in new road construction and in rehabilitation projects. Conventional
flexible pavements are layered systems with high stress intensity on top and low intensity at the
bottom. AASHTO method is widely used by most of the road agencies to design pavements while the
Transport Research Laboratory (U.K) Road Note 31 (TRL RN-31) specifies for the tropical countries.
Both these design guidelines are based on empirical formula or experimental studies conducted in
extreme weather condition. Road Note 31 specifies the layer thicknesses of specific materials. It does
not specify a method to adopt the materials that does not fit the specifications, which is the commonly
encountered problem due to the varying site condition and availability of materials. Empirical design
methods do not have any provision for analysing road failures and propose most suitable
rehabilitation method. Therefore this research focused on evaluating the suitability of a mechanistic
empirical pavement design tool to investigate a pavement failure. In this study, failure of a Sri Lankan
rural road which is failed immediately after completing the construction was selected for the analysis.
This road was designed according to the Overseas Road Note 31(ORN 31) as a Double Bitumen
Surface Treatment (DBST) road and it has shown longitudinal cracking on the surface followed by the
depression and the settlement, approximately after six months from the completion. Heavy axle load
applied on the pavement due to transporting of construction materials to a new project has increased
the propagation of cracks and potholes. Soil samples collected from the critically damaged locations
were tested and the results showed that the inadequate strength of the pavement structure as the cause
to the failure. Failure investigations were done using a mechanistic tool called CIRCLY and reliable
reclamation method was proposed.
