Research & reports
The structural number (SN) of a road pavement is a method for describing the strength of a road pavement, in pavement deterioration models that are currently being calibrated for New Zealand road conditions. To assist in the development of these models in New Zealand, and in implementing them in pavement design software, an investigation was carried out between 1999–2000, into the sensitivity and precision of the methods of obtaining the Structural Number. The methods used are either direct, by CBR or modulus measurements of each layer in a pavement, or indirect, generally based on deflections of the entire pavement. Correlating direct against indirect methods, and the limitations of the correlations, are discussed. Spatial variability of SN on typical pavements in New Zealand, the number of tests required to characterise SNP to different levels of precision, and predicting SNP for subgrades from volcanic materials were investigated.