Designing low-volume roads using the dynamic cone penetrometer

The paper describes an environmentally optimised approach to the design of low-volume roads (LVRs) in which the in situ strengths of the subgrade and pavement layers at the anticipated in-service moisture condition are used for design rather than soaked values. It describes how the assumptions and simplifications inherent in the more traditional California bearing ratio (CBR)-based methods of design tend to produce less-than-optimum solutions compared with the dynamic cone penetrometer (DCP) method. DCP measurements are much more reliable than CBR measurements and are also quick to perform; hence, a relatively large number of measurements of subgrade strengths (for new roads) and pavement layer strengths and thicknesses (for upgrading projects) can be obtained, thereby reducing risks of inadequate data for design purposes. Research has shown how material specifications for LVRs can be relaxed and the paper shows how this aspect is integrated into DCP design methods. The paper reviews the alternative methods of DCP design, summarises the advantages of these methods and recommends some improvements.