Establishing a Mechanistic/Incremental Design Method for Semi-Rigid Pavements through HVS Testing

Abstract

Highway pavements with cement treated bases (CTB) have been disfavoured in Danish construction practice since the end of the 1970's, after a number of projects experienced premature reflective cracking. However, after surveys in 2002-3 had shown superior performance of other pavements with CTB layers, especially on heavily trafficked sections, interest was resurrected. The motivation was partly the need for long-life pavements on critical network links, but also a desire to promote competition to the flexible-pavement construction industry. In 2003 a research consortium was formed to carry out a full-scale test on 6 semi-rigid pavements - 3 types, each replicated. The test was carried out to establish deterioration models and fatigue design criteria for cement- and similarly stabilized layers. 3 of the pavements were instrumented to provide data on critical strains and stresses. Fatigue loading was carried out with a Heavy Vehicle Simulator, and bearing capacity development was monitored through Falling Weight Deflectometer (FWD) and Light Weight Deflectometer (LWD) loading. During loading, the bearing capacity of the stabilized layer decreased at a steadily slowing rate, which could be described through a single, generalized incremental-recursive model based on tensile strain in the bottom of the layer. The deterioration model was verified against data derived from existing, heavily trafficked motorways that had been in service for more than 20 years, and it was found that the model was accurate without any shift factors. On this basis are established new, traditional mechanistic design criteria as well as incremental-recursive models that will go into Danish pavement design standards.