Continuous Monitoring of Subgrade Stiffness during Compaction

In the traditional compaction procedure of pavement subgrade, the level of compaction is checked through spot measurements of density and moisture contents at some selected locations. Such tests can leave soft spots undetected and could result in the premature failure of the pavement. In the intelligent compaction (IC) procedure, the compaction level of the entire compacted area can be estimated in real-time. The University of Oklahoma has developed one intelligent compaction tool known as Intelligent Compaction Analyzer (ICA). This paper presents two field demonstrations for evaluating the ICA in continuously measuring the dry density and modulus of stabilized subgrades. In the first study, it was demonstrated that the ICA can estimate the subgrade density comparable to Nuclear Density Gauge (NDG) measured density. The second project verified the ability of ICA in estimating the modulus of the stabilized subgrade. The ICA estimated moduli correlates well (R² = 0.63) with the resilient moduli. The findings from these two demonstrations suggest that the ICA is capable of continuously measuring the density or modulus during the compaction of subgrade. Such real-time estimates of the subgrade stiffness can aid roller operators obtaining better overall quality by identifying and remediating under-compacted areas during the construction process.