Experimental Investigation of the Depth of Influence of Simultaneously Recorded Compactometer and Machine Drive Power Measurements

One potential drawback with Continuous Compaction Control (CCC) systems is their depth of influence relative to traditional in situ tests, which can make it more difficult to adopt these systems into current earthwork quality assurance/quality control specifications. An experimental study was conducted to investigate the depth of influence of two commercially available CCC measurements, one machine power-based measurement (Machine Drive Power, MDP) and one vibratory-based measurement (Compactometer Value, CMV) that were simultaneously recorded from the same compaction roller instrumented with a CCC data acquisition system. The experimental study involved the construction of a full-scale earthen embankment that was constructed in several lifts, where an underlying weak zone was instrumented at the bottom of the embankment. This approach enabled the authors to investigate the influence of the underlying weak zone on the resulting MDP and CMV measurements that were recorded by the compaction roller as the embankment was being constructed. Results from the experimental investigation revealed that MDP measurements were not influenced by the underlying weak zone, even at depths as shallow as 30 cm. However, CMV measurements were significantly influenced by the underlying weak zone (e.g., recorded CMV values were significantly lower relative to CMV measurements made along other sections of the embankment) at depths as deep as 1.2 m. The results and discussion presented in the current study are useful for understanding the variable nature of CCC measurements, even when recorded from the same compaction roller, and have practical implications for implementing CCC measurement systems within an earthwork construction specification framework.