Extracting Mechanical Properties Of Compacted Geomaterials Using Intelligent Compaction Technology

The primary tool currently used for quality management of earthwork and unbound aggregates is the nuclear density gauge (NDG) to ensure appropriate density and moisture content. Measurement of moisture content and dry density, even though quite practical and straightforward, does not directly tie the construction quality with the mechanistic-empirical design processes where stress and modulus are employed. With the recent popularity of the mechanistic pavement design procedures, research efforts have been undertaken to understand and develop procedures for implementing modulus-based quality control (QC) procedures of compacted geomaterials. These procedures involve the use of in-situ nondestructive testing (NDT) devices that estimate the stiffness parameters of a constructed pavement structure. However, one of the shortcomings of NDT spot testing is that weak areas may be missed. If implemented properly, intelligent compaction (IC) can provide QC over 100% of compacted materials (a major shortcoming of the spot testing). Furthermore, the uniformity of compacted earthwork can be realistically assessed with accelerometer-based IC measurement values (ICMV). Another possible benefit is the instant identification of weak areas that need to be reworked. IC technology takes advantage of a vibratory roller equipped with accelerometers mounted on the drum\u27s axle, a global positioning system (GPS), and an on-board computer reporting system that displays IC measurements in real time. Despite the tremendous efforts to investigate the application of the IC technology in the construction QC, there are still gaps that prevent the IC technology from being used for the eventual construction acceptance of the geomaterials. These gaps include (1) the need of relating the design parameters to the construction QC parameters and the in situ moisture content, and (2) the absence of rational means of relating different proprietary ICMVs reported by different roller vendors. To address these issues, there is a need for field-calibrated numerical models that can be used for the proper evaluation and acceptance of the compacted geomaterials. A realistic numerical model for a roller-soil system can be combined with a state-of-the-art inverse or backcalculation algorithm to provide reliable layer-specific ICMV for construction QC and potentially acceptance. However, this process must be robust and practice-ready so that DOTs can readily incorporate it in their IC specifications