Laboratory Evaluation of GeoGauge for Compaction Control

The use of nuclear methods for compaction control is increasingly problematic for state highway agencies. Regulatory and safety issues have prompted agencies such as the New Mexico State Highway and Transportation Department to look for nonnuclear alternatives for compaction control. A laboratory evaluation of one such commercially available device, known as the GeoGauge, is described. The GeoGauge measures soil stiffness, arguably a more viable engineering parameter than moisture—density measurement. The GeoGauge was found to measure soil stiffness as advertised. Results relating moisture, density, and stiffness were found to be consistent with earlier research on compaction and mechanical strength of soils. However, because of the dynamic nature of the measurement obtained with the GeoGauge and associated boundary constraints, the ability to obtain a target value for stiffness in the laboratory has proved to be elusive. Because of the promising nature of the GeoGauge technology, and because it measures a true engineering mechanical property, a paradigm shift may be necessary for its implementation in field compaction control. Future specifications for compaction using this technology may require specific controls of moisture and compaction equipment with stiffness monitoring via the GeoGauge.