Access Tube Installation For Nuclear Depth Gages

Contract research to measure subgrade moisture variations under Oklahoma highways with nuclear depth moisture and density gages required development of special procedures to install nuclear gage access tubing. A pickup truck mounted drilling unit was designed to core pavement and power a specially-designed auger in heavy Oklahoma clay subgrades. Procedures for field test site location and installation, as well as initial nuclear data collection, are described. The methods were successful as 50 field test sites have been installed in north central and northeastern Oklahoma. A 4-hr to 6-hr on-pavement working time was required to core pavement, install three access tubes at each site, and collect initial nuclear data. Maintenance and downtime of the drilling equipment was negligible. Periodic data collection is now underway at all field test sites.