DENSITY AND STIFFNESS RESULTS FOR THICK LIFT SECTIONS

摘要

A survey of state Departments of Transportation showed that most states limit the compacted thickness of a single lift of unbound aggregate base or subbase course materials to eight inches or less. Recently completed test sections demonstrate the feasibility of adequately compacting thicker single lifts. Test sections were constructed in Georgia, using crushed granite, and in Texas, using crushed limestone. Vibratory sheepsfoot and vibratory smooth drum rollers were in construction. Nuclear Density Gauges (NDG) and the seismic procedure, Spectral Analysis of Surface Waves (SASW), were employed to determine densities, moisture contents, and layers stiffnesses. Test results indicated that for single lifts of 13-in. thick, at least 100% of maximum dry density could be obtained throughout the layer. Density results and stiffness results identified the disturbance caused by the compaction effort to the upper few inches of the lift. Moisture effects on stiffness were documented by significant increases in seismic velocities (and, hence, stiffness) as the materials were allowed to dry. Similarly, stiffness decreased as moisture contents increased. Small changes in moisture content had negligible effect on density with larger effect on stiffness.