Development of a Calibration System for the Laboratory Proctor (Soil Density) Mechanical Compaction Hammer

摘要

Existing techniques used to calibrate soil compaction equipment do not measure the overall imparted energy into the soil. Instead, various parameters (i.e., drop height, shoe weight, etc.) are measured independently and hence one is forced to assume that the theoretical energy is mobilized. Since the results of the Proctor density tests are critical to field compaction control, a calibration system is needed to ensure consistency in the equipment used by the Florida Department of Transportation (FDOT), consultant, and contractor testing labs. A new portable calibration device has been developed that measures rammer speed and base system forces during impact, and outputs and kinetic energy off the rammer. The calibration was used to test 30 compactors in the state of Florida and it was discovered that the statistical variance of the data was acceptable. However, there was a trend indicating a lower than acceptable available energy for compaction. The results of the study will be used by labs to check and adjust their equipment so that results from disparate labs can be used with increased confidence. FDOT's Independent Assurance Inspection teams will also be able to provide a performance-based check.