Depth Measurement.  The Dynamic Deflection Instrument™ measures the ramming deflection results from the bottom of the pier to the top.  This provides a more complete picture of pier/soil stiffness than other random sampling, compaction measurement processes, such as plate load testing or penetration testing.  The plate load test process typically only measures less than 18 feet deep*, and the penetration test measures only a few inches deep.  Depth of measurement validates compaction work and ensures that every lift of every pier meets stiffness requirements.

* Boussinesq pressure bulb theory indicates the majority of added stresses are carried 6-7 times the width of the plate, deep.  18 feet assumes a typical 30 inch round diameter plate.

Deflection Measurement.  The DDI measures stiffness, or the ability of a material to resist deformation under load, rather than density, or the weight of a material per unit volume.  An intelligence package collects data from a patented accelerometer, which measures deflections from ramming events.  The intelligence package graphs and measures the deflections relative to design deflections.
The DDI helps the operator determine when the proper level of compaction has been achieved.  Compaction levels for every lift of the aggregate pier are predetermined by the engineer and are constructed.  Recording of the construction process is made for analysis and long term construction liability control.