A dynamic probe is a cylindrical steel sacrificial or fixed cone which is driven vertically into the ground using a high frequency percussive hammer. The cone diameter and angle will depend upon the chosen method. For example the heavy or super heavy dynamic probe has a cone angle of 90 degrees.
The cone is attached to a 1m section steel rod with a diameter of approximately 0.035m and graduation markings at 0.10m intervals. Depending upon the chosen method, the drop height can be adjusted. The super heavy method is generally the preferred choice, with a drop weight of 63.5kg and a drop height of approximately 0.75m.
Blows are recorded every 0.10m and after every 1m a torque reading is recorded, a further rod is then added and the process is continued until the probe refuses to penetrate the ground or the test reaches the target depth.
The results can be directly correlated to a standard penetration test 'N' value. The results are plotted on a graph, providing a visual interpretation of the different soil strata encountered.