Dynamic probing gives a fast, continuous picture of how the ground's resistance changes with depth. A steel cone is driven into the ground and the blows for every 100mm are counted, showing where the ground firms up and where there are soft or loose layers.
A cone on the end of steel rods is driven into the ground by a standard hammer dropped from a fixed height. The number of blows needed for each 100mm of penetration is recorded and plotted against depth.
The standard, BS EN ISO 22476-2, defines several probe types, from light to super-heavy, depending on the hammer weight. The super-heavy type, DPSH, is the one most often run from window sampling rigs in UK ground investigation.
Results can be correlated with SPT N values from boreholes. The correlation is approximate and depends on the probe, the rods and the soil, so it is used as a guide rather than an exact conversion.
Dynamic probing recovers no sample, so it cannot tell you what the soil is, and results can mislead in ground with cobbles or boulders. That is why we always use it alongside window sampling, trial pits or boreholes, which show what the ground is made of.
How the ground's resistance changes with depth, including where it firms up and where there are soft or loose layers. That helps the engineer choose a foundation depth.
No. It gives no samples, so it is used with window samples or boreholes, not instead of them.
Until the probe refuses or reaches the depth required for your project.
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