Standard Penetration Tests (SPT) shall be performed in boreholes in order to estimate consistency, relative density, and strength-deformation parameters of soils. In addition to this soil samples
obtained from SPT testing are used for classification purposes. SPT testing can also be carried out in weak weathered rock. The SPT testing shall be performed at certain numbers and respective intervals (it is common to apply an interval of 1.5m/test) to the borehole depth termination for all boreholes. The number of blows required to 15cm of penetration or fraction thereof is to be recorded. The first 15cm is to be considered as a seating drive. The number of blows required for the second and the third 15cm penetration is termed as “standard penetration resistance” or the raw “N value”.