The penetration in these tests is intimately related to the potential energy of the hammer (nominal energy). So, it is necessaty to understand correctly and deeply how this energy is transferred to the drive rods and how it is transmitted through the rods to the cone, to realize how the real behavior in these tests is. The penetration length really depends on the energy, not on that nominal energy, but on a portion of that energy that is effectively transferred to the rods (ENTHRU) and, in order to be more precise, the energy that reaches the cone (ENTHRU). The ENTHRU is measured by means of monitoring the upper part of the drive rods (close to the anvil). To calculate the ENTHRU it is necessary to correct the ENTHRU in three ways. First it is needed to take into account the energy loss in the energy transmission through the rods, and the energy loss due to the skin friction of the drive rods with the soil around them. It is also necessary to add the energy due to the rod weight that is penetrating into the soil.
