Incompressible Subsoil
At a certain depth below the ground surface it is possible to specify incompressible subsoil. If the pile exceeds this specified depth the spring method cannot be used, because the pile is assumed rigid and therefore no deformation can develop in its surrounding. If there is incompressible subsoil below the pile heel but not deeper than the depth of influence zone below the heel, the depth of influence zone for the stiffness computation is reduced such that the influence zone reaches the incompressible subsoil. This way also the incompressible subsoil below the base increases its stiffness and consequently also the bearing capacity of the pile base. If the incompressible subsoil is found below the depth of the influence zone, it does not influence the analyzed pile.