Interpretation of static and dynamic penetration tests in coarse-grained soils

Abstract

The purpose of this paper is to introduce a method developed to calculate the dynamic penetration resistance qd from penetration tests without the need to resort to empirical or adjustment factors. From wave propagation analysis and the principles of energy conservation, it is demonstrated that in granular soils qd is conceptually the same measurement as the static cone penetration resistance qt. This hypothesis inherently considers that the damping resistance is negligible under the reference maximum velocities mobilised during in-situ test penetration. The development and validation of the proposed algorithm are achieved by direct comparisons between standard penetration test (SPT) and cone penetrometer test (CPT) data, which are the most commonly used in-situ tests. The method has produced preliminarily sounding comparisons between qt and qd in coarse-grained soils, but further research is required to validate the approach in contractive coarse-grained soils (strain hardening) and fine-grained deposits. It is concluded that a more rigorous interpretation of dynamic tests can circumvent some of the inherent limitations associated with the SPT. Used in combination, SPT and CPT give the necessary redundancy when assessing the critical parameters controlling the soil behaviour or when evaluating the potential for soil liquefaction.