The Impact Efficiency Obtained from Static Load Test Performed on the SPT Sampler

Abstract

The aim of this paper is to show how to obtain the impact efficiency from a static load test performed on the standard penetration test (SPT) sampler. In a dynamic test, the maximum resisting force developed during the hammer impact depends on the displacement (static component), velocity (damping component) and acceleration (inertial component). At the instant corresponding to the dynamic test end, experimental data show that the elastic potential energy is negligible. As a consequence, the work done is almost equal to the potential energy stored in the system. Similarly, in a static load test performed on the sampler right after the dynamic test, the elastic potential energy is also negligible. As a consequence, the work done is almost equal to the potential energy stored in the system. Thus, in both tests, the maximum penetration of sampler into the soil is permanent. Additionally, it was verified that the potential energy stored in dynamic test is almost equal to the potential energy stored in static test, for the same value of sampler penetration. Thus, the efficiency can be obtained dividing the system potential energy by the SPT nominal potential energy (474 J).