Evaluation of internal and external stresses on the SPT sampler

Abstract

The NSPT index is usually used in empirical correlations to estimate parameters of the soil, carrying capacity, foundation settlement, etc. Because these correlations have no scientific basis, researchers have been developing rational methods of analysis, based on energy concepts. The amounts of energy involved in the SPT test are evaluated by the EFV method. With force and acceleration records, amounts of energy, equipment efficiency, experimental dynamic reaction force of the soil and stresses acting on the sampler were assessed. In this study, a sample extractor system was designed, which consists of a base, a hydraulic cylinder and a load cell. The objective of this equipment is to experimentally quantify the internal friction force, allowing the stresses acting on the sampler to be evaluated. Also, the Aoki's a parameter, which is the ratio of internal friction and external friction between the ground and the sampler, could be calculated.