An important factor to consider in geotechnical engineering is the site and the variability of its mechanical properties. In situ tests are interesting investigation techniques as they do not require soil sampling. Brazilian standards consider a minimum number of in situ tests for geotechnical projects; however, this number is not always sufficient to be representative of the study site. The geotechnical variability of a tropical soil site was evaluated based on the dynamic probing light (DPL), a simple and easy to use in situ test. The statistical analysis showed that the variability associated with the DPL data is epistemic; it could be reduced by increasing the number of tests. In this study it was found that the number of tests should be at least eight. As a way to understand the effect of site variability in geotechnical design, a probabilistic analysis using the first-order reliability method was used to evaluate the probability of the prediction of bearing capacity being against safety (Pp.a.s.) for a typical pounded pile. Bearing capacity and the Pp.a.s. showed the same trend as the resistance indexes, with the formation of a plateau after the eight tests.
Herrera et al. (Thu,) studied this question.