Compressibility and consolidation properties of Santos soft clay near Barnabé Island

A geotechnical study based on characterization tests and seventy incremental loading one-dimensional consolidation tests was carried out on high-quality undisturbed samples taken from Santos Harbor Channel subsoil near to Barnabé Island, where a pilot embankment was built. The characterization profiles revealed a stratigraphy following the pattern described by Massad (2009), with a 9 m-thick fluvial-lagoon-bay sediments (SFL) clay layer. The consolidation tests were performed following two loading criteria. In criterion A (series one tests), a new loading was applied whenever the strain rate (ε) reached 10-6 s-1, the highest integer power of 10 after the “end of primary” consolidation for double drained 2 cm thick specimens. In criterion B (series two tests), the standard procedure of 24 hour-long stages was adopted. Criterion A reduced the total duration of the consolidation tests from ten to about three days. The preconsolidation (yield) stress (σ’p) and the compressibility parameters Cc and Cr obtained from “e versus σ’v (log)” compression curves of all tests are provided. Series two tests showed that the 24-hour “e versus σ’v (log)” compression curves are translated to the left of the ε = 10-6 s-1 “e versus σ’v (log)” compression curves, keeping Cr and Cc average values unchanged, but decreasing σ’p by about 8%. The SFL clay Cc/(1+e0) values obtained herein are higher than those presented by Massad (2009) due to the higher-quality samples tested in this study. It is shown that it is feasible to carry out a high-quality laboratory test program for design purposes following current standards.