Comparison between laboratory and in situ values of the coefficient of primary consolidation c_v

Abstract

Many curve-fitting procedures based on the Terzaghi uncoupled consolidation theory have been proposed for the determination of the laboratory coefficient of primary consolidation, cv. This paper presents data from ten oedometer tests performed on clay samples from three different sites, with the cv values having been obtained using four different fitting procedures.The in situ settlements of the clay layers were measured using borehole extensometers. In this way the in situ cv values of the same clay tested in laboratory were determined and compared with the laboratory values. At times, the four methods show considerable differences in the values of cv determinated in the laboratory. Casagrande’s method gives values that differ from those of the other methods and is not always easily usable. The other three methods provide a more consistent evaluation of the values cv. The comparison between in situ and laboratory cv values is not straightforward, since these findings show that the macrostructure of the soil layer influences the behaviour of the whole layer, and the laboratory cv values, apart from the method used for their determination, are sometimes unable to interpret the settlement over time

Clay Slope Stability Computations/Molio Šlaito Stabilumo Skaičiavimas

“…When going deeper, the cohesion increased steadily (Figs 7 and 8). A similar picture may be seen on the graphs of h ϕ − relationship which indicate the same depth of 2 m and 2.5 m. It was assumed that at the indicated depths clay structure was already damaged and the slope would slip along the surface located at this depth in the near future (Cortellazzo 2002). Actually, the slip happened on the site in the following spring after our investigations.…”

The Impact of the Diameter to Height Ratio on the Compressibility Parameters of Saturated Fine-Grained Soils

“…The issue with the remaining methods at D/H less than 2.5 especially at D/H 0.5 was that the secondary consolidation was not clearly observed rendering difficulty in deriving c v from curve fitting procedure. Previous researcher's showed that c v obtained using Taylor's method is higher than that attained using Casagrande method and Inflection method gives quite a similar result to that of Casagrande method [2,12,20,23]. The reason being; Taylor's method is affected by the initial compression (leading to an increase in c v ) and in some cases secondary compression (decrease in c v value).…”

Compressibility characteristics of Sabak Bernam Marine Clay

“…The response of Cv to pressure increase in clays is governed by the mechanical and physicochemical factors that govern the compressibility [23]. The comparison between in situ and laboratory Cv values show that the macrostructure of the soil layer influences the behavior of the whole layer [24]. For soils that are overconsolidated, base the classification on Cr/(1+eo) Figure 12.…”