Soil water retention curves of a silty clayey sand compacted at different dry density

Abstract

The study of the hydraulic behaviour of compacted soils in partially saturated conditions is essential for understanding the engineering performance of geotechnical structures such as river embankments. The paper presents the results of an experimental study focusing on the effects of the initial water content and dry density on soil water retention curve (SWRC) and volume change of a compacted soil mixture under hydraulic loading. For this purpose, soil specimens compacted at different water contents(dry, wet and optimum water content), chosen on the basis of standard Proctor compaction test, were used. Specimens of a mixture composed of 70% Ticino sand (TS) and 30% Pontida silt (PON) have been tested. This is a heterogeneous mixture of sand and silt, that usually constitute the embankments of tributaries of river Po (Italy). The SWRCs along drying paths were performed by means of evaporation tests starting from the saturated conditions gained in permeameter tests. For the investigation of the change in the void index during the evaporation test, the volume variation of the tested specimens was estimated by means of a calliper and photographic comparison. Changes in the SWRCs are consistent with changes in specimen initial condition while the soil volume change exhibited at the end of evaporation test is always negligible.

Analysis of transient seepage through a river embankment by means of centrifuge modelling

“…The river embankment model was prepared by using a mixture [10][11] composed of 70% by dry weight of Ticino sand (TS4 - [12][13]), and 30% of Pontida clayey sandy silt (PON - [10,[14][15]). The grain size distributions of the testing soils are shown in Fig.…”

“…Soils used for the construction of river embankments are usually compacted to obtain adequate shear strength properties and to reduce the permeability, so the embankment model was compacted in four layers to the optimum Proctor Standard water content and dry density. The hydro-mechanical properties of the mixture are discussed in [10][11]. Mechanical and physical parameters assigned to the embankment body and foundation units according to advanced soil constitutive models are reported in [16].…”