Geotechnical characterization and properties of Venice lagoon heterogeneous silts

Abstract

The worldwide-known historic city of Venice continues to preserve a rather precarious equilibrium with the surrounding lagoon, although the margin of security is being eroded at an ever increasing rate. The rate of environmental deterioration is being accelerated by the increasing frequency of the flooding of the historic city -referred as to 'acqua alta' (i.e. literally 'high water') -caused by the natural eustatic rise of the sea level, by natural subsidence and by a regional man-induced subsidence, the latter particularly important between 1946 and 1970(Butterfield et al. 2003. Figure 1 shows the Venice lagoon in the present configuration: through the inlets of Malamocco, Lido and Chioggia flows the tide, becoming, under particular atmospheric conditions, acqua alta, that means flooding of the historic city.The first comprehensive geotechnical and geological studies on Venice lagoon soils were carried out between 1965 and 1975. Mineralogical and paleontological studies on sediments from the site Motte di Volpego (Figure 1) were performed by Bonatti (1968). In 1970 the Italian Government through the Consiglio Nazionale delle Ricerche (CNR) commissioned a 1000 m deep borehole, located at Tronchetto (Figure 1) to estimate the aquifer and aquitard system and the geotechnical properties relevant to an evaluation of the subsidence problem (Favero et al. 1973;Rowe 1973;Ricceri & Butterfield 1974).Between 1970s and 1980s, the shallowest ground of the lagoon has been extensively studied, but only through standard geotechnical investigations necessary for the design of the foundations of new large industrial settlemements on the mainland.Relevant information on the mechanical behaviour of lagoon clayey/silty materials sampled at Fusina (Figure 1), a small village facing to the inner lagoon where a thermoelectric power plant is located, was also provided by Cola (1994).To protect the city of Venice and the surrounding lagoon against the recurrent flooding, a huge project was undertaken at the beginning of the '80s under the directive of Italian

In-situ loading experiments reveal how the subsurface affects coastal marsh survival

“…3d). Interpretation of the displacement records at the trial embankment in Treporti 61 provided C α = 10 −3 − 4 × 10 −3 , one order of magnitude less than the values from the loading experiment. Long-term projections of coastal marsh resilience to RSL rise should not neglect the importance of subsurface processes and the effects of autocompaction.…”

A Critical Review of Cone Penetration Test-Based Correlations for Estimating Small-Strain Shear Modulus in North Sea Soils

“…The sediments are mainly of Pleistocene age. The silts have been extensively studied in the context of coastal defence for the city of Venice [40].…”