3325
Predicting long-term settlements of coastal defences for the safeguard
of the Venetian Lagoon
Évaluation des tassements de consolidation secondaire des structures côtières de protection
pour la sauvegarde de la lagune de Venise
Ton L., García Martínez M.F.
DICAM, University of Bologna, Italy
Simonini P.
DICEA, University of Padova, Italy
ABSTRACT: Over the last decades, a number of engineering solutions, including both nearshore and offshore structures, have been
designed in order to protect human activities of the whole Venetian coastal environment as well as the invaluable historical and
artistic heritage of Venice (Italy) from sea storms, high tides and recurrent flooding. In recent years, in the context of the ambitious
mobile barriers system project known as MOSE, the existing jetties were extended and new breakwaters were set up in front of the
three inlets connecting the lagoon to the Adriatic Sea. In order to preserve integrity as well as effectiveness, a key issue in the design
of such structures is represented by the estimate of both short-term and especially long-term settlements. Indeed, field observations as
well as laboratory evidence have shown that time-dependent phenomena cannot be considered as negligible in the predominantly silty
sediments forming the Venetian lagoon basin. This paper focuses on the prediction of the long-term response of Venetian coastal
defences, using a one-dimensional settlement method in conjunction with a
C
profile determined by piezocone tests and based on a
formulation recently calibrated on field data from a Test Site located in the Venetian lagoon area.
RÉSUMÉ : Au cours de ces dernières décades, plusieurs mesures de protection contre la marée haute et les fréquentes inondations ont
été mises en œuvre afin de protéger la ville historique de Venise (Italie) ainsi que les activités des communautés qui se sont
développées au long de la lagune vénitienne. Récemment, lors du projet MOSE, qui consiste en un système de barrières mobiles
placées auprès des trois bras de mer reliant la lagune à la mer Adriatique, les jetées existantes ont été remodelées et prolongées et de
nouvelles structures de protection ont été construites. L’évaluation des tassements dus à la consolidation primaire et surtout
secondaire est essentielle pour que ces ouvrages soient efficaces et en bon état au long des années. En effet, des études en laboratoire
ainsi que des observations en place ont mis en évidence la contribution élevée de la consolidation secondaire aux valeurs totales des
tassements des sols limoneux du bassin de Venise. Dans cet article on présente un calcul de tassement de consolidation secondaire
d’un brise-lame, à l’aide d’une méthode qui permet d’évaluer
C
à partir des essais de pénétration statique (CPTU). La corrélation
utilisée a été récemment établie sur une base de données assemblée auprès de la station d’essai de Treporti, située dans la lagune de
Venise.
KEYWORDS: piezocone tests (CPTU); silt; sand; secondary compression; coastal defences; Venetian lagoon.
1 INTRODUCTION
Over the last decades, a number of engineering solutions,
including both nearshore and offshore structures, have been
constructed in order to protect human activities of the whole
Venetian coastal environment as well as the invaluable
historical and artistic heritage of Venice (Italy) from sea storms,
high tides and recurrent flooding.
First in the late 19th century, several long jetties were built at
the three inlets (Lido, Malamocco, Chioggia) connecting the
lagoon to the Adriatic Sea (Figure 1). More recently, in relation
to the ambitious project known as MOSE, consisting on a
mobile barriers system for the temporarily closure of the lagoon
inlets, the existing jetties were extended, reinforced and finally
reshaped, new breakwaters were built in front of the inlets and a
small island was realized within the Lido inlet.
In order to preserve both integrity and effectiveness, a key
issue in the design of such structures is represented by the
estimate of both short-term and especially long-term
settlements, being the unexpected or underestimated reduction
in the structure height a probable cause of flooding. Indeed,
field observations as well as laboratory evidence have shown
that time-dependent phenomena cannot be considered as
negligible in Venetian sediments, hence the proper evaluation of
the relevant parameters is of crucial importance for settlement
predictions.
This paper focuses on the prediction of the long-term
response of Venetian coastal defence structures, using a one-
dimensional settlement method in conjunction with a secondary
compression coefficient
C
profile determined from piezocone
test data.
The approach is based on a formulation recently calibrated
on field data assembled during approximately 6 years at the
Treporti Test Site (
TTS
, Venice), within an extensive research
Treporti Test Site
Venice
LIDO
INLET
MALAMOCCO
INLET
CHIOGGIA
INLET
Figure 1. Satellite view of the Venetian lagoon.
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t f
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f r t f
r
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ti
v lu tio s t ss
ts c s lid tio s c ir s str ct r s c tièr s r t ctio
r la s v r la la
is
onni L., García Martínez M.F.
IC , University of Bologna, Italy
imonini P.
IC , University of Padova, Italy
