The natural Venice lagoon dam has been completely eroded in some places and then replaced by artificial breakwaters called "Murazzi". These structures, built between 1739 and 1792, are made up of different thickness walls protected by means of large rock blocks. The breakwaters are mostly subjected to sea-storm action and sea erosion. The dynamic structure stability has been analysed by means of a Distinct Element Model. The numerical model has been validated by the comparison with water pressure measurements carried out on a physical model. The calibrated DEM model has been subjected to increasing sea storm loads in dynamic conditions in order to evaluate break water limit conditions.


la jetee naturelle qui delimite les lagunes de Venise a ete dans aucunes traites erodee et remplacee avec des structures artificiclles applees "Murazzi". Ces structures, baties entre 1739 et 1792, sont constituees de murs d'epaisseur different, renforces par des gros blocs de roche. Ces structures sont soumises à l'action des coups de mer et à l'erosion marine. La stabilite de la structure dans des conditions dynamiques a ete analysee par modelisation à elements distincts. Le modèle numeriquc a ete valide au moyen de la comparaison avec les mesurages de pression de I'eau sur un modèle physique. Le modèle DEM ainsi calibre a ete soumis à des charghes croissantes dynamiques pour evaluer les conditions d'equilibre limite de la structure.


Die natuerliche Sperrung der venezianischen Lagune wurde zum Teil vom Mecr erodiert und deswegen durch einer kunstlichen Struktur, den sogenannten "Murazzi" ersetzt. Diese Mauerwerke wurden zwischen den Jahren 1739 und 1792 mit untersehiedlichen Dicken gebaut und durch Felsblocken verfestigt. Diese Bauwerke sind den Sturzseen und der Auswaschung untergezogen. Die Standsicherheit des Werkes unter dynamischen Beanspruchung wurde duch D.E. Modellierung analysiert; die Ergebnisse wurden mit den Wasserdruckmessungen aus einem physikalischen Modell vergeglichen. Das gecichte Modell wurde entsprechend der Meereswirkungen den zunehmenden, dynamischen Belastungen als Forschung unterworfen um den Gleichgewichtzustand im Grenzfall untersuchen zu können.


The Venice lagoon is an extension of the "Venetian" plane and it has been formed in recent geological times as a consequence of the deposition of a large quantity of solid material. This depositional material came from the erosion of alpine and pre-alpine mountains and it was transported to the Adriatic sea by the rivers Po, Adige, Brenta, Piave and Tagliamento. The natural lagoon dam islands have different width varying from a few metres to some kilometres. In some places, where the sandy beach has been completely eroded, some artificial long shore breakwaters, called "Murazzi", have been built between the years 1739 and 1792. They are made up of large stone blocks fixed by sill and pozzolanic cement and their toes are reinforced by means of seaward irregular block structures. These structures have been improved and reviewed during the centuries and they now present the basic typologies reported in figure 1. A research program, financed by the Italian National Research Bureau (Centro Nationale Ricerche), planned the study of the lagoon system by means of numerical modelling. Particular consideration has been given to the analysis of the breakwater subject to sea storm action and to sea erosion. Two different kinds of studies have been carried out. The first study considered the effect of the increase in pore pressure, and consequent decrease in the effective stresses and in shear resistance, in the sand substrata on which the rocky breakwater were built; the second part of the research analysed, more specifically, the stability conditions of the breakwater itself. Both studies were carried out in sea storm conditions.

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