For centuries Venetians had given in to the Adriatic Sea, learning to meet its unique challenges rather than trying to hold back its tides. Today, Venice remains relatively unchanged. With its centuries-old influence on art, music, architecture and literature, and as the 13th century home to famed explorer Marco Polo, it’s one of the world’s most popular tourist destinations – a destination that many people call a ‘floating museum’.

Venice was built on an archipelago of 118 islands, with over 150 canals and over 400 bridges connecting the islands. Visitors and residents to the old lagoon city travel only by water or on foot. The city is considered Europe’s largest car-free urban area. So why would a city like Venice need a state-of-the-art Cat® AP655D asphalt paver? To help safeguard this historic city for the 20 million visitors who navigate its waterways each year.

In 1966, a major flood caused incalculable damage to the city. Venice and nearby towns and villages were submerged under more than a metre of seawater. The pumping of groundwater and methane gas to meet the region’s industrial needs likely caused Venice to begin to sink. Nearly 28 cm have been lost in just the last century. Although the pumping practices have long since ended, their effects, combined with today’s rising sea levels (widely attributed to climate change) have caused more frequent high-tide events.

Today, Venice experiences high tide events with a frequency eight times more than in the early 1900s. Flood tides especially threaten the city throughout the winter months and ground floor structures are no longer habitable throughout the city.

Safeguarding Venice is delegated to the state and is carried out by the Ministry of Infrastructure – Venice Water Authority, through a consortium of Italian engineering and construction companies.
In 2003, the consortium (Consorzio Venezia Nuova) began what is regarded as the largest public works project in Italian history. Called Modulo Sperimentale Elettromeccanico or Electromechanical Experimental Module (MoSE for short), the project intends to further defend Venice with a system of 78 inflatable mobile flood barriers that will separate the city from the Adriatic Sea during exceptional high-tide events.

The flood barriers will be completely invisible and will remain in their underwater housing on the floor of their inlet canals, until needed. Compressed air will empty water to raise the gates, blocking incoming seawater. The MoSE system has been conservatively designed to allow for a global sea level rise of up to 60 cm, twice as high as worst-case scenarios currently estimated by scientists. Three separate inlet gate locations will be constructed. When combined with 45 km of defenses previously installed along the coastline, these gates will allow even greater flexibility and control.

Temporary construction platforms – man made areas – are in the works at each of the inlet sites. They minimise land use, enable the transportation of equipment and materials by sea, allow for dry storage, and facilitate construction and launching of the structural elements (caissons) for each row of gates.

One such temporary prefabrication is currently under construction for the gates at Malamocco and Lido San Nicoló. A new Cat® AP655D with steel track undercarriage, one of the largest asphalt pavers in the Caterpillar® paver line, is helping to pave each of its 18 plots, 13 hectare (130,000 square metres) in total. Each prefabricated plot needs to be capable of supporting the weight of the concrete structures, some 25 m long and 15 m high.

“To ensure correct construction of these large concrete elements, and avoid possible differential settlements at their base during construction, it was essential for the support surfaces of the structures to be exceptionally sound and comply with extremely precise levelling tolerances,” Enrico Pellegrini, site manager of Grandi Lavori FINCOSIT SpA, said.

“This is why we decided to use the new Cat AP655D paver for construction of the lean concrete binding layer, with a thickness of approximately 8 cm.”

Mr Pellegrini said initial trials of the paver, supervised by a Cat engineer, produced “extremely satisfactory results” and the machine was immediately put to use.

“The advantages of [the machine’s] productivity, precision [paving performance] and timing are more than evident. Fourteen plots have been constructed, for a total of 35,000 square metres of material, with an average daily production of approximately 2,500 square metres. This is a major achievement,” Mr Pellegrini said.

Site Foreman Vincenzo Saragnese and his operators also commented on the machine’s manoeuvrability and stability, and the precision and uniformity of the AP655D’s performance. “Due to the excellent firmness of the material placed, which was [only] obtained by means of tamper vibration…no subsequent compaction with a roller was necessary,” Mr Saragnese said.

The construction of the caissons will begin after the plots are paved. In about 12 to 14 months, the Cat AP655D paver will again be put to use paving the entire area with a cement-stabilised material. Today, the MoSE project is currently on track and 40% complete. With the help of the AP655D, it is scheduled to wrap up in 2012.

Caterpillar would like to recognise and thank the Ministry of Infrastructure—Venice Water Authority and CONSORZIO VENEZIA NUOVA, the consortium of Italian engineering and construction companies working on the MoSE project. A special thanks is also expressed to Enrico Pellegrini (Site Manager) and Vincenzo Saragnese (Site Foreman) of Grandi Lavori FINCOSIT SpA, who arranged a strategic site visit and assisted in the preparation of the images and the final version of this report.

Innovative Features of the Cat® AP655D

The new AP655D offers contractors a versatile high-productive paver solution, meeting a variety of regional needs across the world. With an operating weight of 19,165 kg, it competes in the 18-19 ton major class size Australian market. It is one of the largest and most productive asphalt pavers in the Caterpillar® paver line.
Its versatility lies in the AP655D’s two proven undercarriage systems, the Mobil-trac™ System (MTS rubber track undercarriage) or steel track undercarriage configurations. Each allows the paver to easily handle surface irregularities, for even the most rigorous jobsite environment (wet or dry) while producing machine stability, mobility and mat smoothness.

Its Cat® C6.6 turbocharged 6-cylinder diesel engine delivers ample power (129 kw) and features proven ACERT™ Technology that incorporates a series of innovations working at the point of combustion to optimise engine performance. And, it meets US Tier 3 and European Stage IIIA engine emissions regulations for off-road applications.

The AP566D employs one of the most proven material handling systems in the industry and it delivers precise material control and quality paving results. Its Advisor Monitoring System (AMS) offers an interface, which allows operators to easily maintain optimal machine performance. A dual swing-out operator’s platform delivers ergonomic comfort, control and precise visibility.

Serviceability and reliability are engineered from day one.
The AP655D is suited for motorways, highways, industrial sites, parking lots, urban and rural roads, city streets, residential streets and other production-sized paving jobs.

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