From Concept To Reality
Dredging and development plans for the Port of Tallinn’s Muuga Harbour container terminal were on the agenda at CEDA’s first conference in Estonia’s capital last autumn – today, the project’s well and truly under way
Co-hosted by Tallinn University of Technology’s Marine Systems Institute and themed Dredging and the Environment, the conference took in a Muuga technical visit that outlined not only the very demanding weather conditions, but also the challenges facing the contractors – Danish duo Rohde Nielsen and Per Aarsleff along with Estonian specialist KMG Inseneriehituse.
Muuga, which is 17km east of Tallinn and the biggest of several harbours that make up the Port of Tallinn, suffers freezing temperatures, strong winds and rough seas during the winter – which is when Per Aarsleff engineers found themselves installing the largest tubular profile and longest combination steel pile retaining wall they’d ever had to cope with.
The piles – over 420 of them – are up to 1.67m diameter, 45m long and weigh up to 32t. About two thirds of them are linked together in combination with pairs of shorter steel sheet piles to form both the main combiwall quay frontage and a section of retaining combiwall running parallel with and alongside the existing quay at the terminal.
One end of the combi sidewall links into that existing quay, while the other end’s combined with a new 800m-long breakwater jutting from the coastline. Together, they form an enclosed basin that Rohde Nielsen’s filling with 1.5M m3 of dredged sand to reclaim the new 180,000m2 extension.
A second line of smaller-diameter, equally spaced tubular piles is also being installed behind and parallel to the main quay wall and together they’ll provide the foundation for twin rail tracks to take both existing and new ship-to-shore box cranes.
Piles And Piling
Port of Tallinn’s consulting engineer Merin Konsult produced the project’s concept design, based on a twin combiwall. But marine civils firm Per Aarsleff, in a split joint venture with KMG Inseneriehituse and dredger Rohde Nielsen, won the DKr430M ($83M) contract with a detailed design produced by Estonian consultant Estkonsult based on a single continuous combiwall... which necessitated using much larger-diameter tubular steel piles.
The JV moved on site in September 2008 and started to attack the project on several fronts simultaneously. Initially, Per Aarsleff built up a stock of the huge spirally welded tubular piles – each complete with a pair of interlocking clutche ...