The Project

In the spring, the first tunnel section, named Alara, was successfully submerged. In November, the second and last tunnel section, Isabella, was also placed on the bed of the Scheur River. To manage the complex forces on the tunnel section consortium BAAK, together with Strukton Immersion conducted a detailed flow and force analysis.

Our Approach

Hydrauvision Rental mobilised a special winch spread: redundant HPU sets, mooring/interconnection winches, and submersion guidance winches. These winches ensured full control over guiding the tunnel element to the riverbed. Submersion occurred by slowly pumping ballast water into temporary ballasttanks until the tunnel began to sink. The submersion guidance winches (HydrauWinch 80IG), lowered the tunnel element to its position, more than 30 metres below the surface. An operation with an accuracy of a few centimetres.

Features of Hydrauvision Rental submersion guidance winches:

  • Speed control: controlled acceleration and deceleration to the set cable speed, enabling even payout of the winches
  • Load control: Monitoring and regulating cable load and resulting disk load to prevent overloading of the structure.
  • Payout control: Highly precise cable payout for careful positioning of the tunnel element
  • Communication protocol: throughout the operation, all winch information was continuously transmitted to the survey system for visualisation and logging

Thanks to the dedication of our colleagues, who were on-site day and night, the 50,000-ton Alara and Isabella were successfully submerged to a depth of 30 meters.

Watch the aftermovie of the submersion of Isabella here:

Skyphoto ©Rijkswaterstaat