Queensferry Crossing, Edinburgh

Key Information

Owner: Transport Scotland
Engineer: Grontmij
General contractor: Morrison Construction, Hochtief, Dragados & American Bridge JV
Period of works: November 2012 – April 2013

Project description

The Queensferry Crossing (also known as the Forth Crossing Replacement) involves the construction of a new bridge over the Forth river, North-West of Edinburgh. In order to access to this new bridge, large scale works to the road network had to be carried out both sides of the river.

Vibro-Menard has been contracted to provide a “design and build” ground improvement solution under the future road B981’s embankments (north side of the river). The aim of this solution was to reduce the total and differential settlements under the loads of the embankments and to guarantee the stability of these 9m embankments.

Ground conditions

The ground to treat was loose, at the surface was anthropic fill unconsolidated above marine layers which were made of silty sand with clay layers interbedded. This marine layer had a high organic content.

Solution

Vibro Menard decided to install 360 mm diameter Controlled Modulus Columns (CMCs) along with shear panels using the Trenchmix technique. The Trenchmix panels have been designed in a few zones in order to mostly reduce horizontal displacements and total settlements. Moreover, to resist horizontal displacement, some of the CMCs have been reinforced by installing steel bars or steel cages.

Main Figures

Controlled Modulus Columns

Vibro Menard has installed 4,451 CMCs of 11 m to 18 m length, for a total of 52,675 lm.

Trenchmix

62 no of soil mixing shear walls which represents a surface of 9 200 m².

Stress Load Testing

To ensure the good quality of the execution, Vibro Menard carried out 44 no. load tests on single CMCs.

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