Plan du projet HRBT

INTRODUCTION

The Hampton Roads Bridge-Tunnel (HRBT) is a road infrastructure linking the cities of Hampton and Norfolk in Virginia, USA.

The main goal of the current HRBT project is to decongest one of the region’s busiest roads by adding two new twin tunnels under Hampton Bay. These tunnels will complete the existing infrastructure (from 4 to 8 traffic lanes), offering increased capacity and safer traffic conditions.

This new excavation represents several challenges relating to ground management, wall stability and the environmental impact of the project.

To keep the project running efficiently, it was essential for VDOT (Virginia Department of Transportation) and Hampton Roads Connector Partners (Dragados, VINCI Construction, Flatiron Constructors and Dodin Campenon Bernard) to opt for a slurry mode boring.

 

Slurry treatment plant

OUR SUPPORT

For the project, MS expertise was selected, and we supplied a custom-made slurry treatment plant, specially designed to meet the technical and environmental requirements of the site.

  1. A separating section

This section plays a key role in the treatment of excavated materials, separating the solids (gravel and sand) from the bentonitic pickling slurry:

  • A trommel: to remove the largest solid debris (> 6 mm) at the very start of the process.
  • 6 desanding towers, each equipped with a double cycloning stage, and a dewatering unit adapted to the tonnage and fineness of the excavated sand.
  1. A slurry management section
  • Fresh bentonite preparators: 3 units for preparing and mixing bentonite, which is essential for stabilising the ground.
  • A set of tanks and pumping units for in-line adjustment of sludge rheology
  1. A pressing section
  • 9 filter presses (including 2 remanufactured*): Dehydrates excess sludge, reducing its volume for easier disposal, while recycling the water contained in the sludge.
  1. A control and support infrastructure
  • A control room: to supervise and regulate all operations in real time.
  • A laboratory: for analysing slurry samples to ensure consistent treatment quality.
notre station de traitement des boues, baptisée Katherine Johnsonen, mathématicienne et ingénieur spatiale à la Nasa

expected and observed results

Officially launched in April 2023, our slurry treatment plant, named Katherine (in memory of Katherine Johnson, a mathematician and space engineer at NASA, who played a major role in the American space conquest), immediately got under way to keep pace with the excavation of the Mary tunnel boring machine (also named after an American space mathematician, Mary Jackson), which is moving at about 20 metres per day.

The first section of the STP, the separating section, has been designed to receive a feed of up to 3,000m3/h.

All the excess sludge is sent to the pressing section, where the 9 filter presses treat up to 2,160 tons of dry matter per day, boosted by the Build Better by MS additive.

 

SITE PROGRESS UPDATE

After 51 weeks of excavation, Mary TBM completed the first tunnel in April 2024. Last October, Mary began its second mission, boring the second tunnel.

Two months after the start of the second boring operation, the TBM has already excavated more than 230 meters and placed more than 105 rings in the new tunnel.

* Remanufactured: means that they have been completely renovated. More economical and environmentally friendly.

 

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Build Better by MS

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