Design

The Beacon Hill Tunnels and Station are part of the 22.5km initial segment of the Sound Transit Central Link Light Rail Line that will establish a high capacity commuter connection from downtown Seattle to Tacoma. The 1300m running tunnel under Beacon Hill will be mined by Earth Pressure Balance Machine (EPB), while the deep mined Station will be constructed using slurry walls and the New Austrian Tunneling Method (NATM), referred to as Sequential Excavation Method (SEM) for this project.

The Wayside ventilation shaft is one of five needed to provide ventilation and emergency access for the London Tunnels section of the Channel Tunnel Rail Link. The tunnels were designed as permanent sprayed concrete-lined, constructed in two phases, temporary primary and permanent secondary linings. The required watertightness will be achieved by staggering the joint locations between the two linings, utilising internal curing agents and steel fibres in the secondary lining sprayed concrete and using injectable flexible tubes in the joints of the secondary lining.

The North Shore Connector Project consisted of three underground station structures and running tunnels, excavated with TBM and Cut-and-Cover tunneling methods. It also included a twin bore tunnel under the Allegheny River. Dr. Sauer and Partners provided design review and design support services. The development of the waterproofing system for underground structures including tying into an existing station using a flexible membrane system, combined with a sectioning system that allows for section grouting instead of the entire structure if a leak is detected was also provided.

The Lehigh Tunnel No.2, part of a 4-lane motorway running East-West through Pennsylvania, was one of the first tunnels in the US built using NATM. Capacity problems of Lehigh Tunnel No.1 caused delays during peak times. The new tunnel was excavated using top heading, bench and invert excavation with shotcrete support. To achieve a completely dry tunnel a PVC membrane was installed between primary shotcrete lining and the final cast-in-place lining. Tunnel rehabilitation including the installation of a PVC membrane and thermal insulation in the air duct was performed to the original tunnel.

An extensive underground people-mover train system and a fixed walkway tunnel between terminals are central to a multi-phased mega program of modernization and expansion for the Washington Dulles International Airport. The pedestrian walkback tunnel, a part of the expansion plan, crosses below two airport taxilanes and will connect the Main Terminal with Mid-Field Concourse B. The tunnel was designed as a multiple-drift NATM excavation, whereby cover beneath the taxilanes was less than a tunnel diameter at only 4.5 m. Excavation was therefore designed as a very controlled sequence with top heading excavation further divided into two side drifts.

The Heathrow Express Link provides a 15 minute high speed rail service between Paddington Station and Heathrow Airport. A 7.25 km spur running for the most part in tunnel provides the airport with underground stations at the Central Terminal area (Terminals 1, 2 & 3) and Terminal 4. Provision was also made for a link to the at this point proposed Terminal 5. The 5.5 km long tunnelled section will pass under the M4 motorway with the portal located to the north.