The creation of underground structures to form subways, underpasses, stations and other spaces is an increasing need in the full range of transportation modes: rail, metro, highway, airport etc.

We have experience in design and installation management of a broad range of structures installed so as to avoid disruption and maintain surface operations: road and rail underpasses; underground stations; pedestrian underpasses; and enhanced access tunnels. Our engineers have experience extending back more than 30 years in the field of jacking of underground structures, and pioneered many of the technologies in use today.

Our world-class expertise lies in conceptual and detailed design of the non-disruptive installation of underground structures. We have developed approaches to cover a wide range of structures and site conditions. For this type of work the design of the permanent structures and the temporary works associated with installation have to be integrated and as a result the work is often undertaken on a design & build basis where we work in close co-operation with a contractor.

These techniques include the use of large section concrete jacked structures (often called jacked boxes) or tubes to form the basis of No-Dig bridge foundations or abutments or temporary works for large underground construction (pipe roofing for example). More recent developments such as the innovative use of smaller section jacked boxes (modular structures) and jacked arches are key areas where we have unique and differentiating expertise.

These techniques offer effective alternatives to disruptive open-cut methods where conventional tunneling approaches are inappropriate so close to structures above. Modular systems in which a support or foundation structure of interlinked precast components is jacked into place horizontally enable bridge abutments to be formed under roads or railways with minimal disruption and with less working space and jacking capacity requirement than other methods. Advanced support structures are a variation of the modular approach in which interlinked steel tubes are installed by microtunneling, pipe jacking or pipe ramming to form a support structure within which excavation then takes place. Jacked arches are a new concept in which foundation tubes or boxes are jacked into place and these serve as guides for the bases of precast arch sections jacked behind a shield to form the full canopy structure.

Our knowledge of applying this range of techniques enables us to offer to clients elegant and cost-effective solutions to a broad range of complex situations where new access is required underground or below existing structures that must remain safely in service.