Rock tunnelling is a specialty that is incorporated across all of our market sectors, including transportation, roads and highways, rail and transit systems, underground stations, water and waste water conveyance, power and energy, and underground storage facilities, including petroleum and nuclear waste repositories.

Our engineers have extensive experience in all aspects of rock tunnelling and mined caverns projects, from conception and feasibility studies, to detailed design and construction, as well as the operation and rehabilitation of the facilities throughout their life cycle. We have been involved in rock tunnel design in most major cities the world over.

WSP is accustomed to adapting traditional design and construction techniques to specific site situations, and developing innovative techniques and approaches for projects that demand solutions beyond standard practice. We have experience across various geological settings and different geographies on all six continents. We anticipate the possible complications that could arise during construction and account for them during the preparation of design and construction documents, as well as by overseeing construction.

Drill and blast

Drill and blast is an excavation method used frequently in hard rock tunnelling because its flexibility allows for different layout setups. WSP has used drill and blast to build tunnels with diameters up to 30m wide, mostly supported by steel bolts and fiber reinforced shotcrete (sprayed concrete). We use controlled blasting techniques in our design to control over-break, reduce vibration, and to aid the stability of the remaining rock formation. When vibrations or a damage zone in the rock is not feasible, the method can be supplemented with wire sawing. In these cases, a wire is fed through drilled holes and drawn along the actual surface without causing vibrations.

Tunnel Boring Machines (TBM)

WSP has international experience and capabilities in selection of Tunnel Boring Machines. The main types of tunnel boring machines used in rock are Main Beam Open Face Gripper TBMs, best for hard and competent rock, and shielded or double shielded TBMs like Earth Pressure Balance (EPB) and Slurry Shield TBMs, and Muli-Mode TBMs that are best for highly variable or complex ground.

Sequential Excavation Method

The Sequential Excavation Method (SEM), is based on the understanding of how rock reacts to the creation of a tunnel. WSP has extensive experience of designing and detailing rock support where SEM techniques are used. 

SEM offers the flexibility to build tunnels of almost any size or shape, however curvilinear (oval) is preferred to allow smooth stress redistribution. By adjusting the construction sequence expressed mainly in round length, timing of support installation and type of support, it allows for tunnelling through a variety of ground conditions; with varying tunnel, shaft widths or cavern spans; and at a range of depths from shallow cover tunnels to high stress or deep tunnel environments.

Roadheaders

A roadheader is used as a mechanized method of cutting that has more precise cutting, less vibration, and no overbreak. Recent developments allowed the excavation of rock tunnels in very hard rock. The basic cutting tool is a very large milling head mounted on a boom, which is in turn mounted on tracks or within a shield. The cross section can be cut to almost any desired shape to better distribute the stresses in the rock mass. WSP can provide constructability advice on the use of roadheaders and all related design requirements to support this form of construction.

Ground water control

Pre-grouting is frequently used to handle water leakage in rock tunnelling. Long holes are drilled ahead of the excavation and filled with grouting paste by pressure. This grout spreads along the joints around the tunnel, which minimizes the inflow of water into the tunnel.

WSP also has extensive experience working with the Water Framework Directive and we are able to undertake detailed appraisal of water resources (hydrology and flood prediction) and groundwater flow (hydrogeology), through detailed computer modelling and advanced risk assessment procedures. Our hydrologists and geochemists work closely with our rock engineers, primarily on cases involving joint water tracking, hydraulic testing, and 3D ground water flow.

Rock mechanics

Our engineers have a wide range of expertise in the field of rock engineering and tunnel design for rock tunnels. Using numerical analysis and 3D geological modeling, rock mechanical experts provide innovative technical solutions for our clients. We use software like MicroStation, AutoCAD, and Surpac, BIM for 3D modelling, as well as RS2, RS3, EX3, Unwedge and Dips (by Rocscience) and FLAC 2D and FLAC 3D, UDEC, and 3DEC (by Itasca) for advanced numerical analysis and tunnel design. Services we can provide in rock mechanics are divided into surveys, design, technical solutions, tunnel maintenance service, and cavern maintenance service.

Engineering geology

Our geologists are experienced in all stages of geological surveying, from investigation to construction, as well as beyond to maintenance, across all project types. Software like MicroStation and Surpac are used to analyze structures, rock types, and hydraulic properties. Our expertise includes: geotechnical baseline investigations, geotechnical baseline reports, mining structural geology, industrial minerals, tunnel surveys, and geotechnical mapping.

Services provided by WSP

Rock tunnelling requires an interweaving of knowledge rock mechanics, engineering design, and construction practice and techniques. We have experience in rock tunnel, shaft and cavern construction techniques including the use of roadheaders, drill & blast and TBMs. The use of different construction methods usually results in different rock stabilization techniques and different support system. Sometimes all these methods are used on the same project. WSP provide complete services related to rock tunnels, shafts and caverns under various surface conditions, in mountainous or urban areas, in seismic zones, and for all market sectors.