Building a tunnel means building public infrastructure which will last for decades. A tunnel is built to support modern life – to improve traffic flow, connect locations and shorten distances. With a perspective measured in decades or centuries, millions of people and millions tons of goods will travel through a tunnel built today. The tunnel must not only be efficient when designed and constructed, but also safe and reliable for years to come. This is where Minova comes in.
Minova supports all main methods in tunnel construction, including continuous and cyclic methods as well as cut and cover.
Regardless of method, support is needed before during and after the tunnel is excavated or built – to maintain safety and sustainability.
A significant part of the rock deformation, caused by a change in rock stresses, occurs prior to excavation. In solid ground about 10% of the deformation happens ahead of the face, while in soft ground it can be up to 40%. This means that pre-support is essential to proceed with the tunnel.
Over time, the existing tunnels usually need to be refurbished by either rebuilding them to increase capacity and safety, or by restoring them to prolong service life and increase safety. The difficulty lies in the variety of possible solutions, as geology and tunnel design differs between locations.
Securing tunnels is a complex business, which is not only about quick solutions for today, but needs expertise in dimensioning and designing the tunnel support as well as mechanical and chemical solutions to last the life time of the tunnel. The support solution must for example take into account geological changes, impact from traffic loads, water levels and risk for leakage, and not the least – environmental impact today and in the future.
Minova combines decades of tunneling expertise with world class solutions for mechanical and chemical support. Our combined knowledge about challenges and solutions, makes us a complete partner to discuss construction of any tunneling project – from the design phase to refurbishment or decommissioning.
With presupport, we secure the ground for excavation of the tunnel. The rock is stabilized ahead of the face to reduce rock deformation before excavation. The pre support is executed from a secured area and completely eliminates work in unsecured areas. A proper pre-support also reduces the risk of collapsing roof or face during drilling and blasting.
When excavated, the tunnel is further strengthened and secured for both continued work and for future operation. The rock reinforcement stabilizes the ground and extends the natural arch of the rock. The reinforcement prevents further loosening of rock mass and reduces rock deformation caused by further excavation.
To further stabilize the tunnel and to provide water control, the tunnel is sealed and prepared to be taken in operation. This is done with cement or resin based injection products and shotcretes and membranes.
A rebuild may be necessary to increase capacity or safety as conditions have changed since construction. Depending on tunnel and geology conditions, various actions can be taken to extend usage of tunnel and maintain or increase safety.
The tunnel can be further strengthened to increase standard and safety for a prolonged life. Depending on condition of tunnel and geology, additional reinforcements can be applied during the course of the tunnel life time: