Ground control in tunnel construction and restoration

Minova supports all main methods of tunnel construction, including continuous and cyclic methods as well as cut and cover.
Regardless of the method, support is needed before during and after the tunnel is excavated or built – to maintain safety and sustainability. With our history in mining, our products have been developed for the toughest conditions. Presupport 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 50%. This means that pre-support may be needed to advance the tunnel.

Tunnel refurbishment

Many of the world’s tunnels are nearing the end of or are beyond their original design lives. These tunnels need to be refur­bished by either rebuilding them to increase capacity and safety, or by restoring them to prolong service life and increase safety. Often the tunnels must remain operational while this refurbishment is undertaken. Our fast-acting products are ideal for these cases.

Presupport

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 presupport is executed from a secured area and completely eliminates work in unsecured areas. A proper presupport also reduces the risk of collapsing roof or face during excavation.

– Face stabilisation
– Roof support
– Cavity filling
– Waterstopping
– Forepoling

Strengthen

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.

– Rock strengthening through rock bolting
– Thin Structural Liners (TSL)
– Cavity filling to eliminate future ground movement
– Injection sealing to reduce influx of water and to prevent ground
movement in cracks

Seal

To further stabilize the tunnel and to provide water control, the tunnel is sealed with a temporary lining and then a permanent lining to secure the tunnel throughout its working life.

– Injection sealing to close cracks and fissures in groun
– Mesh to prevent loose rock falls
– Spray applied membranes to prevent water ingress
– Lining to create a smooth surface and redirect water ingress
– Sprayed concrete/TSL

Repair and refurbishment

The tunnel can be further strengthened to extend the life of the tunnel and increase safety. Depending on the condi­tion of the tunnel and geological environ­ment, additional reinforcements
may need to be applied during the course of the tunnel life time.

– Rock consolidation to secure any ground movements that may have occurred
– Cavity and back filling
– Relining
– Water stopping and sealing

Overburden stabilisation

secures the ground above the tunnel, where structures may be affected by the new tunnel below or nearby. Poor ground in combination with vibrations from the tunnel may cause severe damage to buildings or subsidence of the surface.

Tunnel portal support

stabi lises the entrance arch, at the critical place where the tunnel begins. We provide SDA forepoles, canopy tubes for pipe umbrellas, GFRP face dowels and Thin Structural Liners, Tekfl ex, to secure the tunnel face.

Stabilisation of soil and rock

is needed to support the excavated walls at the tunnel entrance. We provide mesh, SDA soil nails (both steel and GFRP), grouts for bolts, Minova Mesh Wall, cable bolts and geotextiles as well as accessories such as MAI grout pumps and hand-held drills for bolting.

Lining systems

are required in almost all situations, for both temporary and permanent cases. The lining manages water ingress. Minova offers bolting systems to support inner insulation linings as well as rockbolts and prebagged fi bre-reinforced sprayed concrete. Minova also offers fast-acting Thin Structural Liners like Tekfex and the spray applied waterproofi ng membrane, Tekfl ex DS-W.

Water stopping and control

prevents leakage and ingress of water, which over time with can destabilize the ground, but also can cause safety hazards when the tunnel is in operation. Minova helps seal potential cracks with injection resins creating a secure seal against water ingress.

Presupport
stabilises the tunnel face by injection and cavity fi lling ahead of the advance area. In some cases umbrella systems or face bolting secures the ground ahead of the immediate advance area, creating a safer environment at the heading.

Ground improvement
is about consolidating all loose material in the ground, to create a consolidated rock mass allowing for improved tunneling conditions. Solutions range from injection resins, high performance cements and grouts as well as the use of GFRP and steel bolts or Self Drilling Anchors (SDAs) in stand-alone applications or in combination together to meet the ground conditions.

Face stabilisation
stabilises the tunnel face at the place of excavation. Depending on the rock conditions face bolting, injection and cavity filling products can be used at the face to consolidate the rock mass.

Tunnel refurbishment
becomes inevitable as tunnels come close to or go beyond their original design lives. To keep the tunnel in operation, it needs refurbishment and often it must be kept operational during the repairs. Time is of the essence and fast-acting products are critical to handle the restoration in the shortest possible time. Fast-reacting waterstopping injection resins or GFRP bolts and resin grout capsules are good examples of this.