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Tunnel Refurbishment Weldgrip Gripforce ® Rockbolts
Maintenance work involved the reinforcement of the tunnel lining by casting concrete toe blocks 1.5m long at 4m centres either side of the tunnel. The toe blocks were anchored to the brickwork by Weldgrip Fibregrip ® Rockbolts. Between opposite toe blocks on either side of the tunnel a 250mm wide waterproofing membrane was positioned round the brickwork before sgortcreteing a 150mm thick permanent arch strip to complete each section. Two Weldgrip Fibregrip ® Rockbolts were used to secure each toe block at 750mm centres. The rockbolts were 22mm diameter, 3m long and fitted with a standard 80kN nut and high load 150mm square plastic end plate. They were installed into 32mm diameter holes which had been drilled by pneumatic rotary drilling machines. Full encapsulation was achieved by spinning the rockbolts through polyester resin. Other GWR Tunnels to have used this system include:
The 205m long Tytherington Tunnel was also refurbished as part of this program. Weldgrip Fibregrip ® Rockbolts were used as the sole means of reinforcement into an area of the limestone roof. These were 25mm diameter x 3m long, installed into 32mm diameter holes and spun through polyester resin capsules. The nut was tightened to a 150mm square high load plastic end plate assembly.
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