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The M and J Yielding Flexibolt has a 300mm yielding element on the dead end of the Mechanical Anchor. A shell anchor with a yield sleeve ± 400mm from the back of the hole anchors the Yielding Flexibolt into the hole. Up to 300mm of convergence can occur before the Dead Stop (a barrel and wedges) stop up against the yield sleeve and the Yielding Flexibolt becomes a normal support anchor.
A plate spherical seat load indicator and a shear pin nut are on the live end to pretension the strand.
Advantages of the Yielding Flexibolt:
Does not require to be cropped, protruding strand is short
Stopper means that load will increase to tensile strength at end of yield stroke
Can be installed within 0,5m of the face before the blast
A Yielding Flexibolt and weld-mesh combination provides a robust system that has excellent areal and energy absorption coverage
Underground test results showed an energy absorption of minimum 25kJ
Yielding Flexibolt showing the yield mechanism
Yielding Flexibolts are currently being installed at South Deep Gold Mine – in destressed areas, resulting in a decrease in the number of F.O.G. (Fall Of Ground) incidents/accidents.
DYNAMIC GARFORD BOLT
Garford Bolt – is a 2.4m long, Ø20mm galvanised bar, enclosed by a galvanised split set. The bar is threaded at the dead end with a tapered cone that fits inside the split set (offering an additional yielding mechanism) which anchors the bolt into the back of the support hole. On the live end it has a threaded, yielding, tensioning, crimped barrel with a nut, spherical seat and washer designed to pre-tension the bolt to the required load using a 50mm cross flat nut.
Garford Bolt – Advantages
1. Easy mechanised installation using rigs
2. Radial support and pre stressed on installation
3. Single pass operation
4. Yielding mechanism at both dead and live ends offering ± 300mm of yield
5. Energy Absorption capability of ± 25kJ
DYNAMIC TESTING RIG
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