Authors: Oldsen, J; Roberts, T


Cite As:
Oldsen, J & Roberts, T 2013, 'High capacity yielding bolt support for rockburst prone workings', in Y Potvin & B Brady (eds), Proceedings of the Seventh International Symposium on Ground Support in Mining and Underground Construction, Australian Centre for Geomechanics, Perth, pp. 323-333.

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Abstract:
Rockbursts are one of the greatest challenges to ground control in the mining industry. The general principle of ground control in rockburst prone conditions is to transfer the dynamic energy of a rockburst event to the yielding support system to facilitate absorption and controlled deformation of rock mass while containing materials, or helping the rock mass to support itself. Jennmar research and development has resulted in a technically reliable and effective yielding rockbolt. The first generation Yield-Lok bolt accepted 150–250 mm of deflection at 8–10 t loads for every 16.4 kJ energy input. The bolt is made of 17.2 mm diameter, Grade 75 round steel bar. The steel bar is upset to specified dimensions at one end and partially or fully encapsulated in an engineered polymer coating to achieve designed yielding performance under dynamic loading. The bolt is tensioned and provides immediate primary support on installation. In low energy, dead weight loading conditions, the Yield-Lok bolt performs similarly to a rebar bolt, providing stiff reinforcement and containment of the rock mass. In high energy loading conditions, the upset transfers the impacts on the surrounding polymer coating and energy is dissipated by ploughing the upset through the polymer. Recent laboratory tests have shown greater loads with reduced deflection. The results were repeatable and uniformly consistent. The bolt is made of 17.2 mm diameter, Grade 100 round steel bar. The steel bar is upset to specified dimensions at one end and partially or fully encapsulated in an engineered polymer coating to achieve designed yielding performance under dynamic loading. Higher energy designs have also been successfully tested. The bolt is manufactured from 23.1 mm diameter, Grade 75 round steel bar. The steel bar is upset to specified dimensions at one end and partially or fully encapsulated in an engineered polymer coating to achieve designed yielding performance under dynamic loading. In static loading this bolt approaches 30 t tensile loads and has the associated higher shear load available.

References:
ASTM D7401-08 (2008) Standard Test Methods for Laboratory Determination Of Rock Anchor Capacities By Pull And Drop Tests, ASTM International.
Doucet, C. and Voyzelle, B. (2012) Technical Information Data Sheets, Review Completed May 29, 2012.
WIPO (2011) World Intellectual Property Organization, Patent Publication No. WO201102879 on Yielding Bolt and Assembly, viewed 24 November 2011, .
Wu, Y. and Oldsen, J. (2010) Development of a new yielding rock support – Yield-Lok bolt, in Proceedings 44th U.S. Rock Mechanics Symposium, 27–30 June, 2010, Salt Lake City, Utah.




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