Modern Quarrying July-August 2015

TECHNICAL FEATURE SAFETY BERMS

rocks or chippings are not normally nec- essary. All benches that are not in opera- tion should be closed with a physical barricade that prevents vehicular access; for example, a solid rock berm. Along haul roads and especially inclined haul roads (ramps), the risk of a machine driving over the crest is signifi- cant and this risk can be reduced by the erection of a safety berm, typically the radius of the largest wheel. It is important that this berm does not add to the rolling rock risk and there- fore should be typically composed of homogeneous, non-binding material, eg 13 mm crushed aggregate. The edge of the berm should be at least 1,0 m from the crest edge. Regular gaps should be left in the safety berm to prevent water ponding and allow for safe viewing into the quarry and examination of any ten- sion cracks. The barricade should be marked by a Competent Person on every operating bench to warn of the high risk crest area and form a Red No-Go Zone between the crest and tension cracks. MQ

travelling too close to the crest edge ( Figure 14 ). Here, a solid safety berm has been erected for vehicles. In addition, a line of cones has been erected to warn of the crest edge and its Red No-Go Zone. A worker transgressing this zone can easily be seen and corrective action taken. Conclusion The crest edge risk in surface mines and quarries varies from virtually no risk for low inclined benches found in many clay mines, to high risk for high benches that are vertical with poor crest conditions. Each operation has to perform a full site-specific risk assessment determin- ing both the probability of a crest failure and fall of worker/machine and its conse- quence. The assessment should include the impact (literally) onto the toe of the bench below. It is suggested that where the risk level is found to be moderate to high, a physical barricade should be erected to warn workers and pedestrians of the high risk area close to the crest. On oper- ating benches, safety berms composed of

About the author Consultant rock engineer Dave Fenn. holds a Master of Business Administration (MBA) from the UCT Graduate School of Business; a Graduate Diploma in (Rock) Engineering, University of the Witwatersrand; AA Advanced Certificate in Rock Mechanics; Chamber of Mines Certificates in Rock Engineering (including Surface Mining); Dip CSM (HND) Mining Engineering, Camborne School of Mining (UK). He is a SANIRE and SAIMM member. He has 25 years mining experience of which 24 have been in rock engineering in soft coal measures as AngloCoal’s section head from surface to 280 m deep, to hard rock gold and platinummining (tabular and bulk UG methods) from surface to 2 600 m deep as a rock engineering officer. He opened a successful independent rock engineering consultant practice (Applied Rock Engineering cc) in 2006, and has gained extensive open-pit experience augmenting his underground work. This includes the compilation of over 50 slope COPs, lecturing for a SAQA-accredited training com- pany, performing operation geotechnical audits and a geotechnical service, including geotechnical feasi- bility studies and pit slope design for many leading mining organisations.