Rockfall Hazard Mitigation

Rockfall refers to quantities of rock falling freely/uncontrolled from a natural slope or man-made excavation. The term is also a synonym for collapse of rock from an underground mine roof or open pit mine highwall (fall of ground). Rockfalls are also a major hazard in excavations for highways and railways in mountainous terrains. However, a rockfall event is may also initiated by climatic and biological events that cause a change in the forces acting on a rock.

In a mining environment, rockfall may occur due to blasting induced vibration and other related disturbances on a rock mass.

Rockfall protection systems refers to the structural elements used for the mitigation of the potential hazards resulting from un-controlled falls of rock or rockfalls.

In general a rockfall event range from minor falls to larger falls that affect safety of people and may also cause damage to infrastructure. Rockfall may also include substantial slope failures that cause serious damage to critical public and private infrastructure. The effect of rockfall events range from a simple damage to private property, injury or loss of life. It may also lead to major disruptions of critical economic systems such as closure of a mine or critical road network. In the mining industry rockfall can have a detrimental effect on the safety and economic position of the mining operations.

Rockfall may be the result of factors both internal and external to the rockmass combined with the action of gravity. The external factors may include chemical changes on the surface surface of the rockmass, temperature variations, surface scour by water and wind action, forces exerted by plant roots, and blasting methods. The internal factors are connected with residual geological stresses in the rock and with fractures or discontinuities. Of all the foregoing factors the one which has the greatest effect is undoubtedly the action of water and the freeze/thaw cycles.

Rockfall protection/mitigation aims at minimising the potential effects of rockfall events through the design and installation of rockfall systems. Rockfall systems are engineered to be durable, effective, and to save lives.

Hoff Geotechnik is highly experienced in the Design and Construction of Rockfall Hazards Mitigation systems. We have successfully completed a number of complex projects for high-level clientele such as De Beers Consolidated Mines Limited (DBCM), Debswana Jwaneng Mines, Assmang Iron Ore Limited, Lesotho Highlands Development Authority (LHDA), Anglo American, Letseng Diamonds, Harmony Gold Mines and other private entities. Our optimal solutions are expertly designed by our consultancy division which conducts geotechnical analysis, design and construction services. All the designs and construction services is offered in-house by a team of experienced engineers and technicians.

A key distinguishing feature of our service offering is the technical and practical experienced gained over 18 years by our Director (Ernst Rankhododo, MSc. Eng.) who is actively involved in all aspects of our projects.

Hoff Geotechnik has been able to demonstrate capability to safety construct mine rockfall mitigation and slope stabilisation systems in excavations that have been declared unsafe and high risk. Our rockfall hazard mitigation and slope stabilisation systems have allowed our clients to enter/access parts of their operations which where previously considered unsafe to operate.

Our offering is a turn-key offering encompassing design and construction of a wide range of rockfall hazards mitigation systems:

Our range of Rockfall Hazard Mitigation Systems include the following:

• Simple drappery system
• Pinned drappery system
• Attenuated wiremesh system
• Rockfall protection barriers
• Specialised non-explosive blasting for over-hangs
• Scaling or barring of unstable rocks