Spatial positioning of sidewall stations in a narrow tunnel environment: a safe alternative to traditional mine survey practice

2.7. Working at heights and the associated risks

It can be argued that the inclusion of an investigation into the standard procedures, lifting equipment and personal protective equipment related to working-at-heights in this research in no way relevant to mine surveying practice. In reality, most mine tunnels survey control is carried in the roof of the excavation. Reaching the roof of the excavation is therefore essential to the daily survey duties performed by a mine surveyor. As such, a ladder and the related PPE¹⁴ becomes an essential if unglamorous piece of equipment of the mine surveyor. The most obvious hazard associated with installing and using survey control points is the hangingwall of the excavation is the risk of falling. Falling may be the result of the equipment failing, over extension by the person at the top of the ladder or the ladder slipping as a result of poor footing. A ladder or other lifting equipment all require a stable level surface free from any clutter in order to provide a stable platform. The very nature of the footwall¹⁵ conditions of most development end in the underground environment excludes all of the above safety pre-conditions. In the underground tunnelling environment the floor of an excavation will be uneven, covered in broken material and mud. In an inclined shaft environment the slope of the floor can be steeply inclined (between 5 to 34 degrees) [54], making it difficult to maintain a safe footing on the footwall. The likelihood of a ladder slipping in such conditions is quite high and it places enormous responsibility on the survey crew to ensure that they are safe when working-at-heights. Realistically, in almost all cases where lifting equipment is used in the underground environment all these pre-conditions cannot be met. In the light of the prevalent underground conditions in most mines, it becomes very difficult to comply with the requirements of the MHSA regulation 7.8.1.:

“No person shall work, or cause or permit any other person to work, in or near any workings of a mine where the inadvertent slipping or overbalancing may result in his sliding or falling down any slope…,or in his falling vertically, unless he is secured by a life-line or otherwise safe guarded.” [17]

In the case where surveyors make use of mechanized machinery such as a basket attached to a boom, the Anglo American Fatal Risk Standards: Working-at-heights , requires that “People in the work basket shall each wear a correctly fitted harness attached by a lanyard to a suitable anchor point.” In such cases where mechanized equipment is used it is easy to see that such equipment will require additional resources in the form of a qualified operator and will undoubtedly restrict the movement around this equipment by both pedestrians and other mechanized equipment. Such obstructions will delay the production cycle and the survey crew and operator will be pressurized to complete the lifting operation as soon as possible. A Working at heights standard procedure obtained from LONMIN Platinum mine classifies working at heights as any work performed at a height of 2 metres or more. This standard requires each supervisor (who will include the shift supervisor and surveyor) to maintain a “working at heights” register in which the permitted types of work, anchor points, and fall-arrest equipment used is listed. [55]

The type and construction of ladders used in the workings of a mine is described in detail in the General Safety Regulations 13(a)(1) and (2) of the Occupational Health and Safety Act [56], Act 85 of 1993 and is incorporated as a whole in most of the “working at heights” corporate standards reviewed. [55]

An additional hazard associated with the use of lifting equipment¹⁶ underground has been identified as the risk of creating a “hot-spark” created by aluminium ladders [31]. Due to this risk aluminium ladders, despite the obvious advantage in portability have been banned from underground use in some mines. According to Chapter 10, Miscellaneous and General Provisions, of the Mine Health and Safety Act, Act 29 of 1996, the definition of a “light metal” is a metal containing 15% aluminium, magnesium or titanium per mass of alloy. The Act requires that ”The employer must take reasonably practicable measures to prevent persons from being injured in any hazardous location as a result of fire, explosion or the ignition of gas, dust, mist or vapour.” [57] and therefore must ensure that no apparatus or component made of light metals is used in a hazardous location unless the component is covered, coated or contained in such a manner so as not to create a significant risk of ignition.
A thermite reaction can be described as an “exothermic chemical reaction” caused by the impact of oxidized steel or iron impacting on a fresh “smear” of aluminium. Such oxidization can occur so rapidly that it is able to ignite a flammable gas such as methane at a sufficient concentration, causing an explosion [58]. Paterson of the Aluminium Federation of Southern Africa states that “Explosion incidents in UK coal mines in the late 1950’s were thought to have been caused by a combination of thermite reaction between the freshly abraded aluminum pit props wedged with rusty steel wedges and methane at a sufficient concentration to result in ignition.” [58] Although the risk of an explosion caused by a thermite reaction from an aluminium ladder is considered to be relatively small, Paterson agrees that mining is an inherently hazardous operation and that the use of aluminium should be “discouraged as far as reasonably possible” in hazardous areas.
From the evidence listed above it is argued that it is evident that the increased focus on safety when working-at-heights has had a direct impact on the number of survey stations that a surveyor can install in a production shift when using traditional surveying methods that relies on repeated access to the hangingwall.