Spatial positioning of sidewall stations in a narrow tunnel environment: a safe alternative to traditional mine survey practice
Chapter 10. Conclusion and Recommendations
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Chapter 10. Conclusion and Recommendations
The objective of this research was to determine whether or not a survey network of survey stations installed in the sidewall of a narrow tunnel in the workings of a mine would offer a safe and accurate alternative to conventional surveying methods, while at the same time meeting the required minimum standards for a primary survey network accuracy as prescribed by the South African Mine Health and Safety Act of 1996 (Act 29). In order to evaluate this objective the following fundamental questions were formulated and answers sought:
The above questions cover the three aspects integral to an evaluation of any type of survey project, namely; is it accurate, is it safe and is it efficient? The conclusions based on the results obtained during this research will be discussed under these three headings. Mine Surveying principles have been used as the method of referencing the surface features of a mine with underground excavations for more than 2000 years. The fundamental purpose of mine surveying namely, the establishment of an accurately aligned connection between excavations while disrupting the core business of mining as little as possible, has remained constant throughout time. According to the International Society of Mine Surveying (ISM), Mine Surveying is defined as “a branch of Mining, Science and Technology which includes all measurements, calculations and mapping which serves the purpose of ascertaining and documenting information at all stages, from prospecting to exploitation, and utilizing mineral deposits by both surface and underground working.” [5] . In recent years the focus in the mining industry has changed to giving safety the number on priority. As previously noted both industry and government has adapted to a “zero-tolerance”: approach to any activity that may lead to potential harm or injury. In order for the Mine Surveyor to perform the activities of their profession it has become essential that all such activities relating to mine surveying measurements be done in such a way as to provide the safe and economical extraction of a mineral resource while at the same time ensuring compliance with all governmental and corporate standards and controls. Within this context safety with a “zero tolerance” to harm has become the primary performance driver of all professionals providing services within the mining environment. The focus on safety and the resultant procedures that are put in place to manage the safe conduct of employees in the production environment has an effect on the productivity of both surveying and production crews. It can therefore easily be imagined that the requirements of the survey- and production crews could be in conflict if the issues of safety, accuracy and efficiency are not optimized in a responsible manner by all parties. The aspects of safety and productivity in the South African mining context are seen to be interlinked entities, the one not being possible without the other. The policy of both the directorate of Minerals and Energy affairs and all mining companies operating in South Africa is that no production will be allowed to take place if it cannot be done safely. The current MHSA Chapter 2 (23) , as discussed in section 2.1 of this thesis, makes provision for workers to refuse to enter a working place or perform work if in their opinion the site or activity is unsafe. It is an offence according to the MHSA to prevent an employee from asserting this right or discriminating against such an employee [17]. It is important to note that most South African mining companies have as part of their mission statement a reference to the fact that no work will be performed if it cannot be done safely. The South African MHSA prescribes the standards of accuracy of mine surveying stations and excavations relative to all surface and underground features, including boundaries. It is of specific importance that the Mine Surveyor should be equipped to advise the production team regarding their relative position in relation to any area where a hazard may be contained. Such hazards will include dangerous accumulations of water or gas, excavations (current or abandoned) or any feature that may have an impact on the safe and profitable extraction of the economic resource. Recent mining disasters such as the Gretley mine disaster in Australia and the rescue of Chilean miners from a seemingly impossible situation underground has underlined the importance of the accuracy of surveying records, not as a “theoretical ideal” to be strived towards but as an integral tool in the safety management protocol of a mining operation. The risks involved in surveying are understood by surveyors but somehow the importance of survey accuracy is not verbalized or documented in a manner that creates awareness of the essential need for survey records in the minds of production personnel. The impact of an inaccurate survey in the control of an excavation can result in substantial financial losses. Such losses as a result of the financial and time impact of re-development may adversely affect the cut-off at which a mine can operate which in itself could lead to resource sterilization as the cost of production increases. The financial and legal consequences as a result of the loss of life or mining into areas in which the mining company does not own the mineral rights may arguably cripple a mining operation. Financial drivers demand that surveyors operate with smaller crews, install more survey control per surveyor and do so within a very strict budget. The production crew on a mine, working under similar demands often takes a non-favourable view on any activities that will impede the production process of drilling, blasting and cleaning. In order to evaluate the accuracy of a sidewall station network a test site was established on the Doornfontein Campus of the University of Johannesburg. A hangingwall network intended to simulate a typical underground network, was established to within the prescribed minimum standards of accuracy defined in the MHSA [17] for a Primary or Class “A” survey network and then checked with a sidewall survey station network. Resection setups made at the position of the hangingwall stations were used to determine the accuracy of closure on one of the previously established hangingwall control network points based on a sidewall survey station network. The accuracy of the closures obtained by using the sidewall survey stations was evaluated in terms of the prescribed minimum standards of accuracy as defined by the current regulations of the MHSA. From the results it was established that obtuse angle observations could be made without any deterioration of accuracy in the network. Factors that were tested included evaluating the geometry of setups, the distance between reference points and the setup point and the effect of small angles on the accuracy of a fix. Upon completion of the experimental evaluation of the sidewall survey station network, the methodology was tested in the underground workings of a mine to verify the experiment findings. At this stage the safety, accuracy and efficiency of the sidewall survey method was compared to the conventional hangingwall survey method. The sidewall survey station method provided closures that were found to be within the prescribed minimum standards of accuracy, providing comparative results with the conventional hangingwall survey method. It was found that parameters of geometry and observation protocol must be adhered to in order to obtain accuracies that will meet the prescribed minimum standards for accuracies for a Class “A” survey. It was also found that a cluster of four survey stations improved the accuracy of the survey network significantly when compared to the use of only two survey stations when calculating the position of a random setup. Furthermore the sidewall station method provide significant time savings while at the same time offering a reduced exposure to risk. In addition three mining operations evaluating similar methods of surveying were investigated. In all the case studies sufficiently accurate results from the principles of the sidewall survey station network were obtained.
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