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Abstract Thin Spray-on Liners resist relative small deformations (< 1 mm) between rock blocks or fragments in terms of a combination of shear, adhesive and tensile-bond strengths. Shear-bond strength addresses the ability of a thin liner to resist stresses that act parallel to the rock-liner interface. Therefore quantification of shear-bond strength is essential in the formulation of design standards and requirements for Thin Spray-on Liners. In this paper Thin Spray-on Liner support mechanisms are reviewed. In addition previous methods of Thin Spray-on Liner shear-bond testing are discussed. The paper also explains the research being carried out at the University of Cape Town to investigate the effect of different parameters on the shear-bond strength.
Introduction Rock surface support is widely used to combat rockfalls and resulting injuries and fatalities in the vicinity of active faces (Potvin, 2002), where workers spend most of their time (Adams & Baker, 2002; Potvin, 2002; Lacerda, 2004). The conventional (traditional) surface support systems in underground rock support include passive methods such as mesh and lacing and active methods such as shotcrete. However, rockfall sources between 1990 and 2000 in Nevada gold mines showed a steady increase in rockfall injury associated with mesh support as shown in Figure 1 (Lacerda, 2004). The conventional methods also negatively impact the mining operations with regards to costs, logistics and mining cycle times due to large material volumes (Tannant, 2001; Ozturk & Tannant, 2010; Ferreira, 2012). Therefore, these systems need to be substituted, with enhanced methods, in order to realize the business target of the mining industry of providing the planned return on investment made without harm and within budget.
As a solution, since the 1990's, diverse kinds of Thin Spray-on Liners were developed with the aim of providing replacements for the conventional methods (Stacey, 2001; Tannant, 2001; Yilmaz, 2011). TSLs have the advantages of low volume, rapid application and rapid setting. They are also applied by simple equipments as demonstrated by Figure 2 (Ferreira, 2012). These are all properties that ease logistics, improve on cycle times, increase mechanisation and improve safety (Adams & Baker, 2002; Tannant, 2001; Hermanus, 2007; Yilmaz, 2011). However, their application in the mining industry is still in its initial stages. Therefore, its design as surface support systems is still based on experience, assumptions, field observations and cost considerations (Tannant, 2001; Saydam, Yilmaz & Stacey, 2003; Yilmaz, 2011). This is because the mechanisms by which TSLs act to provide support are not fully understood (Tannant, 2001; Leach, 2002; Saydam, Yilmaz & Stacey, 2003).
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