Watson, BPMosomane, SMKuijpers, JSRoberts, David P2009-07-232009-07-232008-08Watson BP, Mosomane SM, Kuijpers JS et al. 2008. Investigations into the residual strength of a 2.5 m wide Bushveld Merensky Reef crush pillar.The Journal of the Southern African Institute of Mining and Metallurgy, Vol. 108 pp, 473-4800038-223Xhttp://hdl.handle.net/10204/3510Copyright: 2008 Southern African Institute of Mining and MetallurgyThe first crush pillars on the Bushveld platinum mines were introduced at Union Section in 1978. Before the introduction of crush pillars, serious problems were experienced when stoping advanced to a point 30 m to 40 m on both sides of the centre gully. At least three to four stopes were collapsing per month. Increased incidence of bursting has been reported on some mines at deeper levels but most of these bursts occur in the back areas. Nevertheless, the incidence of bursting increases the risk of falls of ground in already dangerous areas, and the larger pillars decrease the extraction ratio. This paper describes the evaluation of stress measurements conducted in two boreholes over a crush pillar with dimensions 2.5 m x 4.0 m, and a height of 1.2 m.The residual strength of the crush pillar with a width of 2.5 m was determined from a series of strain measurements in two boreholes and a Boussinesq matrix inversion. The calculated peak and residual stresses of the pillar were surprisingly high at 280 MPa and 48 MPa respectively. These high stress conditions are suspected to be associated with the narrow pillar geometry on the up-dip side and the stiff loading conditions under which failure took place. In order to get a more realistic evaluation of residual strength, a series of such measurements is recommended to establish a range of residual strengths for narrow crush pillars.enMicro-cracksCrush pillarsNon-linear stress-strainUniaxial compressive strengthPillar axisIn situ measurementBoreholeBushveld Merensky ReefStopesStopes collapsesBurstingMetallurgyMiningArticleWatson, B., Mosomane, S., Kuijpers, J., & Roberts, D. P. (2008). Investigations into the residual strength of a 2.5 m wide Bushveld Merensky Reef crush pillar. http://hdl.handle.net/10204/3510Watson, BP, SM Mosomane, JS Kuijpers, and David P Roberts "Investigations into the residual strength of a 2.5 m wide Bushveld Merensky Reef crush pillar." (2008) http://hdl.handle.net/10204/3510Watson B, Mosomane S, Kuijpers J, Roberts DP. Investigations into the residual strength of a 2.5 m wide Bushveld Merensky Reef crush pillar. 2008; http://hdl.handle.net/10204/3510.TY - Article AU - Watson, BP AU - Mosomane, SM AU - Kuijpers, JS AU - Roberts, David P AB - The first crush pillars on the Bushveld platinum mines were introduced at Union Section in 1978. Before the introduction of crush pillars, serious problems were experienced when stoping advanced to a point 30 m to 40 m on both sides of the centre gully. At least three to four stopes were collapsing per month. Increased incidence of bursting has been reported on some mines at deeper levels but most of these bursts occur in the back areas. Nevertheless, the incidence of bursting increases the risk of falls of ground in already dangerous areas, and the larger pillars decrease the extraction ratio. This paper describes the evaluation of stress measurements conducted in two boreholes over a crush pillar with dimensions 2.5 m x 4.0 m, and a height of 1.2 m.The residual strength of the crush pillar with a width of 2.5 m was determined from a series of strain measurements in two boreholes and a Boussinesq matrix inversion. The calculated peak and residual stresses of the pillar were surprisingly high at 280 MPa and 48 MPa respectively. These high stress conditions are suspected to be associated with the narrow pillar geometry on the up-dip side and the stiff loading conditions under which failure took place. In order to get a more realistic evaluation of residual strength, a series of such measurements is recommended to establish a range of residual strengths for narrow crush pillars. DA - 2008-08 DB - ResearchSpace DP - CSIR KW - Micro-cracks KW - Crush pillars KW - Non-linear stress-strain KW - Uniaxial compressive strength KW - Pillar axis KW - In situ measurement KW - Borehole KW - Bushveld Merensky Reef KW - Stopes KW - Stopes collapses KW - Bursting KW - Metallurgy KW - Mining LK - https://researchspace.csir.co.za PY - 2008 SM - 0038-223X T1 - Investigations into the residual strength of a 2.5 m wide Bushveld Merensky Reef crush pillar TI - Investigations into the residual strength of a 2.5 m wide Bushveld Merensky Reef crush pillar UR - http://hdl.handle.net/10204/3510 ER -