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ABSTRACT: Merensky reef is mined extensively within the Bushveld Complex. In previously mined out areas on the Merensky reef horizon there are pillars, potholes and remnants that have not been mined. These unmined blocks of ground on the Merensky reef horizon can influence the mining of the underlying UG2 reef. The extent of the influence will depend on the size of unmined ground and the middling between the two reef horizons. This paper quantifies the influence of partially extracted Merensky reef on mining of the UG2 reef, and aims to provide recommendations for mining strategies, as well as regional and local support to achieve efficient and safe extraction of the UG2 reef, for various middlings beneath the Merensky Reef horizon. In some cases it was found that relatively shallow UG2 reef mining could encounter conditions similar to those experienced in deep and ultra deep mining environments. INTRODUCTION Extensive UG2 reef reserves underlie the partially mined Merensky Reef (MR) within the Bushveld Complex. The middling between the two reef horizons varies from 4 m to 400 m. Unmined ground in the form of pillars, potholes and remnants has been left during the mining of the MR horizon. The adverse influence of the unmined portion of MR horizon has become a major concern when mining on the UG2 reef horizon. This paper evaluates the effect of the overlying unmined ground on the MR horizon, on mining of the UG2 reef. General recommendations for mining and support strategies to achieve efficient and safe extraction of the UG2 reef horizon are also provided. The extent of mining in the Bushveld Complex is shown below in Fig. 1.
- Materials > Metals & Mining (1.00)
- Energy > Oil & Gas > Upstream (0.47)
ABSTRACT: Tilt data are being used to study the behaviour of deep-level mine layouts, particularly the performance of dip pillar systems. The tilt data are being recorded by a triggered seismic recording system. The triggered data showed velocity and tilt data that correlated well in time, allowing for separation of the tilt data into coseismic and aseismic tilting. The following results have been obtained from analysis of data recorded over 109 days: Coseismic tilt jumps occur in either direction; The total amount of coseismic tilt in each direction is approximately the same; The time-of-day tilting shows the effect of blasting on the coseismic tilting and, to a lesser degree, on aseismic tilting. As a preliminary interpretation, this can be attributed to the brittle nature of the rock mass and to the stiff mining layouts practiced in the area. As a more definitive interpretation, this observation is compatible with a level of stress of the rock blasted at the face that is very much lower than would have occurred if the rock were infinitely strong and unfractured; and Tilt jumps show a power-law behaviour compatible with the Gutenberg-Richter relationship with b = 1 over more than two orders of magnitude. Numerical tools have been developed to estimate tilting from mining, assuming elastic rock mass behaviour. Some suggestions for further work are made. These include studying changes in aseismic tilting following tilt events associated with shrinking pillars. This might provide more direct insights into pillar stability than are obtained from the general results obtained here.
- Oceania > Papua New Guinea > Papuan Peninsula > Central Province > National Capital District > Petroleum Retention License 15 > P’nyang Field (0.98)
- Oceania > Papua New Guinea > Papuan Peninsula > Central Province > National Capital District > Petroleum Retention License 15 > Elk-Antelope Field (0.98)
- Oceania > Papua New Guinea > Papuan Peninsula > Central Province > National Capital District > Petroleum Retention License 15 > Angore Field (0.98)
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