IMPROVING THE MINING EFFICIENCIES BY MEANS OF A NEW SUPPORT DESIGN AT UNISEL MINE. AMMSA Annual General Meeting 1 December 2017

Transcription

1 IMPROVING THE MINING EFFICIENCIES BY MEANS OF A NEW SUPPORT DESIGN AT UNISEL MINE AMMSA Annual General Meeting 1 December 2017

2 2 OVERVIEW Introduction to Unisel Problem statement Objectives Investigation Lost blast analysis Seismic review of Unisel Passive Vs. active support Underground observations Summary Analysis and results Support Omni 89 props Underground trial Costing Shaft update Conclusion References

3 3 INTRODUCTION - UNISEL Free State, Welkom, RSA Marginal operation Acquired in 1994 (5 years) Scattered mining Conventional Three reef bands, Leader, Middle and Basal Dip of the reef degrees 1150mbs to 2200mbs Limited shaft time, counter weight system.

4 4 INTRODUCTION TO UNISEL - SAFETY Unisel FOG Achievements In March 2017, Unisel Stoping Sections surpassed 20 consecutive years FOG Fatal Free. In July 2017 Unisel Development Sections surpassed 8 consecutive years FOG Fatal Free. On 29 November 2017 the mine surpassed FOG Fatal Free Shifts.

5 5 PROBLEM STATEMENT Ensure and maintain the integrity of the current support system, whilst improving the safety and mining efficiencies of the supporting cycle, reducing the shaft time and possibly reducing the overall costs of the entire support system, thus increasing the production in order to enhance Unisel s profitability.

6 6 OBJECTIVES Improve safety Reduce the workload for underground employees Maintain the integrity of the support design Improve the mining efficiencies (support and cleaning cycles) Replace the passive support with an active support (creep) Reduce shaft time Reduce overall support costs

7 7 INVESTIGATION LOST BLAST ANALYSIS Unisel - Stoping - Lost blast 2016 Machine breakdown Support blasted out Section 54 Cleaning equipment Inadequate water supply/pressure Safety Stoppage Poor planning (material or equipment) Equipping Power failure Inadequate air supply/ pressure Nightshift cleaning incomplete Inadequate/ Incomplete support 1298 Installing additional support Sweeping back areas Total m² lost

8 8 INVESTIGATION - SEISMIC REVIEW OF UNISEL

9 9 INVESTIGATION - PASSIVE VERSUS ACTIVE SUPPORT

10 10 INVESTIGATION UNDERGROUND OBSERVATIONS Poor installation of support Relatively slow closure rates at Unisel Timber is a natural product and has a large range of variability. Poor layouts (German boxes) No timber bays to store support underground Lack of support delivery Inadequate shaft time

11 11 INVESTIGATION - SUMMARY Seismically active environment (Low risk) Ensure the same hanging wall stability (Safety) Stiffer, more active support, rather than a passive support Quicker installation Easier installation Durable support Blast on support Reduce shaft time (reduction in cars) Cater for a stoping width of 1.8 m to 2.5 m Cost effective

12 12 ANALYSIS AND RESULTS - SUPPORT OMNI 89 PROPS Ground conditions 10 tonnes Weight < 30kg Cater for 1.8m to 2.5m stoping width Reduce timber creep Active support Easy installation Reusable if blasted or pulled out Dynamic loading Cater for buckling Costing

13 13 UNDERGROUND TRIAL Underground trial was conducted at L6 22 N4 panel on Unisel. The panel was ledged and then immediately went onto props Time studies and practicality was monitored Minor concerns were raised: 90 degrees installation (Installation tool) Creep on headboards

14 14 UNDERGROUND TRIAL

15 15 UNDERGROUND TRIAL

16 16 UNDERGROUND TRIAL

17 17 UNDERGROUND TRIAL - RESULTS Parameter Current system Original system Variance Support systems Strike pillars Omni 89 props Timber packs (pre-stressed with grout bags) (breaker lines only) Rock studs Grouted shepherds crooks Ease of installation Good Strike pillars Timber packs (pre-stressed with grout bags) Rock studs Grouted shepherds crooks Poor Durability of support/ blast out rate 5% 10% - 15% 10% Transportation into the stope, minutes minutes 84 minutes preparation and installation time per prop Total support installation time 2-3 hours hours 13 hours Labour required to install support 3-4 persons persons 9-10 persons Mono-rope time to transport support 1 hour 8 hours 7 hours Cars per deck 1 0 Cars per trip 3 0 Time to complete one full trip minutes Cars per day

18 18 UNDERGROUND TRIAL - RESULTS The results of the trial are: No injures reported for the trial month Hanging wall conditions improved dramatically Average working hours for the crew over the past year per shift 12 hours Achieved 10 hours Call 320m² - Achieved 450m² The trial was successful and after motivating the results to the EXCO of Harmony a roll out strategy was implemented. June 2017 All 24 qualifying panels have successfully been trained and props have been implemented.

19 19 COSTING Parameter Original system Current system Variance Support systems Strike pillars Timber packs (prestressed with grout bags) Strike pillars Omni 89 props Timber packs (pre-stressed with grout bags) (breaker lines only) Cost per m² (R) R R R Exchange rate R - $ R R Cost per m² ($) $ $ $ Saving % 24.74%

20 20 SHAFT UPDATE 1 2.0m 2.5m 6.0m 7.5m Since June 2017 there has been mixed results in terms of usage in the qualifying panels. 1.0m Trench 1.0m if SW = 2.5m if SW = 2.0m if reef allows it 6.0m 7.5m Due to the low grade, and scattered mining, crews move every few months to new ground and ledging is required m 2.5m 1.0m Another challenge is the increase in reef width s from 2.4m to 3.2m. The introduction of Omni 127 props commenced in November 2017 to allow the same support design to be utilised in a double cut method on a maximum stoping width of 3.5m m 2.5m 2.0m 2.5m 1.0m 6.0m 7.5m 6.0m 7.5m 1.0m

21 21 CONCLUSION Objectives Improve safety Reduce the workload for underground employee Maintain the stability of the mine Maintain the integrity of the support design Improve the mining efficiencies (support and cleaning cycles) Replace the passive support with an active support (creep) Reduce shaft time Reduce overall support costs

22 22 REFERENCES BRADY, B.H.G, BROWN, E.T. (1999). Rock Mechanics for Underground Mining, Kluwer Academic Publishers JAGER, A.J. and ROBERTS, M.K.C. Support systems in productive excavations. Gold 100. Proc. of the Int. Conf. on Gold. Vol 1: Gold Mining Technology. SAIMM, Johannesburg, pp KLOKOW, J. Evaluation of current recommended stope support design methodology as applied to deep level mining. Proc. of the Colloquium for Successful Support Systems for Safe and Efficient Mining, 27 May 1999, South African Inst. of Mining and Metallurgy RYDER, JA and JAGER, AJ (2002) A Textbook on Rock Mechanics for Tabular Hard Rock Mines., SIMRAC RYDER, JA and JAGER, AJ (1999). A Handbook on Rock Engineering Practice for Tabular Hard Rock Mines, SIMRAC

23 QUESTIONS