ANGLO AMERICAN S OPEN CUT COAL MINES IN AUSTRALIA. John Hoelle Ismet Canbulat

Transcription

1 A RISK RATING SYSTEM FOR ANGLO AMERICAN S OPEN CUT COAL MINES IN AUSTRALIA John Hoelle Ismet Canbulat

2 ANGLO AMERICAN PLC Anglo American Metallurgical Coal is a wholly owned subsidiary of Anglo American plc. Anglo American Plc is geographically diverse, with operations in Africa, Europe, South and North America, Australia and Asia. 2

3 ANGLO AMERICAN METALLURGICAL COAL 3

4 CHARACTERISTICS OF OPEN CUT COAL MINES Fast moving faces Relatively shallow Long straight benches Short life slopes Things happen quickly Not practical to have complex geotechnical investigations after each blast 4

5 AAMC GROUND CONTROL APPROACH AT OPEN CUT MINES Design should be appropriate Ground control should be managed pro-actively Continuous improvements in ground control is required No-surprise failures (out of design), and Learn from every failure 5

6 WHY PRO-ACTIVE MANAGEMENT, RISK MANAGEMENT AND CONTINUOUS IMPROVEMENTS REQUIRED? 6

7 WHY RISK ASSESSMENT? 7

8 WHY RISK ASSESSMENT? 8

9 WHY RISK ASSESSMENT? 9

10 WHY RISK ASSESSMENT? 10

11 WHY RISK ASSESSMENT? 11

12 WHY RISK ASSESSMENT? 12

13 WHY RISK ASSESSMENT? 13

14 WHY RISK ASSESSMENT? 14

15 WHY RISK ASSESSMENT? 15

16 WHY RISK ASSESSMENT? 16

17 WHY RISK ASSESSMENT? 17

18 WHY RISK ASSESSMENT? 18

19 ELEMENTS OF GROUND CONTROL 19

20 ELEMENTS OF GROUND CONTROL 20

21 ELEMENTS OF GROUND CONTROL 21

22 WHY ALSO OPENRISK? to enable operations to make quality decisions to pro-actively management strata for a safe and effective production of open cut mines to avoid surprises to learn from the failures 22

23 OPENRISK IS TESTED AND IMPLEMENTED BEFORE Since 2003, the South African mines are individually required by law to draw up Codes of Practice (CoP) to combat rockfall accidents Part of the required the CoP was a risk based approach to open cut slope stability Anglo American Thermal Coal has approach expert in the field (in Australia, South Africa, USA and the UK) to develop a unique risk management system, and After a 12 months of work; OpenRisk was developed for Anglo American Thermal Coal in

24 ADVANTAGES OF OPENRISK The system provides an unbiased, standard quantified assessment of risks (as input parameters are quantifiable, as much as possible); Likelihood of failure and stability can be determined; Consequences/severity of failure can be determined; The risk or change in risk can be monitored over a period of time or face advance; Controls/responses are pre-determined by experts; The performance of a crew can be monitored over a period of time; The change in likelihood of failure when the controls implemented can be monitored; It is user-friendly; everyone at operations can use it; Does not require extensive training (i.e. ½ day); 24

25 ADVANTAGES OF OPENRISK (CONTD.) Can be used after each blast (because it takes approximately 1 hour to complete the assessment) or over a period of time; Controls are automated; however can also be manually entered; It produces a text output that can be signed by all relevant parties (mine manager, geotech, supers) so that everyone knows what needs to be done Chart output makes it easy to follow the change in risks from the previous blast/time; Can be used for highwalls and lowwalls Can also be used in portal/boxcut t designs and risk managements. 25

26 PRINCIPLES OF OPENRISK 1. It is a semi-quantitative risk management system Qualitative scales are given values It produces a more expanded ranking scale; however not to suggest absolute values but educated values The numbers are combined using a formula (i.e. weightings) 2. The input parameters can easily be updated or changed. 3. It assumes that the risk is a function of many parameters of given conditions and mining gp parameters (i.e. responses to given conditions) 26

27 PRINCIPLES OF OPENRISK (CONTD.) Open Cut Risk Rating Rating of uncontrollable parameters, which cannot be changed Rating of controllable parameters (responses), which can be changed Determine likelihood of failure, severity, and risk category Determine likelihood of failure, severity, and risk category Determine the overall likelihood of failure, severity and risk category 27

28 ASSUMPTION IN CALCULATING LIKELIHOOD OF FAILURE AND SEVERITY If worse possible condition is present, it represents the maximum possible risk and the Likelihood of failure is 1.0, which means it will definitely fail Parameter 1 Parameter 2.. Parameter n Likelihood of failure scale

29 ASSUMPTION IN CALCULATING LIKELIHOOD OF FAILURE AND SEVERITY Parameter 1 (Water) Sub-parameter 1 (dry) Sub-parameter 2 (moist) Sub-parameter 3 (flowing) Determine the weightings of each parameter 29

30 CONTROLLABLE MINING PARAMETERS 1) GEOMETRY 1.1 Batter back soft/weathered material Not Applicable Loose blocks at crest Yes / minimum 50 deg. 10 NO 1 No/morethan50deg deg. 20 YES Height of highwall 2) MINING 0-35 m Undercutting spoils m 5 NO m 10 YES 20 > 70 m Undercutting highwall Angle of highwall NO 1 < 65 deg. 1 YES deg Spoils in water > 75 deg. 10 NO Top bench width YES 10 > 10 m Spoiling of weathered material at toe of spoils 0-10 m 5 NO 1 No bench 10 YES Spoils on the highwall 3) BLASTING Not applicable Blasting method of highwall < 15 m high/>10 m from crest 1 Pre-split 1 <15 m high/<10 m from crest 3 No pre-split 10 >15 m high/>10 m from crest Highwall condition due to blasting >15 m high/<10 m from crest 10 Straight H/W no loose material Height of spoils on lowwall Straight highwall, some loose material 5 Not applicable 0 Frozen coal, overhangs, loose material m Pre-split barrels m 5 Not applicable 0 > 95 m 10 Visible Cut width (deviation from standard) Not visible 10 Standard within 5 m Blast holes Not standard (> 5 m deviation) 10 Visible Noses present Not Visible 10 NO 1 YES 20 30

31 AUTOMATED CONTROLS FOR MINING PARAMETERS 1) GEOMETRY Actions/Instructions 1.1 Batter back soft/weathered material High hazard area, batter back, if possible. Mark & barricade off. No people, equipment or machinery under the H/W. Batter to 50-degrees 1.2 Height of highwall Increase the exclusion zone to 15 m. Conduct stability analysis 1.3 Angle of highwall Ensure dragline digs a straight H/W. Check the blasting practice. Review design parameters. Review mining procedure 1.4 Top bench width All crests should have a minimum 10-metre bench 1.5 Spoils on the highwall All crests should have a minimum 10-metre bench; review design and mining i procedure 1.6 Height of spoils on lowwall Check dragline spoiling. Check cut width. Ensure spoil is not undercut. Extended bench may be required. Conduct stabilty analysis Cut width (deviation from standard) Noses present Spoiling room may be an issue. Extended bench may be required. Review 3D-Dig. Cut correct pit width. May require coal safety berm at least 20 m wide. High-risk area. Install monitoring. Initiate better scaling practices 1.9 Loose blocks at crest Make/extend the exclusion zone at the toe of H/W to 15 m and ensure no people, equipment or machinery in the area. Monitor the area. Work under supervision. Scale if possible 2) MINING 2.1 Undercutting spoils Stop undercutting the spoils. Barricade the area. Install monitoring. Review mining procedure 2.2 Undercutting highwall Stop undercutting the spoils. Barricade the area. Install monitoring. Review mining procedure 2.3 Spoils in water Pump the water. Practice should be that spoil should never be dumped or shot into water. 2.4 Spoiling of weathered material at toe of spoils Extended bench may be required. Double handle weathered material or mix with fresh O/B before spoiling. Review mining sequence to minimise placement of weak material at base of spoil 3) BLASTING 3.1 Blasting method of highwall Review blasting design & applicability to conduct pre-split on all highwalls and endwalls 3.2 Highwall condition due to blasting Scale if possible. Review blast design and applicability. 3.3 Pre-split barrels Review blast design and applicability. 3.4 Blast holes 31

32 UNCONTROLLABLE GEOTECHNICAL PARAMETERS 1) GEOLOGY 1.1 Depth of weathering 2) WATER m 1 1 Water coming out of face bedding or structure 5-10 m 5 NO m 10 YES 10 > 20 m Is there water accumulation at toe of slope 1.2 Discontinuities NO 1 None 1 YES 10 1 (simple) Is there water on top of highwall/benches within 30m of crest 2 (complex) 10 NO 1 >3 (complex) 20 YES Direction of discontinuities 4 Rain Not applicable 1 No rain in past 5 days 1 Same direction (<30 deg.) 10 Rained in the past 5 days 5 Different direction (>30 deg.) 20 Has been raining for the past 5 days Dipping structure / bedding 2. 5 Head of water Flat/dipping into the face 1 No water 1 Dipping into the cut 20 Stable, no increase Clay material in bedding Increase in water head 10 NO 1 3) SPONCOM 3. YES 10 1 Is the toe of highwall burning 1.6 Length of structure NO m 1 YES m Is the toe of lowwall/spoil or any layer burning > 5 m 20 NO Presence of floor rolls and dipping seam YES 10 NO 1 3) DRAGLINE 4. YES 10 1 Dragline bench built on 1.8 Major dykes/faults/burnt coal Not applicable (truck & shovel operation) 0 NO 1 Unweathered material 1 YES 10 Weathered material Cracks on highwall/benches within 10 m of crest Weathered material and water 10 NO 1 YES Highwall condition Stable 1 Loose/rock/blocks 5 Wedges/overhangs 10 Zone of weakness 20 32

33 AUTOMATED CONTROLS FOR GEOTECHNICAL PARAMETERS 1) GEOLOGY Actions/Instructions 1.1 Depth of weathering Batter, bench to hard, if it is soil batter to 45 deg., if it is weathered material batter to 60 deg. Conduct stability analysis; evaluate pre-strip ti 1.2 Discontinuities Increase awareness of jointing. Conduct kinematic stability analysis; 1.3 Direction of discontinuities Increase awareness of joint orientation. Conduct kinematic stability analysis; 1.4 Dipping structure / bedding Increase awareness of dip of jointing. Conduct kinematic stability analysis; 1.5 Clay material in bedding 1.6 Length of structure 1.7 Presence of floor rolls and dipping seam Determine the dip of the strata. Install monitoring. 1.8 Major dykes/faults/burnt coal Cracks on highwall/benches h h within 10 m of crest Notify management and Geotechnical Engineering Department immediately. Install monitoring. Haul routes to be moved. Barricade the area. Ensure no equipment or men at the H/W Highwall condition Increase the exclusion zone to 15 m 2) WATER 2.1 Water coming out of face bedding or structure Pump water and monitor the slope. 2.2 Is there water accumulation at toe of slope Pump water and monitor the slope. 2.3 Is there water on top of highwall/benches within 30m of crest Divert water and pump water out. 2.4 Rain Monitor the slope. Pump standing water, if required. Slope may be affected up to 5 days after rain, therefore keep awareness high. 2.5 Head of water 3) SPONCOM 3.1 Is the toe of highwall burning Sand dress the slope. Use water canons. 3.2 Is the toe of lowwall/spoil or any layer burning Sand dress the slope. Use water canons. 3) DRAGLINE 4.1 Dragline bench built on 33

34 OUTPUT Geotechnical Risk Mining Risk Overall Risk Likelihood of failure Severity Risk Category 34

35 OPENRISK 35

36 GEOTECHNICAL PARAMETERS 36

37 MINING/PERFORMANCE PARAMETERS 37

38 OUTPUT 38

39 OUTPUT 39

40 OUTPUT 40

41 APPLICATION AT AAMC & CONCLUSIONS OpenRisk adequately detects areas of high risk and generates appropriate remedial solutions to reduce the risks. Awareness of the personnel is higher at the sites that use OpenRisk. The proactive approach of OpenRisk ensures that all personnel are aware of risks in the pits and how to deal with potential high risk areas. The results indicated that the risk system was consistent with reality and could be trusted to provide relative assessments of the open pits. OpenRisk system empowers the employees on the operation to determine the risk and assists them in identifying the controls for these risks by automatically selecting the operations work procedures necessary to eliminate or reduce the rock fall hazard. A record of potential rock fall hazard is also available in the system. 41

42 FUTURE DEVELOPMENTS UQ & A/PROF. M. KIZIL 42

43 ACKNOWLEDGEMENTS AAMC is acknowledged to allow us to present this paper AAMC open cut mines are acknowledged for their contribution 43

44 THANK YOU