Application of Design by Measurement for Support and Pillar Design in Mechanised Room and Pillar Coal Mining in India

Transcription

1 AusRock2014-5/6 th November Application of Design by Measurement for Support and Pillar Design in Mechanised Room and Pillar Coal Mining in India Keith MacAndrew Alex Garcia Ian Gregson Atul Gandhe

2 Indian Coal Background India is the 3 rd largest coal producer in the World (530mt/annum). India has the 4 th largest coal reserves in the World (approx. 277bt). 2-3bt are estimated to exist as pillars in old mining districts. Almost 90% of India s coal production is accounted for by surface operations. Underground mining is now being expanded due ever increasing environmental restrictions on near surface deposits. India has the 2 nd largest population in the World after China with 1.2 billion. It is expected to increase its current annual consumption of coal from 770mt to 1.5bt/annum by 2030 (with 400mt/annum imported). This will require India to at least double its annual production in the next 20 years. To meet this projected demand, India is looking to highly mechanised underground mining. November 14,

3 Golder in India Rock Mechanics Technology (RMT - now Golder) was formed following the privatisation of the Rock Mechanics Department of British Coal in 1994 and were instrumental in the successful introduction of rockbolting in to the UK coal mining industry, to replace standing steel support. (It should be noted that at the time, this method of support was outside of the current legislation in the UK and was closely supervised by the UK Mines Inspectorate). India s underground coal mines have been worked mainly by unmechanised room and pillar methods and has large coal reserves estimated at 2-3 billion tonnes left as pillars at existing mines. Coal Indian recognised that these untapped reserves could potentially be extracted using modern methods with remote controlled continuous miners, playing a significant role in increasing production in the near future. November 14,

4 Golder Projects in India Golder currently have 5 projects with JMS (Joy Machinery). Plus 2 similar projects with Tractor India (Caterpillar Equipment). Two of the World s largest equipment suppliers. Many more projects in the pipeline. These projects were originally with Joy Mining and Caterpillar equipment. Joy and Caterpillar wanted to reduce their risk and supply equipment only. Both Joy and Caterpillar have transferred their contract mining services to JMSL and Tractor India Private Limited respectively. November 14,

5 Golder Projects in India Working Range of CMs to date in India Mining Depth Pillar Centres Entry Heights Entry Widths 10 m to 410 m 20 m to 47 m 3.0 m to 5.8 m 4.8 m to 6.5 m November 14,

6 Design Approach Use best practice and proven experience for initial design. Measure to confirm that expected behaviour is taking place to confirm design assumptions: Behaviour of roof, ribs, floor and pillars. Progress in stages - prove each stage before changing. Understand roof failure mechanisms. Use an effective rockbolt system. Design by measurement. Monitor the system. Use real data to validate computer models. November 14,

7 Golder Design Process Support Verification Process on Development Geotechnical Assessment Geotechnical Report Initial Support System Support Rules Support Modified Support Implementation Unstable Local area unstable Support Verification Stable Routine Monitoring Local area stable November 14,

8 APPLICATION TO INDIAN ROOM AND PILLAR COAL MINING November 14,

9 Standard Indian Rockbolting System Rebar and Cement Reinforcement November 14,

10 ADVANCED TECHNOLOGY ROCK BOLTING AT Resin 24 mm Fast and Slow Capsules Improved Bolt and End Assemble November 14,

11 Rockbolt Performance (SEPT) UK 22mm A.T. bolt / UK A.T. resin India 22mm bolt / India resin Cement capsule rockbolts have been proven to have a very low capacity (10 50 kn) for a fully encapsulated bolt Minimum Requirement 130 kn With improvement in rockbolt consumables in India, the rockbolt system has easily attained our minimum requirement of 130 kn for 300 mm of encapsulation Short Encapsulation Pull Test (SEPT). 40 Cement Capsules in India Range DISPLACEMENT (mm) November 14,

12 DESIGN BY MEASUREMENT FOR ROCK BOLT SUPPORT November 14,

13 Design by Measurement for Support Falls of ground still cause around one third of all underground coal mining fatalities. A lack of formal systematic design procedures in mining ground control has been highlighted as an industry failing. In deeper mines with relatively weak rocks, such as those typically found in coal mines, failure is predominantly stress driven. Design methods for these conditions need to concentrate on rock mass behaviour under the imposed stresses and the ability of installed reinforcement to resist active rock shear. Few rock bolt support patterns for coal mines are designed in any formal way, most adapt to the encountered conditions. November 14,

14 Design by Measurement for Support Unfortunately, in the early stages of a mining project, only limited data may be available on rock engineering properties, thus it falls to the experience of the designer to specify the initial design. Monitoring rock bolt performance and entry deformation after installation to confirm/optimise design is key to the application of design by measurement. Safety monitoring is also an important part of the process, providing routine monitoring at regular intervals to identify areas outside of the norm for enhanced ground control safety. This can be achieved with visual telltales to target additional remedial support where it is required. November 14,

15 Routine Safety Telltales November 14,

16 Dual-height Telltale Dual height telltales indicate movement in and above the bolted height. November 14,

17 Rock Bolting Telltale Colour Graduation A + B = Total movement A Yellow Green Red 20mm 60mm 40mm B Yellow Red Green Green 55mm 20mm 40mm 0mm B = movement above bolted height B B TOTAL TOTAL 40mm 115mm 60mm 80mm 20mm A = movement within bolted height A A B 70

18 Safety Monitoring Instrumentation Rock Bolting Telltale Simplest form of extensometer Extremely effective and purely visual Traffic light system (red, yellow, green) for action levels Two indicators connected to stainless steel wires Wires anchored in open borehole (35-42mm diameter) Provide visual indication of roof movement above and below the rock bolted height November 14,

19 Action Levels November 14,

20 Rotary Telltale Rotary telltales convert tiny movements onto a readable rotary scale. November 14,

21 How a Rotary Telltale Works R M T Rock Mechanics Technology November 14,

22 How a Rotary Telltale Works R M T Rock Mechanics Technology November 14,

23 How a Rotary Telltale Works R M T Rock Mechanics Technology November 14,

24 How a Rotary Telltale Works R M T Rock Mechanics Technology November 14,

25 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn m 0.0high D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn Entries increased from 4.5 m to 6.5 m wide and 2.5 m to 4.5 RTT Colour Zones Panel Retreat 67L 67L 68L 69L Barrier Pillar November 14,

26 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn RTT Colour Zones Panel Retreat 67L 67L 68L 69L Barrier Pillar November 14,

27 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn RTT Colour Zones Panel Retreat 67L 67L 68L 69L Barrier Pillar November 14,

28 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn RTT Colour Zones Panel Retreat 67L 67L 68L 69L Barrier Pillar November 14,

29 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn RTT Colour Zones Panel Retreat 67L 67L 68L 69L Barrier Pillar November 14,

30 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn RTT Colour Zones Panel Retreat 67L 67L 68L 69L Barrier Pillar November 14,

31 CMP5 Panel, VK7 Rotary Telltale Readings Example of 10 m single height Rotary Telltale readings taken during roadway enlargement operations at VK7 of old bord and pillar workings. Identifying areas requiring additional support prior to partial pillar extraction. RTT Location 15-Mar Mar Mar Mar Mar Mar Mar Mar-11 Remarks 1 23D/67L Jn D/68L Jn NA NA NA D/69L Jn NA NA NA NA D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/68L Jn D/69L Jn D/67L Jn D/69L Jn RTT Colour Zones Panel Retreat 67L 69L 68L 67L Pillars not considered for partial extraction on panel retreat Barrier Pillar November 14,

32 Design Monitoring Instrumentation Roof/Rib Strain Gauged Bolts Roof and Rib Extensometers More accurate instruments Comprehensive set of data on rock and support behaviour Instruments verify pillar design by installing instruments into pillars All instrumentation is remote reading Also used to validate numerical models (FLAC, FLAC3D and MAP3D) November 14,

33 Design Monitoring Instrumentation (cont.) Strain Gauged Rock Bolts Fully encapsulated rockbolts develop a load profile along their length depending on rock properties and stresses around the tunnel. It is important to be able to measure this profile. We glue 9 pairs of resistance strain gauges in opposed machined grooves along the bolt. November 14,

34 Sonic Roof/Rib Extensometers Instrument Anchors Installation November 14,

35 Multiple Wire Roof/Rib Remote Reading Extensometers November 14,

36 Vibrating Wire Stress Cells (Pillar Loading) Proving Ring Platen Vibrating Wire Section through a vibrating wire stress cell November 14,

37 Monitoring of Depillaring at NCPH, SECL Example of an underground remote reading monitoring station in India.

38 Monitoring Roof Displacement During Depillaring, CM5, NCPH, SECL Remnant coal pillars left in Seam No.3, 38 m above. November 14,

39 Monitoring Roof Displacement During Depillaring, CM5, NCPH, SECL Rfx Pillars 16 & 17 mined November 14,

40 Monitoring Roof Displacement During Depillaring, CM5, NCPH, SECL Rfx Pillar 18 mined November 14,

41 Monitoring Roof Displacement During Depillaring, CM5, NCPH, SECL Rfx Pillar 19 mined November 14,

42 Monitoring Roof Displacement During Depillaring, CM5, NCPH, SECL Instrument Lost as Pillar 20 mined Rfx November 14,

43 Monitoring of Depillaring at NCPH, SECL

44 Summary The successful introduction of mechanised room and pillar working in India coalmines would not have been possible without the simultaneous introduction by Golder of advanced technology rock bolting; High capacity support systems; Design based on measurement; Training; and Technology transfer. The wider application of design by measurement approach has the potential to significantly improve ground control safety in coal and other soft rock mines (evaporites). The routine safety monitoring system is also an important element of the design by measurement process. In the future, it is anticipated that the surface monitoring of ground control safety through remote monitoring of roof displacement will be commonplace. November 14,

45 AusRock2014-5/6 th November Thank you for your attention Keith MacAndrew Alex Garcia Ian Gregson Atul Gandhe