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Extraction of developed pillars


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Extraction of developed pillars

  1. 1. Extraction of Developed Pillars By Open Cast Method I. Satyanarayana, M.Tech,MBA,MCADy. Manager, Project Planning, SCCL,, visit at
  2. 2. SCCL OC Mines where Pillars are being extracted by OC Method•GK OC - KGM•JK OC - Yellandu•MNG OC II Extension (Phase-II) - MNG•KTK OC - BHPL•RG OC I Expansion - RG III•RG OC III Extension - RG II•SRP OC - SRP•BPA OC II Extension - BPAPK 1 &2 Inclines, Indaram 1 Incline, MK4 & RK -4&4A,SMG1&1A, SMG3, KK-2&2A are the UG mines projected forconversion to OC.
  3. 3. Why UG mines are converted to OC• In SCCL most of the UG mines are operating with semi mechanised system• Bord & Pillar system is being followed in most of the UG mines for coal extraction• Opencast mining is the prime source of SCCL in generating Profits as well as wiping off losses incurred from UG mines.• The % of coal recovery by Bord & Pillar system varies between 40-45 only• There are nearly 3 to 3.5 BT of coal reserves in standing pillars in the country.• Limited Opencastable reserves• The increased cost of production from UG mines indicates need of opening up new opencast mines to augment the sustainable production.• To extract the thin seams & remnant coal pillars and to reduce the cost of production
  4. 4. Advantages over UG method• Seams which can not be extracted by – UG methods can be extracted by OC Method• No ventilation & fire problems• No strata control problems• Coal recovery is nearly 100 %• Cost of production is less• Manpower requirement is low• Enhanced safety• Early returns on the capital• High capacity can be planned
  5. 5. Associated problems in conversion to OC Collapsing of under ground galleries (Bogging Down of Men & Machinery) Fire Due To Spontaneous Heating Environmental Pollution Degradation of Coal Loss of coal due to fire Presence of foreign bodies in coal (Steel, Timber, Concrete Blocks etc.) 5
  6. 6. OFF SET SURVEY & STANDING ORDERS1. Before intended to close the ug mine for conversion to OC, a detailed off set survey has to be conducted and the position of workings including the disturbances and falls should be clearly demarcated on the plan. For safe extraction of coal and effective compaction of galleries, standing orders for demarcation, drilling, blasting and monitoring of compaction of galleries are framed and being implemented scrupulously. PLAN PARTING AND PROVED PARTINGS Immediately after exposure of the coal seam, when ever the parting inOB reaches critical zone, the surveyor marks the gallery junction points inthe field and demarcated with plan parting on the play cards. After demarcation, drilling will be done to ascertain proved parting andrecorded in the book kept for the purpose. Based on the proved parting, zones are demarcated. 6
  7. 7. MARKING OF THE ZONESCRITICAL ZONE When ever the parting between u/g galleries and top of the coal seam/OB bench reaches 6 to 10 mtrs. the place is termed as critical zone which is safe for extraction coal and OB. The zone is demarcated with yellow flags.DANGER ZONE When ever the parting between U/G galleries and top of the Coal seam/OB bench is with in 6 Mtrs, the place is termed as danger zone. Only operations of drilling and dozing are permitted and demarcated with red flags. No work other than the above is permitted including men and any other machinary.COMPACTED ZONE After drilling and blasting, levelling of the area is done by dozer. After inspection of the area. the area is termed as compacted zone. this zone is permitted for normal extraction of coal/ob as it is safe. 7
  10. 10. Collapsing Of Under Ground Galleries (Bogging Down Machinery)1. The position of all UG galleries is being marked onground with stone dust, before taking up drilling activities.
  11. 11. 2. The gallery junction is being marked with boards showing the locations and parting particularsCRITICAL ZONE DANGER ZONE 6 to 10 mtrs Less than 6 mtrs The place is termed as critical zone. the place is termed as danger zone Which is safe for extraction coal and Only operations of drilling is permitted OB. and demarcated with RED FLAGS. the zone is demarcated with no work other than the above is YELLOW FLAGS.. permitted including men and any other. machinery
  12. 12. 3.The exact position of the gallery is being ascertained by test holes4. Drill is being moved perpendicular to the direction of the galleries5. The operator ensures that drill is standing on the solid pillar6. Drills operated by Remote Control are being usedAfter drilling, blasting and levelling of the area by dozer , The area istermed as compacted zone, This zone is permitted for normal extraction .
  13. 13. WORKING ON DIFFERENT ZONESBased on the proved parting after exposure of the seam/ob bench thecoal/OB benches shall be lowered upto critical zoneWhen ever the area reaches to critical zone, the area is demarcatedwith yellow flags to caution all the concern and to avoid hard digging,excess drilling in the critical zone.When ever the area reaches danger zone the area will be leveled fordrilling under the supervision of an overman then the surveyor will markthe position of underground galleries and drill holes pattern on thebench with stone dust, display the position and parting of galleryjunction with play cards mentioning the place and plan parting on it.The surveyor will hand over the notice of the galleries and parting withsketch to the overman, under manager, blasting in-charge, i/ccompacting galleries & I/C operations. 13
  14. 14. In-charge compacting galleries will instruct the necessary instructions tothe concerned shift persons regarding drilling.Shift under manger and shift overman will inspect the place and instructthe drill operator to carry out drilling as per the conditions.Test holes are drilled to ascertain the parting before commencement ofactual drilling operationsBased on the above the termination of holes over the galleries will beascertained and will be terminated 2 m in coal and 0.5 to 1 m in OBThe drilling on pillars and galleries are done in the pattern as shownbelow under the supervision of shift overman.The overman and under manger will record the proved partings, patternof drilling with depths in the record kept for the purpose 14
  15. 15. PLAN SHOWING THE DRILLING PATTERNAND MARKING OF THE GALLERIES IN THE FIELD FACE 53D/6L 6.6m PP Up to floor of the gallery Test hole 0.5 to 1 m in stone or 2 m in coal less than the test hole 15
  16. 16. DRILLING PROCEDURE OLD PRACTICEPreviously there was a practice of drilling single row ofholes over the galleries for compacting purpose but it wasfound in practice that the galleries were not compacteddue to partial filling of galleries causing pot holes. 16
  17. 17. O L D S Y S T E M N o :1 (S E C T IO N ) 1 M tr C O A L 1 .5 M tr 1 M tr C O A L 150MM 1 .5 M tr0 .7 5 M tr 2 .4 M tr/ 5 .0 M trs 3 .0 M tr G A L L IE R YO LD S Y S T E M N o :1 (P LA N ) 5 .0 M trs 5 .0 M trs 5 .0 M trs G A L L IE R Y 17
  18. 18. MODIFIED PRACTICEAfter experiencing the above problems, the drillingpattern was modified to 2 rows of holes over thegalleries for compaction purpose but it was found inthe stone roof in split seam and some parts of thickseam coal, the galleries were filled only partially dueto boulder formation. 18
  19. 19. Modified System 1 Mtr C O A L 1.5Mtr 1 Mtr C O A L 150MM 1.5Mtr0.75 Mtr 2.4Mtr/ 5.0Mtrs 3.0 Mtr GALLERY 3.0Mtrs 3.0Mtrs 3.0Mtrs 3.0Mtrs 3.0Mtrs 3.0Mtrs GALLIERY 19
  20. 20. PRESENT PRACTICETwo rows of holes are being drilled over the galleriesOne row of holes on either side of the gallery leaving a space of 1 m upto floor of the galleryAfter switching over to the present system there is a considerableimprovement in the compacting of the galleries and reduction in potholing and coal being extracted safely. 20
  21. 21. PRESEN T SYSTEM (SECTION ) 1 Mtr C O A L 1.5Mtr 1 Mtr C O A L 150MM 1.5Mtr 0.25Mtr 0.75 Mtr 0.5Mtr 2.4Mtr/ 3.0 Mtr PILLAR G ALLER Y (PLAN) 3.0M trs 3.0M trs3.0M trs 3.0M trs 3.0M trs 3.0M trs3.0M trs 3.0M trs 3.0M trs 3.0M trs PILLAR 21
  22. 22. PRECAUTIONS WHILE DRILLING OVER THE GALLERIESCode of practice is framed and being implemented and thesalient features are as followsWhile marching the drill, drill should not be marched over theunderground galleriesDrill should not be marched over the gallery junctions.Drilling should be carried out by placing the drill over the pillarWhen ever any hole was inadvertently punctures into thegallery a fresh hole shall be drilled 0.5 m adjacent to the hole.Drilling on the pillars is done either in coal or OB selectively indifferent bands to prevent degradation of coal. 22
  23. 23. PRECAUTIONS WHILE DRILLING OVER THE FIERY GALLERIES• Adequate pool of fire extinguishers is being kept near to the drill machine.• Fire fighting ranges with necessary fire hoses are extended near to the fire area with sufficient number of water jets.• Water tanker with necessary hoses with turbo jets are kept ready at the site.• Drilling is carried out under the constant supervision of an overman. 23
  24. 24. PRECAUTIONS WHILE CHARGING AND BLASTING FOR COMPACTION• At the beginning of the shift, the blasting in-charge will take the report of the drilling of previous shifts• The surveyor along with his team inspects the place and makes a sketch of the area with actual depth of the holes.• After ascertaining the perfectness of the drilling, in-charge gallery compacting will permit for charging and blasting of the area.• Blasting in-charge along with overman will inspect the blast site and instruct the overman regarding the amount of explosive to be charged in various depth holes.• Blasting overmen then takes the measurements of temperature of each hole and note down in the field book irrespective of whether galleries under fire or not with the help of non-contact digital thermometer specially procured for the purpose.• Whenever the temperature of the hole exceeds 800 the holes are filled with water and charging will be done after temperature reduced to below 800.• When temperature of hole exceeds 800 even after watering the holes, the holes are left uncharged. 24
  25. 25. PRECAUTIONS AFTER BLASTING• Immediately after blasting, blasting in-charge, overman and in- charge compacting galleries will inspect the site and ensures proper compacting and permit for levelling of the area.• The levelling operations shall be conducted under the supervision of an overman and experienced dozer operator.•• The dozer operator will level the area from outcrop to dip side to ensure proper filling of the galleries and to prevent bogging down of dozer. 25
  26. 26. PRECAUTIONS WHILE EXTRACTING IN COMPACTED ZONE• After ascertaining the effectiveness of compactness a limit line of extraction is marked on the ground keeping 5 m safe distance from the compacted area. the limit line is demarcated with white flags.• No extraction is permitted beyond the limit line.• In-charge compacting galleries will permit the extraction of area 26
  27. 27. COMPACTING NEAR FAULT/DISTURBED AREAS• After experiencing pot holing even though the partition is more than 10 m near the fault area.• It was decided to compact the galleries upto 15 m on either side of the fault irrespective of zones immediately after exposure of seam 27
  28. 28. SAFETY EDUCATION AND PROPAGANDA• Every month incharge compacting galleries will conduct safety meeting on gallery compacting, programme for the month and areas compacted during the previous month and also experiences. all the members were educated by explaining them the programme on the plan with all details.• Suggestions are invited from the supervisors/ executives.The following information will be handed over to the members – Gallery compacting programme sheet – Part plan showing the compacted galleries, proposed compacting programme, rl’s of the benches and plan partings – All the minutes are recorded in a bound paged book kept for the purpose. 28
  29. 29. EXPERIENCES• Only with the experience and visual observation SCCL officals are acertaining the effectiveness of gallery compacting• It is not possible to acertain the compactness by drilling as drilling is not possible in the compacted zone.• It is observed that sometimes the compaction is not effective at galleries filled with water 29
  30. 30. RECOMENDATIONSBefore converting the under ground mine as aopencast the traversing and offset survey of the underground mine must be done and the following detailsshall be marked on the plan specially prepared for theoperational purpose. • Complete off set survey details including the heights of the galleries. • All major faults, slips, disturbances • All major falls, air crossings, area heightened for the hauler places, cross overs • All iron girders, w-straps with roof bolts, roof bolts, roof stitching used for supporting the under ground galleries and junctions. 30
  31. 31. – Diesel operated shovels and drills are preferred.– High density explosives are to be used in watery holes.– Sand bags stemming is preferred instead of normal drill cuttings in watery holes.– Automatic fire suppression system should be mandatory on HEMM used over fiery galleries.– Heavy duty magnetic separators shall be installed in the hopper and on the running belt conveyors.– Controlled dewatering of the mine is most important to prevent fires in galleries and to improve safety in gallery compacting. 31
  32. 32. ConclusionTo avoid collapsing of under ground galleriesand bogging down of men and machineryeffective compaction of galleries is to bedone meticulously and scrupulously toliquidate coal from standing pillars byopencast method safely. 32
  33. 33. Thank you all,