Geo-Tech Studies for Longwall


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Geo-Tech Studies for Longwall

  1. 1. <ul><ul><li>Development of Guidelines </li></ul></ul><ul><ul><li>for </li></ul></ul><ul><ul><li>Effective design of Longwall layout based on </li></ul></ul><ul><ul><li>Geo-technical studies with reference to Ramagundam region, SCCL </li></ul></ul>Venkat
  2. 2. <ul><ul><li>LITERATURE REVIEW </li></ul></ul>From the extensive literature survey very important points related to the present topic were collected and few of them are presented in the next slides.
  3. 3. LITERATURE REVIEW <ul><li>Use of geotechnical instrumentation is started in 1930s and 1940s with convergence monitoring and later stress components. The development of borehole extensometers (Merrill 1954, Potts 1957) and of stress meters for underground use took off in the 1950s. Micro seismic monitoring is introduced this time. </li></ul><ul><li>All the measurements done using different instruments in covering the geotechnical aspects will finally results into observation two physical responses, which are displacement and pressure. </li></ul>
  4. 4. LITERATURE REVIEW <ul><li>3D aspects of Longwall geo-mechanics that are to be monitored in every Longwall project are: </li></ul><ul><ul><li>Stress control </li></ul></ul><ul><ul><li>Effect of geometry </li></ul></ul><ul><ul><li>Effect of faulting </li></ul></ul><ul><ul><li>Effect of depth </li></ul></ul><ul><ul><li>Effect of width </li></ul></ul><ul><ul><li>Changes in lithology </li></ul></ul>
  5. 5. LITERATURE REVIEW <ul><li>Stress around the Longwall face, which is a prime cause for rock breakage is due to abutments from the previous Longwall on one side, relief of horizontal stress both towards the current Longwall goaf and the previous mined out area and fluid pressure. </li></ul><ul><li>It is found from the investigations that the rock breakage in front of the Longwall is coincident with goafing activity behind i.e. change in stress in front of the face is also responsible for the relief of stress behind the face. </li></ul>Stress Control
  6. 6. LITERATURE REVIEW <ul><li>Geometry of Longwall with respect to the virgin stress field and the previously mined out areas plays a major influence in the development of abutment stress. </li></ul><ul><li>Starting a Longwall midway along the length of the previous block exposes the new Longwall to a fully developed side abutment, thus decreasing ‘honeymoon period’ i.e. resulting in full goafing and weighting conditions much earlier than normal for a new block. </li></ul>Effect of Geometry
  7. 7. LITERATURE REVIEW <ul><li>Effect of faulting on Longwall geo-mechanics is mainly dependent on cohesion and friction angle of the fault plane and the surrounding rock and the incidence of the abutment loads upon that plane. </li></ul>Effect of Faulting
  8. 8. LITERATURE REVIEW <ul><li>With increasing depth the mechanics becomes biased towards the tailgate side because of the magnitude of overlap between the side abutment from the previous Longwall and the forward abutment from the retreating face. </li></ul>Effect of depth
  9. 9. LITERATURE REVIEW <ul><li>There are two critical widths for a Longwall face in a given set of conditions quite different in magnitude and controlled by different geo-mechanical factors. </li></ul><ul><li>The first is the width beyond which there is no further subsidence. The second is the width beyond which there will not be an increase of shield loading at the centre of the face. </li></ul>Effect of width
  10. 10. LITERATURE REVIEW <ul><li>Issues emanating from alteration in characteristics of massive zones or weaker horizons, changes of grade or soft floor, changes of seam thickness or presence of splits can all be sufficiently important to warrant detailed management plans. </li></ul>Effect of Lithology
  11. 11. LITERATURE REVIEW <ul><li>Bi-axial stress meters are the new instruments used to detect the mining induced stress changes mostly horizontal stresses around a Longwall panel. Experience has shown that horizontal stress changes are preferably carried in zones with the highest modulus of elasticity. </li></ul><ul><li>With Bi-axial stress meters, stresses are measured in the horizontal plane. The measured values are change in major principle stress, change in minor principle stress and angle measured from the line of Longwall advance counterclockwise to the direction of major principle stress (in plan view). </li></ul>
  12. 12. LITERATURE REVIEW <ul><li>The geo-technical parameters related to bedding discontinuities are orientation, spacing, persistence, roughness/shape, aperture and filling. </li></ul><ul><li>According to Voussoir beam theory vertical joints are present in the beam and which can fail in one of three ways, by vertical shear along the joints if the confirming stresses are low, by buckling if the bed thickness/ span ratio is high, or by compressive failure. </li></ul>
  13. 13. LITERATURE REVIEW <ul><li>Stresses observed in coal mines are caused by global plate-tectonic forces. </li></ul><ul><li>The magnitude of the principal horizontal stress, especially at depths less than 800m, is often two to three times that of the vertical stress. </li></ul><ul><li>In Longwall mines, the observed effects of horizontal stresses include: </li></ul><ul><ul><li>Compressive type roof failures. </li></ul></ul><ul><ul><li>Directionality of roof falls – entries oriented nearly perpendicular to max. Horizontal stress suffers much greater damage than those oriented parallel. </li></ul></ul><ul><ul><li>Head gate failures. </li></ul></ul>
  14. 14. LITERATURE REVIEW <ul><li>Franklin (1997), Brady and Brown (1985) suggested that, generally geotechnical monitoring may be carried out for four main reasons. </li></ul><ul><ul><li>To record the natural values of, and variations in geotechnical parameters such as water table level, ground levels and seismic events before the initiation of an engineering project. </li></ul></ul><ul><ul><li>To ensure safety during construction and operation. </li></ul></ul><ul><ul><li>To check the validity of the assumptions made in designing. </li></ul></ul><ul><ul><li>To control implementation of ground treatment and remedial works. </li></ul></ul>
  15. 15. LITERATURE REVIEW <ul><li>Any monitoring system should satisfy the following. </li></ul><ul><ul><li>Easy installation even under adverse conditions. </li></ul></ul><ul><ul><li>Adequate sensitivity, accuracy and reproducibility of measurements. </li></ul></ul><ul><ul><li>Robustness and durable for the required period of operation. </li></ul></ul><ul><ul><li>Ease of reading and immediate availability of the data to user. </li></ul></ul><ul><ul><li>Negligible mutual interference with mining operations. </li></ul></ul>
  16. 16. LITERATURE REVIEW <ul><li>In Rock Mechanics sense, ‘success’ can mean: </li></ul><ul><ul><li>An optimum economic result through reduced costs, increased mine life or extraction ratio or increased productivity. </li></ul></ul><ul><ul><li>Increased practical knowledge of the mine environment. </li></ul></ul><ul><ul><li>Increased confidence in planning and management. </li></ul></ul><ul><ul><li>A safe mining operation. </li></ul></ul>
  17. 17. LITERATURE REVIEW <ul><li>The main reasons for success of Longwall in China are </li></ul><ul><ul><li>the policy thrust of the coal sector, </li></ul></ul><ul><ul><li>massive investment in imported and indigenous faces, </li></ul></ul><ul><ul><li>the focus on ‘walking on two legs’, </li></ul></ul><ul><ul><li>fast decision making, </li></ul></ul><ul><ul><li>highly developed manufacturing base for mining equipment and </li></ul></ul><ul><ul><li>above all the work culture in a mandarin-dominated society. </li></ul></ul><ul><li>These critical success factors are simply missing in Indian coal industry resulting in poor performance. </li></ul>
  18. 18. LITERATURE REVIEW <ul><li>The contributory factors that have been identified for the not so successful operation of Longwalls in India are: </li></ul><ul><ul><li>Inadequate assessment of geological and geotechnical aspects. </li></ul></ul><ul><ul><li>Flawed equipment selection. </li></ul></ul><ul><ul><li>Failure in planning, operation, provision of service back-up and spares availability. </li></ul></ul><ul><ul><li>Failure in inculcating a culture for mechanised Longwall. </li></ul></ul><ul><ul><li>Issues of power supply, material supply, ventilation, dust control and availability of clean water </li></ul></ul><ul><ul><li>Absence of viable manufacturing capacity for Longwall equipment. </li></ul></ul>
  19. 19. <ul><ul><li>GEO-ENGINEERING STUDIES AT SCCL </li></ul></ul>
  20. 20. Geo-Engineering studies at SCCL <ul><li>Geo-engineering is defined as ‘the application of geological sciences to engineering practice for the purpose of assuring that the geologic factors affecting the location, design, construction, operation and maintenance of engineering works are recognized and adequately provided for’. </li></ul><ul><li>These studies in SCCL are divided broadly into </li></ul><ul><ul><li>Pre-mine development </li></ul></ul><ul><ul><li>In-mine development </li></ul></ul>
  21. 21. Pre-Mine development studies <ul><li>To assess the strength behaviour of rock different laboratory tests were conducted on NX size core samples collected from the boreholes. </li></ul><ul><li>From the tests the following geo-engineering properties are collected: </li></ul><ul><ul><li>Density </li></ul></ul><ul><ul><li>Compressive, tensile & shear strength </li></ul></ul><ul><ul><li>Young’s modulus </li></ul></ul><ul><ul><li>Impact strength index </li></ul></ul><ul><ul><li>Protodyaknov index </li></ul></ul><ul><ul><li>Point load strength index </li></ul></ul><ul><ul><li>Slake durability index </li></ul></ul>
  22. 22. Pre-Mine development studies <ul><li>The following properties are calculated from the core collected: </li></ul><ul><ul><li>Rock Quality Designation (RQD) – is done for a minimum of 25m of roof strata of coal seam and 6m of floor strata. </li></ul></ul><ul><ul><li>Caving Index – To assess the cavability of roof rock during the extraction. </li></ul></ul>
  23. 23. In-Mine development studies <ul><li>Underground Mapping – </li></ul><ul><ul><li>Roof ‘guttering’ or roof ‘pots’ are mapped in underground and the stress direction is inferred from their orientation and severity. </li></ul></ul><ul><ul><li>The features like joints, cleats, fractures, slips, sandstone dykes etc are demarcated on the underground working plan. </li></ul></ul><ul><ul><li>Rose diagrams are drawn to find out the most prominent set of the structural features influencing the roof instability. </li></ul></ul>
  24. 24. In-Mine development studies <ul><li>Rock Mass Rating (RMR) – is determined to know the type of roof so as to design the support requirement. </li></ul><ul><li>Geo-Modeling – Basic seam structure and lithological interpretation by preparing a model from the data collected from the boreholes is done with the help of ‘MINEX’ software. </li></ul>
  25. 25. <ul><ul><li>DATA COLLECTION </li></ul></ul>- LW Production trend in SCCL - Data from completed LW panels of GDK.10A
  26. 26. INTRODUCTION <ul><li>The first Longwall was commissioned in SCCL at GDK.7 Incline, RG-II in September, 1983. </li></ul><ul><li>Till now 10 sets of Longwall were purchased by SCCL. Mainly the equipment was purchased from UK and China. </li></ul><ul><li>Till now 71 Longwall panels have been completed in SCCL and presently 4 Longwall units are in operation in 4 Underground mines. </li></ul>
  28. 28. SALIENT FEATURES OF GDK 10A INCLINE <ul><li>Mine started on :16-06-1985 </li></ul><ul><li>Introduction of Longwall : FEB,1994 </li></ul><ul><li>No. of workable seams : 2 (No.1& 2) </li></ul><ul><li>Present working seam : No.1 Seam </li></ul><ul><li>No of LW panels completed : 9 </li></ul><ul><li>Total production : 5.1 MT </li></ul><ul><li>Balance reserves : 3.5 MT </li></ul><ul><li>Balance life : 3.5 Years </li></ul><ul><li>Grade of coal : “E” </li></ul><ul><li>Project cost : Rs. 116.53 Crores </li></ul>
  29. 29. GDK.10A INCLINE <ul><li>GDK 10A produced 5.40 LT of coal against the target of 5.38 LT in the year 2005-06. </li></ul><ul><li>Presently, One Longwall unit, Two road headers and 4 SDL’s are working in this mine. </li></ul>
  30. 30. Panel no.3A Panel no.8 P L A N
  31. 31. GDK.10A INCLINE Borehole Section showing 1 seam
  32. 32. GDK.10A INCLINE PANEL WISE PRODUCTION SN Panel No. Panel/Face length Coal Extraction (T) Avg. monthly prod (T) 1 1 980/150 764148 63679 2 2 990/150 756663 68787 3 3 1024/150 761927 69266 4 10 850/140 551577 55158 5 10A 555/158 434416 39492 6 11 900/110 358791 25812 7 7 955/1118 532620 33171 8 12 720/93.5 361126 51589 9 8 515/115 + 496/135 619384 51615
  34. 34. DATA COLLECTED AT 10A MINE <ul><li>Geological conditions & PMP of strata. </li></ul><ul><li>Details of the equipment. </li></ul><ul><li>Gist of data collected for all the panels </li></ul><ul><li>Breakdown analysis of different panels. </li></ul><ul><li>Variation in Main fall and periodic fall distances with changes in face lengths. </li></ul><ul><li>Support health monitoring. </li></ul><ul><li>Average Weighting zone. </li></ul>
  35. 35. Longwall Equipment Specification 1 SHEARER Make Anderson Type AM – 500 DERDS chainless power track haulage with twin traction drive Weight 45T Length 12M Power 2X375 KW(500HP) Capacity 800TPH@ 3M/Min & 1600 TPH @ 6M/Min Haulage speed 0- 9 M/Min. 2 ARMOURED FLEXIBLE CONVEYOR Make Anderson Type Chain 26 MM twin inboard Power 2 X 150 KW Capacity 1000TPH Speed 1.08 M/ Sec.
  36. 36. Longwall Equipment Specification 3 BEAM STAGE LOADER Make Anderson Type Chain 26 MM, Twin inboard Power 150 KW Capacity 1200TPH Speed 1.15 M/ Sec. 4 LUMP BREAKER Make Becorit Power 90KW Capacity 1200TPH 5 POWER PACK Make Hauhinco Capacity Pump supplying 150 LPM(33GPM) at 300 bar Tank capacity 2x 2000 Ltrs. Coupled together Power 125 KW.( 94 HP)
  37. 37. Longwall Equipment Specification 6 POWERED ROOF SUPPORTS Make Meco/LW International Weight 20. 5 T Capacity 4 Leg X 800T Supply Pr. & Yield Pr. 300bar & 400 bar respectively Support height range 2.2 M to 3.3 M 7 BELT CONVEYORS MAKE Meco Huwood Capacity 1200TPH Width 1200MM Power 2 X 150 KW Huwood Chieftan type
  38. 38. GIST of ALL PANELS Description P. NO1 P. NO.2 P. NO.3 P. NO.10 P NO.10A P. NO.11 P. NO.7 P. NO.12 P. NO.8 P. Length (m) 980 990 1024 850 555 900 955 720 990 Face Length(m) 154.2 154.2 156.2 144 164.4 115.7 125.8 98.9 120.7 / 141 Ht.of extr. (m) 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 No.of chocks 101 101 101 94 111 78 80 66 77/90 Min. Depth (m) 154 184 215 184 166 223 247 263 268 Max. Depth (m) 203 234 272 260 228 285 297 300 322 M. fall span(m)     77.7 63.4 64.4     70.7 72.65 Avg. retreat for local fall (m) 17.94 13.8 15.92 14.9 12.9   15.26 19.1 18.4/14.4 Local fall varying (m) 10.15-26.10 6.8-26.6 7.5-24 7.4-22.5 6.6-18.8   8.6-23.4 10.7-29.5 10-25.8 / 8.5-23.7 Avg Ch Bleeding 54 48 27 25 12   10 6 4.6 / 5 Weighting zone C25-86 C21-79 C29-79 C20-71 C30-82   C22-53 C21-40 C27-53/ C39-59 Dt. of Starting 19-Oct-94 02-Jan-96 26-May-97 02-Aug-98 16-Aug-99 22-Jun-01 19-Dec-02 11-Sep-04 25-Sep-05 Dt of completion 12-Sep-95 08-Nov-96 05-Apr-98 20-Apr-99 19-Jul-00 31-Jul-02 30-Mar-04 25-May-05 10-Oct-06 Date of meshing 28-Aug-95 23-Oct-96 20-Mar-98 09-Apr-99 25-Apr-00 20-Jul-02 13-Mar-04 15-May-05 23-Sep-06 days worked 269 220 275 220 253 295 404 194 305 Avg. Retreat (m/day) 3.64 4.50 3.72 3.86 2.19 3.05 2.36 3.71 3.25 Coal extr. (T) 764148 756663 761927 551577 434416 358791 532620 361126 619384 Max. Subsi. (m) 1.59 1.5 1.2 1.19 1.98 0.6 1.3 Nil Nil Static Test % Drop downs 8.0 7.6 18.5 26.2 66.0 70.3 48.6 56.6 48.9 % Drop to Zero 0.0 0.6 2.1 4.5 26.0 35.2 13.6 8.3 5.6
  39. 39. GIST of ALL PANELS <ul><li>Till now, 9 Longwall panels have been extracted at GDK.10A Incline with varying face lengths from 93m to 158m and depths from 154m to 322m. </li></ul><ul><li>The average rate of retreat is varied from 2.19m to 4.5m per day. </li></ul><ul><li>The make of water observed from working goaf is about 200 to 300 GPM/day. </li></ul>
  41. 41. <ul><li>Longwall equipment worked successfully in the first three years as long as warranty spares were available. </li></ul><ul><li>With the increased problems and non availability of OEM spares, critical components were indigenized which resulted in compatibility problems. </li></ul><ul><li>with all the refurbishment with indigenous spares, any new panel will only work without problems for only four months after installation. </li></ul>GDK.10A INCLINE BREAKDOWN ANALYSIS
  42. 42. Face length Vs Main Fall distance
  43. 43. Face length Vs Periodic Fall distance
  44. 44. <ul><li>The face advance for first local fall was varying from 30.5m to 44.7m while the span of main fall varied from 63m to 78m as obtained from field observations. </li></ul><ul><li>The periodic weighting distance is varied from 12m to 20m. </li></ul><ul><li>By observing the span of main fall for various face lengths, it is can be understood that the main fall span will vary only for face lengths ranging between 90 and 170m. </li></ul>Face length Vs Main & Periodic Fall distance
  45. 45. Face length Vs Weighting zone
  46. 46. <ul><li>The critical face length (which is double the equivalent main fall span) from the observation of worked out Longwall panels is found to be 140m as the average main fall span is found to be around 70m. </li></ul>Face length Vs Weighting zone
  47. 47. Supports Health condition STATIC TEST RESULTS
  48. 48. Supports Health condition STATIC TEST RESULTS <ul><li>Percentage of pressures drop down to zero in static test are within permissible limits upto Panel no.10. </li></ul><ul><li>Due to non availability of spares for dowel pack system, the percentage has increased in Panel no.10A and 11. </li></ul><ul><li>After switching over to linear control system from Panel no.7 onwards, the health of supports is improved. </li></ul><ul><li>The following additional benefits also achieved with linear control system like </li></ul><ul><ul><li>Easy availability of spares. </li></ul></ul><ul><ul><li>simplification of total circuit. </li></ul></ul><ul><ul><li>reduction in number of hoses in the circuit, etc. </li></ul></ul>
  49. 49. The work of literature survey and collection of data from other longwalls of SCCL will be continued in the next Six months.
  50. 50. Thank you all...