Impact of geo technical factors on strata behavior in longwall panels of Godavari Valley coal field-a case study
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摘要
Understanding the cantilevers formed by thick, massive beds in the near-seam overburden above longwall panels and the associated loads and strata fracturing effects developed during caving(main and periodic weightings) are key elements for the successful implementation of longwalls. Such caving mechanisms rely on the geotechnical conditions within the panel. In India, the majority of longwall downtime and/or roof failures were caused by a lack of knowledge on overburden caveability, in particular when the main and periodic weightings will impact the face and longwall support selection to effectively mitigate such weightings. Godavari Valley Coal Fields is no exception as longwall faces were adversely affected due to the presence of thick, massive beds in the near-seam overburden at both Godavarikhani(GDK) 7 and 9 Incline mines. In contrast, overburden weightings were negotiated successfully in GDK10 A and Adriyala Longwall Project(ALP) mines by detailed geotechnical studies, the use of adequate longwall support capacities, and effective operational practices. Thirteen longwall panels with varying face width, at different depths have been extracted under massive sandstone beds of 18 m to28 m thickness at GDK 10 A and ALP mines. This study elucidates that the main roof weighting interval decreases with an increase in face width and attains a constant value with further increases in face width under the same geo-mining conditions. In addition, this study also concludes that with increases in face width, the periodic roof weighting interval decreases and shield loads increase. Similarly with increasing panel width to depth ratio, the main and periodic roof weighting intervals decrease but shield loads again increase. Lastly, the strata behaviour of the longwall face retreated along up-dip direction is demonstrated. The results of this paper improves the mechanistic understanding of the impact of face width,depth and main roof thickness on periodic weighting and associated roof control problems on the longwall face.
Understanding the cantilevers formed by thick, massive beds in the near-seam overburden above longwall panels and the associated loads and strata fracturing effects developed during caving(main and periodic weightings) are key elements for the successful implementation of longwalls. Such caving mechanisms rely on the geotechnical conditions within the panel. In India, the majority of longwall downtime and/or roof failures were caused by a lack of knowledge on overburden caveability, in particular when the main and periodic weightings will impact the face and longwall support selection to effectively mitigate such weightings. Godavari Valley Coal Fields is no exception as longwall faces were adversely affected due to the presence of thick, massive beds in the near-seam overburden at both Godavarikhani(GDK) 7 and 9 Incline mines. In contrast, overburden weightings were negotiated successfully in GDK10 A and Adriyala Longwall Project(ALP) mines by detailed geotechnical studies, the use of adequate longwall support capacities, and effective operational practices. Thirteen longwall panels with varying face width, at different depths have been extracted under massive sandstone beds of 18 m to28 m thickness at GDK 10 A and ALP mines. This study elucidates that the main roof weighting interval decreases with an increase in face width and attains a constant value with further increases in face width under the same geo-mining conditions. In addition, this study also concludes that with increases in face width, the periodic roof weighting interval decreases and shield loads increase. Similarly with increasing panel width to depth ratio, the main and periodic roof weighting intervals decrease but shield loads again increase. Lastly, the strata behaviour of the longwall face retreated along up-dip direction is demonstrated. The results of this paper improves the mechanistic understanding of the impact of face width,depth and main roof thickness on periodic weighting and associated roof control problems on the longwall face.
Understanding the cantilevers formed by thick, massive beds in the near-seam overburden above longwall panels and the associated loads and strata fracturing effects developed during caving(main and periodic weightings) are key elements for the successful implementation of longwalls. Such caving mechanisms rely on the geotechnical conditions within the panel. In India, the majority of longwall downtime and/or roof failures were caused by a lack of knowledge on overburden caveability, in particular when the main and periodic weightings will impact the face and longwall support selection to effectively mitigate such weightings. Godavari Valley Coal Fields is no exception as longwall faces were adversely affected due to the presence of thick, massive beds in the near-seam overburden at both Godavarikhani(GDK) 7 and 9 Incline mines. In contrast, overburden weightings were negotiated successfully in GDK10 A and Adriyala Longwall Project(ALP) mines by detailed geotechnical studies, the use of adequate longwall support capacities, and effective operational practices. Thirteen longwall panels with varying face width, at different depths have been extracted under massive sandstone beds of 18 m to28 m thickness at GDK 10 A and ALP mines. This study elucidates that the main roof weighting interval decreases with an increase in face width and attains a constant value with further increases in face width under the same geo-mining conditions. In addition, this study also concludes that with increases in face width, the periodic roof weighting interval decreases and shield loads increase. Similarly with increasing panel width to depth ratio, the main and periodic roof weighting intervals decrease but shield loads again increase. Lastly, the strata behaviour of the longwall face retreated along up-dip direction is demonstrated. The results of this paper improves the mechanistic understanding of the impact of face width,depth and main roof thickness on periodic weighting and associated roof control problems on the longwall face.
引文
[1]Peng SS.Topical areas of research needs in ground control-a state of the art review on coal mine ground control.Int J Min Sci Technol 2015;25:1-6.
[2]Obert L,Duvall WI.Rock mechanics and the design of structures in rock.New York:John Wiley and Sons,Inc.;1967.
[3]Mechanized Sarkar SK.Longwall milling the indian experience.India:Oxford and IBH publishing Co.Pvt.Ltd;1998.p.240.
[4]Kelly M,Gale W.Ground behavior about Longwall faces and its effect on mining.ACARP Project C5017 Final Report;1999.
[5]Frith RC,Stewart AM.Optimisation of powered support performance in relation to strata loading and engineering criteria.End of Grant Report,NERDDC Project 1445;1993.
[6]Strawson C,Moranbah Moodie A.North tests the critical caving theories.In:Proc.26th Int.Conf.on Ground Control,Morgantown.p.180-7.
[7]Khanal Manoj,Adhikary Deepak,Balusu Rao.Effect of strata properties and face widths on chock performance.J Rock Mech Geotech Eng 2011;3(1):407-14.
[8]Mills KW,Grady PO.Impact of Longwall width on overburden behavior.In:Coal Operators’Conference;1998,Wollongong.
[9]Peng SS.Coal mine ground control.3rd ed.ISBN:979-0-9789383-4-5.Printed in United States of America;2008,pp.363-366.
[10]Frith R,Creech M.Face width optimization in both Longwall and shortwall caving Environments.Final report:ACARP Project C5015;1997.
[11]Peng SS,Li HM,Feng JF,Du F,Li L,Jiang DJ.Effects of major mining and geological factors on overburden movement and shield capacity in Longwall mining.Min Eng Mag 2015:58-64.
[12]Bigby DN.Surface monitoring of weighting conditions on United Kingdom Longwall faces.In:CARE’88(Conference on Applied Rock Engineering).The Institution of Mining and Metallurgy;1988.p.23-34.
[13]Trueman R,Callan M,Thomas R,Hoyer D.Quantifying the impact of cover depth and face width on Longwall support-strata interactions.In:Proceedings of 10th Underground Coal Operators’Conference;2010.p.97-107.
[14]Medhurst TP,Reed K.Ground response curves for Longwall support assessment.Trans Inst Min Metall A Min Technol 2005;V114:81-8.
[15]Singh Gauri Shankar Prasad,Singh Upendra K.Numerical modeling study of the effect of some crtitical parameters on caving behavior of strata and support performance in a Longwall working.Intern J Rock Mech Rock Eng 2009.
[16]Kelly Michael.3D aspects of Longwall geomechanics.The Australian coal review;2000.p.20-25.
[17]Frith,RC.Half a career trying to understand why the roof along the Longwall face falls in from time to time?In:Proc.24th Int.Conf.on Ground Control in Mining,West Virginia;2005.
[18]Peng SS,Chiang HS.Longwall mining.New York:John Wiley and Sons,Inc.;1984.
[19]Sarkar SK.Mechanized Longwall mining e the Indian experiences.New Delhi:Oxford and IBH Publishing Company Private Limited;1998.
[20]Frith R.Development and demonstration of Longwall monitoring system for operational decision making.ACARP Project Report No.4017;1996.
[21]Trueman R,Thomas R,Hoyer D.Understanding the causes of roof control problems on a longwall face from support monitoring data-a Case Study.In:Coal Operator’s Conference.p.40-7.
[22]Green DR,Ward B.Determination of goaf delamination horizons and other roof geomechanical features using downhole acoustic logs,ACARP Project C9003 report;2002.
[23]Kuznetsov ST,Pekarskii DG,Korovkin VT.Determining the normal stresses in a uniform bent beam cantilever.Soviet Min Sci 1973;9(5):478-82.
[24]Singh GSP,Singh UK,Banerjee G.Cavability assessment model for Longwall working in India.In:Proceedings of the 3rd Asian rock mechanics symposium(Organized by ISRM,Kyoto,Japan);2004.p.295-300.
[25]Verma AK,Deb D.Effect of lithological variations of mine roof on chock support using numerical modelling technique.J Sci Ind Res 2006;65:702-12.
[26]Dyke MAV,Su HW,Wickline J.Evaluation of seismic potential in a longwall mine with massive sandstone roof under deep overburden.Int J Min Sci Technol 2018;28:115-9.
[27]Medhurst TP.Practical consideration in longwall support behavior and ground response.In:Coal Operator’s Conference.Brisbane:University of Wollongong;2005.p.49-57.
[28]Frith R,McKavanagh B.Optimisation of Longwall mining layouts under massive strata conditions and management of the associated safety and ground control problems.End of Grant Report,ACARP Project C7019;2000.
[29]Wiklund B,Kizil MS,Canbulat I.Development of a cavity prediction model for Longwall mining.In:Proceedings of the 11th underground coal operators’conference;2011.p.48-59.
[30]UdayBhaskar G,Srinivasa Rao A,Prasad GVS,Prasad KAVL.Geo-mining conditions of seam-I of Godavari sub-basin-a geophysical study.J Indian Geophys Union 2016;2(20):178-90.
[31]Das SK.Observations and classification of roof strata behaviour over Longwall coal mining panels in India.Int J Rock Mech Min Sci 2000;37:585-97.
[32]Boothukuri V,Madhav B,Charan P,Benerjee G.Geotechnical challenges and experiences of working a deep and wide Longwall face:a case study of Adriyala Longwall project,SCCL.
[2]Obert L,Duvall WI.Rock mechanics and the design of structures in rock.New York:John Wiley and Sons,Inc.;1967.
[3]Mechanized Sarkar SK.Longwall milling the indian experience.India:Oxford and IBH publishing Co.Pvt.Ltd;1998.p.240.
[4]Kelly M,Gale W.Ground behavior about Longwall faces and its effect on mining.ACARP Project C5017 Final Report;1999.
[5]Frith RC,Stewart AM.Optimisation of powered support performance in relation to strata loading and engineering criteria.End of Grant Report,NERDDC Project 1445;1993.
[6]Strawson C,Moranbah Moodie A.North tests the critical caving theories.In:Proc.26th Int.Conf.on Ground Control,Morgantown.p.180-7.
[7]Khanal Manoj,Adhikary Deepak,Balusu Rao.Effect of strata properties and face widths on chock performance.J Rock Mech Geotech Eng 2011;3(1):407-14.
[8]Mills KW,Grady PO.Impact of Longwall width on overburden behavior.In:Coal Operators’Conference;1998,Wollongong.
[9]Peng SS.Coal mine ground control.3rd ed.ISBN:979-0-9789383-4-5.Printed in United States of America;2008,pp.363-366.
[10]Frith R,Creech M.Face width optimization in both Longwall and shortwall caving Environments.Final report:ACARP Project C5015;1997.
[11]Peng SS,Li HM,Feng JF,Du F,Li L,Jiang DJ.Effects of major mining and geological factors on overburden movement and shield capacity in Longwall mining.Min Eng Mag 2015:58-64.
[12]Bigby DN.Surface monitoring of weighting conditions on United Kingdom Longwall faces.In:CARE’88(Conference on Applied Rock Engineering).The Institution of Mining and Metallurgy;1988.p.23-34.
[13]Trueman R,Callan M,Thomas R,Hoyer D.Quantifying the impact of cover depth and face width on Longwall support-strata interactions.In:Proceedings of 10th Underground Coal Operators’Conference;2010.p.97-107.
[14]Medhurst TP,Reed K.Ground response curves for Longwall support assessment.Trans Inst Min Metall A Min Technol 2005;V114:81-8.
[15]Singh Gauri Shankar Prasad,Singh Upendra K.Numerical modeling study of the effect of some crtitical parameters on caving behavior of strata and support performance in a Longwall working.Intern J Rock Mech Rock Eng 2009.
[16]Kelly Michael.3D aspects of Longwall geomechanics.The Australian coal review;2000.p.20-25.
[17]Frith,RC.Half a career trying to understand why the roof along the Longwall face falls in from time to time?In:Proc.24th Int.Conf.on Ground Control in Mining,West Virginia;2005.
[18]Peng SS,Chiang HS.Longwall mining.New York:John Wiley and Sons,Inc.;1984.
[19]Sarkar SK.Mechanized Longwall mining e the Indian experiences.New Delhi:Oxford and IBH Publishing Company Private Limited;1998.
[20]Frith R.Development and demonstration of Longwall monitoring system for operational decision making.ACARP Project Report No.4017;1996.
[21]Trueman R,Thomas R,Hoyer D.Understanding the causes of roof control problems on a longwall face from support monitoring data-a Case Study.In:Coal Operator’s Conference.p.40-7.
[22]Green DR,Ward B.Determination of goaf delamination horizons and other roof geomechanical features using downhole acoustic logs,ACARP Project C9003 report;2002.
[23]Kuznetsov ST,Pekarskii DG,Korovkin VT.Determining the normal stresses in a uniform bent beam cantilever.Soviet Min Sci 1973;9(5):478-82.
[24]Singh GSP,Singh UK,Banerjee G.Cavability assessment model for Longwall working in India.In:Proceedings of the 3rd Asian rock mechanics symposium(Organized by ISRM,Kyoto,Japan);2004.p.295-300.
[25]Verma AK,Deb D.Effect of lithological variations of mine roof on chock support using numerical modelling technique.J Sci Ind Res 2006;65:702-12.
[26]Dyke MAV,Su HW,Wickline J.Evaluation of seismic potential in a longwall mine with massive sandstone roof under deep overburden.Int J Min Sci Technol 2018;28:115-9.
[27]Medhurst TP.Practical consideration in longwall support behavior and ground response.In:Coal Operator’s Conference.Brisbane:University of Wollongong;2005.p.49-57.
[28]Frith R,McKavanagh B.Optimisation of Longwall mining layouts under massive strata conditions and management of the associated safety and ground control problems.End of Grant Report,ACARP Project C7019;2000.
[29]Wiklund B,Kizil MS,Canbulat I.Development of a cavity prediction model for Longwall mining.In:Proceedings of the 11th underground coal operators’conference;2011.p.48-59.
[30]UdayBhaskar G,Srinivasa Rao A,Prasad GVS,Prasad KAVL.Geo-mining conditions of seam-I of Godavari sub-basin-a geophysical study.J Indian Geophys Union 2016;2(20):178-90.
[31]Das SK.Observations and classification of roof strata behaviour over Longwall coal mining panels in India.Int J Rock Mech Min Sci 2000;37:585-97.
[32]Boothukuri V,Madhav B,Charan P,Benerjee G.Geotechnical challenges and experiences of working a deep and wide Longwall face:a case study of Adriyala Longwall project,SCCL.