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Discussion is presented of the design of an array of chain pillars suitable for deep-seated, multi-seam retreat longwall mining in deep coal mines in India. It was found that a chain pillar 80 m wide and 195 m long is necessary for long-term stability without any reinforcement. It was also observed that an optimum chain pillar can be designed by providing suitable side reinforcement (side bolting) which will reduce the chain pillar dimensions to 55 m width and 160 m length. The optimum design of chain pillars will reduce the coal locked up in these chain pillars by around 77%. This will also reduce the gestation period of longwall mining panel development. Based on subsidence monitoring of over 200 panels at the Moonidih coal mine it was found that subsidence at the surface could be controlled if the mining-induced tensile subsidence strain is less than 3 mm/m., 48 refs., Discussion is presented of the design of an array of chain pillars suitable for deep-seated, multi-seam retreat longwall mining in deep coal mines in India. It was found that a chain pillar 80 m wide and 195 m long is necessary for long-term stability without any reinforcement. It was also observed that an optimum chain pillar can be designed by providing suitable side reinforcement (side bolting) which will reduce the chain pillar dimensions to 55 m width and 160 m length. The optimum design of chain pillars will reduce the coal locked up in these chain pillars by around 77%. This will also reduce the gestation period of longwall mining panel development. Based on subsidence monitoring of over 200 panels at the Moonidih coal mine it was found that subsidence at the surface could be controlled if the mining-induced tensile subsidence strain is less than 3 mm/m.

The production and productivity of most mechanised longwall faces in India are well below expectations. The main reason for this is the under-performance of shearers. Proposed selection criteria for shearers are considered. A computer programme has been developed to calculate and optimise cutting drum parameters and longwall system variables., The production and productivity of most mechanised longwall faces in India are well below expectations. The main reason for this is the under-performance of shearers. Proposed selection criteria for shearers are considered. A computer programme has been developed to calculate and optimise cutting drum parameters and longwall system variables.

Face lengths in shortwall mining range between 40 and 90 m, with the aim of controlling caving of overlying strata, the load on supports and overall operation of the supports. Field observations and three-dimensional numerical modelling were carried out for longwall panel extraction of the Passang seam at Balrampur in India, to understand the caving behaviour of the overlying strata. A large area of the seam adjacent to the longwall panels had already been developed by bord and pillar. Modelling studies are presented that assess cavability over bord-and-pillar workings as well as the support requirement for the face and advance gallery. Caving nature is predicted for varying face lengths, strata conditions and depths of cover and estimates are made of the support resistance required at the face, the load in the advance gallery and its optimum obliquity for faster exploitation of the developed pillars by shortwall mining., Face lengths in shortwall mining range between 40 and 90 m, with the aim of controlling caving of overlying strata, the load on supports and overall operation of the supports. Field observations and three-dimensional numerical modelling were carried out for longwall panel extraction of the Passang seam at Balrampur in India, to understand the caving behaviour of the overlying strata. A large area of the seam adjacent to the longwall panels had already been developed by bord and pillar. Modelling studies are presented that assess cavability over bord-and-pillar workings as well as the support requirement for the face and advance gallery. Caving nature is predicted for varying face lengths, strata conditions and depths of cover and estimates are made of the support resistance required at the face, the load in the advance gallery and its optimum obliquity for faster exploitation of the developed pillars by shortwall mining.

The methodology of routine condition monitoring is outlined and a description given of a case study of longwall equipment at the Kumda 7 & 8 incline. The objectives were to test the bearings of belt conveyors, armoured face conveyors and roadheaders using shock pulse methods, to monitor the condition of oil-filled gearboxes by debris testing, to test the system leakage of powered supports and the efficiency of a power-pack pump, and to determine the pretension and elongation of armoured face conveyor and BSL chains. Field observations are presented., The methodology of routine condition monitoring is outlined and a description given of a case study of longwall equipment at the Kumda 7 & 8 incline. The objectives were to test the bearings of belt conveyors, armoured face conveyors and roadheaders using shock pulse methods, to monitor the condition of oil-filled gearboxes by debris testing, to test the system leakage of powered supports and the efficiency of a power-pack pump, and to determine the pretension and elongation of armoured face conveyor and BSL chains. Field observations are presented.

Routine condition monitoring techniques to prevent breakdowns and improve system reliability include orifice testing to check power pack performance, emulsion analysis, monitoring of wear debris, shock pulse monitoring, testing of chain pretension and elongation, and monitoring of oil levels, vibration and temperature. The accurate status information provided by predictive maintenance data can make proper balancing of preventive and proactive maintenance both possible and cost-effective., Routine condition monitoring techniques to prevent breakdowns and improve system reliability include orifice testing to check power pack performance, emulsion analysis, monitoring of wear debris, shock pulse monitoring, testing of chain pretension and elongation, and monitoring of oil levels, vibration and temperature. The accurate status information provided by predictive maintenance data can make proper balancing of preventive and proactive maintenance both possible and cost-effective.

Mechanised longwall mining in India has shown that coal seams are overlain by hard, massive sandstone beds within the active caving zone. Hard roof management helps to eliminate the need for costly high-capacity powered supports while ensuring coal is extracted safely and economically. Experience of deephole surface blasting, which has been successfully introduced for managing the caving difficulty at some shallow longwall faces in South Eastern Coalfields, is discussed and results are presented from experiments with hard roof management by water injection under high pressure at Churcha colliery. The scope and limitations of the techniques are considered and it is concluded that for a deeper mine with a hard-to- cave roof, blasting from the surface will not be cost-effective and water injection will be an appropriate alternative; although tested in bord-and- pillar workings, it should prove equally applicable to longwall panels., Mechanised longwall mining in India has shown that coal seams are overlain by hard, massive sandstone beds within the active caving zone. Hard roof management helps to eliminate the need for costly high-capacity powered supports while ensuring coal is extracted safely and economically. Experience of deephole surface blasting, which has been successfully introduced for managing the caving difficulty at some shallow longwall faces in South Eastern Coalfields, is discussed and results are presented from experiments with hard roof management by water injection under high pressure at Churcha colliery. The scope and limitations of the techniques are considered and it is concluded that for a deeper mine with a hard-to- cave roof, blasting from the surface will not be cost-effective and water injection will be an appropriate alternative; although tested in bord-and- pillar workings, it should prove equally applicable to longwall panels.

In a number of Indian coalfields, a hard, massive sandstone roof is encountered in the active caving zone. Induction of caving by induced blasting or hydrofracturing will help overcome difficulty in caving such beds. Induction by induced blasting was first investigated experimentally at the Balrampur longwall face, Bishrampur area, in 1998. Findings are presented from the use of deep blastholes drilled in the underlying strata from the surface and details are also given of the steps needed to identify the rock formations where this technique can be applied. The scope and limitations of the technique are discussed., In a number of Indian coalfields, a hard, massive sandstone roof is encountered in the active caving zone. Induction of caving by induced blasting or hydrofracturing will help overcome difficulty in caving such beds. Induction by induced blasting was first investigated experimentally at the Balrampur longwall face, Bishrampur area, in 1998. Findings are presented from the use of deep blastholes drilled in the underlying strata from the surface and details are also given of the steps needed to identify the rock formations where this technique can be applied. The scope and limitations of the technique are discussed.

The Indian refractory industry has a production capacity of 2 000 000 tpa, but capacity utilisation is currently at about 60%, with applications in the steel, cement and ceramic, non-ferrous metals and glass industries accounting for 70%, 12%, 5%-6% and 4% of the output, respectively. The country is self-sufficient in only a few refractory raw materials, and the refractories industry is largely dependent on imports. Major sources of bauxite in India are in Gujarat, Madhya Pradesh and Bihar, but the bauxites contain considerable amounts of impurities such as iron oxides, titania and lime and are not suitable for refractories production. The potential use of biological leaching for removing the impurities is discussed, and research into the production of high-alumina aggregate from Indian bauxite with or without minor beneficiation is described. India has very large beach sand deposits, including beach sand sillimanite which is a potential source of aluminosilicates for use in refractory systems, and zircon beach sand. The production and properties of high-alumina and mullite-zirconia aggregates produced from the two types of beach sand deposit are discussed. Significant deposits of low-quality magnesite occur in the Salem and Almora regions which are only suitable for low-end applications. Possible treatments being investigated include biological leaching and modification of the phase composition of sintered/fused products, The Indian refractory industry has a production capacity of 2 000 000 tpa, but capacity utilisation is currently at about 60%, with applications in the steel, cement and ceramic, non-ferrous metals and glass industries accounting for 70%, 12%, 5%-6% and 4% of the output, respectively. The country is self-sufficient in only a few refractory raw materials, and the refractories industry is largely dependent on imports. Major sources of bauxite in India are in Gujarat, Madhya Pradesh and Bihar, but the bauxites contain considerable amounts of impurities such as iron oxides, titania and lime and are not suitable for refractories production. The potential use of biological leaching for removing the impurities is discussed, and research into the production of high-alumina aggregate from Indian bauxite with or without minor beneficiation is described. India has very large beach sand deposits, including beach sand sillimanite which is a potential source of aluminosilicates for use in refractory systems, and zircon beach sand. The production and properties of high-alumina and mullite-zirconia aggregates produced from the two types of beach sand deposit are discussed. Significant deposits of low-quality magnesite occur in the Salem and Almora regions which are only suitable for low-end applications. Possible treatments being investigated include biological leaching and modification of the phase composition of sintered/fused products

A case study is presented of double-section contiguous depillaring of a 12.6 m thick coal seam under massive and uncaveable sandstones in an Indian coal mine. Drilling results indicate the sandstone to be 20-55 m thick with high RQD values. Depillaring has so far been completed in five extraction panels, leaving properly designed yield pillars in the goaf for prevention of air blasts. A description is presented of the design procedure adopted for yield pillars and the results of long-term pillar displacement monitoring., A case study is presented of double-section contiguous depillaring of a 12.6 m thick coal seam under massive and uncaveable sandstones in an Indian coal mine. Drilling results indicate the sandstone to be 20-55 m thick with high RQD values. Depillaring has so far been completed in five extraction panels, leaving properly designed yield pillars in the goaf for prevention of air blasts. A description is presented of the design procedure adopted for yield pillars and the results of long-term pillar displacement monitoring.