Assessment of Cavability and categorization of coal measure roof rocks by parting plane approach

From the observations of caving of the overlying roof rock in longwall panels it can be inferred that the caving is dominated by the weak parting layers, laminated nature and massiveness of the roof rock formation. This caving process is controlled by the presence and geo-technical properties of strong beds and weak parting beds in the roof rock layers. Based on the study conducted at different coalfields over longwall panels a ‘Parting Plane Approach’ has been developed for identifying the parting planes in the roof along with strong and weak rock beds. The strata caving behaviour over longwall workings is manifested by local and main falls. They are governed by the thickness, rock mass strength and the induced stresses in the Caving Layer 1 or the Immediate Roof and the Caving Layer 2 or the Main Roof respectively. A software has been developed in MATLAB platform to identify the rock beds as belonging to the Caving Layer 1 and the Caving Layer 2 or the Immediate Roof and the Main Roof. A parameter, Equivalent Main Fall Span (aeq), has been introduced for classifying the overlying roof rock. In this paper the various methods for determination of aeq, viz. an Empirical method, a Mathematical approach, and a Numerical modelling based approach have been discussed along with case studies

Hard roof management - a key for high productivity in longwall coal mines

At present, the share of underground coal production in India has dropped from 73% in 1974-75 to 20% in 1999-2000. The main reason of under-performance of our U/G coalmine projects is its failure to adopt the high production technology like longwall mining. A careful scrutiny of experience gained from the mechanized longwall mining in Indian coal industry reveals coal seams are overlain by hard and massive sandstone rock beds within the active caving zone. Hard roof management helps in eliminating the need of high capacity costly powered supports and ensuring safe and economic extraction of coal. This paper deals with the experience gained during some recent practices of deep hole surface blasting, which has been successfully introduced for managing the caving difficulty at some of the shallow depth longwall faces in South Eastern Coalfields Limited (SECL). Further, this paper describes the findings of experimentation on hard roof management by water injection under high pressure at Churcha colliery. The scope and limitations of these techniques are further elaborated

Maintenance strategy for longwall equipment a condition monitoring approach

Longwall coal mining is a capital-intensive technology involving integrated system of equipment. An unpredicted downtime of a short period of any of its subsystems results in underperformance of the total system causing increased cost of production creating a bad impact on economic viability oi the project. In this paper, a condition based monitoring approach for the different subsystems are discussed which is believed to help in providing optimum utilisation of the equipment, reducing the unwanted downtime and the overall operating cost. Further, a balance among various maintenance strategies and evolution methodology for Expert management Information System (EMIS) are discussed

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Not AvailableA study was conducted to assess the status of available secondary nutrients (Ca, Mg and S) along with physico-chemical properties of soils under continuous vegetable based cropping systems at the Central Research Farm of Indian Institute of Vegetable Research, Varanasi situated at 82.52°E longitude and 25.10°N latitude in the alluvial belt of Indo-Gangetic Plains (IGP) of Eastern Uttar Pradesh. The soils at this farm have been under continuous vegetable cultivation with the exception of intermittent cultivation of paddy in some blocks for the last 15 years. The experimental farm has a total area of 45 ha spread over 16 blocks. The analysis of soil samples collected from different blocks for various physico-chemical properties and status of secondary nutrients revealed that the soils of the research farm were neutral to slightly alkaline in reaction having pH in the range of 6.61 to 7.82 with a mean value of 7.29. Electrical conductivity was found within the normal limits (ranged from 0.09 to 0.76 dSm-1 with a mean value of 0.28 dSm-1). Twenty two per cent soil samples of the research farm were found low, 73 per cent medium and rest 5 per cent high in organic carbon content. Water retention at field capacity and permanent wilting points was 25.6 and 6.3 per cent, respectively, and available water content was estimated to be 19.4 per cent. The soils of the entire farm were found to be silt loam in texture. Among the secondary nutrients, available Ca ranged from 1206 to 2302 ppm, whereas, available Mg ranged from 164 to 723 ppm, which indicated that these soils are sufficient in calcium and magnesium. With regard to the status of available sulfur, 3 per cent soils were found to be in low, 13 per cent in medium and 84 per cent in high range.Not Availabl

Not Available

Not AvailableA study was conducted to assess the status of available secondary nutrients (Ca, Mg and S) along with physico-chemical properties of soils under continuous vegetable based cropping systems at the Central Research Farm of Indian Institute of Vegetable Research, Varanasi situated at 82.52°E longitude and 25.10°N latitude in the alluvial belt of Indo-Gangetic Plains (IGP) of Eastern Uttar Pradesh. The soils at this farm have been under continuous vegetable cultivation with the exception of intermittent cultivation of paddy in some blocks for the last 15 years. The experimental farm has a total area of 45 ha spread over 16 blocks. The analysis of soil samples collected from different blocks for various physico-chemical properties and status of secondary nutrients revealed that the soils of the research farm were neutral to slightly alkaline in reaction having pH in the range of 6.61 to 7.82 with a mean value of 7.29. Electrical conductivity was found within the normal limits (ranged from 0.09 to 0.76 dSm−1 with a mean value of 0.28 dSm−1).Twentytwoper centsoilsamplesoftheresearch farm were found low, 73 per cent medium and rest 5 per cent high in organic carbon content. Water retention at field capacity and permanent wilting points was 25.6 and 6.3 per cent, respectively, and available water content was estimated to be 19.4 per cent. The soils of the entire farm were found to be silt loam in texture. Among the secondary nutrients, available Ca ranged from 1206 to 2302 ppm, whereas, available Mg ranged from 164 to 723 ppm, which indicated that these soils are sufficient in calcium and magnesium. With regard to the status of available sulfur, 3 per cent soils were found to be in low, 13 per cent in medium and 84 per cent in high range.Not Availabl

Uptake of cadmium from water by beech leaves

Salim R, Al‐Subu MM, Sahrhage E. Uptake of cadmium from water by beech leaves. Journal of Environmental Science and Health . Part A: Environmental Science and Engineering and Toxicology. 1992;27(3):603-627