|Publisher||International Society for Rock Mechanics||Language||English|
|Content Type||Conference Paper|
|Title||A STUDY OF SLOPE FAILURES IN THE OPENCAST COAL MINES OF WARDHA VALLEY COALFIELD IN CENTRAL INDIA|
|Authors||J.C.JHANWAR, Central Institute of Mining and Fuel Research Regional Centre; N.R.THOTE, Department of Mining Engineering, Visvesvaraya National Institute of Technology|
|Source||ISRM International Symposium - 6th Asian Rock Mechanics Symposium, October 23 - 27, 2010 , New Delhi, India|
|Copyright||2010, Central Board of Irrigation and Power (CBIP) and International Society for Rock Mechanics (ISRM)|
This paper presents the results of a study into slope failures in different coal mines of WVC (Wardha Valley Coalfield) in India. The main objectives of this study are to understand various aspects of slope failures and to derive slope design curves applicable to the coal mines of WVC. The slope materials mainly consist of soil and sandstone followed by coal seam. The sandstone rock mass is classified as poor to fair. Slope failures mostly occur during rainy season under the effect of one or more than one conditions like presence of soil, very weak rock, high slope angle, overburden dump near slope crest and fault plane near mine workings. Cohesion and angle of internal friction of soil and sandstone are derived in the ranges of 5 - 40 KPa and 5 - 230 and 20 - 70 KPa and 11 - 300 respectively from back analysis of slope failures. The safe distance of overburden dump from slope crest is derived for different dump heights. Overall slope angles for soil and rock slopes are derived to vary from 28 to 580 for slope heights between 10 and 30 m and from 26 to 680 for slope heights between 40 and 220 m respectively.
The WVC (Wardha Valley Coalfield) is situated in central India towards the south of the city of Nagpur. The WVC is a NW-SE elongated structural basin with its coal bearing zone spreading over an area of 800 sq. km. along a length of 116 km. Ground water occurs in the form of unconfined aquifer at a depth of about 30 m below ground level in Kamthi formation. The slope forming materials in the mines are mainly soil and sandstone, which form the overburden followed by a single composite coal seam with thickness varying from 15 to 20 m. The soil consists of mainly clay and silt (85%) with little proportion of gravel and sand (15%). Sandstone constitutes the predominant part of rock slope in the opencast mines of this coalfield. Based on RMR (Bieniawski, 1989), the sandstone rock mass is classified as poor to fair. The slope stability problems in this coalfield occur mainly during the rainy season and are mostly restricted to the soil benches and/or the very weak and weathered sandstones or the sandstones, which are geologically disturbed. Sometimes, slope failures also occur due to the loading of mine slopes by overburden dumps. A study was conducted to understand the slope stability problems in this coalfield and to derive broad slope design curves for soil and rock slopes of opencast mines in this coalfield.
2.0 CHARACTERISATION OF SLOPE MASS AND SLOPE FAILURES
2.1 Slope Forming Materials
The slope materials mainly consist of soil and sandstone followed by coal seam. The soil thickness varies from 6 to 30 m. The soil consists of mainly clay and silt (85%) with little proportion of gravel and sand (15%). Sandstone constitutes the predominant part of rock slope in the opencast mines of this coalfield.
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