19-01-2013, 10:41 AM
FIELD INVESTIGATION FOR THE STUDY OF METHOD OF MINING IN UNDERGROUND COAL MINES AT CHINACURI MINE NO. –III; ECL
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ABSTRACT
Energy resources and its best utilization decide the industrial growth and prosperity of a country. Coal is basic source of energy for the industrial development in the world. The gas found in coal is also a source of energy which is being utilized to a great extent these days. For the extraction of this energy various methods are developed. Among these methods ‘BORD ANDPILLAR’ method is one of the prominent methods. This method is mainly deals with the development and depillaring of the pillars and extraction of coal along this process.
This process of mining tells about the economical and safety extraction of coal from the mines. There are various methods present for the working which are applied for different seam thickness and extraction depth.
Except the method of mining Bord and Pillar division deals with various other factors. Subsidence is one of the chapters which estimate the amount of down faulting of the overlying strata after the caving method is carried out.In numerical modeling section 50m distance is taken from the seam and the total overlying strata up to the surface. Then the total model is processed in the computer and the real estimated load given on the model and the stability of the model is checked out. After this process is done in the computer in practical the mines is started.
INTRODUCTION
One of the oldest methods of mining is the Bord and Pillar. It is a method in
which the mined material is extracted across a horizontalplanewhile leaving “pillars" ofuntouched material to support the overburden leaving open areas or "rooms" underground.
It isusually used for relatively flat-lying deposits, such as those that follow a particular stratum.
The key to the successful Bord and Pillar mining is selecting the optimum pillar size. If thepillars are too small the mine will collapse. If the pillars are too large then significant quantitiesof valuable material will be left behind reducing the profitability of the mine. The percentage ofmaterial mined varies depending on many factors, including the material mined, height of thepillar, and roof conditions. So proper designing of a pillar is necessary for successful Bord and Pillar working.
Manymethods are available for designing of pillars. The most important parameter before designing apillar is the Safety factor. The main purpose of this project is to increase the extraction ratio ofBord and Pillar workings without compromising the safety factor,
METHOD OF MINING
WHAT IS MINING…?
Before we proceed forward we must know what is mining. “Mining is the process of excavating minerals of economic value from the earth’s crust for benefit of mankind”. For mining operations one should have a working knowledge of GEOLOGYand MINING ENGINEERING. Mining is the process of extraction of ore from the earth surface.
SPONTANEOUS HEATING
Automatic heating of carbonaceous materials by the contact of outside air is known as spontaneous heating and by this heating coal sometimes catches fire within 9-12 months after the depillaring has started. The size of the panel depend on this combustion period of the coal.
COAL+O2=HEAT+CO+CO2
PILLAR
These are the automatic support developed in the mines which are square shape and made up of coal. Its width given in two manner as center to center or corner to corner. When distance taken from the boundary of the pillars it is called corner to corner and when it is taken from the mid of the two adjacent gallery it is called center to center.
OPEN CAST MINING METHOD.
In o/c method, soil and rock (called overburden) lying over small area of the coal seam is blasted, excavated and dumped on non-coal bearing surface nearby. The exposed coal is blasted and mined. After coal has been removed over a large area, the overburden is dumped in the trench formed by the removal of coal. This is called ‘back filling’.
The overburden is excavated in steps called ‘benches’ .Coal seams are also extracted in more than one bench if it is thick. The various benches are approached by wide roadways called ‘haul roads’. These are used to transporting of coal to the outside the mines.
As overburden increases, more overburden has to be removed per ton of coal and cost goes up. After mining the seam to an economic depth, rest of the seam is worked by underground method
DIAGONAL GOAF LINE.
This type of goaf line is formed where the roof condition is fair. It is slanting goaf line making an angle of 45 degree with the direction of dip of the seam. It is the most adopted method because it is along goaf line producing large number of working face. Depending upon the experience and behavior of the roof, any angle other than 45 degree may also be chosen.