Longwall Mining Method

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INTRODUCTION
Longwall Mining Method is a very popular method of Coal Mining. It is widely in all over the word. In this method, mining is done below the ground by forming a long face(60 to 200m). The production of Longwall Mining Method is by Shearer Machine. It is maintain a continuous line of advancement leaving behind a goaf or void. The roof is supported by packing the packing of stand or other crushed stone(partially or completely) to prevent collapse. Only a few meter is left from face (up-to 3 to 6m) and it is supported by timber, steel props, bars or chocks. 

ADVANCING
In Longwall Advancing, the extraction of coal is from the vicinity of shaft and advance towards the boundary of mine. Face is approached by parallel roads. The over may support by sand or pack wall or allow to cave in.

RETREATING
 In Longwall Retreating pair of headings are in solid coal at certain interval to the pre-determined boundary. The extraction of coal is from the boundary and retreats towards the shaft.

APPLICABILITY CONDITIONS
•This method is employed for thin seams with dirt band.
•For gassy seams, good planning of ventilation is required.
•Tough roof is so that gradually bend and rest on packing.
•Weak roof is so it cave in.

ADVANTAGES
•Ventilation is easier as it has direct route.
•It has maximum extraction percentage as all the seam extracted in one working.
•It provides good supervision.
•Only a few roads are maintained so floor control is good.
•Dirt bands are used for packing of goaf.
•Longwall Mining makes possible of quicker return of capital.
•It is most successful method of mining.

DISADVANTAGES
•In Longwall Mining, the large goaf is left behind in which the fire damp is accumulated, so it is dangerous.
•If the packing is not good, it leads to ventilation leakage.


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