Longwall Mining Method

-

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.


Popular posts from this blog

Secondary Blasting Technique

-
Image
In this post we will deal about the Definition of Secondary Blasting and types of Secondary Blasting . Some other Blasting are also available you can read about that. So let's start... Definition of Secondary Blasting The technique used to blast the boulders to achieve the fragmentation is called secondary blasting. This blasting is done to get the rocks which can be easily handled. Why and how to do secondary blasting? Why secondary blasting? We does secondary, in case when the primary blasting don't give fragmentation of rock which can be easily handled. The secondary blasting is followed after the primary blasting. How to do secondary blasting? To do secondary blasting we have to follow some methods which will give us batter resultant. These are here 1. Plaster shooting or Mud Capping.. As name indicates mud capping, the primer cartridge is place at top of Boulder and covered with mud. The blasting is done from the safe place by electric detonator...
Read more

Bord and Pillar Method

-
Image
Bord and Pillar Method of mining involves in the formation of roadways and the development of Mines. The first stage of working of Bord and Pillar Method is Called Development. In the development stage parallel roads are driven nearly at right angle to the first set. These roads are also use to join the separated coal blocks. The network of roads regularly increases as development of the mine. The second stage of working of Board and Pillar Method  of mining is called Depillaring. The Depillaring can be understood by It's name(De-Pillaring). In Depillaring the working involves in the extraction of coal from the Pillars. These are two stages of this mining method. The another name of Bord and Pillar method is "Pillar and Stall". For the application of Bord and Pillar Method there are some conditions to be full filled. Conditions are.... •The thickness of seam seam should be more than 1.5m. •There is less amount of dirt bands present in seams. •Se...
Read more

Shaft Sinking

-
Image
Q. What is shaft? Ans. :- It is a vertical or inclined entry made to touch seams. The word shaft is used for underground mining entrance. Q. Why shaft? Ans.:- The shaft is excavated after getting approval to mine the mineral bed by underground method of mining. Simple View of Working Shaft Shape of Shaft Generally the shaft are of circular in shape but in some mines it is of rectangular in shape. The circular shafts are best because they resist heavy side pressure and offers least rubbing surface area for ventilation. Bricking and concreting job are easy and diameter of these shaft may be varies from 4.2mts to 6.7mts. ◆The shaft sinking process is costliest and time taking process. So it is necessary to drill pilot hole within the radius of 50m of main shaft which has to be drill. This pilot hole give us an idea about the rock and how we have to encounter those problem which will we face during shaft thinking. From this we will get a data about       ...
Read more