Mining Paper 2 WASSCE (SC), 2016

Question 13

  1. Define the term mine.
  2. Write explanatory notes on:
    1. the room and pillar method of coal mining;
    2. the longwall method of coal mining.


This question was fairly popular among the candidates and their performance was poor. A good number of the candidates gave definition of Mining for that of a mine. A mine is an opening made in the earth for extracting useful minerals.

The following should be noted about the room and pillar method of coal mining:

  • It involves the extraction of coal by creating rooms
  • Pillars of coal are left unremoved at regular intervals in between the rooms to give support
  • After the removal of coal, crosscuts are made at right  angles to the general direction of mining
  • The size of the pillars that is used in supporting the roof should be the same dimension
  • The rooms and cross cut could be created using two system namely- the conventional mining system and continuous mining system.
  • The conventional mining method involves creation of kerf/slots at the floor on the surface of the coal
  • Holes are drilled into which permissible explosives are used to blast off the coal
  • Loading machines are used to evacuate the blasted pieces of coal
  • The main entry point is created on evacuation of the blasted coal
  • The continuous method involves the use of a highly integrated machine
  • The machine rips off coal from the mine face
  • Broken coals are rolled automatically to an inbuilt conveyor belt which rolls them to the collection point at the rear (back) of the machine.
  • Proper arrangement are made for mine ventilation
  • Provisions are made for seepage water
  • Care is taken to give the required support for the roof of the mine

 

The following should be noted about the longwall method of coal mining:

  • Unlike the room-and-pillar method, this method leaves little coal unmined in the pillar.
  • Large panels of coal are created
  • The faces are mined in slices back towards the shaft
  • Coal is usually skimmed from the face using a shearer machine
  • The face conveyor moves the skimmed fragments of coal to the permanent conveyor in the main entry.
  • Massive hydraulic jacks are used to support the roof of the mine
  • The face conveyor and powered support are repositioned as the mining progresses
  • The roof of the mine is allowed to collapse in a regulated manner at the gob/goaf