Pillars And Protective Pillars Essay

In mining industry of coal, particularly in any underground mining operation, two different categories of pillars are observed namely support pillars and protective pillars. The dinstinguishing factors between the two types of pillars are often not clearly available , and there are number of instances when pillars fulfil both requirements. However, there are a number of significant differences in the design of the two types of pillars.
Support Pillars—--Support pillars can be divided into two classes: pillars that provide local support, and pillars that provide regional support. However, pillars often provide both local and regional support. A good example of this is a conventional bord-and-pillar mining layout that has been designed at a high …show more content…
One of the practical means of achieving this is to leave portions of the coal seam unmined to form protective pillars. The design criteria for these pillars depend largely on the nature of the structure that needs to be protected. In the case of surface structures, the design criterion is based on the magnitude of the surface movements and strains that can be tolerated by the structure. In the case of underground structures such as bunkers, pump stations, service excavations, etc., it is usually the magnitude of the stresses that determines the size of protective …show more content…
Weak roof and floor strata in the immediate vicinity of the coal seam can affect the following in bord-and-pillar mining: (i) the local roof support in the bords, (ii) the working conditions and the use of mechanized equipment, and (iii) the long-term stability ofthe bord-and-pillar system. As far as local roof control in bord-and-pillar workings is concerned, the problems tend to increase as the density of the bedding planes in the immediate roof strata increases, or the strength of the rock composing the individual beds decreases. In principle, there are two ways of improving the behaviour of the immediate roof: (a) by increasing the apparent strength of the roof, (b) by reducing the induced stresses in the roof. The former can be achieved by the introduction of support, whereas the latter concerns mine design and layout. The most important parameters that control the magnitude of the induced stresses are the size of the pillars and the bord