Page 388 - Rock Mechanics For Underground Mining

13 Pillar supported mining

methods

13.1 Components of a supported mine structure

A mining method based on pillar support is intended to control rock mass displace-
ments throughout the zone of influence of mining, while mining proceeds. This im-
plies maintenance of the local stability of rock around individual excavations and
more general control of displacements in the mine near-field domain. As a first ap-
proximation, stope local stability and near-field ground control might be considered
as separate design issues, as indicated schematically in Figure 13.1. Stopes may be
excavated to be locally self-supporting, if the principles described in Chapters 7–9
are applied in their design. Near-field ground control is achieved by the development
of load-bearing elements, or pillars, between the production excavations. Effective
performance of a pillar support system can be expected to be related to both the di-
mensions of the individual pillars and their geometric location in the orebody. These
factors are related intuitively to the load capacity of pillars and the loads imposed on
them by the interacting rock mass.
Leaving pillar support in an orebody results in either temporary or permanent
sterilisation of a fully proven and developed mining reserve. An economic design
of a support system implies that ore committed to pillar support be a minimum,
while fulfilling the essential requirement of assuring the global stability of the mine
structure. Therefore, detailed understanding of the properties and performance of
pillars and pillar systems is essential in mining practice, to achieve the maximum,
safe economic potential of an orebody.
Room-and-pillar mining, and the several versions of longhole, open and bench
stoping, represent the main methods based on temporary or permanent pillar support.

Figure 13.1 Schematic illustration
of problems of mine near-field stabil-
ity and stope local stability, affected
by different aspects of mine design.

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