Page 31 - Rock Mechanics For Underground Mining

IMPLEMENTATION OF A ROCK MECHANICS PROGRAMME

advance through an orebody; the sequence of extraction of stope blocks and pillar
remnants, simultaneously noting the need to protect service installations, maintain
access and preserve mine structural stability; and the need for and specification of the
strength parameters of any backfill in the various mined voids. In all of these design
activities, effective interaction must be maintained with planning personnel, since ge-
omechanics issues represent only part of the complete set of engineering information
required to develop an operationally acceptable mining programme.
Extraction system design is concerned with the details of stope configuration and
ore recovery from the stope. This involves, initially, consideration of the stability of
stope boundaries throughout the stope working life, and requires close examination
of the possibility of structurally controlled failures from stope and pillar surfaces.
The preferred direction of stope retreat may be established from such studies. The
design of the extraction horizon requires consideration of the probable performance of
stope drawpoints, tramming drives and ore-flow control raises, during the stope life.
Particular problems can occur on the extraction horizon due to the density of openings,
resulting in stressed remnants, and the potential for damage by secondary breakage
of oversize rock during ore recovery. A final issue in this segment of stope design is
primary blast design. The issue here is blasting effects on remnant rock around the
stope periphery, as well as the possibility of damage to access and adjacent service
openings, under the transient loads associated with closely sequenced detonations of
relatively large explosive charges.
A mine rock mechanics group also has a number of important rˆoles to play during
production. It is good and common practice for a rock mechanics engineer to make
regular inspections of production areas with the production engineer responsible
for each area, and to make recommendations on local support and reinforcement
requirements based on the mine’s established support and reinforcement standards.
Usually, these standards will have been developed by the rock mechanics engineers
in consultation with production personnel. The rock mechanics group will also be
responsible for monitoring the geomechanical performance of excavations and for
making recommendations on any remedial actions or measures that may be required to
manage unforeseen events such as falls of ground or the ingress of water. A close daily
working relationship between production and rock mechanics engineers is required in
order to ensure the safe and economic operation of the productive areas of the mine.

1.5 Implementation of a rock mechanics programme

It has been stated that an effective rock mechanics programme should be thoroughly
integrated with other mine technical functions in the development and implementation
of a coherent mining plan for an orebody. However, the successful accomplishment
of the goals of the programme requires the commitment of sufficient resources, on
a continuous basis, to allow rational analysis of the range of problems posed by the
various phases of mining activity.
A methodology for the implementation of a rock mechanics programme is illus-
trated schematically in Figure 1.7. Five distinct components of the programme are
identified, and they are postulated to be logically integrated, i.e. deletion of any
component negates the overall operating philosophy. Another point to be observed
from Figure 1.7 is that the methodology implies that the programme proceeds via a
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