Pulacayo Project Feasibility Study - Apogee Silver

Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report
090644-3-0000-20-IFI-100
Figure 16.8: Below Shows a Schematic Cross-Section Through a Bulkhead
Backfill placement: All stopes will be filled from the level above (top access) to facilitate
pipeline flushing. Backfilling will be conducted at filling rates in the range from 30-40 m 3 /hour.
This flow rate will provide a satisfactory rate of rise of the uncured pastefill against the fill
barricades and allow operations within time constraints of sequenced mining and backfilling.
The pastefill will comprise tailings from the process plant and about 6% by mass,
cementitious binder. A high cement content is required due to the high clay content of the
ore, as well as the tailings derived from it.
An initial lower backfill plug will be placed into each stope. The plug will extend vertically to
about 1 m above the top of the ore drive tunnel hanging wall. The initial lower plug will be left
to cure undisturbed for about seven days, after which, the remainder of the stope will be filled
with cemented backfill paste. In the case where there is a shortage of tailings, development
waste can be used. The waste has to be dump into the stopes simultaneously with cemented
backfill paste to prevent uncemented voids from forming between rocks! In addition, the
development waste cannot be dumped into the stopes during the initial plug filling, as this
would knock over the upright backfill anchors.
16.8 Ventilation
The planned ventilation system for Pulacayo mine is complicated in some respects by a
number of unknowns with respect to the existing workings. The planned operations cover a
vertical extent of some 150 m over seven levels. The ventilation system is intended to
ultimately establish through-ventilation on the main haulages of all levels, from which fans
and ducts can draw air for stopes and ore access development. There will not be any ‘main
fan’ installations on surface; instead, a number of relatively small (30 m 3 /s each) ‘booster’
fans will be installed underground at positions leading to surface connections. The intent is to
ensure that a positive flow of air [from whichever source, including those that may be
unknown] will report underground to the position of the fan inlets. Ventilation controls [walls,
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