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
16.7 Backfill
Backfilling of mined out long hole stopes is planned to facilitate safe mining. Cemented
backfill will provide permanent support to the stope excavation, particularly with regard to the
mining of adjacent areas. Mitchell’s equation was used for the determination of the required
strengths of a cemented backfill block with freestanding heights of 20 m and 30 m. The
results indicate a UCS strength in the range of 0.35 MPa to 0.40 MPa.
16.7.1 Test Work
The backfill system presented in this study is conceptual. Appropriate detailed site specific
project engineering work for detailed system design is recommended on process flow
diagrams, process and instrument diagrams, mass balances, detailed equipment selection,
detailed site specific equipment locations, and plant and equipment general arrangement
drawings etc. Furthermore, only limited test work has been done on the hydraulic
transportation properties of Pulacayo tails as part of the Feasibility Study. As a result, the
pump, pipeline and equipment suggestions made in the Feasibility Study are based purely on
industrial experience.
16.7.2 Stope Backfilling Process
Backfill bottom reinforcement: The sequence of mining, as proposed for Pulacayo mine,
requires backfilled stopes to be undermined. As a result, the backfill in the lower portion of
each stope will be reinforced to prevent the possible collapse of backfill into the lower stope.
Mesh reinforcement, as practiced at Lucky Friday Mine in the United States, has therefore
been suggested. F2416.7 shows the suggested reinforcement design.
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