Aya Gold & Silver Inc.

Table 16-3 Pillar Dilution Based by Mining Sequence.

Source: RockEng

Rib & Sill Pillars

Rib pillar dimensioning will rely on a 1:0.7 width (rib pillar horizontal thickness) to height (HW to FW span) aspect ratio with a minimum dimension of 3 m. Permanent sill pillar dimensioning relies on a 1:1 width (vertical dimension) to height (HW to FW span) aspect ratio with a minimum dimension of 5 m.

Crown Pillar

Based on empirical crown pillar evaluations, a 20 m pillar (in rock, ignoring overburden thickness) is deemed appropriate for stable crown pillar conditions during active mining operations. This dimension relies on the assumption that backfill will be utilized to manage long term stability for mine closure. Further, it is not unreasonable to expect that, with appropriate engineering and planning, full crown pillar recovery may be achieved (assuming surface disturbance is permitted, and environmental risks are tolerably low).

16.2.2.5 Infrastructure Siting

Given the relatively shallow mining depth, the geotechnical risks associated with stress induced damage to permanent infrastructure are considered low; thus, allowing for reasonable design flexibility, general guidance

AYA GOLD & SILVER INC., BOUMADINE POLYMETALLIC PROJECT 205 is as follows: cross-cut lengths ensure that haulage drive stand-offs are at least 15 m from the deposit body contact; either HW or FW infrastructure placement is acceptable given the near-vertical nature of the deposit; lateral development lay-outs will ensure that wide spans and intersections are not stacked level-to-level.

16.2.2.6 Ground Support

Standard lateral development (4 to 6 m spans) will be supported by 2.4 m rebar at a 1.25 x 1.25 m square pattern applied to the back and walls, with welded wire mesh in the back and shoulders. Cable bolts will be utilized in intersections and wide spans wit bolt lengths equal to ½ the span, at a 2 m square pattern. It is assumed that 2% of development will require shotcrete.