technical report on the nechalacho deposit, thor lake project ...

feasibility design recommendations is based on geo<strong>technical</strong> logging completed in conjunction
with the Avalon 2009 exploration drill program.
The 2009 exploration drill program at the TLP included drilling five (5) HQ diameter drill holes
from each pad positions. In general, at least two (2) holes from each drill pad were logged by
Avalon geological staff. The selected holes covered a range of azimuths in order to reduce
directional sampling bias. Geomechanical data collection was focused on the depth ranges of
greatest interest (20 to 30m into the HW, the Ore and at least 5 to 10 m into the FW).
During the 2009 program, Avalon geological staff geomechanically logged approximately 2,300
m of core divided among 22 drill holes. The logging focused on gathering the rock mass
characteristics needed to classify the encountered rock masses using both the Norwegian
Geo<strong>technical</strong> Institute Tunneling Quality (NGI-Q) and the 1989 version of the Rock Mass Rating
system (RMR89). These holes were used to assign rock mass characteristics to the HW, Ore
and FW.
The results suggest that the rock masses encountered at the TLP are generally good quality
and that there is little variation with depth. General observations include the following:
• Drill core recovery was consistently close to 100% suggesting that few zones of reduced
rock mass quality were encountered.
• RQD values were generally in the 90 to 100% range.
• RMR values were generally ranged between 60 and 80 and would be typical of a good
quality rock mass.
The rock mass was grouped into domains with similar engineering characteristics. Given the
relatively minor down hole variations in rock mass quality and the focus of this study on the rock
masses in and around the ore body, it was decided to utilize only three geomechanical domains:
HW, Ore and FW. A comparison of the design values determined for each domain suggested
that they do not vary enough to justify different design values. As such, RMR = 67 and a Q’ of
4.2 were initially selected for pre-feasibility design purposes for all domains. Lower and upper
bound values were also used for certain analyses.
Subsequent review of the number of joint sets and the rationalization of the design parameters
to the expected “good” rock conditions led to a revision of the Q’ value to 8.3. In addition the
performance of the rock as openings are developed will be used as a guide in the final stope
design sizing.
Technical Report 43-101 – March 13, 2011 Page 18-5
Prepared by Avalon Rare Metals Inc.