June 2022 G-14642.71-006-R-Rev0_FINAL 17 Drillhole interval (m) Geological description Geotechnical characteristics Comments 129.5 – 146.2 Porphyritic ANDESITE Slightly weathered, strong rock 146.2 – 151.6 CLAY Highly weathered, weak soil 5 m zone of clay 151.6 – 231.7 (EOH) Autoclastic breccia ANDESITE Moderately- slightly weathered, strong rock Varying thicknesses of breccia/porphyritic lava flows interceded by highly hydrothermally altered clays. 1 m zone of clay at 162 m 3 m of clay at 166 m 3 m of clay at 203 m 0.6 m fault gouge breccia and clay at 212.2m 6.3.1 Ground conditions Predominantly volcaniclastic tuff breccias (Figure 9), and flow andesite (Figure 10) were encountered in borehole WNDD007, with zones of clay altered material (Figure 11). The core appears to have a gently inclined, east dipping, weakly developed fabric. The typical thickness of volcanic units in the core ranges from metres to tens of metres. Unconfined compressive strength of selected intact WNDD007 core samples typically range between 11 MPa and 49 MPa, which is consistent with a weak to moderately strong rock. Much of the core, by contrast is logged as a strong rock. The upper 50 m of the ground profile mainly comprises very weak andesite including a highly weathered profile, with andesite strength generally increasing with depth. Multiple crush zones were encountered between 42 m and 65 m BGL. Crush zones are between 0.1 m and 1.3 m thick. There is a total of 5.1 m of crushed rock over a 20 m length of core. Groundwater was encountered at about 10 m BGL and hydraulic testing indicates a relatively low permeability rock mass. The extent of weathering appears to correlate strongly with rock mass strength. Tuff breccias and lapilli tuffs that were present in WNDD008 (refer to Table 7) are not encountered in WNDD007.
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