Gutierrez, LAF, Viterbo, VC, McLemore, VT & Aimone-Martin, CT 2008, 'Geotechnical and Geomechanical Characterisation of the Goathill North Rock Pile at the Questa Molybdenum Mine, New Mexico, USA', in AB Fourie (ed.), Rock Dumps 2008: Proceedings of the First International Seminar on the Management of Rock Dumps, Stockpiles and Heap Leach Pads, Australian Centre for Geomechanics, Perth, pp. 19-32, https://doi.org/10.36487/ACG_repo/802_2
(https://papers.acg.uwa.edu.au/p/802_2_Gutierrez/)
Abstract: Physical changes due to weathering are of interest with respect to predicting long-term geotechnical slope 
stability of rock piles at the Questa molybdenum mine, New Mexico, USA. Geotechnical and geomechanical 
characterisation was conducted on matrix soil and rock fragments in the Goathill North (GHN) rock pile 
and on non-weathered drill core samples of rock typical of GHN. Shear strength and rock durability was 
estimated by performing direct shear, point load strength, and slake durability tests. Measurements for 
Atterberg Limits, particle size, moisture content, and density were also performed.  
Samples had high peak internal friction angles (φ) between 42º and 47º, which can in part be attributed to 
the grain shape (subangular to very angular). Point load strength index (Is50) and slake durability index 
(ID2) classified the samples as medium to very high strength and having high to extremely high durability, 
respectively. Lowest values of φ, Is50, and ID2 were observed for samples from the outer margin of the pile. 
ID2 results suggest that samples from the interior of the pile have been weathered little since deposition. In 
general, GHN rock pile samples have high durability and strength even after having undergone 
hydrothermal alteration and blasting prior to deposition and after potential exposure to weathering for 
about 40 years. Collectively, these results suggest that future weathering will not substantially decrease the 
friction angle of the rock piles with time.