Rock mass properties and edifice strength data from Pinnacle Ridge, Mt. Ruapehu, New Zealand - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Volcanology and Geothermal Research Année : 2018

Rock mass properties and edifice strength data from Pinnacle Ridge, Mt. Ruapehu, New Zealand

S.P. Mordensky
  • Fonction : Auteur
M.C. Villeneuve
  • Fonction : Auteur
B.M. Kennedy
  • Fonction : Auteur
Michael Heap
  • Fonction : Auteur
  • PersonId : 923962
D.M. Gravley
  • Fonction : Auteur

Résumé

Volcanic edifices exhibit spatially variable physical and mechanical properties. Magmatic intrusions are common at shallow depths within the volcanic edifice and are a poorly-understood contributor to this spatial variability. Intrusion-related alteration has been found to weaken rock mass strength through the development of joints and fractures; however, there is a paucity of research investigating how intrusions affect rock mass strength specific to the geotechnical units that define the rock masses. In this study, we employ a range of field techniques—field permeametry, rock hardness assessment, rock mass classification, and discontinuity mapping—to characterise an exposed fossil geothermal system produced by a shallow intrusion at Pinnacle Ridge, Mt. Ruapehu (New Zealand). We find that intrusions detrimentally affect the rock mass characteristics of altered brecciated lava margins. The resulting change in rock mass strength may be offset by an increase in intact rock strength as a product of alteration mineral precipitation in microfractures. Consequently, the final strength of the rock mass of the altered brecciated lava margins has the potential to be lowest of any of the geotechnical units in the volcanic edifice. We also conclude that these discontinuities increase permeability of the host rock at distances from the intrusion roughly proportional to 1–2 times the thickness of the intrusion itself under near-surface conditions. The data and conclusions presented in this study help to bridge the gap between the lab- and the field-scale and have immediate relevance to engineering geology and geothermal applications worldwide, and to rock mass classification assessments in volcanic environments.
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Dates et versions

hal-01937194 , version 1 (28-11-2018)

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Citer

S.P. Mordensky, M.C. Villeneuve, J.I. Farquharson, B.M. Kennedy, Michael Heap, et al.. Rock mass properties and edifice strength data from Pinnacle Ridge, Mt. Ruapehu, New Zealand. Journal of Volcanology and Geothermal Research, 2018, 367, pp.46 - 62. ⟨10.1016/j.jvolgeores.2018.09.012⟩. ⟨hal-01937194⟩
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