Anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole, Mont Terri Underground Rock Laboratory - IN2P3 - Institut national de physique nucléaire et de physique des particules Access content directly
Journal Articles Engineering Geology Year : 2013

Anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole, Mont Terri Underground Rock Laboratory

B. Thomas
K. Wieczorek
  • Function : Author
B. Lavielle
  • Function : Author
B. Kergosien
  • Function : Author
F. Nicollin
  • Function : Author
K. Mahiouz
  • Function : Author
N. Lesparre

Abstract

Before the excavation of the new gallery Ga08 in the Mont Terri Underground Rock Laboratory (Switzerland), which joined the existing gallery Ga04 in 2008, the end-face of gallery Ga04 was instrumented in 2007 to characterize the evolution of the rock mass with geochemical and geophysical methods. The noble gas content of a 12-m long horizontal borehole evidenced that desaturation processes occurred in the first 2 m, where pre-existing fractures accommodated the stress change during excavation of gallery Ga04 four years before. These first 2 m are associated with the so-called Excavation Damaged Zone (EDZ). As an inflow of pore water was observed in this borehole few weeks after its drilling, continuous self-potential (SP) measurements were performed to characterize its dynamics. After the drilling of new sub-horizontal boreholes in the end-face, strong localized variations of SP occurred. The comparison with the geological features of the rock mass suggests that these dynamic anomalies have to be associated with fluid circulation in pre-existing tectonic fractures that were primarily reactivated by the excavation of the gallery Ga04 and subsequently by the drilling operations.

Dates and versions

in2p3-00825385 , version 1 (23-05-2013)

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Cite

A. Maineult, B. Thomas, C. Nussbaum, K. Wieczorek, D. Gibert, et al.. Anomalies of noble gases and self-potential associated with fractures and fluid dynamics in a horizontal borehole, Mont Terri Underground Rock Laboratory. Engineering Geology, 2013, 156, pp.46-57. ⟨10.1016/j.enggeo.2013.01.010⟩. ⟨in2p3-00825385⟩
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