Analysis of stress and moisture induced changes in fractured rock permeability at the yucca mountain drift scale test

Abstract

Abstract This paper presents a coupled thermal-hydrological-mechanical analysis of a large-scale underground heater test conducted in unsaturated fractured welded tuff at Yucca Mountain, Nevada. Key processes in this study are thermal-hydrological (TH) changes in fracture moisture content and thermal-mechanical (TM) changes in fracture aperture, which both contribute to changes in local fracture-permeability. The soundness of the modeling approach and in particular the model for thermal-mechanical induced changes in fracture permeability is demonstrated through good agreement between simulated and measured changes in air-permeability in several boreholes at DST. This shows that a continuum modeling approach is appropriate and indicates that fracture opening/closure caused by changes in fracture normal stress is the dominating mechanism for TM-induced changes in permeability at the site.