Permeability fractured tuff

Tsang, Y.W., K. Huang, and G. S. Bodvarsson. Estimation of the Heterogeneity of Fracture Permeability by Simultaneous Modeling of Multiple Air-Infection Tests in Partially Saturated Fractured Tuff. Dynamics of Fluids in Fractured Rock. Geophysical Monograph 122, American Geophysical Union. 2000... 

The specific nature of the host rock (fractured tuff) makes it necessary to recognize that a double porosity and double permeability play a role in the hydrological problem. Properties that correspond to the tuff in the vicinity of the drift (tptpmn) are sutiunarized in Table 1. Properties for tptpul and tptpll are in the same range and can be found elsewhere. 

The evolution of the chemical regime in the unsaturated zone surrounding a heat source is closely related to the spatial distribution of temperature and the transport of water and vapor. An important aspect of the unsaturated fractured tuff at Yucca Mountain is that the highly permeable fractures are nearly dry, whereas the low permeability and porosity rock matrix has a water saturation of about 90 percent. Thus, heating of the rock induces boiling of the matrix pore water, transport of water vapor into fractures, and condensation along fracture walls. 

The numerical model for reaction-transport processes in the fractured welded tuffs must account for the different rates of transport in fractures, compared to a much less permeable rock matrix. Transport rates greater than the rate of equilibration via diffusion leads to disequilibrium between waters in fractures and matrix. Because the system is unsaturated, and undergoes boiling, the transport of gaseous species, especially CO, is an important consideration. The model must also capture the differences in initial mineralogy in fractures and matrix and their evolution. 

Steefel Lichtner (1994) Lichtner et al. (1998) Model >500 a Marl tuff Cement leachate Mainly calcite brucite, C-S-H and C-A-H phases Permeability decreases perpendicular to fracture and increases parallel to it matrix sealed off from fracture... 

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