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- Robert W Ritzi, Zhenxue Dai, David F Dominic, Yoram N Rubin, Z Dai, D F Dominic +1 other
- 2004

[1] Cross-stratified deposits can give rise to a hierarchy of permeability modes, across scales, corresponding to a hierarchy of sedimentary unit types. The shape of the sample semivariogram for permeability can be largely controlled by the shape of the cross-transition probabilities of unit types having the greatest contrast in permeability. The shape of… (More)

Permeability, k, and porosity, φ, were measured in mixtures of fine, medium, and coarse sand, where the volume fraction of each of the three components was systematically varied. The k was modeled well by the Kozeny-Carman equation for three-component mixtures by using a representative grain size parameter, d, computed by averaging the grain diameters of… (More)

- Zhenxue Dai, Robert W Ritzi, David F Dominic, Z Dai, R W Ritzi, D F Dominic
- 2005

[1] As analogs for aquifers, outcrops of sedimentary deposits allow sedimentary units to be mapped, permeability to be measured with high resolution, and sedimentary architecture to be related to the univariate and spatial bivariate statistics of permeability. Sedimentary deposits typically can be organized into hierarchies of unit types and associated… (More)

- Zhenxue Dai, Robert W Ritzi, Chaocheng Huang, Yoram N Rubin, David F Dominic
- 2003

We consider here the Lagrangian approach for stochastic modeling of the transport of inert solutes in porous media. A general global covariance function of log conductivity in sediments with hierarchical organization has been developed by combining proportions, transition probabilities, and covariances of log conductivity. The global integral scale is… (More)

- Caleb M Conrad, Robert W Ritzi, David F Dominic
- Ground water
- 2008

We considered small-scale measurement of permeability in pebbly sands having coarser grains supported in a finer grained matrix (fine packing). Our central question was whether air-based measurements are representative if made with a permeameter tip seal pressed in the sand matrix. We created pebbly sands and variably sorted sands, with systematic variation… (More)

Deposits of open-framework gravel occurring in gravelly streambeds can exert a significant influence on hyporheic flow. The influence was quantified using a numerical model of the hyporheic zone. The model included open-framework gravel stratasets represented with commonly observed characteristics including a volume fraction of about one-third of the… (More)

- Robert W Ritzi, Zhenxue Dai, David F Dominic, Yoram N Rubin, R W Ritzi, Z Dai +2 others
- 2006

[1] We appreciate the commentary by Neuman [2006] and the opportunity for discussion and further clarification of our article [Ritzi et al., 2004]. In his commentary, Neuman expounds upon his derivation of a model for the permeability semivariogram [Neuman, 2003, equation (53)] and describes aquifer architecture that would be represented by such a model. As… (More)

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