Characterization of unsaturated zone hydrologic properties and their influence on lateral diversion in a volcanic tuff at Yucca Mountain, Nevada.

摘要

The study of the subsurface flow and distribution of water is critical to the evaluation of the unsaturated zone for a potential geologic high-level radioactive waste repository. This site is located at Yucca Mountain, Nevada in the northern Mojave Desert, and was chosen on the basis of its low precipitation, deep unsaturated zone, and layered volcanic rocks providing the potential for natural hydraulic barriers to reduce the downward percolation of water through the waste storage area. The detailed characterization of hydrologic properties is necessary to evaluate the mechanisms responsible for the distribution and flow of water in the unsaturated zone. Analyses in this study have provided detailed hydrogeologic units with unique hydrologic properties and hydraulic parameters. Porosity was determined to be a useful physical property for predicting hydraulic parameters, as it relates to the large-scale deterministic processes that created the volcanic rocks. The detailed property dataset, along with field measurements of moisture status, temperature, and chemistry, were used to evaluate the potential for lateral diversion, in the rocks above the potential repository. It was determined that lateral diversion is a small-scale process in this natural system. On the basis of analyses performed in this study, it is suggested that large-scale diversion is not likely to occur at this site. This mechanism should not, therefore, be relied upon to perform as a natural hydraulic barrier to flow reducing percolation through the unsaturated zone.*; *This dissertation includes a CD that is compound (contains both a paper copy and a CD as part of the dissertation). The CD requires the following applications: Microsoft Office.