COMPARISON OF VARYING APERTURE CALCULATIONS

There exist many studies on contaminant transport through fractures, and there are a number of methods to calculate fracture aperture that control contaminant transport. The analysis of hydraulic, mechanical, and transport aperture is, thus, critical. The hydraulic aperture of a fracture is defined by its hydraulic and transmissive properties as the aperture that produces a given discharge. The transport aperture of a fracture can be defined by average aperture that matches the velocity calculated by solute transport. Mechanical aperture can be defined two ways: 1) the arithmetic mean of all the aperture values in flow path and 2) a generic measure of physical separation of two walls of a fracture. Solute/contaminant transport through fractures was calculated using the Ogata-Banks formula. The differences in methods to calculate aperture create discrepancies in contaminant flow transport calculations. Comparing the three different types of apertures provides insight on the similarities or differences in methods of analyzing flow and transport in fractures. Numerical models calculate a solute/contaminant flow (Cesium). Results show that the three different calculations of aperture produce conflicting data sets. The models suggest fracture aperture calculations are inconsistent and the methods used to calculate fracture aperture require attention.