FLOW BETWEEN AQUIFERS THROUGH FILLED CYLINDRICAL CONDUITS - ANALYTICAL SOLUTION AND APPLICATION TO UNDERGROUND NUCLEAR TESTING SITES

Simple analytical solutions are derived for groundwater flow in filled cylindrical conduits connecting multiple aquifers. Artificial conduits of this type are found in underground mining and nuclear testing settings, and can have a profound impact on groundwater flow and contaminant transport. The solutions demonstrate that conduit flux will depend on the bulk transmissivity of the conduit-aquifers system, and will be large only when there is little variation from this average throughout the system. If the upper aquifer is unconfined, flow is generally double that for a confined upper aquifer. Transmissivity of the unconfined aquifer has little effect on the magnitude of conduit flux. Application of these solutions at a representative underground nuclear testing site in fractured rock indicates a conduit flow approximately equal to that allowed by an unsealed borehole 0.3 m in diameter. In general, the impact of a large filled conduit will be similar to that of an abandoned well, as the effect of the greater conduit radius is offset by resistance to flow in the conduit fill.