| Summary: | 碩士 === 國立交通大學 === 環境工程所 === 89 === This thesis is to study the effects of fracture width on the transport of radionuclide in a multiple and parallel fractured rock formation. Due to the very low hydraulic conductivity of the rock matrix, the water flow is assumed to take place only within fractures. Besides, the diffusive flux due to concentration gradient across the interfaces between the fracture surfaces and the rock matrix is neglected in the system. The equation describing the transport of radionuclide includes the following mechanisms: advection, dispersion, radioactive decay, and adsorption on the fracture surfaces. An analytical solution for this equation was derived by using the Laplace transform technique. This solution indicates that identical concentration distributions can be observed in each fracture of the equal-width fractured system. For an unequal-width fractured systems, however, the travel distances along wide fractures are substantially larger than the travel distance in a single uniform fractured system. The radionuclide concentration in the wide fracture reaches source concentration rapidly. This confirms that the fracture width plays an important role in radionuclide transport through a system of multiple and parallel fractured media.
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