| Summary: | 碩士 === 國立中正大學 === 地震研究所暨應用地球物理研究所 === 96 === A new power series solution, abbreviated as PRTSF, for short-term, convergent radial tracer transport in a single fracture is developed. Fracture network structure can be simplified as a single fracture system as long as the considered time scale is small enough such that tracer transport within two distinct fractures can be considered to be independent of one another. Transport mechanisms considered in PRTSF include advection, hydrodynamic dispersion, matrix diffusion and mixing. Besides, the non-axial symmetry effect (Zlotnik and Logan, 1996) is also taken into account in order to derive a more realistic boundary condition at the injection borehole. An exponential transform equation is adopted in order to eliminate the advection term in the Advection-dispersion equation (ADE). The resultant ADE in the Laplace domain is then solved by the power series method such that no oscillating functions, such as Airy functions, are present and thus the numerical instability caused by oscillating functions can be avoided. Finally, de Hoong et al.’s algorithm is adopted to numerically transform the Laplace domain solution back to the time domain solution. If matrix diffusion is neglected and the maximum aperture angle is used, PRTSF is exactly the same as the Moench’s solution (Moench, 1989). If mixing is not considered, PRTSF is close to the analytical solution considered by Maloszewski and Zuber (1990) for tracer transport in a linear single fracture. Calculation results show that BTC tailing becomes more noticeable as the effects of matrix diffusion and mixing grow stronger. Similarly, BTC tailing can be produced as the Peclet number and/or aperture angle are reduced. Hence, the mixing conditions in the injection and the extraction boreholes should be carefully examined in order not to ascribe the observed BTC tailing to an attenuation mechanism that does not actually exist in the field. PRTSF is applied to analyze the cross-hole, forced gradient tracer test conducted in a test site located in the eastern Kingmen island. Geophysical as well as hydraulic test results indicate that the test zone, at approximately 360 m in depth, is located within a fracture zone that is induced by a fault. The best-fit parameters of Pe, matrix porosity, and half fracture aperture are 425, 7.0% and 767um, respectively. Results from this study can be applied in site characterization of contaminant remediation in fractured rocks and the final disposal of spent nuclear fuels, for evaluating transport characteristics and obtaining representative transport parameters.
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