The effect of local flow on flow and contaminant transport in discrete fracture networks
碩士 === 國立中央大學 === 應用地質研究所 === 105 === The dead-end fractures in discrete fracture networks (DFNs) play an important role in the analysis of flow and contaminant transport. In two-dimensional DFN cases, the dead-end fractures have usually been considered as no-flow zones and have been removed at the...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2017
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| Online Access: | http://ndltd.ncl.edu.tw/handle/374kk9 |
| Summary: | 碩士 === 國立中央大學 === 應用地質研究所 === 105 === The dead-end fractures in discrete fracture networks (DFNs) play an important role in the analysis of flow and contaminant transport. In two-dimensional DFN cases, the dead-end fractures have usually been considered as no-flow zones and have been removed at the stage of constructing a DFN. Such simplification is not valid for three-dimensional DFNs. The local flow effect induced by dead-end fractures can considerably influence the flow and transport mechanism in the three-dimensional fracture networks. The study developed a full three-dimensional DFN model to assess the effect of dead-end fracture on flow and conservative solute transport in relatively simple DFNs. The testing scenarios included different fracture orientations intersected by two fracture plates. This study also employed the HYDRUS model to quantify the influence of matrix porosity and hydraulic conductivity on flow and contaminant transport. The results from HYDRUS provided indications for neglecting the influence of rock matrix. The results from the developed DFN model showed that the dead-end fractures can lead to local flow when the angle between the background hydraulic gradient and the fracture intersection is non-orthogonal. The smaller the angle the stronger the local flow in the dead-end fractures. Additionally, the local flows in dead-end fractures can trap contaminant plume and enhance retardation behavior in the solute transport procedure.
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