Abstract
This study presents a hybrid approach for simulating flow and advective transport dynamics in fractured rocks. The developed hybrid domain (HD) model uses the two-dimensional (2D) triangular mesh for fractures and tetrahedral mesh for the three-dimensional (3D) rock matrix in a simulation domain and allows the system of equations to be solved simultaneously. This study also illustrates the HD model with two numerical cases that focus on the flow and advective transport between the fractures and rock matrix. The quantitative assessments are conducted by comparing the HD results with those obtained from the discrete fracture network (DFN) and equivalent continuum porous medium (ECPM) models. Results show that the HD model reproduces the head solutions obtained from the ECPM model in the simulation domain and heads from the DFN model in the fractures in the first case. The particle tracking results show that the mean particle velocity in the HD model can be 7.62 times higher than that obtained from the ECPM mode. In addition, the developed HD model enables detailed calculations of the fluxes at intersections between fractures and cylinder objects in the case and obtains relatively accurate flux along the intersections. The solutions are the key factors to evaluate the sources of contaminant released from the disposal facility.
Highlights
Modeling groundwater flow and solute transport in fractured rocks is essential in engineering, geology, and hydrogeology studies
Case I used the steady-state flow fields from discrete fracture network (DFN), equivalent continuum porous medium (ECPM), and hybrid domain (HD) models, while Case II focused on comparing flow and advective transport obtained from the ECPM and HD models
The results of the HD model agree well with those obtained from the ECPM model in the entire domain region and the DFN model in the fracture network
Summary
Modeling groundwater flow and solute transport in fractured rocks is essential in engineering, geology, and hydrogeology studies. In the procedures of site characterization investigation for the spent nuclear fuel final disposal, the solute transport in the fractured systems plays an essential role because the critical issue has been focused on the release of radionuclides from the deposition holes (DHs) in the disposal facility to the human environment, i.e., the biosphere [5,6]. The high flow velocity in fractures could erode the buffers, and the flow might contact the canister at relatively high flux. Such high-velocity water carries corrosive materials and could cause the copper canister to corrode. Once the canisters are destroyed by corrosion, the radionuclides will release from the deposition holes through the fractures and migrate to the human environment. The flow and transport dynamics near the disposal facility might considerably influence the evaluations of long-term transport behavior
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