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21.
Development of a discontinuous approach for modeling fluid flow in heterogeneous media using the numerical manifold method 
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下载免费PDF全文 In the numerical modeling of fluid flow in heterogeneous geological media, large material contrasts associated with complexly intersected material interfaces are challenging, not only related to mesh discretization but also for the accurate realization of the corresponding boundary constraints. To address these challenges, we developed a discontinuous approach for modeling fluid flow in heterogeneous media using the numerical manifold method (NMM) and the Lagrange multiplier method (LMM) for modeling boundary constraints. The advantages of NMM include meshing efficiency with fixed mathematical grids (covers), the convenience of increasing the approximation precision, and the high integration precision provided by simplex integration. In this discontinuous approach, the elements intersected by material interfaces are divided into different elements and linked together using the LMM. We derive and compare different forms of LMMs and arrive at a new LMM that is efficient in terms of not requiring additional Lagrange multiplier topology, yet stringently derived by physical principles, and accurate in numerical performance. To demonstrate the accuracy and efficiency of the NMM with the developed LMM for boundary constraints, we simulate a number of verification and demonstration examples, involving a Dirichlet boundary condition and dense and intersected material interfaces. Last, we applied the developed model for modeling fluid flow in heterogeneous media with several material zones containing a fault and an opening. We show that the developed discontinuous approach is very suitable for modeling fluid flow in strongly heterogeneous media with good accuracy for large material contrasts, complex Dirichlet boundary conditions, or complexly intersected material interfaces. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
22.
Non-isothermal flow in low permeable porous media: a comparison of Richards’ and two-phase flow approaches 总被引：1，自引：1，他引：0
Wenqing Wang Jonny Rutqvist Uwe-Jens Görke Jens T. Birkholzer Olaf Kolditz 《Environmental Earth Sciences》2011,62(6):1197-1207
The present work compares the performance of two alternative flow models for the simulation of thermal-hydraulic coupled processes
in low permeable porous media: non-isothermal Richards’ and two-phase flow concepts. Both models take vaporization processes
into account: however, the Richards’ model neglects dynamic pressure variations and bulk flow of the gaseous phase. For the
comparison of the two approaches first published, data from a laboratory experiment are studied involving thermally driven
moisture flow in a partially saturated bentonite sample. Then a benchmark test of longer-term thermal-hydraulic behavior in
the engineered barrier system of a geological nuclear waste repository is analyzed (DECOVALEX project). It was found that
both models can be used to reproduce the vaporization process if the intrinsic permeability is relative high. However, when
a thermal-hydraulic coupled problem has the same low intrinsic permeability, only the two-phase flow approach provides reasonable
results. 相似文献
23.
Fixed wavelength fluorescence (FF) of bile was used as a biomarker for PAH exposure in fish caged adjacent to an aluminium works. After 30 days of caging, a 20–50 fold increase of pyrene fluorescence was found in groups caged adjacent to the works as compared to two control groups. The PAH uptake occurred mainly from suspended particles rather than from PAH contaminated sediments at the caging sites. Our results demonstrates the combined use of fish caging and bile-fluorescence measurements as a powerful field model for the monitoring of coastal waters subjected to PAH pollution. 相似文献
24.
Modeling of damage,permeability changes and pressure responses during excavation of the TSX tunnel in granitic rock at URL,Canada 总被引：1，自引：0，他引：1
Jonny Rutqvist Lennart Börgesson Masakazu Chijimatsu Jan Hernelind Lanru Jing Akira Kobayashi Son Nguyen 《Environmental Geology》2009,57(6):1263-1274
This paper presents numerical modeling of excavation-induced damage,
permeability changes, and fluid-pressure responses during excavation of a test tunnel associated with the tunnel
sealing experiment (TSX) at the Underground Research Laboratory (URL) in Canada. Four
different numerical models were applied using a wide range of approaches to model damage
and permeability changes in the excavation disturbed zone (EDZ) around the tunnel.
Using in situ calibration of model parameters, the modeling could reproduce observed
spatial distribution of damage and permeability changes around the tunnel as a
combination of disturbance induced by stress redistribution around the tunnel
and by the drill-and-blast operation. The modeling showed that stress-induced
permeability increase above the tunnel is a result of micro and macrofracturing
under high deviatoric (shear) stress, whereas permeability increase alongside
the tunnel is a result of opening of existing microfractures under decreased mean
stress. The remaining observed fracturing and permeability changes around the periphery
of the tunnel were attributed to damage from the drill-and-blast operation. Moreover,
a reasonably good agreement was achieved between simulated and observed
excavation-induced pressure responses around the TSX tunnel for 1 year following its
excavation. The simulations showed that these pressure responses are caused by
poroelastic effects as a result of increasing or decreasing mean stress, with
corresponding contraction or expansion of the pore volume. The simulation results
for pressure evolution were consistent with previous studies, indicating that the
observed pressure responses could be captured in a Biot model using a relatively
low Biot-Willis’ coefficient, α ≈ 0.2,
a porosity of n ≈ 0.007, and a relatively
low permeability of k ≈ 2 × 10−22 m2,
which is consistent with the very tight, unfractured granite at the site. 相似文献
25.
Thanh Son Nguyen Lennart Börgesson Masakazu Chijimatsu Jan Hernelind Lanru Jing Akira Kobayashi Jonny Rutqvist 《Environmental Geology》2009,57(6):1239-1254
In order to demonstrate the feasibility of geological disposal of spent CANDU fuel in Canada, a safety assessment was performed
for a hypothetical repository in the Canadian Shield. The assessment shows that the maximum long term radionuclide release
from such repository would meet international criteria for dose rate; however, uncertainties in the assumed evolution of the
repository were identified. Such uncertainties could be resolved by the consideration of coupled Thermal-Hydro-Mechanical-Chemical
(THMC) processes. In Task A of the DECOVALEX-THMC project, THM models were developed within the framework of the theory of
poroelasticity. Such model development was performed in an iterative manner, using experimental data from laboratory and field
tests. The models were used to perform near-field simulations of the evolution of the repository in order to address the above-mentioned
uncertainties. This paper presents the definition and rationale of task A and the results of the simulations. From a repository
safety point of view, the simulations predict that the maximum temperature would be well below the design target of 100°C;
however, the stress on the container can marginally exceed the design value of 15 MPa. However, the most important finding
from the simulations is that a rock damage zone could form around the emplacement borehole. Such damage zone can extend a
few metres from the walls of the emplacement holes, with permeability values that are orders of magnitude higher than the
initial values. The damage zone has the potential to increase the radionuclide transport flux from the geosphere; the effect
of such an increase should be taken into account in the safety assessment and mitigated if necessary by the provision of sealing
systems.
Prepared for publication in Environmental Geology.
DECOVALEX-THMC Special Issue. 相似文献
26.
Coupled hydro-mechanical (HM) processes are significant in geological engineering such as oil and gas extraction, geothermal energy, nuclear waste disposal and for the safety assessment of dam foundations and rock slopes, where the geological media usually consist of fractured rock masses. In this study, we developed a model for the analysis of coupled hydro-mechanical processes in porous rock containing dominant fractures, by using the numerical manifold method (NMM). In the current model, the fractures are regarded as different material domains from surrounding rock, i.e., finite-thickness fracture zones as porous media. Compared with the rock matrix, these fractured porous media are characterized with nonlinear behavior of hydraulic and mechanical properties, involving not only direct (poroelastic) coupling but also indirect (property change) coupling. By combining the potential energy associated with mechanical responses, fluid flow and solid–fluid interactions, a new formulation for direct HM coupling in porous media is established. For indirect coupling associated with fracture opening/closure, we developed a new approach implicitly considering the nonlinear properties by directly assembling the corresponding strain energy. Compared with traditional methods with approximation of the nonlinear constitutive equations, this new formulation achieves a more accurate representation of the nonlinear behavior. We implemented the new model for coupled HM analysis in NMM, which has fixed mathematical grid and accurate integration, and developed a new computer code. We tested the code for direct coupling on two classical poroelastic problems with coarse mesh and compared the results with the analytical solutions, achieving excellent agreement, respectively. Finally, we tested for indirect coupling on models with a single dominant fracture and obtained reasonable results. The current poroelastic NNM model with a continuous finite-thickness fracture zone will be further developed considering thin fractures in a discontinuous approach for a comprehensive model for HM analysis in fractured porous rock masses. 相似文献
27.
Mapping and analysing virtual outcrops 总被引：1，自引：0，他引：1
Immo Trinks Phillip Clegg Ken McCaffrey Richard Jones Richard Hobbs Bob Holdsworth Nick Holliman Jonny Imber Steve Waggott Robert Wilson 《Visual Geosciences》2005,10(1):13-19
Laser scanning is a very efficient way to generate realistic, high-resolution digital models of 3-D geological outcrops. This paper discusses the methodologies involved in the creation and analysis of virtual outcrops, based on laser scanner data. The visualisation of the laser scanner data as a photorealistic 3-D object is described. Geological features picked out on the virtual outcrop (e.g. fractures, faults or bedding planes) can be extrapolated outward, into space, and inward, into the subsurface, using tension surfaces.Electronic Supplementary Material Supplementary material is available in the online version of this article at Reviewed by: J.D. Clemens, D. Yuen 相似文献
28.
29.
Rolf C. Sundt Sonnich Meier Grete Jonsson Steinar Sanni Jonny Beyer 《Marine pollution bulletin》2009,58(9):1382-1388
A biotest system for environmentally realistic exposure of fish to produced water (PW) was developed and tested. Authentic PW was collected at an oil production platform in the North Sea and preserved by freezing in multiple aliquots a 25 L. After transport to the test laboratory onshore, daily PW aliquots were thawed, homogenised and administered to the test fish, Atlantic cod (Gadus morhua), in two diluted exposure concentrations, 0.1% and 0.5%, during a 15 d period, using a continuous flow-through exposure setup. Positive control groups were exposed to two crude oil treatments for comparison. Chemical analyses showed that alkylphenol (AP) and PAH concentrations in PW exposure waters were very low. Observations of significantly increased AP and PAH metabolite levels in PW exposed fish demonstrated the suitability of the biotest system for its use in biological exposure/effect studies of PW, and it also demonstrated the sensitivity of bile metabolites as PW exposure markers in fish. The relevance of the biotest system for PW effect studies and for validating modelled environmental risk estimates of PW dischargers from offshore oil production is discussed. 相似文献
30.
Masakazu Chijimatsu Lenart Börgesson Tomoo Fujita Petri Jussila Son Nguyen Jonny Rutqvist Lanru Jing 《Environmental Geology》2009,57(6):1255-1261
In the international DECOVALEX-THMC project, five research teams study the influence of thermal-hydro-mechanical (THM) coupling
on the safety of a hypothetical geological repository for spent fuel. In order to improve the analyses, the teams calibrated
their bentonite models with results from laboratory experiments, including swelling pressure tests, water uptake tests, thermally
gradient tests, and the CEA mock-up THM experiment. This paper describes the mathematical models used by the teams, and compares
the results of their calibrations with the experimental data. 相似文献