In this paper we describe the OpenGeoSys (OGS) project, which is a scientific open-source initiative for numerical simulation of thermo-hydro-mechanical-chemical processes in porous media. The basic concept is to provide a flexible numerical framework (using primarily the Finite Element Method (FEM)) for solving multifield problems in porous and fractured media for applications in geoscience and hydrology. To this purpose OGS is based on an object-oriented FEM concept including a broad spectrum of interfaces for pre- and postprocessing. The OGS idea has been in development since the mid-eighties. We provide a short historical note about the continuous process of concept and software development having evolved through Fortran, C, and C++ implementations. The idea behind OGS is to provide an open platform to the community, outfitted with professional software-engineering tools such as platform-independent compiling and automated benchmarking. A comprehensive benchmarking book has been prepared for publication. Benchmarking has been proven to be a valuable tool for cooperation between different developer teams, for example, for code comparison and validation purposes (DEVOVALEX and CO2 BENCH projects). On one hand, object-orientation (OO) provides a suitable framework for distributed code development; however, the parallelization of OO codes still lacks efficiency. High-performance-computing efficiency of OO codes is subject to future research.

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OpenGeoSys: an open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media

/pdf/opengeosys-an-open-source-initiative-for-numerical-4it7wxohfd.pdf

OpenGeoSys: An open-source initiative for numerical simulation of thermo-hydro-mechanical/chemical (THM/C) processes in porous media

Experimental results obtained from thermomechanical tests on three clays are analyzed in light of the constitutive equations of soil thermoplasticity presented in a companion paper. Heating and cooling drained tests at constant isotropic stress show a strong dependence of the elastic domain on temperature. Thermal sensitivity of elastic domain was found to be different in overconsolidated and in normally consolidated clays. Thermoplastic strain hardening builds up to compensate for thermal softening in normally consolidated clays at plastic compression during drained heating, if the constant stress is imposed. Triaxial compression tests at constant elevated temperatures show an increase in ductility and a decrease in dilatativity at high temperatures. Undrained heating tests show a significant water pressure buildup. At constant principal stress difference, the water pressure growth leads to an effective stress drop and an eventual failure at the critical state line. A temperature‐rate‐dependent non‐assoc...

Thermoplasticity of Saturated Clays: Experimental Constitutive Study

[1] To better inform the subsurface scientist on the expected performance of parallel simulators, this work investigates performance of the reactive multiphase flow and multicomponent biogeochemical transport code PFLOTRAN as it is applied to several realistic modeling scenarios run on the Jaguar supercomputer. After a brief introduction to the code's parallel layout and code design, PFLOTRAN's parallel performance (measured through strong and weak scalability analyses) is evaluated in the context of conceptual model layout, software and algorithmic design, and known hardware limitations. PFLOTRAN scales well (with regard to strong scaling) for three realistic problem scenarios: (1) in situ leaching of copper from a mineral ore deposit within a 5-spot flow regime, (2) transient flow and solute transport within a regional doublet, and (3) a real-world problem involving uranium surface complexation within a heterogeneous and extremely dynamic variably saturated flow field. Weak scalability is discussed in detail for the regional doublet problem, and several difficulties with its interpretation are noted.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2012WR013483

Evaluating the performance of parallel subsurface simulators: An illustrative example with PFLOTRAN

The Cam-Clay model for isothermal mechanical behaviour of clays has been extended to take account of the effects of temperature on stressstrain behaviour. The assumptions used in constructing the ...

Modified cam-clay modelling of temperature effects in clays

A study of the compaction properties of potential clay—sand buffer mixtures for use in nuclear fuel waste disposal

Swelling capacity and permeability of an unprocessed and a processed bentonitic clay

During decommissioning of the tunnel sealing experiment (TSX) at AECL’s Underground Research Laboratory, many samples were taken from the clay bulkhead (70% bentonite and 30% sand) to determine microbial occurrence and viability (culturability) in this clay seal. All samples taken from the TSX showed culturable populations of heterotrophic aerobic and anaerobic bacteria, sulphate-reducing bacteria (SRB) and facultative anaerobic nitrate respiring and nitrate-reducing bacteria. Aerobic and facultative anaerobic populations were significantly higher in the various interface environments. This was likely due to the presence of more water and larger pore spaces at the interface locations, especially at the clay–rock (shotclay) interface, and to persisting aerobic conditions at these locations. Heterotrophic anaerobic and SRB populations were almost constant with no significant differences between the interface locations and the bulk clay. This could suggest that the heterotrophic anaerobes and SRB survived in a metabolically inactive but resistant state because the conditions in the clay were still essentially aerobic. Samples taken in the backfill region of the seal (10% bentonite, 90% sand) showed higher SRB and a noticeable decrease in heterotrophic aerobes and facultative anaerobes. This suggested that moisture, space and nutrient conditions in the backfill region were conducive to microbial activity, causing a reduction in O 2 , followed by a decline in aerobic and an increase in anaerobic populations. Concurrently, higher temperatures in the backfill region of the seal during the second phase of the TSX may have had negative effects on the aerobic and facultative anaerobic populations, while stimulating the anaerobic (seemingly hardier) species. These results suggest that microbial culturability (and in situ activity) in clay-based materials is controlled by a combination of local redox conditions, suitable pore space and moisture availability. In clays the latter two factors are difficult to address separately because they are mutually dependent. In order to reduce or minimize microbial activity in clay-based materials, it is crucial to restrict both pore space and moisture availability as much as possible. This can be achieved by using very high dry densities (>1.8 Mg/m 3 ) or, more generally applicable, very high effective montmorillonite dry densities.

Microbial analysis of samples from the tunnel sealing experiment at AECL’s Underground Research Laboratory

Hydraulic and Ionic Diffusion Properties of Bentonite-Sand Buffer Materials

/pdf/backfilling-of-deposition-tunnels-use-of-bentonite-pellets-19aaimc0il.pdf

D.A. Dixon

Papers

A study of the compaction properties of potential clay—sand buffer mixtures for use in nuclear fuel waste disposal

Swelling capacity and permeability of an unprocessed and a processed bentonitic clay

Microbial analysis of samples from the tunnel sealing experiment at AECL’s Underground Research Laboratory

Hydraulic and Ionic Diffusion Properties of Bentonite-Sand Buffer Materials

Backfilling of deposition tunnels: Use of bentonite pellets