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Velenje, Slovenia

Kanduc T.,Jozef Stefan Institute | Markic M.,Geological Survey of Slovenia | Zavsek S.,Velenje Coal Mine | McIntosh J.,University of Arizona
International Journal of Coal Geology | Year: 2012

Stable isotopes of carbon were used to trace organic and inorganic carbon cycles and biogeochemical processes, especially methanogenesis within different geologic substrates of the Pliocene lignite-bearing Velenje Basin in northern Slovenia. Lithotypes of lignite, coalbed gases, calcified woods (xylites), carbonate-rich sediments, and groundwaters were investigated. Carbon isotope (δ 13C) values of the different lignite lithotypes ranged from -28.1 to -23.0%, with the variability likely a function of the original isotopic heterogeneity of the source plant materials and subsequent biogeochemical processes (i.e. gelification, fusinitization, mineralization of organic matter) during the early stage of biomass accumulation and diagenesis. In the lignite seam, CO 2 and CH 4 were the major gas components with small amounts of N 2. The carbon isotope values of CO 2 (δ 13C CO2) and CH 4 (δ 13C CH4) were highly variable, ranging from -9.7 to 0.6% and -70.5 to -34.2%, respectively. Carbon dioxide is likely sourced from a mixture of in situ microbial activity and external CO 2, while CH 4 is dominantly sourced from microbial methanogenesis, with possible addition of thermogenic gas from deeper formations, and the influence of microbial oxidation of methane. Calcified xylites enriched with 13C (δ 13C values up to 16.7%) indicate that microbial methanogenesis was active during formation of the basin. The δ 13C DIC values (from -17.4 to -3.2%) of groundwaters recharging the basin from the Triassic aquifer are consistent with degradation of organic matter and dissolution of dolomite. Groundwaters from the Pliocene sandy and Lithotamnium carbonate aquifers have δ 13C DIC values (from -9.1 to 0.2%) suggestive of degradation of organic matter and enrichment via microbial reduction of CO 2. © 2011 Elsevier B.V..

Dmitriev A.I.,RAS Institute of Strength Physics and Materials Science | Shilko E.V.,RAS Institute of Strength Physics and Materials Science | Zavsek S.,Velenje Coal Mine | Psakhie S.G.,RAS Institute of Strength Physics and Materials Science
19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012 | Year: 2012

Using the computer simulation the real loading conditions around the coal-bed deep under the surface was reproduced. The calculations were done on the basis of the method of Movable Cellular Automata (MCA). According to the results of simulations the mechanism of fracture of lignite lithotypes can changes from typically brittle to degradation-like or quasi-plastic depending on boundary conditions. Also the influence of loading conditions on fracture process was shown. Obtained results are in good agreement with experimental data. It shows that MCA method can be successfully applied for investigation of behavior and fracture of various heterogeneous media under standard test conditions as well as under very complex loading that is very difficult or impossible to reproduce using experimental procedures.

Kanduc T.,Jozef Stefan Institute | Grassa F.,Italian National Institute of Geophysics and Volcanology | McIntosh J.,University of Arizona | Stibilj V.,Jozef Stefan Institute | And 3 more authors.
Hydrogeology Journal | Year: 2014

The geochemical and isotopic composition of surface waters and groundwater in the Velenje Basin, Slovenia, was investigated seasonally to determine the relationship between major aquifers and surface waters, water-rock reactions, relative ages of groundwater, and biogeochemical processes. Groundwater in the Triassic aquifer is dominated by HCO3 -, Ca2+, Mg2+ and δ13CDIC indicating degradation of soil organic matter and dissolution of carbonate minerals, similar to surface waters. In addition, groundwater in the Triassic aquifer has δ18O and δD values that plot near surface waters on the local and global meteoric water lines, and detectable tritium, likely reflecting recent (<50 years) recharge. In contrast, groundwater in the Pliocene aquifers is enriched in Mg2+, Na+, Ca2+, K+, and Si, and has high alkalinity and δ13CDIC values, with low SO4 2- and NO3 - concentrations. These waters have likely been influenced by sulfate reduction and microbial methanogenesis associated with coal seams and dissolution of feldspars and Mg-rich clay minerals. Pliocene aquifer waters are also depleted in 18O and 2H, and have 3H concentrations near the detection limit, suggesting these waters are older, had a different recharge source, and have not mixed extensively with groundwater in the Triassic aquifer. © 2014 Springer-Verlag Berlin Heidelberg.

Psakhie S.G.,Tomsk Polytechnic University | Shilko E.V.,Tomsk State University | Smolin A.,Tomsk State University | Dimaki A.V.,RAS Institute of Strength Physics and Materials Science | And 4 more authors.
Physical Mesomechanics | Year: 2011

The paper concerns the development of a formalism of the movable cellular automata method for simulation of consolidated heterogeneous elastoplastic media at different scale levels. Using the developed formalism as the basis, an approach was formulated for construction of structural models that describe mesoscopic response (including fracture) of heterogeneous media to loading with regard to hierarchical organization of their internal structure. In the approach, the effect of structural scale levels higher than the level under consideration is taken into account by a technique combining the particle method and conventional methods of continuum mechanics. The effect of lower structural scale levels is taken into account by determining integral response characteristics of lower-scale representative volumes and by specifying appropriate values of particle interaction parameters. The proposed formalism was advanced for description of contrast heterogeneous media whose components can assume different aggregate states. The potentialities of the particle method for description of hierarchically organized media are illustrated by studying the response and fracture mechanisms of materials, including contrast media, with a developed porous structure. © 2011.

Dimaki A.V.,RAS Institute of Strength Physics and Materials Science | Dmitriev A.I.,RAS Institute of Strength Physics and Materials Science | Zavsek S.,Velenje Coal Mine | Psakhie S.G.,RAS Institute of Strength Physics and Materials Science
19th European Conference on Fracture: Fracture Mechanics for Durability, Reliability and Safety, ECF 2012 | Year: 2012

The connected physical-mechanical model of gas-saturated coal seam with explicit taking into the account the processes of filtration and diffusion of the gas mixture in the pores of the solid skeleton has been proposed. The developed model as been verified on the basis of experimental data on desorption of CO2 from the sample of brown coal (lignite). An anomalous increase in strength and deformation capacity of gas-saturated coal sample during uniaxial loading in a certain range of pressure of gas in pores has been revealed. It has been shown that in this pressure range the destruction of the samples occurs with the formation of a large number of small fragments that can serve as a model of gas-dust emission into mine area.

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