|
|
Determination of the initial stress tensor from deformation of underground opening-theoretical background and applications
Malík, Josef ; Kolcun, Alexej
In this paper a method for the detection of initial stress tensor is proposed. The method is based on measuring distances between some pairs of points located on the wall of underground opening in the excavation process. This methods is based on the solution of eighteen auxiliary problems in the theory of elasticity with force boundary conditions. The optimal location of the pairs of points on the wall of underground work is studied. The pairs must be located so that the condition number of a certain matrix has the minimal value, which guarantees a reliable estimation of initial stress tensor.
|
|
|
Pseudo-triangulations and their use in applied computational geometry
Trčka, Jan ; Kolingerová, Ivana (advisor) ; Kolcun, Alexej (referee)
This thesis shows fundamental properties of pseudo-triangulation, its use as a planar tesselation and implementation of minimal pseudo-triangulation algorithm, which has triangulation as its input. Furthermore, this thesis examines usability of a walking algorithm and two versions of algorithm are proposed. The walking algorithm is also used in an incremental algorithm for a pseudo-triangulation construction. All proposed algorithms have been verified with implementation and experiments.
|
|
|
RTIN-based strategies for local mesh refinement
Kolcun, Alexej ; Sysala, Stanislav
Longest-edge bisection algorithms are often used for local mesh refinements within the finite element method in 2D. In this paper, we discuss and describe their conforming variant. A particular attention is devoted to the so-called Right-Triangulated Irregular Network (RTIN) based on isosceles right triangles and its tranformation to more general domains. We suggest to combine RTIN with a balanced quadrant tree (QuadTree) decomposition. This combination does not produce hanging nodes within the mesh refinements and could be extended to tetrahedral meshes in 3D.
|
|
|
Comprehensive geological characterization of URF Bukov – part II Geotechnical characterization.
Souček, Kamil ; Vavro, Martin ; Staš, Lubomír ; Kaláb, Zdeněk ; Koníček, Petr ; Georgiovská, Lucie ; Kaláb, Tomáš ; Konečný, Pavel ; Kolcun, Alexej ; Králová, Lucie ; Kubina, Lukáš ; Lednická, Markéta ; Malík, Josef ; Martinec, Petr ; Ptáček, Jiří ; Vavro, Leona ; Waclawik, Petr ; Zajícová, Vendula
This final report was processed as a part of Radioactive Waste Repository Authority project Research support for safety evaluation of the deep repository, which is a part of the preparation for the deep repository of nuclear waste (further DR). The aims of the project were collection and interpretation of geological data, the creation of models and obtaining information necessary for evaluation of potential sites for DR emplacement regarding long-term safety. On the basis of public submitting act, a 4-year contract was signed with ÚJV Řež, a.s. and its subcontractors: Czech Geological Survey, Czech Technical University in Prague, Technical University in Liberec, Institute of Geonics of Czech Academy of Sciences, and companies Arcadis CZ, Progeo, Chemcomex Praha and Centre for Research Řež about providing research support for evaluation of long-term safety.
|
|
|
Final research report to the project PB-2014-ZL-U2301-004-BUKOV
Souček, Kamil ; Vavro, Martin ; Staš, Lubomír ; Kaláb, Zdeněk ; Koníček, Petr ; Georgiovská, Lucie ; Kaláb, Tomáš ; Konečný, Pavel ; Kolcun, Alexej ; Králová, Lucie ; Kubina, Lukáš ; Lednická, Markéta ; Malík, Josef ; Martinec, Petr ; Ptáček, Jiří ; Vavro, Leona ; Waclawik, Petr ; Zajícová, Vendula
Bukov Underground Research Facility (Bukov URF) has been built as a test site to assess the properties and behaviour of the rock mass analogous to selected candidate sites. It is situated at a depth corresponding to the proposed storage depth of the final locality for the Czech Republic´s deep repository of high-level radioactive waste. Bukov URF is located in the Vysočina Region, the cadastral district of Bukov, approx. 3 km south-eastwards from the municipality of Dolní Rožínka. The underground research facility is placed approx. 300 m from the Bukov-1 shaft, namely on the level 12 of the shaft, at the depth of about 550 – 600 meters below the Earth’s surface. As for the regional geology, Bukov URF is found at the southern part of the Rožná uranium deposit, at the north-eastern edge of the Strážek Moldanubicum close to its contact with the Svratka Unit. The rock mass is composed of a relatively monotonous sequence of differently migmatized biotite gneisses to stromatic migmatites, continuing with amphibole-biotite to biotite-amphibole gneisses and amphiboles, with occasional fine intercalations of aplites, pegmatites or calc-silicate rocks (erlanes). Between 2013 and 2017 and within the complex geotechnical characterization of the Bukov URF, the Institute of Geonics of the Czech Academy of Sciences (Ústav geoniky AV ČR, v.v.i.) in Ostrava carried out a series of laboratory and field works in order to provide a detailed description of the geotechnical and geomechanical properties and quality of the rock mass. The works included the determination and assessment of the physical-mechanical properties of the rocks sampled from the walls, boreholes and ground surface in the locality, the determination of stress state and deformation properties of the rock mass using the methods of hydrofracturing of borehole walls, Goodman Jack and CCBO, or CCBM, determination of the rock mass quality based on selected index geomechanical properties, periodic, long-term strain-gauge measurements and convergence measurements, and the assessment of the effect of technical and mine-induced seismicity on the rock mass of interest. The implemented set of research works was supposed to render a sufficient and integral whole of geotechnical and geomechanical knowledge vital for the subsequent implementation of extensive research experiments focused on long-term safety and technical feasibility of the future national deep repository of radioactive waste.
|
|
|
Large-scale geosimulations using GEM and trilions
Blaheta, Radim ; Jakl, Ondřej ; Hrtus, Rostislav ; Kolcun, Alexej ; Kohut, Roman ; Starý, Jiří ; Turan, E.
The project deals with efficient solution of singular symmetric positive semidefinite problems. Our motivation arises from the \nneed to solve special problems of geotechnics, e.g. to perform upscaling analysis of geocomposites. In that and other applications we have to solve boundary problems with pure Neumann boundary conditions. We show that the stabilised PCG method with various preconditioners is a good choice for systems resulting from the numerical solution of Neumann problems, or more generally problems with a known small dimensional null space. The work was also taken as an opportunity to compare parallel implementations of the orresponding solvers, namely implementations in the in-house finite element software GEM and implementations employing components of the general Trilinos library. The studies show that the solvers based on GEM are highly competitive with its recognised counterpart.
|
|
|
Pseudo-triangulations and their use in applied computational geometry
Trčka, Jan ; Kolcun, Alexej (referee) ; Kolingerová, Ivana (advisor)
This thesis shows fundamental properties of pseudo-triangulation, its use as a planar tesselation and implementation of minimal pseudo-triangulation algorithm, which has triangulation as its input. Furthermore, this thesis examines usability of a walking algorithm and two versions of algorithm are proposed. The walking algorithm is also used in an incremental algorithm for a pseudo-triangulation construction. All proposed algorithms have been verified with implementation and experiments.
|
|
| |
|
|
Slightly generalized regular space decompositions
Kolcun, Alexej
Space decomposition methods represent an important part of numerical modelling process. In many applications it is suitable to use the simplest case of decomposition { regular rectangular grid: the whole raster graphic concept can be seen from this point of view. Dierent raster concept, based on regular hexagonal mesh, is analyzed e.g. in [18]. Generalized task { decomposition of the space to the set of the identical elements have been presented in various research areas since a long time, and it is connected with Hilbert's 18th problem [9], [10].
Fulltext: content.csg -  PDF
Plný tet: UGN_0425285 - PDF
|
|
|
(Semi) regular tetrahedral tilings
Kolcun, Alexej
Triangulation 2D and 3D methods represent an import ant part of numerical modeling process (e.g. FEM). In many applications it is suitable to use triangulati ons with a regular structure. Moreover, decompositi on with a limited number of different types of tetrahedra ena bles to reduce the storage and computational demand s in the whole modeling process. The submitted contribution presents an overview of possible 3D decompositions using one tetrahedron (regular tilings). These decomposit ions are confronted with decompositions using six d ifferent types of tetrahedra (orthogonal structured tilings) . Considering the shape expressivity of particular methods, the paper presents a structure of possible decompositio ns and comparison of storage demands of the used decompositions.
|
guest ::
