The stress-strain state modelling of the autochthonous sedimentary complex in the dynamic influence zone of the thrust wedge

: pp. 58-71
Ivan Franko National University of Lviv
Ivan Franko National University of Lviv

Purpose. Computer modelling in the framework of continuum mechanics is a powerful tool to obtain qualitative and quantitative deformation parameters in the geological media. The purpose of this work was to study stress and strain fields of the sedimentary autochthonous complex owing to moving a thrust wedge. Subject of inquiry is layered rocks with different geometrical and mechanical properties bounded by the basement of the peleobasin and compressive thrust wedge taking into account the gravitational forces and contact frictions. Methodology. Series of the finite-element 2D-models of dynamic influence of thrust wedge on the sedimentary autochthonous complex are constructed. We consider layered structures with different mechanical properties, transferring of tectonic compression through mechanical frictional contact, morphology of a fault surface and dependence on deformation ratio. The stress-strain state of rocks in front of the thrust wedge are calculated. The developed technique of the complex analysis of stress and strain invariants for visualization was used. Distributions of the equivalent strains and stresses, pressures, maximal tangential stresses, stress trajectories and slide lines traced under angle of the internal friction to them, as well the probable fracturing zones that defined by Byerlee's criterion are mapped. All together they are most important for geological interpretation. Results. The analyzed stress and strain fields of the models found that successive thrust fault in the autochthonous occurred in front of the allochthonous structure and had primarily an arc-like surface. The sizes of thrust structures depend on sedimentary rocks thickness, order of competent and incompetent layers, less – on velocity of sliding. Originality. The explanation of morphology, the thrusts proportion and pattern of the stress and strain distribution inside these structures are resulted. Practical significance. The revealed regular dependences of the thrust formation mechanism are important to consider controversial questions of tectonic zoning and structural evolution of the Ukrainian Carpathians, interpretation of geophysical data about deep parts of the thrust nappes and its para-autochthon, in particular, related to exploration of the oil-and-gas bearing structures.

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