Perm State National Research Institute, Perm, Russia:

V. V. Seredin, Head of Chair, Professor, Doctor of Geologo-Mineralogical Sciences, seredin@nedra.perm.ru

NIPPPPD Nedra, Perm, Russia:
A. S. Khrulev, Geological Engineer

Perm National Research Polytechnical University, Perm, Russia:
A. V. Rastegaev, Professor, Doctor of Geologo-Mineralogical Sciences
V. I. Galkin, Head of Chair, Professor, Doctor of Geologo-Mineralogical Sciences

Construction engineering has proposed some methods to estimate strength of rocks and geomaterials mostly in the form of mathematical and other models. These models enable selecting a type of material, construction of foundations and technical parameters of structures. On the whole, these models meet operational requirements but occasional failures result in accidents in building projects. The status control of critical structures uses stress sensors but this approach is random, laborious and expensive. On the whole, assessment of stress state in materials composing elements of engineering structures need to be advanced. It is particularly important to develop the stress state assessment techniques for materials suitable for service with already defective structural elements (for instance, pillars, beams, foundations). In this case, it will be possible to determine critical stresses causing material failure and, based on this information, to adjust the mathematical model of ultimate stress state of the structural element. As a consequence, the reliability of design models will be improved, and, accordingly, the life of structures will be extended. This study aims to develop the stress state assessment procedure for engineering materials using the science-based information criteria. It is experimentally found that in rocks and geomaterials under compression, roughness of fractured surfaces becomes smaller than in the iniaxial tension. The standard deviation also regularly decreases with increasing normal stress. Consequently, these characteristics can be assumed as the classification features of stress causing failure of a material. The tests show that in the uniaxial tension, the temperature in the fracture zone is minimal while it regularly grows in the uniaxial compression. The maximal temperatures are recorded in the materials in the triaxial stress state. The proposed procedure of stress state assessment in materials is based on the interrelation between the values of fractured surface roughness, temperature and normal stresses in the fracture zone.

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