Acoustic Emission of Rock Salt at Different Uniaxial Strain Rates and Under Temperature
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ACOUSTIC EMISSION OF ROCK SALT AT DIFFERENT UNIAXIAL STRAIN RATES AND UNDER TEMPERATURE V. L. Shkuratnika,∗ , O. S. Kravchenkoa , and Yu. L. Filimonovb
UDC 622.179.19
Abstract: Acoustic emission activity and longitudinal and volumetric deformations in rock salt samples subjected to uniaxial mechanical loading with a constant strain rate and thermal stress are measured. The features of acoustic emission during deformation under various thermobaric experimental conditions are analyzed. It is shown that, in contrast to the deformation parameters, the change in the activity of acoustic emission at the boundaries of the indicated stages is nonmonotonic in nature, as well as features that make it possible to accurately determine each stage and estimate the elastic and strength properties of the rock salt. Keywords: rock salt, acoustic emission, thermobaric effect, deformation stages. DOI: 10.1134/S0021894420030207 INTRODUCTION Rock salt is a unique geomaterial characterized by high strength and plasticity, as well as extremely low permeability and porosity. It easily dissolves and has pronounced rheological properties even with minor stresses. The noted features make it possible to develop artificial reservoirs in rock salt deposits, which are underground gas storages (UGSs) whose tightness eliminates the penetration of a stored product into the surrounding massif. UGSs are characterized by a significant depth of occurrence, a complex shape, extremely large volumes, lack of attachment, long working lifespan, and high requirements for a long-term functional and structural stability. The possibilities of controlling such stability during storage are limited and mainly reduced to an increased pressure inside of it, which counteracts the compressive forces of the contour array. Therefore, stability is ensured mainly by appropriate design decisions at the stage of constructing UGSs, based on information about the mechanical properties and condition of the host geological environment. The source of this information is, as a rule, laboratory studies, including measurements of the deformation of mechanically loaded samples [1]. Due to the above-mentioned specific properties of rock salt, measuring the sample deformation is barely accurate and quite laborious. Moreover, such measurements are always performed on a sample surface, so it is impossible to estimate the structural damage dynamics in the entire investigated volume of a geomaterial. This leads to acoustic emission measurements under mechanical loading of rock salt, which makes it possible to study its damage dynamics, identify the stages of deformation and creep, and determine the most important physical and mechanical properties [2–5]. There are various ways of processing the results of acoustic emission measurements [6, 7]. However, the acoustic emission studies of rock salt have not been accounting for real thermobaric conditions a
National University of Science and Technology “MISiS,” Moscow, 119049 Russia; ∗ [email protected]; b [email protected]. Joint Stock Compan
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