METHODICAL ASPECTS OF DETERMINATION OF THERMOBARIC EFFECTS ON ULTRASONIC VIBRATION VELOCITY IN ROCKS

Estimation of stresses in rock mass by ultrasonic techniques based on measurement of P-wave velocities is incompetent due to poor correlation of the latter and the level of mechanical stresses. On the other hand, addition of temperature in ultrasonic measurement can considerably improve sensitivity of in-situ testing. This article is devoted to the methodical aspects of determination of elastic P-wave velocities as function of pressure and temperature in laboratory tests of rock specimens. The basic approaches to obtaining such relationships are the measurement of the velocity–stress characteristic at fixed temperatures and the measurement of the velocity–temperature characteristic at fixed levels of mechanical loading. The second approach is more laborious and results in no accumulation of microdefects in a specimen. It is important to control and maintain thermal equilibrium in a specimen (equal temperatures in the center and on the surface). Indirect estimability of achieving such equilibrium by the flattening of P-wave velocity recorded in the course of heating is experimentally proved. Specific attention is paid to the post-treatment of the obtained three-dimensional relationships. It is proposed to present them in the form of a family of curves and 3D surfaces. The latter are possible to obtain using a polynomial regression (for estimation of general trend), or by interpolation by the Shepard or Kriging methods. The article exemplifies evaluation of uniaxial mechanical stress by the measured values of velocity and temperature and using the known three-dimensional relationship.


Acknowledgements: The study was supported by the Russian Foundation for Basic Research, Agreement No. 19-05-00152\19.


For citation: Nikolenko P. V. Methodical aspects of determination of thermobaric effects on ultrasonic vibration velocity in rocks. MIAB. Mining Inf. Anal. Bull. 2019;(9):160-167. [In Russ]. DOI: 10.25018/0236-1493-2019-09-0-160-167.

Keywords

Thermobaric effects, rocks specimens, Peltier effect, ultrasound, control, stress state.

Issue number: 9
Year: 2019
ISBN: 0236-1493
UDK: 622.02:539.2
DOI: 10.25018/0236-1493-2019-09-0-160-167
Authors: Nikolenko P. V.

About authors: Nikolenko, Cand. Sci. (Eng.), Assistant Professor, e-mail: petrov-87@mail.ru, National University of Science and Technology «MISiS», 119049, Moscow, Russia.

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