Experimental Investigation of the spatial-temporal localization of deformation and damage in sylvinite specimens under uniaxial tension

摘要

A good deal of experimental and theoretical data gained from studying the behavior of salt rocks under compressive loads can serve as a basis for computation of the stress-strain state of the mine field elements. However, the specific features of the deformation behavior of rock salts under the action of tensile stresses are still not clearly understood. With reference to geomechanics the emphasis has been placed mainly on studying the strength properties of the salt rocks under tensile loads. The significance and necessity of exploring the process of strain and damage localization in salt rocks under tension is related to a possibility of transition of the shear crack growth mode in the field of compressive stresses to a mode of rapidly growing tensile cracks due to the appearance of tensile stresses. With this scenario, there always exists probability of failure of the working, in addition to the formation and growth of quasi-vertical cracks in the waterproof stratum. In mining of water -soluble minerals these processes can lead to disastrous effects. This paper is concerned with experimental studying the spatial-temporal localization of the deformation and damage processes in sylvinite under quasi-static tension based on the method of acoustic emission and construction of deformation fields on the specimen surface. A series of quasi-static tensile tests were carried out using the original device for specimen fixture. The loading rate varied in the range from 0.025 mm/min до 0.1 mm/min. During experiments the acoustic emission signals were recorded with the Amsy-5 system (Vallen, Germany) over two frequency ranges of 50-400 kHz and 350-2000 kHz. The construction of the deformation and displacement fields on the specimen surfaces was accomplished through the use of the optical system Strain Master (Germany). A comparative analysis of the constructed deformation fields and the results of acoustic emission allowed us to define special features of the localized deformation and damage. Research was supported by the Russian Foundation of Basic Research (grant № 10-05-96065-р_урал_а, 11-05-96005-р_урал_а, 12-05-00253-a), program of RAS Presidium № 09-П-1-1010.