ROCKS – SEGNETOELASTICS

Abstract

Purpose. Identification of the features and the properties of segnetoelastics in rocks. Research Methods. Laboratory experiments on the deformation of rocks in a volume field of compressive stresses, macro- and microscopic studies of the deformations and the orientations of an optical indicatrix, analysis of the data obtained. Research results. As a result of microscopic and optical studies of rocks in thin sections on a polarizing microscope, tests of rocks under the conditions of unequal triaxial compression, analysis of the results obtained, it was found that the rock-forming minerals of the sedimentary sequence at a normal temperature and in the absence of an external load have a domain structure. Under the conditions of a triaxial unequal component compression, the volumetric deformations at the micro and macro levels do not exceed hundredths, while the relative micro deformations fully correspond to the dilatancy volume at the macro level. Shear rotational deformations reach 15–20%, their resonant increment increases several times over three periods before the destruction. During the loading, the direction of the rotation is changed 3-4 or more times, an optical indicatrix changes the direction. All deformations are alternating in sign and, until resonance, the amplitude of their increment does not exceed 0.5%. During the loading, the deformation, elastic, optical, electromagnetic, and other parameters are changed abruptly (structural-phase transitions of the second, and upon the destruction, of the first and third kind). The interconnection between the load and the deformations is nonlinear, a number of characteristic deformations are distinguished at which these jumps occur. All said indicate that rocks are classical distortion segnetoelastics. The following parameters can be taken as parameters of a segnoelastic transition: the value or increase in the value of relative deformation; an elastic modules varying within ± ∞; the sign and the magnitude of the increment of the Lode angle for the deformations; the angle of rotation of the optical indicatrix, the presence of structural-phase transitions in the minerals. Scientific novelty. It has been shown for the first time that all five signs and traits of segnetoelastics are present in sedimentary rocks. Practical significance. The possibility for isolating of segnetoelastics without laborious microscopic and electromagnetic studies.