Investigation of mechanical properties of salt rock based on its microstructure

In this paper, initial microstructure effect of salt rock on its deformation behavior was investigated. Studied samples were taken from Deh Kuyeh salt diapir located at about 27 km NE of Lar city, Fars province. Initial microstructure of two samples from the top of the fountain and one sample from middle part of the diapiric stem were studied by electron backscatter diffraction at Otago University, New Zealand. A slight difference was observed between the initial microstructure of the samples. In the sample from the stem, most grains had been internally deformed, and the grain size is smaller and frequency of low angle boundaries is higher than those in the sample from top of the fountain. The uniaxial compressive strength, elastic modulus and tensile strength values of this sample are lower and its elastic strain, creep strain and creep rate under axial stress of 12 MPa are higher than those in the sample from top of the fountain which can be due to the higher percent of microscopic pores along its grain boundaries. In contrast, the dominant deformation mechanism in the samples from top of the fountain is the grain growth via grain boundary migration. This mechanism removes voids and defects within the grains and along the grain boundaries. Therefore, these samples have higher values of strength and elastic modulus and their grains more easily deformed plastically during mechanical tests.