INTRINSIC VARIABILITY OF THE MECHANICAL PROPERTIES OF MAHA SARAKHAM SALT
Keywords:
Strength, rock salt, anhydrite, inclusion, elasticity, plasticityAbstract
A series of laboratory mechanical tests were carried out to study the intrinsic variability of rock saltspecimens obtained from the Middle and Lower Salt members of the Maha Sarakham formation. Priorto the mechanical tests, the types and amount of inclusions were identified by visual examination andafter testing by X-ray diffraction and dissolution methods. The uniaxial compressive strength of thespecimens linearly increases linearly from 27 MPa to about 40 MPa as the anhydrite inclusionincreases from 0% (pure halite) to 100% (pure anhydrite). The combined stiffness between the saltand anhydrite also causes an increase of specimen elasticity from 22 GPa (pure salt) to as high as 36GPa (pure anhydrite). Tensile strengths increase with increasing anhydrite inclusion, particularlywhen the inclusion is beyond 60% by weight. Below this limit the anhydrite has an insignificantimpact on the specimen tensile strength. The tensile strength of salt crystals can be as high as 2 MPa,while that of the inter-crystalline boundaries is estimated as 1 MPa. The salt visco-plasticityincreases exponentially with crystal size as dislocation glide mechanisms becomes predominant forthe specimens comprising large crystals. Pure salt specimens with fine crystals are deformed mostlyby dislocation climb mechanisms, and hence reduce the specimen’s visco-plasticity.
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