DETERMINATION OF THE STATIC ELASTICITY MODULUS AND POISSON'S RATIO OF THE ROCKS PASSING FROM THAWED TO FROZEN STATE

Abstract

The elastic properties of enclosing rocks at diamond deposits in Yakutia are studied with the help of internal standard STO 05282612-001-2013. The standard has been developed based on an original procedure that enables determination of static elastic properties (modulus of elasticity, Poisson’s ratio) under variation of temperature or water content in a material, which is neglected by the effective Russian and international standards but is of critical importance in mine construction in permafrost
zone. The testing includes multiple loading of specimen within the range of low reversible strains, which enables highly accurate measurement of strain and physically correct estimation of temperature effect on change in properties of the material passing from thawed to frozen state. The uni-axial compression tests involved specimens of rocks (limestone, siltstone) in air-dried and wet condition. Specimen with extensometers attached to it was placed in a temperature control chamber and tested sequentially under room temperature and, then, under 0°С, –20°С and –40°С. It has been found that as the temperature is lowered, the elasticity modulus of the specimen grows and Poisson’s ratio remains unaltered. For investigation of
moisture effects a specimen was placed in water until complete saturation. Testing was carried out in the course of specimen, natural drying in certain time intervals, and the elastic modulus and Poisson’s ratio were evaluated based on the resultant stress-strain diagrams. It was found that the change in the elastic properties as a function of water saturation has essentially nonlinear character.