EFFECTS OF CARNALLITE CONTENT ON EXTRACTION RATIO AND BOREHOLE STABILITY OF POTASH MINES
Keywords:
Elastic modulus, strength, sylvite, rock saltAbstract
The mechanical properties of rock salt with various amounts of carnallite content aredetermined in the laboratory. The compressive and tensile strengths and elastic moduli ofthe specimens decrease exponentially with the increasing carnallite content (C%). ThePoisson’s ratios increase linearly from 0.27 for pure halite to 0.39 for pure carnallite. Theeffects of the carnallite content tend to act equally throughout the range of the confiningpressures used here (0-12 MPa). The Hoek-Brown strength criterion fits well with thestrength results under the various amounts of C%, and can be applied to determine theappropriate extraction ratio and stability of exploratory boreholes. When the C% increases,the pillar strength and extraction ratio decrease, but the excavated rock contains a higherconcentration of sylvite (KCl). Conversely, for the lower C% the pillar strength andextraction ratio are higher, but the extracted rock contains a lower concentration of KCl.The dilation and failure zones around the exploratory boreholes increases with the depthand carnallite content.
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