EFFECT OF LOW TEMPERATURE DAMAGE ON TENSILE STRENGTH OF COAL UNDER THE LIQUID NITROGEN FREEZING

Abstract

To explore the influence of low temperature damage on the tensile strength of coal under the liquid nitrogen freezing, the Brazilian splitting tests are conducted on the bedding coal in this paper. The tensile strength, macro fracture surface morpholgy, failure path and micro-structures of the coal samples before and after liquid nitrogen treatment were analyzed systematically. The results show that the tensile strength of coal after liquid nitrogen freezing is reduced, the macro fracture surfaces with greater roughness or fractal dimension were induced in the coal treated by liquid nitrogen freezing during the Brazilian splitting tests, the opening and number of the failure paths of coal after liquid nitrogen freezing increase significantly, and the microscopically, the bedding and matrix structures of coal are destroyed due to the temperature stress caused by large temperature difference between the liquid nitrogen and coal matrix.