EFFECTS OF BACKFILL COMPOSITIONS ON INTEGRITY OF UNDERGROUND SALT AND POTASH MINES

Abstract

The objective of this study is to laboratory investigate the effects of various backfill compositions on the integrity of rooms and pillars in salt and potash mines.  Uniaxial creep tests have been performed on halite and carnallite core specimens for up to 21 days.  A total of 20 specimens have been tested.  The constant axial stresses are varied from 2 to 12 MPa.  After the specimens are under loading for 7 days, they are separately submerged in three types of solutions prepared from halite, carnallite and magnesium chloride.  The solution is removed after 7 days.  The visco-plastic coefficients are calculated for each phase of solution submersion.  They are used as an indicator of the sensitivity between the tested specimens and the types of solution.  The results indicate that the specimens that are composed of pure halite is insensitive to these solutions, as evidenced by that the creep strain rates measured before, during and after brine submersion remain unchanged.  The specimens containing carnallite of 30% to 90% by weight are sensitive to halite and carnallite solutions, but insensitive to magnesium chloride solution.  The percentage weight loss of the carnallite specimens during submersion in these solutions confirm that saturated magnesium brine has insignificant effect on the dissolution of the carnallite specimens.  The findings can be used for the material selection and the performance assessment of the installed backfill compositions in salt and potash mines.