ABSTRACT
Three types of mechanical property tests were conducted for characterization of the strength and deformational behavior of potash. The three test types include the (1) constant confining pressure test, (2) constant mean stress test (Mellegard & Pfeifle 1999), and (3) constant stress creep test. Each of these tests was performed in our laboratory to standards that meet or exceed all applicable American Society for Testing and Materials (ASTM) or International Society of Rock Mechanics (ISRM) specifications. All testing was performed under strict quality guidelines applied by trained personnel operating calibrated,
1 INTRODUCTION
The stability of a potash mine is a crucial consideration when assessing a tentative mine design. The stability assessment generally involves finite element modeling of the underground openings to predict the potential for fracture development and potash failure, closure rates, and surface subsidence. A critical component of the modeling effort is the determination of the geo mechanical properties of the potash through an intensive laboratory program. This laboratory testing program generally involves tests to determine the elastic constants, onset of micro cracking, and creep properties of the potash specimens. It is theorized that a slight variation within the mineralogical constituents of the potash specimens; more speci fically, the percentage of potassium-bearing minerals, could significantly affect the geo-mechanical properties of the potash, and therefore, the stability and closure rate of the mine both in the modeling and, ultimately, in the field.
