Crushed Salt Consolidation for Borehole Sealing in Potash Mines

Consolidation tests have been performed to determine the mechanical properties of crushed salt as affected by applied stresses and consolidation period. The crushed salt with particle sizes ranging from 0.075 to 4.76 mm mixed with 5% saturated brine are consolidated under axial stresses ranging from 2.5 to 10 MPa. The consolidation curves show instantaneous and transient strains. The densities, uniaxial compressive strengths and elastic moduli measured after consolidation for 3–180 days increase with applied stresses and time. The crushed salt properties are determined as a function of mean strain energy required during consolidation. The relations are used to predict the crushed salt properties installed in exploratory boreholes under various external pressures. Two main mechanisms strengthen and stiffen the crushed salt mass: (1) consolidation by volumetric change due to particle rearrangement and cracking, and (2) recrystallization and healing processes. The borehole depth and installation time are significant factors controlling the long-term density, strength and stiffness of the crushed salt seal.