Pressure solution creep and non-associated plasticity in the mechanical behavior of potash mine openings

Abstract

During the process of analysis and investigations associated with a potash mine rock mechanics project, a great amount of information regarding underground creep deformations was obtained from a long-term, extensive in situ instrumentation campaign under different opening geometries and geological conditions. Over 300 samples were tested in laboratories to define the elasto-plastic parameters of the seven existing different layers of the Saline Formation. The analysis of all this information by regression analysis, optimization numerical search techniques, and by the numerical modeling simulation of several control stations, where measured and calculated room movements were matched, made it possible to demonstrate that the in situ mechanical behavior of fine-grained salt rocks under actual mining conditions is controlled by non-associated plasticity and by pressure solution creep mechanisms, that is, under equivalent stresses, temperatures and strain rates, below 25 MPa (3625 psi), 100°C and 10 −11 sc −1 , respectively.