Analysis of Cracking in Rock Salt

Abstract

¶The use of underground mines in salt-rock formations for waste repositories makes the precise analysis of isolation properties of rock salt very important. One of the main mechanisms responsible for a degradation of isolation ability of the rock salt is the generation and development of cracks under influence of mining processes. Various aspects of cracking in salt rocks are studied – both in situ and in laboratory tests – for rocks of the world's largest Verkhnekamskoe potash-ore deposit (Russia). It is shown that not all the discontinuities (fractures) are closed in the course of the creep deformation of rocks. Parameters of cracking are determined for various conditions: age of pillars, mining technology, etc. Different methods – filtration, electrometric, nuclear magnetic resonance, mechanical tests – are used for crack observation and characterisation, both in specimens and in situ. Traditional investigations (partly with specially designed equipment) are accomplished by the testing methods of fracture mechanics for determination of critical values of stress intensity factors KIc and KIIc. The problems and ways of the use of the obtained results in analysis of isolation properties for areas in vicinity of underground mines and/or waste repositories are discussed.