Changes in rock properties following immersion in various chemimcal solutions

Many clay-bearing rocks will undergo changes in material properties after immersion in water. This is often accompanied by a reduction in strength and cuttability properties associated with increased degradation. In extreme cases such as with water active shales, it can lead to complete collapse or sloughing of the material. This can have important implications for Australian coal mining operations in terms of maintaining ground stability where clay-bearing rocks are in close proximity to coal formations. Previous research has examined whether chemical solutions containing potassium chloride and copper sulphate could arrest these changes in rock properties. While they provided encouraging results, they did not fully explore the effects of altering the exposure times or concentrations of chemical solutions. The purpose of this paper is to outline the effect of changes in the concentration and exposure times of potassium chloride, magnesium chloride and copper sulphate solutions on clay-bearing rock. The Slake Durability Index Test was used to examine the degradation of a claystone after immersion in a range of chemical solutions at different concentrations. There was little quantitative change due in part to the low permeability of the rock. Qualitatively it was found however that degradation was exacerbated following immersion in a copper sulphate solution and to a lesser extent with magnesium chloride. Conversely, potassium chloride at all concentrations was found to reduce the degradation effects of water. Immersion of the test specimen in each of the solutions of potassium chloride, magnesium chloride and copper sulphate improved rock cuttability relative to dry, untreated rock.