Improving the understanding of the processes governing ground movements in and around brown coal open cuts is of significant interest for both operating stability and rehabilitation. Brown coal, lignite, is a low-rank coal that is best described as a soft rock, with geotechnical characteristics that derive from its organic origin. It is well-known that low-rank coals exhibit creep behaviour; however, little has been reported on the impacts of chemical processes on brown coal creep behaviour even though organic substances are susceptible to chemical alterations and mining processes will contribute to changes to the geochemical environment; around most mines, groundwater flow patterns are altered leading to enhanced surface water infiltration. Here we study the deformation behaviour of brown coal in response to ion exchange reaction. Our experimental results show that for different ion exchange conditions different characteristics of secondary compression are observed. With the addition of Ca2+, the ratio between coefficients of secondary and primary compression (C/Cc) initially decreased, presenting a minimum value at the concentration of 0.005M, then increased significantly. This implies the importance of ion exchange process for the long-term deformation of brown coal. On the other hand, increasing Na+ concentration did not affect C/Cc values significantly over all tested concentrations. The suppression of diffuse double layer was still observed for Na+-treated samples as increasing Na+ concentration decreases C values. From a practical perspective, this study did not consider the tertiary creep behaviour and eventual creep failure.CITATION:Kim, S, Mackay, R and Wight, B J, 2014. Creep due to chemical alteration of rocks - a case study in brown coal, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 61-64 (The Australasian Institute of Mining and Metallurgy: Melbourne).