CO 2 Sequestration effect on Outburst in Coal Mining M.S.A. Perera, Department of Civil Engineering, Monash University, Building 60, Melbourne, Victoria, 3800, Australia. (samintha.perera@monash.edu) P.G. Ranjith, (samintha.perera@monash.edu) Department of Civil Engineering, Monash University, Building 60, Melbourne, Victoria, 3800, Australia. S.K. Choi, Division of Earth Science and Resource Engineering, Commonwealth Scientific and Research Organization (CSIRO), Ian Wark Laboratory, Victoria 3169, Australia. (samintha.perera@monash.edu) Abstract Coal mass has the potential to store substantial amounts of CO 2 in the coal matrix and that CO 2 has the ability to move through the coal seam pore and fracture systems, which influences the release of gases during coal mining and the CO 2 sequestration process. In addition, the reduction of coal mass strength due to CO 2 adsorption greatly affects the outburst process. The sudden and violent failure of coal seam with releasing large amount of gas is called outburst in coal mining. Up to date only few have been conducted to investigate the effect of CO 2 adsorption induces strength reduction on the outburst process. The main objective of this study is to investigate the effect of CO 2 injection on outburst in coal mining. Uniaxial Compressive Strength (UCS) experiments were therefore conducted on black coal samples, which have been saturated with CO 2 and N 2 at various pressures at 33 ºC. According to the results CO 2 adsorption causes the UCS strength of coal to be reduced by up to 53 % and this higher strength reduction is due to the CO 2 adsorption induce coal matrix swelling. However, N 2 saturation causes the coal strength to be slightly increased. According to these observations, there is a high risk associated with CO 2 sequestration process in coal seam as it significantly reduces the coal seam strength, which has direct influence on outburst process in coal. Keywords: CO 2 sequestration, UCS test, strength reduction, outburst in coal mining