ABSTRACT
The risk of instability faced by room and pillar mining method has different shapes and match a variety of failure mechanisms. The historical accidents in underground mines are often associated with the failure of the pillars (ex. Coalbrook collapse in South Africa, Clamart in France, etc.). The failure of the pillars is due to:
• the mechanical properties due to an insufficient intrinsic compression resistance;
• the buckling of the pillars becoming too slender or such as a result of roof falls;
• the geological structural and discontinuities may affect isolated pillars or whole districts of the mine;
• the exogenous factors can significantly reduce the resistance, it is primarily water and time.
