the rock pillar stress analysis in order to obtain an effective dimensioning and guarantee the mining void stability

In the room and pillar mining method is of fundamental importance the dimensioning of the pillars. the area of influence method is typically used today for dimensioning of the pillars, but an overdimensioning or critical stability conditions can happen with this method. a parametric analysis with tri-dimensional numerical modelling was carried out to study in the detail the stress conditions in the rock pillars. this made it possible to identify a critical point, where the minimum local safety factor is reached, at the corners of the pillar close to the roof of the mining room. through the estimation of the major principal stress at the critical point it was possible to evaluate the minimum local safety factor in function of the geometric and geomechanical parameters of the problem. the dimensioning of the pillars through the local safety factor at the critical point makes it possible to avoid overdimensioning and static problems, which instead can occur when simplified calculation methods are used. the use of proposed figures can allow a fast pre-dimensioning of the pillar, leaving the more detailed numerical modelling only to the found geometric configuration.