Mechanical behavior of a coal seam penetrated by a karst collapse pillar: mining-induced groundwater inrush risk

A karst collapse pillar (KCP) is caused by the karst subsidence that occurs in carbonate rock distribution areas. Current KCP studies focus mainly on aspects such as the cause of formation, rule of development, groundwater inrush, and structural characteristics of the pillar and sidewall rock body. However, few existing studies focus on the influences of mining activity on the damage to KCP, its surrounding rocks, and the formation of the fracture zone, especially the mechanical behavior. In this paper, a numerical fast Lagrangian analysis of continua in three dimensions model was created to understand the mechanical state of a coal seam penetrated by a KCP during mining panel extraction. The numerical results suggest that (1) because of the structure defect, the stress field strongly depends on the mining activity, and the stress distribution varies in different parts of the KCP; (2) KCP and the surrounding rocks show dislocation when the working face passes the KCP, at which point shear failure may then occur, which will lead to a sidewall channel for groundwater inrush; and (3) as mining advances, the plastic zone in the KCP and its broken area develop gradually until the upper and lower plastic zones connect when the working face passes the KCP, which will cause a channel for groundwater inrush. Copyright Springer Science+Business Media Dordrecht 2015