ABSTRACT
Based on their characteristics analyzing in detail of exterior shape and interior substance, basic control factors, hydrogeology and so on, mechanisms of water inrush from Karstic collapse columns is studied, excavation process of working face are simulated with FLAC3D when a collapse column exists in the coal floor. Numerical simulations and experiments show that: (1) because of the collapse column existed in the coal floor, stress and strain distribution are asymmetric, concentrating coefficients of stress become bigger, the closer distant with it, the bigger its influence, but influence for failure modes of rock masses is less. When the border cliff of the collapse column and division of compressive and expand zones on coal floor are superposition on the same line, that is the best state of shear yield and water inrush from coal floor takes place most often. (2) Rock failure mechanism under hydraulic pressure is shear-tension-pressure complex and giving priority to shear. When there is a Karstic collapse column in coal floor, mining pressure and seep intenerating as well as dilatancy cause fractures expanded in all directions. When value of hydraulic pressure is larger than that of the minimum principal stress on key stratum, fractures transfix at last and water inrush takes place.
