Study Of The Mechanism About Karst Collapse Column Reactivation-Induced Water-Conducting

In north China coal fields, there are many Karstic Collapse columns, a small number of Karstic Collapse columns possesses water permeability to threaten safety.But formation mechanism of Karstic Collapse columns , karst Collapse Column reactivation-induced water -conducting in the condition of weak runoff ,the influence to karst Collapse Column reactivation-induced water -conducting by exploitation were not studay deeply. This paper using some theory of mechanics and numerical simulation to study the mechanism of formation and reactivation-induced water -conducting of karst Collapse Column.Using principle of elasticity mechanics, rockmass mechanics, fracture mechanics, The base and the process of Karstic Collapse columns formation were studyed . the author considers that: The criterion of cracks on edge of crest slab expanded to form perimetervandalizatation zone is ; Acted by gravity, the crest slab of cave would formed separation , and the criterion of separation collapsed is 2cb + 2λρg tanφhb < (hρg -P₀)r.It showed that the crest slab of cave collapsing are relative with size of cave,thickness of crest slab,the press by overlying rock formation and its character. The collapse continued formed karst collapse column.On the base of studying water-resisting ability of different layer of Karstic Collapse columns,according elasticity mechanics,rockmass mechanics analyzed the stress distribution of Karstic Collapse columns and its around. Derive the stress distribution formula by gravity, country rock stress and ground water stress are (3.3),(3.4),(3.20),(3.21), (3.27),(3.28); According to water-resisting ability of different layer and each part of probably reactivation-induced water -conducting , criterion of reactivation-induced water -conducting of the different part of Karstic Collapse columns are :.