岩溶陷落柱是内部结构杂乱无章的特殊地质构造，易成为隐伏于煤层底板下的垂向导水通道，是华北地区石炭二叠系煤田的重大安全隐患。在采动影响下，底板隐伏陷落柱的突水通道通常由底板破坏带和陷落柱共同组成，为了研究其渗流突变机制，利用自行研制的破碎岩体渗透性试验系统，对不同底板破坏带条件下，隐伏陷落柱的渗流特性进行了试验研究。研究结果表明：渗流突变发生的根本原因是大颗粒流失导致破碎岩体孔隙结构改变；发生渗流突变时，流速随渗流边界孔隙直径的增大而增大，同时试样的初始孔隙度均大于0.21；未发生渗流突变时，渗流边界对渗流无显著影响，并且试样的渗透率随孔隙度的增大而增大，渗透率比和孔隙度比存在幂函数关系；非Darcy流 因子为负是渗流突变发生的充分必要条件，非Darcy流 因子的大小决定渗流突变的剧烈程度。

Karst collapse column, as a special geological body with chaotic internal structure, is easy to be a vertical water channel under the coal floor. Thus it is a major potential safety hazard in Carboniferous coalfield of North China Permo. The water channels in collapse column under the coal floor are composed of collapse column and floor water-conductive fissure zone. To investigate the mutation mechanism of seepage in the hidden collapse column, a broken rock permeability test system is independently developed. A series of experiments is conducted to examine the seepage in the collapse column under different floor damage conditions. Experimental results show that: the fundamental reason of the seepage mutation is caused by the changes of broken rock pore structures resulting from the large particle loss. The flow velocity increases with the increase of the pore diameter at the seepage boundary, and the initial porosity of the sample is higher than 0.21 when the seepage mutation occurs. The seepage boundaries have negligible effect on seepage without the occurrence of seepage mutation. The permeability of the sample increases with the increase of its porosity, and there is a power function relation between permeability ratio and porosity ratio. The negative non-Darcy factor is a sufficient and necessary conditions for the occurrence of seepage mutation, and the non-Darcy factor controls the degree of the seepage mutation intensity.