<p>Collapse columns are columnar accumulations formed in the limestone underlying coal measures due to long-term dissolution by groundwater that can serve as major channels for dangerous water inrush accidents in mines. We used a self-developed triaxial seepage test system capable of simulating mass loss in fractured rock masses to investigate the seepage characteristics of karst collapse columns in fractured rock masses under different confining pressures, degrees of compaction and cementation, and particle grading. Additionally, a numerical model for variable-mass seepage in karst collapse columns of fractured rock masses was established using COMSOL software to further elucidate the formation of water-conducting pathways under conditions of mass loss in collapse columns. The research indicates that the particle mass loss rate is inversely proportional to the Talbol power index and axial displacement, and that the porosity increases rapidly during the initial stages of the seepage process. The time-varying process of seepage velocity in fractured rocks can be divided into three stages: initial seepage, sudden increase in seepage, and stable seepage. In the process of variable mass seepage in different graded crushed rocks, the relationship between pore pressure gradient and seepage velocity is more consistent with Forchheimer's law than Darcy’s law. Numerical simulations show that as particles in the karst collapse columns erode away, there are initial changes in fracture aperture and permeability, followed by the formation of several discontinuous seepage pathways at the top of the collapse columns. As the fracture aperture and permeability of these seepage pathways increase, water-conducting pathways are formed, which can potentially lead to water inrush disasters.</p>