Abstract：The dissolving process of karst fracture is theoretically simplified according to the dissolution mechanism of carbonate rock. A model coupled with the fissure surface chemical-kinetic and fissure seepage is set up, then the single-fissure widening features and laws under different boundary conditions are analyzed and studied. The results show that the dissolution widening rate is determined by the hydraulic gradient and initial width of fracture. If either the rock fracture is closed or the groundwater flow is slow, karst evolution is difficult. During the karst development and evolution process, the permeability of water-bearing medium significantly enhanced, the flow status change from laminar to turbulent, and the flow rate increase exponentially, while the dissolution rate is almost invariable, and the gradient of water table tends to slow.

Keyword：karst fracture;development and evolution;water-bearing medium;dissolution widening;