Numerical simulation method for the karst development of carbonate fracture networks with both laminar and turbulent flow

The development process of karst water systems is of great significance to many resource and environmental problems. The issues such as the prediction and exploitation of water resource, oil and gas resources, and the prevention of soil erosion are all closely related to this process. Karst conduits are formed by the gradual dissolution of fractures by groundwater. In the early stage of karstification, the width of the fractures is small and the whole flow field is laminar flow. With the progress of karstification, the flow in some fractures becomes turbulent because of preferential dissolution, and the flow in other fractures remains laminar. This paper presents a numerical method to simulate the karst development of fracture networks with both laminar and turbulent flow. The initial fracture networks are constructed by Monte-Carlo simulation. The groundwater flow is simulated by the discrete fracture network method. The dissolution enlargement of fractures is calculated by the empirical equations of dissolution rate of carbonate rock surface. The nonlinear equation system for the water heads of the flow field, with both laminar and turbulent flow, is solved using the iteration method. The numerical method and software of this work are proved by comparing the calculation results of the analytical and numerical methods.