| Karst groundwater resources are abundant in China,but the evaluation and effective exploitation and utilization of karst groundwater resources are seriously restricted by the highly heterogeneous karst multi-aquifer media and the complexity of flow movement.It is a prospective scientific proposition to solve the problem of karst water resources evaluation by studying the law of flow movement of karst multi-media,which plays an important role in the management,prediction and exploitation of karst water resources.In this study,the hydrodynamic characteristics of karst matrix-conduit dual aquifer media are studied by means of field investigation and test,laboratory test,physical simulation and numerical simulation.The results obtained are as follows:(1)The structure,formation mechanism and vertical zoning characteristics of fractured media in Karst aquifer are summarized.The monitoring data of water level,flow rate,temperature,conductivity,rainfall and hydrochemistry are obtained by deploying an automatic hydrodynamic monitoring system for conduit and fracture media in the field.The hydrodynamic characteristics of karst conduits and matrix fissures are quite different,and the discharge at the outlet is 825 times of that at high and low water periods.According to the dynamic relationship of rainfall,discharge and hydraulic gradient,the movement law of fissure flow in Karst conduit and bedrock is studied.Through linear and non-linear regression equation of multiple groups of discharge and hydraulic gradient,the critical flow rate of conduit flow and fissure flow is 0.8 m~3/s.(2)The permeability coefficients of conduit medium(ZK13)and fissure medium(ZK16)are 2.63 m/d and 0.018 m/d respectively by borehole water injection test,and the average velocity,dispersion coefficient,water storage volume and Reynolds number of karst conduit and fissure are calculated by tracer test and QTRACE2.The hydrogeological parameters of conduit are much larger than those of bedrock fissure medium,and the two media have water exchange.However,different hydrodynamic characteristics,conduit media have better water circulation and permeability than fracture media.(3)Through the parameters of conductivity,nitrateion(NO3-)and pH value of conduit medium(ZK7)and fissure medium(ZK6)during rainstorm period,it is confirmed that there exists flow exchange between the two media.The velocity and direction of flow from bedrock fissure to pipeline medium are determined by AquaLITE flowmeter,which is between 305um/s-1056.7 um/s and 324.7 NW-257.3 SW.Judge the flow of groundwater from bedrock fissures to karst pipeline media.(4)Designed the physical model of hydrodynamic simulation of karst conduit and fissure media,and quantitatively studied the hydrodynamic characteristics of fissure media and fissure media and the law of flow exchange between media under different flow conditions.Through a series of experiments and regression analysis,it is concluded that the flow exchange rate is proportional to the square root of head difference.(5)Modify the flow exchange equation between conduit and bedrock fissure in the source code of CFP Conduit Flow Process to make it conform to the law of flow exchange.An ideal model is built and the effects of permeability coefficient of fractured media and water supply,conduit shape,flow exchange coefficient,rainfall intensity and conduit non-confined pressure on flow exchange are discussed.CFP model is applied to flow simulation of karst aquifer system in Zhaidi.The results show that the movement law of karst flow is well simulated. |
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