Water Hammer And Gas Explosion Of Karst Collapse In Mine Drainage Area

Heavy rainfall will lead to the rapid rise of the water level in the karst cavity,the development of the underground river and good drainage conditions or engineering activities lead to rapid decline in water levels.The rise and fall of the groundwater level will cause the change of the water vapor pressure in the karst pipeline.Field ground water vapor pressure monitoring station often monitors very large changes in water vapor pressure and this mutation is closely related to the water level decline.Therefore,the rise and fall of the water level in the karst cavity can be simulated by the water level fluctuation of the indoor water tank,and the variation law of the water vapor pressure in the karst cavity is summed up.In this paper,Ningxiang Dacheng-bridge in Hunan Province as the research area,through the analysis of the monitoring data of water vapor pressure in the study area,using the model experiment to simulate the phenomenon of water hammer gas explosion.Through the construction of water hammer numerical analysis model of karst pipeline to analyze and calculate the instantaneous water vapor pressure.Firstly,the effect of water hammer gas explosion was studied by indoor model experiment.The model is divided into five experimental plate,increased respectively on the decline of water level and water level rise,the water level decreased,water level decreased first and then increased,water tank drain while it is inletting,In each case,different inlet and outlet water velocities are set up for comparative analysis.show that the rapid decrease of water level in the cavity will cause the sudden change of water vapor pressure,that is,gas explosion,and the faster the water level drops,the greater the mutation pressure will be.By using water hammer software the karst pipeline water hammer numerical analysis model is established,the parameters such as the distance of the pipeline,the diameter of the pipe and the water head of the joints are set up and then the initial condition parameters of karst pipeline model are calculated.By simulating the operation of the pump in the model and the initial flow rate of the flow control valve,the dynamic change of groundwater in the karst pipeline is simulated.The model can be used to calculate the pressure and flow velocity of each node,pipeline of model in the steady state,and calculate the occurrence of water hammer at a time when groundwater is unsteady so as the limit volume of gas in cavitation or gas explosion and the limit pressure and flow of each node,pipeline.