Study On The Impact Of Underwater Drilling And Blasting On Typical Fish In Chaofu Section

With the development of Yangtze River Economic Belt and the construction of ecological civilization,the construction of ecological waterway gradually becomes the direction of future inland waterway development.In the long-term channel improvement process,due to the low efficiency of traditional mechanical reef removal,it is necessary to use underwater blasting to remove the reefs to improve the navigability of inland waterways.Therefore,it is of great theoretical value and practical significance to study the impact of underwater blasting shock waves on typical fishes and to propose a safety protection plan for typical fishes.In this paper,based on the combination of theoretical analysis,indoor measurement test,outdoor monitoring test and numerical simulation calculation,the critical wave pressure model of fish safety under the action of underwater blasting shock wave is studied for three typical fish species: grass carp,silver carp and bighead carp,and the safety distance of typical fish species and the control of the safe amount of chemical used in the project are established based on the engineering background of the "Chaotianmen-Fuling river section upstream of Yangtze River".standards,and clarify the attenuation effect of bubble curtain on underwater shock waves,the main research findings are as follows:(1)Based on the underwater blasting field monitoring test and numerical simulation,the transmission law of underwater blasting shock wave is clarified,and the results show that: the underwater shock wave diffuses to the surrounding water body in a spherical shape with the blasting source as the origin;the analysis has obtained the empirical formula of underwater drilling blasting shock wave pressure transmission applicable to the Chaofu section project.(2)The impact mechanism of underwater blast shock waves on typical fish was analyzed and a safety critical wave pressure model for typical fish was constructed.It was found that: the underwater shock waves propagate to the intersection of different media with reflection and transmission,and the transmitted shock waves generate a large pressure difference inside and outside the wall of the swim bladder,which causes radial tensile stress to form at the upper and lower walls of the swim bladder,and when the radial tensile stress exceeds the critical tensile stress that the swim bladder tissue can withstand,the swim bladder will be damaged;based on the impact mechanism of underwater blast shock waves on the swim bladder,a physical model of safety critical wave pressure for typical fish under the action of underwater blast shock waves was constructed.(3)The model parameters were clarified according to the indoor measurement tests,and the results of the maximum and minimum typical fish safety critical wave pressure models were obtained,which showed that: the swim bladder width coefficients were 0.046,0.084 and 0.093,the swim bladder wall thickness coefficients were 0.002,the radial critical tensile stress coefficients of the swim bladder were 47,50 and 61,the swim bladder shape coefficients were in the range of 0.60～1.10,0.61～1.06 and 0.65～1.09,respectively.The wave impedance ratios of the water medium and swim bladder wall medium were 0.46～1.92,0.31～3.21 and 0.28～3.54,respectively;the safety critical wave pressure of typical fish was positively and linearly correlated with the fish body length.(4)The results show that the damage conditions of typical fish of different body lengths under different shock wave pressures are basically in accordance with the maximum and minimum safety critical wave pressure range that they can withstand;based on the results of the model,the fish mortality zone,survival zone and survival zone are reasonably divided.(5)LS-DYNA numerical analysis method to study the air curtain protection,and the establishment of typical fish safety control standards,the results show that: when the bubble group density decreases,the peak shock wave increases,the air curtain attenuation rate decreases,when the bubble group density is consistent,underwater shock wave attenuation rate decreases with the increase of the air curtain burst source distance;towards the ful section of the minimum safety critical distance of typical fish are 7m,the maximum no effect critical distance of 83m;burst source distance of 7m from the engineering safety of the drug impact range of 0.03 ～ 49.20 kg,burst source distance of 83 m from the engineering safety of the drug impact range of 50 ～ 82010 kg.