Study On The Dynamic Responses Of Bridge Piers Under The Synergistic Effects Of Seismic Wave And Water Shock Wave Induced By The Underwater Drilling And Blasting

With the increasing requirements for the navigation of inland waterways,underwater reef blasting with bulk volume and large doses has become the tendency of practical works.The continuous development of urbanization results in the increasingly complex environment for blasting engineering.Thus,it is essential that the harmful effects of seismic wave and water shock wave induced by underwater blasting are under desirable scope.In the reef blasting engineering,bridges are the vital protection objects.As the piers are located on the bedrocks and surrounded by water,they must sufferthe synergistic effects of seismic wave and water shock wave when nearby blasting center,which gives rise to the dynamic responses of piers.If it is not properly controlled,it would exert a lot of damage to the piers and even affect the overall stability of the bridge.Therefore,the synergy effects of seismic wave and water shock wave induced by underwater blasting,and the resulting dynamic response and evolution mechanism of bridge piers are the urgent tasks to be solved.The current researches for the harmful effects of seismic wave and water shock wave induced by underwater blasting are mainlyconcentrated in thepropagation law of seismic wave and water shock wave,the effects those have on the shoreside buildings,ships and fishes,the control technique for underwater drilling and blasting,etc.However,the synergy effects of seismic wave and water shock wave,and the resulting dynamic responseof bridge piers are indistinct.Therefore,it is urgent that the above problems are solved and the safety control system for underwater drilling and blasting are improved,which will provide precise guidance for the design and construction of the practical works.Based on the waterway construction project of Jiu Longpo to Chao Tianmen section on the upstream of Yangtze River,which is nearby bridge piers,the paper is focused on the synergy effects of seismic wave and water shock wave.The research techniques as field investigation,theoretical analysis,site monitoring,field test and numerical simulation were employed to study the dynamic response of bridge piers under thesynergistic effects of seismic wave and water shock wave.The main contents are as follow.(1)Study for the properties and the propagation law of seismic wave.The mentioned contents were analyzed from 4 aspects,characteristic parameters,signal analysis,energy performances and propagation law for seismic wave.Seismic wave energy was treated as main characteristic indexes,and the time-frequency characteristics of seismic wave were extracted by time-frequency analysis.The local characteristics of time-frequency domain,the resolution ratio and the cross term suppression condition of the measured signal were analyzed,and the optimal time-frequency analysis method for underwater drilling and blasting were acquired.The effects that different factors have on the energy performances of seismic wave were revealed via the synthesized wavelet decomposition and reconstruction technique.Besides,the prediction formula for seismic wave energy was established through dimensional analysis.(2)Study for the properties and the propagation law of water seismic wave.Based on the waterway construction project of Jiu Longpo to Chao Tianmen section on the upstream of Yangtze River,water shock wave tests for single-hole blasting,multiple differential blasting and on the different directions of free faces were carried out.With the help of field tests,the waveform features and propagation law of water shock wave for single-hole blasting and multiple differential blasting were studied,and the effects that the directions of free faces have on propagation law of water shock wave were discussed.(3)Study for the dynamic responses of bridge piers respectively under the action of seismic wave and water shock wave.In consideration of the differences between the actions of seismic wave and water shock wave respectively exerted on the bridge piers,the seismic wave model and water shock wave model were respectively established based on the underwater drilling and blasting model with small distances from blast center to piers.The stresses,vibrationvelocities and displacements of piers under the action of seismic wave and water shock wave were analyzed,and the change laws of each dynamic response factors were obtained.(4)Study for the dynamic responses and the evolution mechanism of bridge piers under the synergistic effects of seismic wave and water shock wave.Based on the results of previous chapters,models with small distances from blast center to piers were analyzed.Moreover,the synergistic effects of seismic wave and water shock wave as well as the resulting dynamic responses were stated,and the differences between the actions of seismic wave and water shock wave were further discussed.Various models with small distances from blast center to piers under different factors were built,and the effects that the maximum charge per delay,the distances from blast face to monitoring points and the water depth have on the dynamic responses under the synergistic effects of of piers were comprehensively analyzed.And the evolution mechanisms for stresses,velocities and displacements of piers were studied,and the evolution model of the dynamic responses,the dynamic response function,was structured.(5)Study for the safety criterion of underwater drilling and blasting nearby piers.Based on the existing blasting safety criterion and according to the results of the dynamic responses and the evolution mechanism of bridge piers under the synergistic effects of seismic wave and water shock wave,the velocity-frequency synthesized safety criterion were acquired with the help of dynamic strength criterion for concrete the equivalent peak power theory.