Study On Large-scale Model Test And Dynamic Response Characteristics Of Submerged Floating Tunnel Under Wave-current Coupling

With the gradual development of construction waters into bays and straits with trench development,traditional methods of underwater tunnel construction face increasingly severe challenges.A new type of transport structure,the submerged floating tunnel has been created.The construction of submerged floating tunnel is a global problem that faces severe challenges and requires the cutting-edge technology of the future.To date,there have been no precedents for the construction worldwide.The dynamic response of submerged floating tunnel structure under wave-current action has become an important problem to be solved in the field of tunnel engineering.Therefore,the research on the dynamic response characteristics of submerged floating tunnel structures under wave-current conditions is of significant importance in the future development of cross-sea transportation.Based on the National Natural Science Foundation of China project "Experimental study and response of submerged floating tunnel under dynamic load coupling wave flow and solid transport(51978600)",this paper focuses on the dynamic response characteristics of submerged floating tunnel structures under wave and current conditions.By combining model experiments with theoretical analysis,the paper conducted three types of model experiments: wave-current calibration and circular foundation wave force accuracy verification model experiment,regular wave action submerged floating tunnel structure dynamic response model experiment,and wave-current coupling action submerged floating tunnel structure dynamic response model experiment.The dynamic response characteristics of submerged floating tunnel structures under wave and current loads were analyzed.The impact of wave current parameters on the dynamic response of submerged floating tunnel acceleration,point pressure,displacement and anchor cable force were investigated.The mainconclusions are as follows:(1)Through large-scale model tests,the acceleration dynamic response characteristics of submerged floating tunnel under wave and current action are analyzed.The acceleration time histories all increase with the increase of wave height.The acceleration time history shows a high-frequency multi-peak trend in small wave periods.The peak value increases first and then decreases with the increase of the wave period.In the wave-current coupling,the reverse current causes a decrease in acceleration.The decrease amplitude increases with the increase of wave height.The forward current leads to an increase in acceleration.However,the amplitude decreases with the increase of wave height.(2)By conducting model tests,the point pressure dynamic response characteristics of submerged floating tunnel under wave-current loads are obtained.The pressure time history at the center point of the top of the tube body shows periodic changes.The highfrequency component of the point pressure decreases with the increase of wave height,and the quasi-static effect is the main component.The reverse current in the wave-current coupling leads to a decrease in the pressure at the center of the top of the tube body.The forward current causes a small change in the numerical value of the pressure at the center point on the top of the tube body,which can be ignored.(3)The anchor cable is an important component that affects the stability and safety of submerged floating tunnel.The dynamic response characteristics of submerged floating tunnel anchor cable are analyzed by using a model test.The anchor cable below the tube joint bears more cable force,while the lateral anchor cable bears less tension but still shares the cable force.Due to the complex motion of submerged floating tunnel under wave-current coupling,there is a certain phase difference between the time history curves of the anchor cable below and on the side of the tube body.This anchor cable arrangement can effectively share the cable force,which is convenient for maintenance and replacement and reduces safety hazards.(4)An experimental study on the lateral and vertical displacement dynamic response characteristics of submerged floating tunnel under wave-current loads is carried out.The ratio of wavelength to the structural size of the submerged floating tunnel has a greater impact on the vertical displacement dynamic response than on the horizontal displacement within a certain range.The reverse current in the wave-current coupling causes a large decrease in the vertical displacement.Due to forward current,the maximum horizontal displacement value increase slightly at small wave heights and decrease when the wave height gradually increases.