Research On Dynamic And Motion Response Of Anchor Cable Submerged Floating Tunnel With Different Cross Sections

Nowadays,in the era of large-scale construction and development of transportation facilities,the development of land and air transportation has gradually saturated,and people begin to pay attention to the research and development of tunnel engineering and underground space.Under the circumstance that traditional bridges,immersed tunnels and other spanning methods are limited by environmental conditions and engineering technology,the emergence of the concept of the submerged floating tunnel provides a new scheme for crossing waterways,and it is highly competitive in the future transportation development because of its low cost and environmental protection.In the design of the submerged floating tunnel,there are many important parts that need to be considered,including address selection,material selection,stiffness design,and section design,etc.The section form of the main part of submerged tunnel will have a great impact on the overall structure under the wave and other loads.This paper mainly studies the dynamic and motion responses of tunnels with different cross sections under the action of waves.Based on the potential flow theory,this paper first used a high-order boundary element method to establish a mathematical model in the frequency domain.The wave excitation force,additional mass,and radiation damping of circular,elliptical,ear-shaped,polygonal,and double-circular cross-section structures were firstly analyzed and compared.The influences of different submergence depth,section shape and structural characteristic parameters on the hydrodynamic characteristics of the structure are studied.The results indicate that the increase of the submergence depth will lead to the reduction of wave force and radiation damping,but the added mass does not change much;the hydrodynamic characteristics of different crosssectional shapes are significantly different;the center distance has a greater influence on the hydrodynamic characteristics of double circular cross-sections.Secondly,the anchor cable system is simplified and replaced by linear springs in the horizontal and vertical directions to establish a two-dimensional time-domain model.The highorder boundary element method is also used to solve the boundary integral equation.The standard Runge-Kutta method is used to numerically integrate the boundary conditions on the free water surface and the motion equation,and the Newmark-β method is used to solve the equation of motion of the submerged floating tunnel section.The motion response of the circular,elliptical,ear-shaped,polygonal,and double-circular cross-sectional shape structures are analyzed and compared with the wave frequency changes at different buoyancy-weight ratios and anchor cable inclination angles.The results show that the structure will be stable under the action of waves when the inclination of the anchor cable is 56.25 °,and the elliptical section is also more stable than other sections under the inclination of the anchor cable.Comparing the motion response of five cross-sections under the action of irregular waves,the elliptical crosssection is more stable,and the displacement is positively correlated with the change of the effective period and wave height;when the submerged water depth reaches a certain depth,the effect of the wave on the motion response of the structure gradually reduce.The buoyancyweight ratio increases from 1.1 to 1.4,the structural gravity decreases,and the natural frequency moves to high frequency,so that the resonance peak moves to high frequency and its peak decreases with the increasing of buoyancy-weight ratio.The variation of different cross sections with the frequency of the incident wave shows different motion characteristics under the action of waves.In the actual design of the submerged floating tunnel,the influence of its cross-section form on the dynamic characteristics and movement should be fully considered,and the appropriate cross-section,submergence depth,anchor cable angle and buoyancy-weight ratio should be selected according to the actual situation to find the balance point of structural stability and overall economy.The research in this paper can provide a reference for structural selection and other subsequent calculation models,also provide a data reference for the overall motion analysis of the structure.The results have general regularity and have certain reference significance for engineering design research.