| Our country is surrounded by two major seismic zones in the world(the Circum-Pacific seismic zone and the Eurasian seismic zone).The Tibet region on the Qinghai-Tibet Plateau is an earthquake-prone area in China.It has the characteristics of high intensity and wide distribution.Therefore,the hydraulic structure of Tibet is Research on seismic characteristics is extremely important.By studying the dynamic response characteristics of hydraulic structures under earthquake loads,the basic characteristics of ground motion and the basic principles of earthquake resistance and disaster reduction are mastered.With the development of computer technology,the finite element numerical simulation of hydraulic structures has also developed rapidly.In the finite element numerical simulation of earth-rock dams,usually a certain range of foundation boundary is artificially intercepted to change the infinite domain into a finite domain,and then boundary conditions are applied at the boundary to simulate the "radiation damping" effect of the infinite foundation,thereby obtaining more accurate calculation results.Based on the complex geological conditions of Tibet’s high-cold,high-altitude,and high-seismic intensity areas,this article takes an earth-rock dam in Tibet as the analysis object.According to the actual structural parameters of the earth-rock dam,a three-dimensional simulation analysis model is established and the equivalent linear method is used to analyze the dam bodyThe dynamic characteristics of the reservoir water-foundation structure are simulated and calculated,and the calculation results are analyzed.The specific work content is as follows:According to the actual structural parameters of an earth-rock dam in Tibet,a three-dimensional simulation analysis model of the infinite element boundary and the viscoelastic boundary is established.First,the Duncan EB model is used for static calculation of an earth-rock dam in Tibet,and the result of the static calculation is used as the initial dynamic calculation.condition.Then the equivalent viscoelastic model is used to calculate the dynamics of an earth-rock dam in Tibet,and the ground motion input adopts the quality input model.The dynamic numerical calculations were carried out under 18 calculation conditions,mainly studying different artificial boundary conditions(viscoelastic boundary conditions,infinite element boundary conditions),different ground motion input peaks(0.1 g,0.3 g,and 0.4 g)and whether to consider The influence of hydrodynamic pressure on the dynamic response characteristics of the dam.Applying hydrodynamic pressure to the upstream dam surface and bottom in the form of additional mass,and applying viscoelastic boundary conditions to the cut-off surface of the dam foundation,both involve many nodes,and manual application is time-consuming and labor-intensive.Programming software can be used.The application process is simplified,so that the application of viscoelastic artificial boundary,infinite element artificial boundary,and hydrodynamic pressure can be well realized in the finite element analysis software ABAQUS,and it also makes the iterative calculation process easier.A comparative analysis of the static and dynamic nonlinear numerical calculation results,and the following conclusions are drawn:(1)There is basically no tensile stress unit in the dam body,and the displacement and settlement are small,which will not have a major impact on the safe operation of the dam.(2)The viscoelastic boundary conditions can more truly reflect the radiation damping effect of the foundation and ensure the accuracy of numerical calculations.(3)The acceleration response of the dam has a high degree of fit with the input seismic time history curve,but there is a certain hysteresis effect.The acceleration response of the dam increases with the increase in the amplitude of the input ground motion.(4)The acceleration amplification factor of the dam under the viscoelastic boundary condition gradually increases with the increase of the dam height.Under infinite element boundary conditions,the acceleration amplification factor of the dam body decreases first and then increases with the increase of the dam body elevation.The minimum appears at about 1/5 of the height of the dam.The hydrodynamic pressure makes the acceleration amplification factor under the viscoelastic boundary condition larger than the acceleration amplification factor under the infinite element boundary condition to increase.(5)Under the action of seismic load,the deep overburden has a certain inhibitory effect on the acceleration response of the dam body,and the dynamic response of the hydrodynamic pressure dam body has a certain incentive effect.However,the relationship between the inhibitory effect of the deep overburden layer and the excitation effect of hydrodynamic pressure needs further analysis and discussion.In the dynamic nonlinear analysis of ultra-high earth-rock dams,the reservoir water volume is larger,and the influence of hydrodynamic pressure and many other complex influencing factors on the dynamic response of the dam still needs to be analyzed and discussed in depth.As more and more high earth-rock dams are built,this is of great significance to the seismic research of high earth-rock dams on deep overburdens. |
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