Study On Hydrodynamic Effect Of Zipingpu Concrete Face Rockfill Dam

During the earthquake,the reservoir was driven by the ground and the dam in the reservoir area,generating hydrodynamic pressure on the face of the dam.For the CFRD,this part of the hydrodynamic pressure directly acts on the face plate,which has a crucial impact on the face deformation and the dynamic response of the dam.The water level in front of the dam changes with the seasons,and the earthquake occurs randomly.Therefore,it is necessary to find the most unfavorable load combination for dam to ensure dam seismic safety.The Zipingpu CFRD is the only high CFRD in the world that experienced strong earthquakes above ?.During the Wenchuan earthquake,the water level of the Zipingpu Reservoir was low.Although the dam as a whole remained stable,it still caused significant damage.Studying the seismic dynamic response of Zipingpu face rockfill dam at different reservoir water levels has important theoretical significance for understanding the hydrodynamic mechanism of the reservoir and the seismic design of the face rockfill dam.This paper relies on the Zipingpu concrete face rockfill dam project and uses the finite element method to discretize the reservoir water.A series of studies on the fluid-structure coupling problem of the concrete face rockfill dam and reservoir water under the action of an earthquake are carried out.First,the ABAQUS acoustic-solid coupling method is used to calculate the dynamic water pressure of the upright rigid dam surface,and the accuracy of this method for the fluid-solid coupling problem of the dam reservoir is verified.Then the model of face rockfill dam-reservoir-foundation was established,and the dynamic analysis of Wenchuan earthquake on Zipingpu face rockfill dam was carried out.Then taking Zipingpu CFRD as an example,the effects of foundation-reservoir interaction,seismic excitation frequency,seismic excitation direction,and reservoir compressibility on dynamic water pressure were studied.Finally,the seismic dynamic response of Zipingpu Slab Rockfill Dam under different reservoir water levels was studied.The following main conclusions are obtained:(1)Adopt ABAQUS acoustic element discrete reservoir water,with nonreflection boundary to simulate the radiation tail damping effect of reservoir,establish a finite element model of reservoir water area,calculate the ground motion water pressure under the vertical rigid dam surface,the error between the result and the theoretical solution is only 4%,indicating that the method can be reasonably applied to the dynamic fluid-solid coupling problem of the dam and reservoir.(2)An equivalent linear model was used to analyze the seismic dynamic finite element of the Zipingpu concrete face rockfill dam.Studies have shown that during the earthquake,the acceleration of the top of the dam downstream of the rockfill dam is relatively large,and the rock may loosen and slip at this location.At the same elevation of the dam body,the acceleration on the downstream side is greater than that on the upstream side,indicating that the hydrodynamic pressure restrains the dam body movement and reduces the dynamic response on the upstream side of the dam body.(3)The influence of different influencing factors on the hydrodynamic pressure of the face rockfill dam is studied.The research shows that: 1)Under the vertical excitation,the interaction between the foundation and the reservoir water has an important influence on the hydrodynamic pressure.Ignoring the interaction between the foundation and reservoir water will underestimate the hydrodynamic pressure on the face of the dam;the traditional massless foundation model will overestimate the hydrodynamic pressure at the junction of the foundation and reservoir water.When stimulated along the river,the interaction between the foundation and reservoir water has little effect on the hydrodynamic pressure on the water surface.2)The dynamic water pressure of the face rockfill dam is affected by the dynamic response of the dam body.The stronger the dynamic response of the dam body,the greater the dynamic water pressure,and vice versa.3)The dynamic water pressure generated by vertical excitation is 1.6 to 2.6 times that of downstream excitation.It shows that vertical earthquakes will stimulate large hydrodynamic pressures.In seismic analysis of rockfill dams,the hydrodynamic pressures generated by vertical excitations cannot be ignored.4)Ignoring the compressibility of reservoir water may overestimate or underestimate the dynamic water pressure,the error can reach -17.7%?29.7%,depending on the excitation frequency.When the excitation frequency is less than the base frequency of the reservoir water,whether the compressibility of the reservoir water has little effect on the acceleration response of the entire dam body is considered,and when the excitation frequency is greater than the base frequency of the reservoir water,ignoring the compressibility of the reservoir water will overestimate the dam body Upstream dynamic response.(4)The dynamic response of the Zipingpu Slab Rockfill Dam encountered earthquakes at different reservoir water levels was studied.The research shows that: 1)When the depth of the reservoir water is low(50m water depth),the dynamic calculation result is similar to that under the waterless condition,indicating that the dynamic water pressure has no significant impact on the dam body at this time.As the depth of the reservoir water increases,the action of hydrodynamic pressure reduces the acceleration response on the upstream side of the dam body,and increases the acceleration response on the downstream side of the dam body from 0.4 times to 0.9 times the dam height.It is recommended to strengthen the anti-seismic measures of the middle and upper dam slopes downstream of the rockfill dam in the design.2)As the reservoir water level rises,the dam body's dynamic displacement along the river decreases,while the dam body's vertical displacement does not change much.3)As the water level of the reservoir increases,the dynamic shear stress of the dam body decreases accordingly,and the full reservoir decreases by about 10% compared with the empty reservoir.4)As the water level of the reservoir increases,the dynamic stress of the panel decreases accordingly.Under full storage conditions,the tensile stress and compressive stress along the slope of the faceplate are reduced by 18.5% and 27.4% compared with the empty storage.