Study On The Influence Factors And Methods Of Inversion Of Dynamic Parameters Of Earth-rock Dam Considering Fluid-solid Coupling

With the development of hydropower resources in the southwest of China,the analysis of dynamic characteristics of earth-rock dams under seismic loading and the inversion of dynamic parameters of dam construction materials has become an increasingly important area of interest for dam structures.Under the above research background,this paper takes the three aspects of " Model building-Property inversion-Numerical analysis " as the main line,and constructs an earth-rock dams dynamic parameter inversion model that combines the global optimization algorithm with the uncertainty model,while taking into account the full coupling factors of dam,reservoir water and foundation.And establish a dynamic parameter inversion method suitable for earth-rock dams,explore the influencing factors of dam dynamic parameter inversion,and further improve the research on dynamic parameter inversion of earth-rock dams.The main results are as follows:(1)By secondary development of ABAQUS and considering the impact of static and dynamic artificial boundary transformation on dynamic analysis,an input method for vertical incidence of ground vibration of high earth-rock dams was established.The method better eliminates the problem of reflection of outgoing scattered waves at the boundary due to structure and topography,and simulates the radiation-damping effect of an infinite foundation.By converting the fluid medium into an acoustic medium to simulate the propagation of acoustic waves in the flow field,the impedance boundary is converted into the dam-reservoir water boundary,and the simulation analysis of the fluid-solid coupling is realized,taking into account the dynamic interaction between the high earth-rock dams-reservoir water-foundation.The typical calculation example shows that the fluid-solid coupling method can more accurately simulate the coupled vibration effect of the dam in the dynamic analysis and improve the accuracy of the parameter inversion.The traditional rigid boundary and empty reservoir dynamic models can overestimate the seismic response of the dam during the dynamic parameter inversion process,resulting in deviations in the parameter inversion accuracy.(2)Based on the shortcomings of traditional parametric inverse intelligence algorithms,such as low search accuracy and easy falling into local extremes,two approaches are proposed to optimize the algorithm: on the one hand,by embedding nonlinear inertia weights based on chaotic maps,the entire optimization process can adaptively increase or decrease the search step size to better balance global exploration and local development;On the other hand,by mixing heuristic operators from cloud theory in standard PSO algorithms to increase population diversity,external intervention is used to guide algorithms trapped in "precocity" to restore search vitality,thereby enhancing the ability of particles to jump out of local extremum.The analysis of typical function simulation experiments shows that the improved approach has good performance in terms of the algorithm’s ability to jump out of local optima,computational efficiency,iteration accuracy,and other aspects when facing complex optimization problems.(3)By establishing two-dimensional and three-dimensional finite element models of dams to change the initial stress state of the dam and considering the effect of dynamic water pressure,the accuracy of the inversion results of dam material dynamic parameters is explored through the influence of the initial stress state and fluid-solid coupling effect.The results show that the inversion analysis of the initial stress state of the two-dimensional model results in a higher dynamic response of the structure than the actual value by about 8%,while the inversion analysis ignoring the fluid-structure coupling vibration effect results in a higher dynamic response of the structure than the actual value by about 10%.(4)Through the sensitivity analysis of the dynamic parameters and the analysis of the weight of the dam material partitioning,an objective function was constructed for the inversion of the Zipingpu concrete face rockfill dam considering the weight of the dam material in the time and frequency domains of ground shaking.The inversion results of dam dynamic parameters indicate that after the construction period,operation period,and seismic load,the material parameters of the dam have a significant change compared to the original indoor test values.When using design parameters for safety assessment,there will be significant deviations in the dynamic analysis results.The results of the seismic response of the dam using the inversion parameters are in good agreement with the measured seismic response law of earth-rock dams,where the maximum absolute acceleration in all three directions occurs near the middle of the top of the dam.The inversion method described in this paper can provide a new reference for the application and improvement of intelligent algorithms in inversion analysis and the establishment of a dynamic parameter inversion method applicable to earth-rock dams and provide a technical reference for evaluating and analyzing the dynamic response of earth-rock dams under seismic loading and dam safety identification.