Random Dynamic Response Analysis Of Asphalt Concrete Core Dam On Deep Overburden

Although the southwest region of China is rich in hydropower resources,the widespread distribution of deep riverbed overburden and the high frequency of strong earthquakes pose a significant challenge to the seismic safety of hydropower projects.Due to their excellent environmental adaptability,asphalt concrete core wall dams have become the preferred dam type for deep overburden sites in strong earthquake regions.Therefore,it is of great significance to conduct seismic safety research on asphalt concrete core wall dams in deep overburden sites.Due to the complex and loose structure of riverbed overburden,it often exhibits significant spatial variability in its physical and mechanical properties.Similarly,in the case of the dam body,the physical and mechanical properties of rockfill materials in the dam body also demonstrate certain spatial variability due to the relatively imprecise control of grading and parent rock properties in both domestic and foreign specifications,as well as the uncertainty in construction quality control.In previous studies on the seismic response of asphalt concrete core wall dams built on deep overburden sites,the spatial randomness of the overburden and rockfill material properties were often neglected.As a result,the precise analysis of the structure was limited by rough empirical guidelines,making it difficult to draw more accurate conclusions regarding the seismic safety of the dam body.Large structures,particularly earth-rockfill dams,often exhibit nonlinearity or even strong nonlinearity under earthquake loading due to the complexity of their physical properties.In order to better assess the seismic safety of dams,the traditional response spectrum method is no longer applicable.The use of seismic acceleration time history analysis to study the seismic response process of structures has become the current research focus.However,due to the significant uncertainty of earthquake loads,the seismic response of asphalt concrete core wall dams also exhibits a certain degree of randomness.The use of different earthquake records with different intensity levels and spectral characteristics in the analysis can lead to significant differences in the dam response results.Therefore,relying on only a few earthquake records is insufficient for a comprehensive analysis of the seismic performance of asphalt core wall dams.To carry out a more scientific and reasonable seismic safety assessment of asphalt concrete core wall dams,it is necessary to conduct response analysis studies of these dams under non-stationary random seismic loads.Based on the consideration of the spatial variability of material parameters,seismic randomness,and dual stochastic factors,this paper conducts a stochastic seismic response analysis of asphalt concrete core wall on thick overburden from the perspective of stochastic dynamics.The study employed the K-L series expansion method to construct the spatially varying random fields of material parameters and a non-stationary stochastic earthquake generation model.On the basis of the commercial finite element software ABAQUS,a stochastic finite element analysis of the asphalt concrete core wall on a deep overburden layer was conducted,considering the spatial variability of material parameters,the randomness of seismic loads,and the bivariate stochastic factors.By combining the nonlinear finite element time history analysis method with probabilistic and statistical methods,this study aims to reveal the random dynamic response characteristics of asphalt concrete core walls on thick overburden layers under various stochastic factors.This can provide references and basis for the seismic safety evaluation of the asphalt concrete core wall dam.The specific content is as follows:(1)A comparative analysis of different methods for generating spatially varying random fields was conducted,and the Karhunen-Loeve expansion method was found to be efficient with better continuity after discretization.The K-L expansion method was combined with Latin hypercube sampling and Gaussian autocorrelation function to simulate the spatial random field.Sensitivity parameters from the static Duncan-Chang E-v constitutive model and dynamic equivalent linear viscoelastic constitutive model were selected as random parameters to implement the spatial variability of the cover layer and dam material parameters.The seismic response of the asphalt concrete core wall dam-cover system was analyzed using a random finite element method with seismic wave input.The statistical characteristics,including the mean value,coefficient of variation,and 95%confidence interval limits,were obtained for the peak horizontal acceleration at the top of the dam and core wall,as well as the permanent deformation in the vertical direction of the dam body.The probability distribution conclusions of the responses were determined using an Anderson-Darling test for normal distribution.The effect of seismic intensity on the degree of random response and the probability of exceeding the determined value was also discussed.(2)This article uses an improved Clough-Penzien power spectrum combined with a random function to fully consider the non-stationary characteristics of earthquake frequency and intensity,generating a series of non-stationary stochastic earthquake motion sets that fit response spectra.Using a deep asphalt concrete core wall dam with a thick covering layer as an example,this study conducted a statistical analysis and distribution test on the mean and variation range of the horizontal acceleration and vertical permanent deformation response.It revealed the variation pattern of the response mean and variability of the covering layer and dam body along the elevation,and through the probability density evolution method,it revealed the evolution process of the probability density of horizontal acceleration at the dam crest over time.At the same time,55 non-stationary random seismic motions were amplitude-modulated,and the MSA vulnerability analysis method was used to develop non-stationary random seismic vulnerability curves for the deep asphalt concrete core wall dam with a thick covering layer,and provided a dam vulnerability curve with the seismic settlement rate as the control index for the seismic safety evaluation of the deep asphalt concrete core wall dam with a thick covering layer,providing new methods and ideas for seismic safety evaluation.(3)In order to investigate the probability statistics of the response of the dam under the joint action of two random factors,the analysis of random response under the dual random factors of asphalt concrete core wall dam on deep cover layer will be carried out,taking into account the influence of these two random factors,based on the single random factor mentioned above.Furthermore,the horizontal acceleration,vertical permanent deformation,and stress of the core wall under the influence of the dual random factors were compared and analyzed with the results obtained under the single random factor.The goal was to investigate the impact of different random factors on the response of the dam.Finally,the failure probability of the dam under the dual random factors was calculated based on a deformation-controlled failure probability model,providing a reference for the seismic safety evaluation of the dam.