Seismic Deformation Evaluation Of High Concrete Faced Rockfill Dam Based On Stochastic Dynamic Analysis

Water resources in China are mainly concentrated in the west region.In order to effectively utilize water resources,many high-dams and large reservoirs are planned and constructed in this area,including several concrete-faced rockfill dams(CFRDs)up to 250 m,these dam sites are characterized by high seismic intensity,frequent seismic activity and complicated geological and topographical conditions,and earthquakes are sudden and uncertain,which pose huge threats to the seismic safety of the 250m～300m ultra-high earth-rock dams.The suddenness and uncertainty of earthquake are its inherent properties.Currently,the seismic safety evaluation of face dam is mainly based on the deterministic analysis method,which cannot consider the influence of random ground motion on the structural response.In addition,the current seismic codes for face rockfill dams have not made explicit provisions on the settlement and deformation of the dam body.It is of great engineering significance to study the influence of random ground motion on the deformation law of concrete faced rockfill dams.In view of the above problems,this paper was supported by the National Natural Science Project "Standard for Stochastic Dynamic Analysis and Safety Control of High Earth-rockfill Dams(No.51979026)",which starts from the perspective of random dynamics and focuses on the randomness of ground motions.By generating random ground motion samples and performing amplitude modulation processing on them,numerical simulations are carried out on four 250m-level CFRDs.Establishing the seismic analysis method of concrete faced rockfill dams from the perspective of probability provides scientific basis for seismic design and ultimate seismic capacity analysis of high concrete faced rockfill dams.The main work is as follows:(1)Based on the spectral representation-random function method combined with the latest hydraulic seismic code,a strength-frequency non-stationary ground motion model is established and a time history sample of ground motion acceleration with rich probability information is generated quikly;(2)Consider the influence of random ground motion sample size and the sensitivity of finite element mesh size on random dynamic analysis.The sample size grouping of different random ground motions is compared,and the results show that the displacement results when the sample size is 144 are within 2% of the results when the sample size is large;the sensitivity analysis of the grid size shows that the displacement of the 10 m grid Compared with 2m,the maximum difference is within 5%,which meets the engineering accuracy.(3)Taking Gushui,Rawa,Dashixia and Cihaxia as the research objects,three-dimensional finite element models are established to carry out stochastic dynamic analysis,using probability density evolution theory and equivalent extreme value ideas,The probability density information and probability of exceedance of acceleration and rockfill deformation under random earthquakes with different strengths(0.1g～1.0g)of high-face rockfill dams are studied.Based on the numerical analysis results of 4 projects,it is recommended that the ultimate seismic capacity of 250m-level high-face rockfill dams based on the settlemen safety control standards is 0.7g～0.8g,which provides a reference for the seismic design of projects.