Dynamic Response And Permanent Deformation Analysis Of Rockfill Dam Based On Modified Dynamic Shear Modulus Model

Because of its ability to make full use of local materials and good seismic performance,the rockfill dam has gradually developed into a new dam type with promising prospects and competitiveness.With the development of hydropower development and the expansion of development scale unceasingly,there are nearly 20 rockfill dams over 200 m.Most of the dams are built in the western region,while the geological conditions in the western region are relatively complex,with frequent earthquakes and high intensity.It is easy to affect the safety and stability of the dam.Therefore,the dynamic response and seismic safety of high rockfill dams under earthquakes have become a major concern.Accurately grasping the dynamic characteristics of the rockfill is the basic premise for analyzing the seismic dynamic response of the rockfill dam,and the permanent deformation analysis calculation is affected by the dynamic response analysis.Therefore,the dynamic material parameters of the rockfill are accurately and reasonably described for the high-intensity earthquake.The seismic safety study of high-rise rockfill dams in the region is of great significance.The dynamic stress-strain relationship of rockfill under cyclic loading has two basic characteristics: nonlinearity and hysteresis.Generally,two parameters,equivalent dynamic shear modulus and equivalent damping ratio,are used to reflect these two properties.And they are expressed as a function of the amplitude of the dynamic shear strain.This paper introduces an improved model that considers the confining pressure and stress ratio effects in the original dynamic shear modulus model.The improved model can simultaneously reflect the dynamic shear modulus ratio curve of the rockfill material with consolidation confining pressure and consolidation stress.The characteristic of increasing and increasing the ratio,and the wider application range,is more in line with the relationship between the dynamic shear modulus of the rockfill material and the dynamic shear strain,and more realistically reflects the dynamic characteristics of the rockfill material.The improved model is used to analyze the dynamic response of a simple homogeneous dam,and the influence of different factors on the dynamic response of the homogeneous dam is analyzed.The dynamic response of the monkey rockfill dam project is calculated by using the improved model and Hardin-Drnevich model,and the difference between the two is compared.The soft deformation method is used to calculate and analyze the permanent deformation of monkey rock engineering,and other The permanent deformation of the project is compared.The main research contents are as follows:The improved model was used to fit the test data of the dynamic characteristics of the rock dam and the rock dam,and the feasibility of the improved model was verified.Based on the improved model,the dynamic response analysis of the homogeneous dam is carried out.The dynamic response distribution law is in line with the general situation,and the feasibility of using the improved model to calculate the dynamic shear modulus of the rockfill material is further verified.The dynamic response analysis of different dam heights,different input acceleration peaks and different response spectrum characteristic periods were selected to study the influence of various factors on the dynamic response of rockfill dams.Taking the Houziyan rockfill dam project as an example,considering the filling and staging water storage of the dam body,the Duncan EB model is used for the static calculation,and the dynamic response analysis is carried out by using the time-course method.The dynamic shear modulus is determined by the Hardin-Drnevich model and the improved model.and analysis the dynamic response law of rockfill dam.The similarities and differences between the dynamic response results of the two models under seismic design conditions and calibration conditions are compared.The results show that the dynamic acceleration and dynamic displacement response distributions of the two models are basically the same,and basically increase with the increase of dam height,and the calculated values of the calibration conditions are basically larger than the design conditions.The difference is that the dynamic acceleration response in all directions of the improved model is larger than the Hardin-Drnevich model,and the difference between the two is larger under the calibration conditions;the dynamic displacement of each model in each direction is in the design and calibration conditions.The maximum dynamic displacement difference is smaller than the acceleration difference,that is,the dynamic displacement response is less affected by the confining pressure and stress ratio parameters than the acceleration response.The permanent deformation analysis of the Houziyan rockfill dam was carried out by the softening modulus method.The permanent deformation distribution calculated by the two models was basically the same.The permanent deformation value calculated by the improved model was larger than the calculated permanent deformation value calculated by the Hardin-Drnevich model.The vertical permanent deformation calculated by each working condition accounts for less than 1% of the specified value of the dam.Therefore,the permanent deformation of the Houziyan rockfill dam under various working conditions meets the seismic requirements.The maximum relative settlement of the dam crest calculated by the improved Hardin-Drnevich model is compared with the settlement values of other embankment dams.The relative settlement of the dam crest calculated by the improved model is near the fitted curve,indicating that the permanent deformation value calculated by the improved model is within the reasonable range.