Due to the capability of reproducing complex nonlinear characteristics of cyclic behavior,the Bouc-Wen smooth hysteresis model was widely used in the seismic analysis of soil.In order to study the complex dynamic characteristics of gravel material,i.e.,the dynamic shear modulus,damping ratio,and accumulative deformation of soil,under cyclic loading,Bouc-Wen constitutive model was applied to soil drawing stress-strain hysteresis loops and the model parameters were analyzed in this paper.The method of parameter sensitivity analysis and simulation of experimental data was applied to Bouc-Wen model.Discussions were made on the parameters of the Bouc-Wen model and their influences on the dynamic stress-strain hysteresis loops and the dynamic shear modulus ratio and damping ratio.According to the mean curve of the attenuation dynamic shear modulus ratio and the increasing damping ratio of gravel materials based on statistical experimental data of gravel materials in China and overseas,the parameters of the Bouc-Wen model were determined by genetic algorithm program written in MATLAB.Accumulative deformation characteristics of core gravelly soil of Nuozhadu rockfill Dam under cyclic loading was studied by conducting GDS dynamic triaxial experiments.The stress strain hysteresis loops measured from cyclic triaxial tests were simulated by Bouc-Wen model.From the parameter analysis and simulation of experimental data,the applicable ranges of the Bouc-Wen model parameters used in geotechnical engineering were given.The mean square error of dynamic shear modulus ratio and damping ratio fitting curves were less than 0.4%.The accumulative axial strain of cyclic triaxial experiment measurement and calculated value during eight vibration periods for gravel soil were 1.2% and 1.18%,respectively.The conclusions could be made that Bouc-Wen model was able to describe the dynamic modulus and damping and accumulative deformation characteristic of gravel material accurately based on parameters scopes reported in this paper,which is helpful for dynamic characteristics analysis of gravel materials.
