筑坝料动力分析中的Bouc-Wen模型及其参数研究

Bouc-Wen Model and Parametric Research for Dynamic Analysis of Gravel Material

Bouc-Wen光滑滞回模型因其能够描述动力荷载下的复杂非线性,广泛应用于材料的动力分析。为研究筑坝料在循环加载条件下动剪切模量和阻尼比以及累积变形等复杂动力特性,将Bouc-Wen模型应用于土体,绘制应力应变滞回圈并分析其模型参数;采用参数敏感性分析方法研究Bouc-Wen模型,并对动力试验数据进行数值模拟;讨论模型参数变化对土体应力应变滞回圈及动剪模量和阻尼比的影响。根据国内外筑坝料动力试验数据统计得到筑坝料模量衰减及阻尼比增长的均值曲线,应用MATLAB软件编制遗传算法程序确定模型参数;利用GDS动三轴仪探究糯扎渡土石坝的心墙掺砾土在循环荷载下的累积变形特性,并应用Bouc-Wen模型对循环三轴试验测得的应力应变滞回圈进行数值模拟。基于参数分析和数值拟合结果,本文提出适用于筑坝料的Bouc-Wen模型参数范围;筑坝料动剪模量衰减曲线和阻尼比增长曲线拟合结果均方误差小于0.4%;糯扎渡掺砾土循环三轴试验8个振动周期累积应变试验值与模型预测值分别为1.2%和1.18%。基于本文研究得到的模型参数范围,Bouc-Wen模型可以有效地模拟筑坝料动模量阻尼和累积变形特性,为筑坝料动力分析提供帮助。

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 experi- mental data of gravel materials in China and overseas,the parameters of the Bouc-Wen model were determined by genetic algorithm pro- gram 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 simula- ted by Bouc-Wen modal. 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.