小应变硬化模型(HSS)在Rayleigh波作用下场地响应分析中的应用

为研究冲击荷载或地震作用下产生的,以Rayleigh波为主的面波对浅层地表土体动力响应特征以及数值模拟中土层阻尼的设置方法,以厦门地区浅层的素填土及粉质黏土为研究对象,采用有限元动力分析,土体本构采用小应变硬化模型(HSS),利用模型本身的滞回环特性,输入变化的小应变参数,考察HSS模型的小应变参数对场地动力响应的影响,并与土体采用摩尔-库伦模型结合Rayleigh阻尼("MC+Rayleigh阻尼")的计算结果进行对比。研究表明:当采用带有滞回环的HSS模型时,波速随初始剪切模量Gref0的增大而增大,但振幅减小,残余变形量也有所减小;小应变参数γ0.7对波的影响较小;HSS模型能够给出残余变形量,而"MC+Rayleigh阻尼"由于本构模型为理想弹塑性模型,在卸载重加载条件下表现为纯弹性行为,无法反映出卸载重加载过程中塑性应变的积累及其累积阻尼效应;但HSS模型还不能够全面反映循环加载作用下塑性体积应变的累积,因此在考虑滞回阻尼的基础上,仍然建议借助Rayleigh阻尼来更加全面地模拟土体的实际阻尼特性。

Application of Hardening Small Strain Model in the Site Response Analysis under Rayleigh Wave Excitation

This study examines the dynamic response characteristics of surface waves mainly comprising Rayleigh waves in surface soils under impact and seismic loads. Moreover, the study analyzes, through numerical simulation, the settling methods of soil layer damping. The research area for this study is the shallow plain fill and silty clay of the Xiamen area. The model was generated using finite element dynamic analysis, with a hardening small strain model (HSS) for soil constitutive. The hysteresis characteristics of the model allowed the input of different small strain parameters to study the influence of HSS model''s small strain parameters on site dynamic response. Results were then compared with the combined Mohr-Coulomb (MC) model and Rayleigh damping model (MC+Rayleigh damping). The study shows that when using HSS model with hysteresis, the wave speed increases with increases in the initial shear modulus; however, amplitude and residual deformation decline. While the HSS model can reach the residual deformation value, "MC+Rayleigh damping" cannot. This reflects the accumulation of plastic strain and the damping effect during the process of unloading and reloading as the constitutive model is an ideal elastic-plastic model that demonstrates pure elastic behavior under the conditions of unloading and reloading. However, as the HSS model cannot fully reflect the accumulation of plastic volume strain under the effect of reloading and taking hysteresis damping into consideration, the use of the Rayleigh damping model is advised to allow full simulation of the real damping characteristics of the soil.