基于粘弹性边界的三维土体地震响应分析

Seismic response analysis of three-dimensional soil based on viscoelastic boundary

利用有限元软件ANSYS建立了三维成层土体模型,分别进行了在EL-Centro波作用下土体的线性、等效线性化和非线性地震响应分析,其中采用了Extended Drucker-Prager模型模拟土体的非线性特征。通过对不同模型在多遇地震、设防地震和罕遇地震作用下计算结果的对比分析,得到如下结论:(1)当土体埋深较大时土的非线性影响不够明显,线性、非线性及等效线性化计算结果相差较小。随着埋深变浅和地震动强度的增大,三者出现显著的差异。(2)考虑土体非线性后,随着埋深变浅和输入地震动强度的增加,加速度峰值表现为线性条件大于非线性条件,非线性条件大于等效线性化条件。(3)随着埋深变浅和输入地震动强度的增加,考虑土体非线性时模量衰减,刚度和频率降低。在地震动输入较大时,由于等效线性化过高估计了场地土的非线性特性导致其高频部分快速降低。

In this paper,the finite element software ANSYS was used to establish a three-dimensional layered soil model,and the linear,equivalent linearization and nonlinear seismic response analysis of soil under the action of EL-Centro seismic wave were carried out,and the Extended Drucker-Prager model was used to simulate the nonlinear characteristics of the soil.Through the comparative analysis of the calculation results of different models under the action of frequent earthquakes,fortified earthquakes and rare earthquakes,the following conclusions are obtained:(1)When the soil buried depth is large,the nonlinear influence of soil is not obvious enough,and the linear,nonlinear and equivalent linearization calculation results are small.With the shallower burial depth and the increase of ground motion strength,there are significant differences among the three aspects.(2)After considering the nonlinearity of the soil mass,and with the shallower burial depth and the increase of the input ground motion strength,the acceleration peak is manifested as the linear condition is greater than the nonlinear condition,and the nonlinear condition is greater than the equivalent linearization condition.(3)With the shallower burial depth and the increase of the input ground motion strength,the modulus attenuation,the stiffness and frequency decrease owing to the nonlinear soil mass.When the ground motion input is large,the nonlinear characteristics of the site soil are overestimated due to equivalent linearization,resulting in a rapid decrease in its high-frequency part.