在含有低渗透性土层的可液化地基中,液化引起的超静孔压累积和重分布可能导致孔隙水集中至低渗透性土层底局部区域,从而引发剪切应变局部化和延迟破坏现象.引入一种正则化技术——非局部近场动力学(peridynamics,简称PD)理论来模拟此类现象,以克服采用经典有限元方法(finite element method,简称FEM)模拟应变局部化时通常具有的网格依赖性问题.计算模型采用PD和FEM分别模拟固相和流体相,并使用砂土液化大变形本构模型(CycLiq)模拟可液化砂土.在验证了所提出方法的有效性后,使用多种不同离散密度的计算模型,分析了具有低渗透性夹层的一维倾斜场地的地震响应.从理论和数值上,说明了所提出的方法在模拟液化引起的剪切应变局部化时,可以消除网格依赖性.同时参数分析表明,相同条件下,低渗透性夹层位置越高,夹层渗透系数相比砂层越小,则地基因剪切应变局部化产生的侧向位移量越大.
Numerical simulation for liquefaction-induced shear strain localization based on peridynamics
The liquefaction-induced diffusion and redistribution of the excess pore pressure in inhomogeneous strata may lead to pore water concentration in local areas beneath low permeability layers and cause shear strain localization and delayed failure.In this study,the nonlocal peridynamics(PD)theory is introduced as a novel regularization technique to model this phenomenon,overcoming the mesh-size dependency problem associated with the classical finite element method(FEM).The computational model couples PD and FEM for the solid and pore fluid phases,respectively.Liquefiable sand is modelled using a unified plastic model for large post-liquefaction shear deformation of sand(CycLiq).After validating the proposed method,the seismic response of an idealized one-dimensional sloping site with a low-permeability interlayer is analyzed using various discretization resolutions.It is demonstrated that the proposed method for liquefaction-induced strain localization analysis is insensitive to spatial discretization theoretically and numerically.At the same time,the parametric study shows that a higher location and a smaller permeability coefficient of the interlayer could lead to a greater lateral displacement of the stratum induced by shear strain localization.
万方数据
维普
