桩承式路堤土拱数值模拟中路堤土本构模型的选择

Study on embankment fill constitutive model in numerical simulation of soil arching in a piled embankment

数值模拟方法已成为研究桩承式路堤中土拱最重要的手段,其关键在于路堤填土要采用合理的本构模型。建立桩承式路堤平面土拱分析的弹塑性有限元模型,考虑摩尔-库伦模型(MC)、硬化土模型(HS)和小应变硬化土模型(HSS)3种不同的路堤土本构模型,用有限元方法模拟不同路堤土本构模型下桩承式路堤中的土拱形态和土拱效应。计算结果表明:3种不同路堤土本构模型下平面土拱的形态都是半个椭圆。路堤土采用HS和HSS模型,获得的土拱形态、效应和桩帽-土差异沉降相同。较之HS和HSS模型,路堤土采用MC模型时计算得到的桩帽-土差异沉降较小,桩帽荷载分担比略大。当路堤高度较小时,采用MC模型获得的土拱远小于HS和HSS模型下的计算结果。土拱效应的数值模拟中路堤土可采用简单的MC模型,但土拱形态的数值模拟中路堤土宜采用HS模型。

Numerical simulation has become an important method to investigate the soil arching mechanism in a piled embankment.The key lies in the need of reasonable constitutive model for embankment fill.A 2-D elastic-plastic finite element model simulating soil arching in a piled embankment is established.Three different constitutive models for embankment fill,such as Mohr-Coulomb model(MC),Hardening Soil model(HS)and Hardening Soil Small model(HSS)model,are used when the shape and effect of soil arching in a piled embankment are simulated by FEM.The results show that the shapes of the soil arch are all semi-elliptic from the three different soil constitutive models for embankment fill.By using HS and HSS models,the arch shapes,load sharing ratios of pile cap and the differential settlements between pile cap and subsoil are almost identical.Compared to HS or HSS model,when using MC model to model the embankment fill,the differential settlement between pile cap and subsoil is smaller and the load sharing ratio of pile cap is slightly larger.Moreover,when the height of embankment is relatively low,the soil arch from the MC model is much smaller than that from HS or HSS model.It is concluded that MC and HS models for embankment fill are recommended when the effect and shape of soil arching in a piled embankment are simulated numerically,respectively.