强度折减有限元在堤防稳定分析中的应用研究

APPLICATION OF STRENGTH REDUCTION FEM TO STABILITY ANALYSIS OF EMBANKMENT SLOPES

采用强度折减有限元法,研究非均值堤防塑性区的开展特征和失稳破坏过程,并根据堤防应力场分布和临界滑动面的形成来分析堤岸整体失稳破坏的机理。结果表明:把强度折减有限元应用到非均质土层的堤防边坡稳定分析,在理论上、数值模拟实现上都是可行的;有限元静力平衡和位移计算不收敛作为堤防边坡整体失稳的标志,同时考察滑移面上某些特征点的位移与荷载增量的关系、参考土体内坡脚向坡顶上方贯通的塑性滑动带的形成,可以准确判别堤防边坡失稳破坏状态;此外,堤防失稳时的应力场分布特征表明,有必要应用张拉-剪切复合屈服准则,以真实反映堤防边坡的临界滑动面形成机理。

The characteristics of the development of plastic strain and the process of unstable failure for embankment of heterogeneous soils are studied with the strength reduction FEM.The unstable mechanism for embankment is analyzed according to the stress field of unstable state and formation of the critical slip surfaces.The results indicate that the strength reduction FEM is applied to stability analysis of embankments of heterogeneous soils in the theory and numeric simulation.Furthermore,the numerical non-convergence of FEM global equilibrium and displacement can be taken as a failure criterion of embankment slope.The unstable failure state can be evaluated correctly using the criterion.The relationship between the nodal displacement in the slip surface and the load increment can be investigated with reference to the plastic zone deformed from slope toe to slope crest at the same time.In addition,the stress field of unstable state in the embankment shows that it is necessary to adopt the tension-shear composite failure criterion for stability analysis of embankments to reflect the mechanism for formation of critical slip surfaces.