【作者】 陈琰；

【导师】 宫必宁；

【作者基本信息】 河海大学 ， 水工结构工程， 2006， 硕士

【摘要】 基于强度折减的有限元稳定分析方法是目前应用及研究较多的一种分析方法,如何根据有限元计算结果来判别边坡是否处于整体破坏状态,是强度折减有限元稳定分析方法的一个关键性问题。 本文首先从非线性有限元方程的求解入手,介绍了求解非线性方程的迭代法、增量法及混合法,对各自的基本理论、求解过程及特点作了分析。并对有限元计算中采用的位移收敛准则、不平衡力收敛准则和能量收敛准则做了阐述。 有限元强度折减法的失稳判别标准主要有三种:第一种以有限元解的收敛性确定失稳状态,第二种根据计算域内最大节点位移与折减系数之间关系曲线的变化特征确定失稳状态,第三种通过计算域内塑性区是否贯通确定失稳状态。本文利用ADINA有限元通用软件,对三个不同的算例进行强度折减计算,然后分别采用三种失稳判别标准进行稳定性分析,对三种失稳判别标准适用性、三者之间的一致性、各自的适用范围进行了分析研究。对于均质边坡,三种失稳判别标准存在较好的一致性,但第三种失稳判别标准在应用范围上存在局限性。之后对计算精度进行了分析,主要分析了网格密度、容许限值对计算精度的影响。网格太稀疏、容许限值设太大都会使计算结果的精度降低,在稳定性判别时就容易出现偏差。 最后,对一实际边坡工程进行有限元计算,对其应力、变形进行了分析,并利用前面分析研究的三种失稳判别标准对其稳定性进行了判定。在计算工况下,边坡最大拉应力出现在坡面,由于边坡表层为强风化岩石,其强度很低,可能出现拉剪破坏。交通洞四周岩体强度较低,且弹模较小,变形较大,可能发生压剪破坏。结合三种失稳判别标准判定该边坡在计算工况下可能发生深层滑动破坏,需采取一定工程措施进行加固。更多还原

【Abstract】 The stability analysis methods using FEM, which based on strenght reduction, has been made a lot of applying and researching in its fields. How to judge the calculated slope’s states, stability or instability, is a key problem for shear strength reduction methods.Firstly, this paper introduced the solution methods of nonlinear static equations and its basic theory, the solve steps and characteristics. Except for those, three convergence criteria were introduced.There are three major criterions for evaluating of failure state. The instability state is judged by the convergence of equation’s solution in the first criterion. The curve which expresses the relationship of node largest displacement with reduction coefficient is the judgment of the second criterion. The connectivity of plastic flag is the judgment of the three criterions. Three different case were calculated using the general FEM software------ADINA. Based on the results of FEM, this paper analyzed the stability of calculatedslope separately by three failure evaluation criterions. Besides, the influence factors for accuracy of results were analyzed. The density of grid and tolerance of convergence criteria have relatively big influence for the accuracy of calculated results.Finally, this paper made use of FEM to analyze the stress state and transformation state of a slope in practice. Then combining three failure evaluation criterions to analyze the slope’s stability, the analysis result is that the slope is instability. So there need to take some engineering measures to reinforce the slope.更多还原