基于动力有限元分析的任意滑块稳定分析方法

Stability analysis method for arbitrary slip block based on dynamic finite element method

提出采用有限元法与刚体极限平衡法相结合分析边坡、坝肩等结构物在地震波作用下的动力稳定性,并将该方法用于沙牌拱坝在"5.12"地震下的坝肩稳定性分析。该方法新颖之处在于采用任意结构面组合自动切割地表三角网,形成块体并网格化。块体网格与有限元计算模型网格相互独立,通过有限元动力或静力计算所得的应力场,插值得到滑块滑面应力场,然后将滑面应力在滑面上积分得到总滑动力和阻滑力,从而得到滑块安全系数。该方法采用一种新的滑块网格自动生成算法,吸取了刚体极限平衡法能给出明确定义的安全系数的优点,克服了其不能给出地震作用下任意时刻即时安全系数的缺点,为拱坝坝肩稳定性分析提供了一个新的思路。算例表明,该方法计算结果合理,具有较好的工程实用性。

A hybrid method which combines the finite element method and the limit equilibrium method is proposed to evaluate the dynamic stability of slopes or dam foundations under earthquakes. It is used in the stability analysis for dam abutment of Shapai arch dam under '5.12' Earthquake subsequently. The proposed method can cut arbitrary slip blocks with different structural plane combinations from ground surface triangular mesh. And then the block is meshed automatically. The block mesh is independent of finite element calculation mesh. Based on the stress field of static and dynamic FEM calculations, the stress field of all slip surfaces of the block is obtained by interpolating stress on block mesh. By integrating stress on block faces, the slip force and anti-slip force can be calculated, and then the safety factor of slip block is computed by means of the theory of the limit equilibrium method. The advantage of limit equilibrium method is that it can provide safety factor with specific meaning, but it cannot provide instant safety factor for slip blocks during the whole seismic action. A new algorithm of automatic mesh generation for slip blocks is employed by the proposed method which combines the advantages of the limit equilibrium method and the finite element method. It provides a new way for analytical technique of dam abutment stability evaluation. The examples show that the calculated results by the proposed method is reasonable and applicable in engineering practice.