土石坝有限元分析中土体卸载时计算方法分析

Analysis of Calculation Method in Finite Element Analysis of Unloading Rockfill Dam

对糯扎渡心墙堆石坝进行了三维有限元计算,对比分析两种常用于邓肯E-B模型的加卸载准则以及回弹模量取值对土石坝应力变形的影响。结果表明:大坝施工过程中,基于加载函数的加卸载准则(简称准则1)判断的卸载回弹区域一直较大;准则1下数值计算所得的坝体位移较小,仅为采用基于应力水平s与偏应力(σ1-σ3)的加卸载准则(简称准则2)时计算位移的一半左右,加卸载准则的选取对坝体应力影响较小;监测数据表明糯扎渡大坝采用准则2时计算位移更为准确,在准则2下回弹模量取值对大坝应力变形的影响主要表现为满蓄期坝体水流向位移随回弹模量的增大而减小。

A three-dimensional finite element analysis of the model of the Nuozhadu core wall rockfill dam is performed to make a comparison of the two loading-unloading criteria commonly used in the Duncan-Chang model. The influences of the value of the rebound modulus on stress and deformation of the dam are analyzed. The results demonstrate that in the process of construction and impounding,the loading and unloading criterion based on the loading function(law 1 for short) will lead to a bigger unloading fracture zone. The calculation of settlement in this law is nearly half of that in the loading and unloading criteria based on stress level s and deviatoric stress(σ1-σ3)(law 2 for short). The alternative of loading-unloading criteria has little influence on the stress of dam. Monitoring data of Nuozhadu rockfill dam demonstrates that the calculation of settlement is more accurate in law 2. In case of taking law 2 as the loading and unloading criteria,the influence of modulus of resilience mainly shows that the settlement of impounding dam is decreased when modulus of resilience increase.