摘要
针对小湾拱坝坝基开挖中出现的卸荷松弛问题,采用三维非线性有限元法对卸荷松弛效应进行了评价。通过松弛方案与未松弛方案计算,对小湾拱坝的应力和位移、屈服区分布以及坝基浅部关键截面的抗剪安全度、点安全度等方面进行了比较分析。研究结果表明,建基面地基松弛后,主要影响低高程局部区域的变形和应力,对拱坝整体变形和应力分布的影响很小;地基松弛后,拱冠梁建基面(953m高程)坝踵处第一主应力有所增大,坝趾处第三主应力有所减小;拱冠处梁的作用减弱,拱冠梁处距坝踵20m范围的点安全系数也略有降低;原设计方案在未松弛情况下基本可以满足《混凝土拱坝设计规范》关于建基面抗剪(断)安全系数的要求;坝基松弛后,抗剪(断)安全系数降低明显,与规范规定的要求相差较大,需采取适当的工程措施。该研究成果已为设计决策提供了依据。
The effects of unloading and relaxation during the excavation of Xiaowan arch dam foundation are evaluated by 3-D nonlinear finite element method. Based on the analysis, the relaxed and un-relaxed cases are compared on the basis of stress, deformation, yield zone and the shear safety factor of critical section in shallow dam foundation. It is found that the relaxed foundation mainly affects the deformation and stress distribution in local section at low elevation, but has little effect on the whole dam. Compared with the un-relaxed case, the first principal stress in dam heel on dam foundation surface（EL.953.0 m） have increased to some extend atter the foundation relaxation, while the third principal stress in dam toe decreased appreciably. It is also found that the contribution of cantilever beam has been weakened slightly and the shear safety factor of crown cantilever has a little decrease. The shear safety factor of dam foundation surface in the original design with un-relaxed foundation can basically satisfy the request of ＂Design Specification for Concrete Arch Dams＂; but in the relaxed case it reduced obviously. Therefore proper measures should be taken in order for the improvement. This research has provided a reliable basis for the decision-making.
出处
《岩土力学》
EI
CAS
CSCD
北大核心
2009年第4期1175-1180,共6页
Rock and Soil Mechanics
基金
国家自然科学基金资助项目(No.50679066)资助。
关键词
拱坝
坝基
卸荷松弛
有限单元法
arch dam
dam foundation
unloading and relaxation
finite element method
