【作者】 高泰；

【导师】 李锋；

【作者基本信息】 大连理工大学 ， 固体力学， 2010， 硕士

【摘要】 静冰压力是寒区水库护坡的主要控制荷载,合理地预测极值静冰压力是一个长期以来尚未完善解决的问题,这一问题因涉及固体力学中的蠕变、屈曲、断裂等几个不同的领域而带来困难,因此这项研究具有重要的工程意义和学术研究价值。本文首先针对课题相关研究进行了文献综述,回顾了现有的静冰压力预测模型并讨论了其适用性和局限性。基于经典冰荷载理论,分析论证了冰盖极限承载能力准则是极值冰压力分析的控制机理。基于2008年冬季红旗泡水库冰盖破坏过程的现场观测资料,通过分析提出了冰盖发生失稳破坏的假设。为了证实这一假设,设计实施了室内模拟破坏试验,试验结果表明当应变速率小于3.33x10-7s-1时暖冰试件破坏的主导模式为蠕变屈曲。确认了冰盖的破坏机理和主导破坏模式之后,基于通用有限元程序ANSYS开展了数值模拟研究。首先针对室内模拟试验中低应变速率下的蠕变失稳破坏过程进行了数值分析,采用了弹塑性失稳分析模式并借用了有效弹性模量E与名义屈服强度σ的概念来近似考虑蠕变屈曲变形过程中的时间效应及应变率效应。将计算结果与试验数据相对比,得出典型应变速率下该分析模式所对应的有效弹性模量值和名义屈服强度值。其次,采用隐式蠕变方程中修正的时间硬化模型对蠕变试验全过程进行了仿真,计算结果与试验值能够很好地吻合。在上述分析基础上,最后采用弹塑性-蠕变本构关系,对开挖冰槽后的原型冰盖进行了蠕变屈曲破坏过程的数值模拟,冰盖的极限承载力和极限挠度的计算结果与理论预测值和现场观测基本一致。这些研究证明了开挖破冰槽对于降低极限冰压力的有效性,为实际工程应用提供了有价值的参考。更多还原

【Abstract】 Static ice pressure is a main controlling load on slope lining of reservoirs in cold region. The reasonable prediction of extreme static ice pressure is an issue that has not yet been satisfactorily resolved till now. Difficulty of this problem is due to several different solid mechanics regions are involved, such as fracture mechanics, creep and buckling etc. This study therefore has important engineering significance and academic value.First of all, a literature review is presented. The existing prediction models of static ice force are reviewed and their applicability and limitations are discussed. Based on the classical ice load theory, it is confirmed that the criteria of extreme bearing capacity is the dominant mechanism to determine extreme static ice pressure.According to observations on failure process of ice cover at Hongqipao reservoir in winter of 2008-2009, a hypothesis of buckling failure of the ice cover is proposed under analysis. To validate this hypothesis, we designed and carried out laboratory failure simulating tests. The results indicated that creep buckling is the dominant failure mode when the strain rate is below 3.33×10-7s-1.According as above failure mode, a series of numerical analysis is accomplished based on finite element program ANSYS. First of all, the creep buckling failure process in the test is simulated under low strain rate conditions. This analysis adopts elastic-plasticity constitutive equation, and uses the conceptions of the effective elastic modulus E and effective yield strengthσof ice to accord for the time effect and strain rate effects during creep process. Values E of andσare obtained by compared between calculated result and the similar test data, which are function of some typical strain rates. Secondly, the whole creep test process was simulated using modified time hardening model of implicit creep equation, the calculated results are fit well to the test ones. Finally, a creep buckling simulating analysis of the proto-type ice cover is carried out. The calculated results of the limit load and limit deflection of the notched ice cover with theoretical predicting and the observations values are consistent. These studies have proved effectiveness of the ice-breaking trench to reduce the limit ice pressure. It provided valuable information for practical engineering applications.更多还原