Study On Extreme Static Ice Pressure Of Ice Cover In Reservoirs

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.