Reservoir Ice In The Limit State Of Deformation And Failure

According to the engineering experience,excavation for many years to break the ice reservoir tank mearsures to control extreme ice pressure.Recognized the practical effect of this measure,we need to understand the fail process of ice-breaking groove on the ice and limit the impact of destructive mechanism,further mechanical model by a reasonable simulation and prediction of ultimate failure,so this reasearch has important engineering siginificance and academic reasearch value.Specific contents are as follows:PartⅠ: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 ultimate 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 compress fracture is the dominant failure mode when the strain rate is below 3.33×10-7s-1.Part II:Compression simulation failure test of ice specimens.Taking On-site ice sheet failure process as the simulation object, three different sizes of prototype compression ice specimen was used through a series of simulated failure tests.The experiments show that there existence several ice damage failure modes such as tensile fracture, compression fracture, and creep instability. The research confirmed how the loading rate, temperature, eccentricity, internal defects and pre-crack and other factors influence the failure mode and ultimate load. The test results of this article supply a gap in relative research, provide the experimental evidence and the necessary parameters for establishment the theoretical and numerical models of static ice force Analysis.Part III:Basic fracture toughness tests research. By using Standard size three-point bending specimen, determine the fracture toughness of S1-type lake ice. The test temperature are-2℃and-8℃Strain rates are 6.25×10-5s-1,6.25×10-6s-1 and 6.25×10-7s-1.In the published literatures, it is rarely associated within such parameter scope. Total get 36 sets of test data. The results show that the fracture toughness of K1C increased with lower loading rate and higher test temperature and the incision depth has no significant impact on the test results.Part IV:Numerical simulation.Identified the failure mechanism and the dominant ice failure modes,and associated tests,carried out based on the general finite element numerical simulation.Use of the ANSYS in the crack tip singular elements of the stress intensity factor of the facture toughness,the ice beam model that is occurring damage.Second,the cross section of ice tank study conducted by the limits of the different parametres calculated ice pressure obtained the release of the key factors is the ice-breaking groove depth.These studies demonstrate the effectiveness of the excavation ice slot.