| In cold regions, ice sheet temperature changes with the air temperature, and the phenomenon of frozen heavily occurs in winter period in reserviors. Temperature expansion force in ice sheet is one of the main loads of slope protection in the plain reservoirs especially on the Northeast China. There is a high value expansion force while the ice sheet reaches a critical thickness and the air temperature increases suddenly. Accordingly, destruction occurs when the expansion force pushed up the reservoir revetment. Thus the anti-ice ability of sloping structure design should be firstly taken into account in reservoir constructions, which involves design ice parameters of engineering, e.g. the design ice parameters are based on2D model of ice focus on sloping structure when ice sheet ride-up. Based on the field measurements carried out in Hongqi-pao reservoir in Heilongjiang province within winter periods in2008-2011, above basic problems have been studied. The concrete works were carried out in order to provide design ice parameters for reservoir sloping protection engineering in cold region, the implementation process as follows:The first part, we focused on the field investigation, including the observations in-situ the site sampling analysis, and the laboratory experiments. Field investigation included measurements of meteorological conditions, ice temperature, air temperature, in duration of the whole ice season, monitoring of ice freezing and melting by using under ice ultrasonic range-finders, thermal resistance wire and radar observation. Ice cracks were also observed which related to the thermal expansion force of the reservoir ice. A new apparatus for micro observation of ice surface deformation was developed based on the laser range-finders, macro deformation of the reservoir ice climbing phenomenons was observed. The field sampling analysis, including various kinds of ice crystal structure, grain size, C-axial orientation, distribution, and size of ice bubble with natural hydrological and meteorological environment variables, ice and snow density at different depth were measured. The design ice density was determined. The flexural strength, elastic modulus, friction coefficient and the freezing strength between ice and protecting materials under natural conditions of low temperature of ice-samples were also conducted.Secondly, the scientific data obtained in the field investigation were analyzed. The influence and quantitative relationship were conducted between ice freezing process and ice physical properties. These relationship including air temperature in-situ with reservoir surrounding stations (Anda weather station), the relationship between negative accumulated temperature and ice thickness, the relationship between in-situ air temperatures and the ice temperatures, the vertical variation along the ice thickness of different stages, the relationship between variation rate of ice temperatures and ice growth rate. The correctness of Zubov model was inspected through measuring ice thickness of ice continuous growth in the winter. At the same time historical datas were used to estimate ice thickness during the different return periods. The design ice thicknesses of two ways were compared. The result show that: the lack of historical data, the winter continuous datas and reservoir surrounding stations of historical data were used to back step ice thickness sequence, and to calculate design ice thickness of different return periods. This method was scientific and feasible which established model for the design ice thickness.Thirdly, the design ice mechanical parameters used for slope protection engineering were researched. The design ice mechanical parameters are based on2D model of ice focus on sloping structure, namely flexural strength and elastic modulus of ice, and friction coefficient. Mechanical parameters based on analysis and observation ice clinbing phenomenon. On the basis of the typical ice conditions correspond to the second ice climbing in winter, and the quantitative influence were investigated with ice temperature, equivalent stain rate, ice crystal types, loading direction, roughness of the material surface, etc. The design ice flexural strength, elastic modulus, and the frictional coefficient with concrete sloping structure materials were determined combine ice mechanical experiments in laboratory.The results derived from this study can provide background data and validation data for numerical simulation on the growth and decay processes of ice; it also provided the scientific data for the design ice parameters of slope protection engineering in cold region. |
