| The construction experiences and research results show that the frost heaving deformation which is caused by the periodical freeze-thaw cycle role in the deep seasonal permafrost regions causes serious frost damage of the constructions that build there and shortens their application time. For many years, most studies are about the normal saturated soil, warm and ice-rich high land soil and the low-water contained subgrade soil, but few of them are about the underwater saturated soil, and cold and high-water contained soil in the seasonal frost regions. In fact, the lakeshore soil is quite wide in seasonal frozen region of the mid-latitude and high-altitude in the world, and the effect of different water containing level and the lowest temperature are various, so it is necessary to do some research on the mechanism and prevention technology to avoid or reduce the waste of labor and resources needed by the present inefficient and repeated repairing work. It will be beneficial to the anti-freeze design work of the lakeshore buildings in seasonal frost region as well as the treatment of the frost damage to the existing buildings.Combining the soft science project of the Ministry of Construction "Analysis and Treatment of Frost Damage to Lakeshore Structures" (NO.06-K1-10), which was taken the South Lake Park, Changchun Park and Changchun Sculpture Park as research objects, laboratory tests, outdoor observation and numerical simulation as research methods, this dissertation was done a systemic research about the forming mechanisms, developing laws and influencing factors of the two typical lakeshore structures frost damages that were the soil-lifting frost of the lakeshore slipway pile foundation and the level frost heaving of the lakeshore retaining wall.First, it was studied on the material composition, physical and chemical properties, heat exchange parameter and mass exchange parameter of the seasonal frozen soil in the study area. Secondly, it was done the indoor frost heaving sensitivity experiment on the saturated and unsaturated frozen soil samples of the three observation field. Then, it was taken a three-year insitu observation experiment on the two typical lakeshore structures frost damage, and analyzed the changing laws and affected factors of the frost damage displacement curves, and the essential reason for frozen damage. Finally, it was set up the three fields coupling models for the two cases basing on experimental data of indoor and outdoor, and carried on the numerical simulation on slipway pile foundation in South Lake Park and straight lakeshore retaining wall in Sculpture Park with the finite element software ANSYS, and then proposed the practical solutions.Based on the above process, the main conclusions were as follows:1. It was done the experimental analysis of grain composition, mineral composition and the physical properties of the seasonal frozen soil including easy soluble salt content, specific surface area and cation exchange capacity and so on, and summarized the characteristics related to the nature of the study area soil, which provided the basic data and theoretical basis for the frost heaving.2. It was focused on the changing law of the unfrozen water content with the different soil property, initial water content, dry density in the frozen process, and then done a further study on the relationship between the temperature change and heat exchange parameters and mass transfer parameters of freeze-thaw soil. It showed that, the frame specific heat of both frozen soil and thaw soil was lower than that of water and ice, the water content and pattern of the above two soils played a key role in the soil specific heat; as the temperature elevates, soil thermal conductivity and temperature diffusivity lowered lightly, and the extent was just obvious in the transformation zone. It showed that the heat preservation capability of frozen soil was significantly better than thaw soil. The soil grain composition, density, volumetric water content and temperature were the main factors of the diffusion coefficient and hydraulic conductivity.3. It was carried on the laboratory test on the effect of the initial water content, cold end temperature, multigelation and hydrating condition to the frost sensitivity of the silty clay sample of South Lake Park and clay samples of Sculpture Park. It was summarized the soil frost heaving law in various conditions, analyzed the reason of all kinds of changes during frost heaving process which was combined with the material composition and the results of the physical and chemical experiment, and provided the theoretical basis and support for the formulation of lakeshore structures frozen prevention project.4. It was conducted the low-temperature in-situ measurement on the soil-lifting frost phenomenon of slipway pile foundation by precise leveling measurement, and drawn the displacement characteristic curves of soil-lifting frost and analyzed the displacement characteristic according to the experimental result; presented the external factor for the soil-lifting frost of slipway pile foundation. It was the first to be measured the level frost heavy displacement of retaining wall at a low temperature with precise steel ruler measurement method. It was found that the different effects of the curve shape of retaining wall and the landscape to its frost heaving characteristic, and the national gap was filled.5. In combination with the indoor and outdoor research results, based on the O'Neill and Miller's rigid ice model, part heat balance and force balance attitude, Duhamel theory, Harlan model and thermal elastic-plastic frost heave calculation model, it was set up the three coupled equations of three-dimensional saturated frozen soil and the two-dimensional unsaturated frozen soil. With the finite element software ANSYS, it was carried on a numerical simulation about frost heaving processes of the saturated frozen soil and unsaturated frozen soil in the open system, and provided the theoretical basis and scientific evidence for the study of prevention methods of the frost heaving damage.6. It was proposed the ice thermal insulation, increasing weight, reducing pile numbers and adding sleeve setting, the four effective soil-lifting frost prevention methods. Among the above methods, adding sleeve setting was the one that costs was the least and suitable for repairing projects. It was taken a comparison and analysis among the observation results of the slipway pile foundations with rigidity sleeve setting, flexibility setting and without sleeve setting, and proved that the two methods were effective and feasible, but still need to observe for their the durability.7. It was compared with the frost heaving prevention methods provided by the< Anti-freeze hydraulic structure design> (SL211-98), the researched single-isolation-layer retaining wall anti-freezing prevention methods were cheaper, effective and suitable for lakeshore landscape architecture, which was filled the domestic gap in lakeshore retaining wall frost heaving prevention methods in seasonal frozen region. Finally, it was put forward the double-isolation barrier retaining wall frost damage prevention methods and provided the reference for the further study. |
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