Analysis On Bearing Capacity Of Refreezing Process Of Cast-in-place Bored Pile In Permafrost Region

We are abundant in permafrost, it is inevitable to build in permafrost region in China. The technology of cast-in-place bored pile frame is widely used to buildings,bridges,water works and public works in permafrost region, because of its high bearing capacity,small settlement of pile end displacement and strong adaptability. However, it brought heat remolding to stable permafrost by the construction of cast-in-place bored pile frame, especially by the heat of hydration of concrete, which led to the variation of bearing capacity of pile frame in permafrost region. So it is difficult to design pile frame in permafrost region because of the formation and development of bearing capacity of refreezing process of cast-in-place bored pile. This paper analyzes thermal transmission course pile earth and the change of soil mass temperature and divides refreezing process of pile earth prophase into three stages: metaphase,anaphase and telophase, based on interaction research ways and basic theory,considering especial character of permafrost and influence after concrete pile is affused effect of concrete on frozen earth around pile and analysis bearing capacity of cast-in-place pile's refreezing process in permafrost regions according to thawing and frosting condition of frozen earth surrounding pile. Single pile bearing capacity of cast-in-place pile refreezing metaphase is calculated in permafrost regions using earth pressure computational method and combining quality which is caused by thaw of frozen earth around pile to test the accuracy of this computational method through result of the provision calculation of the norm and the calculation result of the number model formula contrast analysis ,and analysis some influence about single pile bearing capacity in refreezing metaphase, when pile length pile diameter length diameter ration are changed. Load transfer function adopts basic differential equation and simulate. Earth which is on one side of the pile displacement by hyperbola model and earth which is on one end of the pile displacement by hyperbola model, get the solution against refreezing anaphase and telophase, and calculate single pile bearing capacity of cast-in-place pile refreezing anaphase and telophase in permafrost regions. It is tested the accuracy of this computational method by a comparative analysis of test pile data in pile base testing range of permafrost regions in the Kunlun range and calculations of load transfer function. Freezing resistance of cast-in-place pile base side, pile axis force,resistance of the end of pile and single bearing capacity are analyzed in the refreezing process, according to the research method of single pile bearing capacity in metaphase, anaphase, and telophase and using Microsoft Visual Basic 6.0 to draw up correspond calculation procedure. The effect of change in temperature to single pile bearing capacity of Cast-in-place pile in permafrost is especially analyzed. At last, for a cast-in-place bored pile in practical bridge structure that was built in the representative humid permafrost in the Qinghai-Tibet plateau, the variation of bearing capacity of the single pile and influence of temperature on the plan of bridge construction according the bridge code were analyzed by the calculation method of this thesis, and researching on the formation and development of bearing capacity of refreezing process of cast-in-place bored pile in permafrost region. The presented procedure and conclusions achieved can provide a theoretical basis for shortening construction period and laying out bridge construction plan in permafrost region.