| The frost heaving and thaw settlement of foundation is the main problem in cold region engineering,which seriously affects the stability of the structure.The screw pile is a new type of pile foundation with anti-uplift bearing capacity and overall stability,which has been verified in the non-frozen area.The photovoltaic engineering which developing in recent years,has begun to use the screw steel pile as the foundation of the photovoltaic panels.At present,the research on the frost heaving and thaw settlement characteristics of the screw piles at home and abroad is relatively lacking,the research results are not yet ripe.Therefore,the study on the characteristics of frost heave and thaw settlement of the screw steel piles not only has an important significance to the photovoltaic engineering,but also has important guiding significance to the selection of the pile foundation in cold regions.In this paper,the indoor model test is used to study the frost heaving and thaw settlement characteristics of the screw steel piles with different parameters,the main contents are as follows:1)Based on the frost heaveing stress analysis of the traditional pile and the bearing capacity study of the screw piles under the non-frozen area,the characteristics of frost heaving stress of the screw steel piles are put forward.This paper analyzes the influence of the screw blade on the frost heaving force,and puts forward a simple calculation model of the pile top frost heaving force of half-helix pile.2)The physical parameters of the filling soil are determined by the basic tests,which provides the foundation for the following tests.Through the test results can determine the filling soil is silty soil,which is a kind of strong frost heaving soil.3)In the case of unrestricted pile top,the one-dimensional frost heaving test and the thawing test for different types of screw steel piles were carried out.The variation of soil temperature field,the frost heaving displacement of piles and the thaw settlement of pile were analyzed,and the polynomial equation of the frost heacing displacement and the freezing depth is fitted.Compared with the experimental results,the arrangement of screw vanes in the frozen soil will greatly increase the frost heaving displacement,reduce the pitch of the screw steel piles in the non-frozen soil and increase the diameter of the screw blade will improve the stability of frost heave and thaw settlement.4)In the case of limiting pile displacement,the one-dimensional frost heaving test and the thawing test for different types of screw steel piles were carried out.The variation of the pile top frost heaving force was analyzed,and fitted the exponential equation of the pile top frost heaving force and the freezing depth.Compared with the experimental results,the arrangement of screw vanes in the frozen soil will greatly increase the pile top frost heaving force.Reducing the pitch of the screw steel piles in the non-frozen soil and increasing the diameter of the screw blades have a certain effect,but the effect is not obvious. |
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