Study On Thermal Insulation Measures Of High-Speed Railway Subgrade In Cold Regions

Strict deformation standard is used on ballastless track subgrade engineering in seasonal frozen regions.The typical problem is frost heave disease.Thus,it is a practical subject to be solved urgently to explore the development law of frost heave deformation and its influencing factors in high-speed railway subgrade.This paper relies on the research and development project of Science and Technology of China Railway Corporation.The first project is "Deep study on key technology to railway subgrade in different levels——the performance evolution law on structural design optimization of subgrade in different conditions under the effect of freeze-thawing and high-speed train load"(2014G003-F).The second project is "Study on the optimization of subgrade structure design under different environmental conditions for high-speed railway"(2014G003-A).The subgrade of Ha-Qi high-speed railway in seasonal frozen regions is taken as research object.To study the law of freezing and thawing of high-speed railway subgrade,monitoring in project site and numerical simulation is chosen as the main means.The main contents and results are as follows.(1)The feature of the project environment and the monitoring scheme of a typical section of the Ha-Qi high-speed railway is analyzed.The data shows that the temperature of subgrade change in the form of sine when external heat propagates to the subgrade.With the increasing of the depth,the amplitude temperature of the subgrade decays exponentially.And the changing of subgrade temperature lags behind the changing of total solar radiation.The characteristics of unidirectional freezing and bi-directional melting of the subgrade are obvious.The amplitude temperature and the frozen depth of the left and right subgrade shoulder are different,which shows the phenomenon that the difference of solar thermal radiation.The process of frost and heave includes five stages that are initial frost fluctuation,rapid development,sustainable development,low volatility thawing,and stable development.(2)The thermal parameters and linear expansion coefficient of different soil of the subgrade are measured in laboratory.The main influenced factors of the frost heave mechanism are analyzed.The control equations of the temperature and deformation field are theoretically studied.The initial conditions and the boundary conditions are identified.The coupled model of the temperature-deformation field is established and verified,which is in good agreement with the measured value.(3)The numerical simulation results show that the deformation in right line are larger than the left relative position,which shows the phenomenon that the solar radiation difference.(4)The foam concrete whose thickness is 10 cm are used as the insulation measure.By taking this measure,the temperature line of the subgrade is raised.The deformation of the subgrade surface are gradually reduced.The deformation is declined at 8.9% in the right shoulder of the subgrade.It is recommended that this measure should be used in practical engineering to restrain frosting-heaving.