Study On The Freeze-thaw Simulation Of The Pile-plank Subgrade Of Moscow-kazan High-speed Railway

The highlighted problem of high-speed railway in the seasonal frozen regions like frost heaving and shrinkage cracking of the roadbed has seriously affected the comfort and safety of high-speed railway operation.The existing pile-plank subgrade has been widely used in the non-frozen regions and successfully solved the settlement deformation problem of the high-speed railway embankment.However,there is little application of foundation treatment in seasonally frozen areas.Moscow-Kazan high-speed railway is in the seasonal frozen soil area with design speed of 400 km/h,and the pile-plank subgrade is designed to control the frost heave deformation.The freeze-thaw deformation of high-speed railway in seasonal frozen areas is affected by temperature field,moisture field and stress field,so in this paper,based on the hydro-thermal-force control equations,a 2-D pile-plank subgrade simulation model which suffering freeze-thaw cycles is established through COMSOL Multiphysics to study the influence of frost heaving and thaw settlement characteristics on the deformation and long-term service performance of high-speed railway pile-plank subgrade,through which the theoretical basis for the design and construction of the high-speed railway subgrade in the following quarters and the prevention and treatment of the disease can be provided.This paper obtained the following major conclusions and recognitions:1.The temperature gradient is the main factor that induces the moisture migration in seasonally frozen soils,and the temperature field and moisture field in seasonally frozen soils have a strong interaction,which shows a strong coupling effect,while the stress field has a weak coupling effect with temperature and moisture fields.2.The redistribution of ground temperature caused by embankment construction will achieve a new stable state within five years.The atmospheric temperature affects the distribution of ground temperature periodically in the deep-freezing range,while the ground temperature remains stable in other locations.3.The water content in subgrade will accumulate with the increase of freeze-thaw cycles.Therefore,it is necessary to strengthen the high-grade railway drainage measures in seasonal frozen regions.When the subgrade height in seasonal frozen regions is large enough,the moisture migration at the top of the subgrade is weak,and the frost heave deformation is small.4.The pile-plank subgrade can effectively reduce the frost heave deformation and the uneven lateral deformation of the whole subgrade structure after suffering the freeze-thaw cycles.The reasonable design of the thickness of the plate of pile-plate subgrade is checked by checking the maximum reduction of rail fasteners and the allowable strain of concrete materials.