Applicability of Novel Pile-Plank Embankment in Seasonally Frozen Regions

In order to control the frost heaving damage in the seasonally frozen regions of the Moscow−Kazan high-speed railway, a novel pile-plank subgrades with an insulation board was proposed. Comparing the performance of three kinds of thermal insulation materials, expanded polystyrene (EPS) foam board, polyurethane (PU) board and extruded polystyrene (XPS) foam board shows that the XPS insulation board could be used in the new subgrade for its better performance in heat insulation, waterproof, impervious and compressive properties. The thermo-elasto-plastic model was established to study the influences of laying range, insulation board thickness, filling height, and external temperature on the mechanical deformation of the new type subgrade. The results show that when the laying range of the insulation board is extended to the signal wire slot, it can do better to preventing the downward transfer of negative temperatures (reducing the frozen depth), and diminishing the harmful effect of soil frost heaving surrounding the pile-plank structure. With increasing board thickness, the heaving amount decreases exponentially and frozen depth decreases close to a parabolic curve. The upper surface of the insulation board can prevent the downward transfer of negative temperatures and its lower surface plays a role in controlling the soil temperature dissipating under embankment. Increasing the filling height of embankment is helpful to suppress the subgrade heaving amount and reduce the usage thickness of the insulation board. The insulation board thickness should be greater than 0.4 m when the filling height is 0.8 m; and the board thickness should be greater than 0.31 m when the filling height is 2.8 m.