Abstract: Cracking of early-age concrete can occur in the track beds of high-speed railways due to changes in material properties, environmental effects, and construction processes. This is a multi-field, time-varying issue involving hydro-thermo-chemo-mechanical coupling. However, to date, research has not adequately described the early-age cracking mechanisms in track beds, and few risk control measures have been proposed. To solve this problem, we incorporated the hydration degree of concrete into multi-field coupling equations for early-age concrete, and set boundary conditions that account for environmental influences and various stress factors that typically cause early creep of concrete. A four-field coupled risk prediction model was built based on hydro-thermo-chemo-mechanical properties, and was used to calculate and analyze various time-varying behavior (including the risk and form of cracking) in the hydro, thermo, chemo, and mechanical fields of early-age concrete. Finally, we focused on material-related factors (maximum heat of hydration and peak heat release time), environmental factors (temperature difference between day and night, average daily cooling rate, and intensity of solar radiation), and construction technique factors (molding temperature, pouring time, and thermal insulation coefficient). The influence of these factors on the early-age cracking risk of the track bed was analyzed, and risk control measures against early cracking were proposed accordingly.

Key words: Ballastless track; Early-age concrete; Hydro-thermo-chemo-mechanical coupling; Early cracking of track bed

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