Thermal insulation and strengthening properties of anti-frost heaving subgrade structure of the high-speed railway in seasonally frozen soil region

Frost heaving deformation of the subgrade in the seasonally frozen region affects the running speed and safety of high-speed trains. Taking ordinary-graded macadam subgrade structure as the prototype, we established the thermal-mechanical coupling model of subgrade foundation and the external force model of subgrade whole structure. Then the temperature field, deformation field and structural mechanical parameters were calculated and compared with literature data, which further verified the reliability of the model. On this basis, three anti-frost heave structural models were established, including the cement stabilized gravel subgrade, thermal insulation strengthening layer with graded macadam subgrade, and thermal insulation strengthening layer with cement stabilized macadam subgrade. Finally, the frost heave deformation and stress characteristics were calculated. The results show that the thermal insulation strengthening layer and cement stabilized macadam filler can effectively reduce the frost heaving deformation of the subgrade. The frost depth and maximum frost heaving of the thermal insulation strengthening layer with cement stabilized macadam structure are the smallest, which are 0.8 m and 1.585 mm. Moreover, the thermal insulation strengthening layer can reduce the vertical stress of the surface layer of the subgrade, and the cement stabilized macadam with larger elastic modulus can accelerate the attenuation of vertical stress and reduce the stress of bottom layer of subgrade. The thermal insulation strengthening layer with cement stabilized macadam subgrade surface structure can provide references for the selection of high-speed railway subgrade structure in the seasonal frozen zone.