Study on arch expansion characteristics and meso-mechanism of semi-rigid base in desert regions under temperature-time effect

To reveal the formation mechanism of transverse band-shaped uplift distress in semi-rigid bases in desert regions, cement-stabilized graded macadam was taken as the research object. A self-designed arch expansion test system was adopted to systematically investigate the influences of gradation type, cement content, and fine aggregate type on the arch expansion characteristics of the base under temperature-time coupling effects. Combined with the discrete element particle flow code PFC 3D numerical simulation method, the formation mechanism of uplift distress was explained from a mesoscopic perspective, and a modified prediction model for the thermal expansion coefficient was established. The results show that gradation type exerts a significant effect on the arch expansion characteristics of the base. Among them, the C-B-3 inverse S-shaped gradation with a high coarse aggregate content presents the minimum expansion force and expansion deformation. On the premise of meeting the strength requirements, appropriately reducing the cement content and adopting stone chips of the same lithology as coarse aggregates for fine aggregates can effectively restrain the arch expansion deformation of the base. The base material is most significantly affected by temperature loading in the range of 40℃ to 50℃. The modified thermal expansion coefficient prediction model based on the Kerner model achieves high accuracy with a correlation coefficient ≥ 0.99. Discrete element simulation results show that force chains in the maximum expansion force zone are convex upward under thermal stress constraint. The longitudinal expansion displacement agrees well with field distress. The derived mesoscopic evolution law can qualitatively explain the inherent initiation mechanism of pavement heave distress. The findings of this study can provide theoretical support and technical references for the prevention and control of semi-rigid base uplift distress in desert regions.