Previous research has illustrated the exceptional shear resistance afforded by the rubber powder-modified asphalt gravel bonding layer. This study introduces an innovative interlayer torsional shear testing apparatus to evaluate shear performance between the base and surface layers of semirigid asphalt pavements under torsional shear, further proposing a methodology for calculating maximal torsional shear stress in a square section. The investigation assessed shear strength at the interface under various ambient temperatures (-10 degrees C, 25 degrees C, and 45 degrees C) and normal stresses (0.35 MPa, 0.525 MPa, 0.7 MPa). Moreover, a finite-element model, integrating the rubber powder-modified asphalt macadam bonding layer through cohesive contact, was developed to explore alterations in interlayer shear stress under diverse conditions. Findings reveal a pronounced temperature-dependent effect on interlayer shear strength, with a notable decrease in strength as temperature increases. Torsional shear strength consistently falls below obliqued shear strength, particularly under colder conditions, showing a 48% reduction. Conversely, torsional shear strength significantly improves with increasing normal stress. Mechanical response analysis demonstrated a direct link between interlaminar shear stress and vehicular load, indicating that interlayer shear stress exceeds those levels observed during linear travel upon vehicular turning. Nevertheless, the interfacial shear stress between the base and surface layers reliably satisfies the requisite shear strength criteria, irrespective of vehicular movement. Indoor torsional shear testing has proven to be an indispensable technique for assessing bonding efficacy between semirigid bases and asphalt pavement surfaces, given the dynamic nature of vehicular motion.
