Shear behavior of subglacial debris-clean ice interface: experimental study and constitutive modeling

The shear characteristics of the subglacial debris-clean ice interface (SDCI) play a critical role in glacier stability. Increasing global warming has amplified glacier-related geohazards, posing significant risks to infrastructure and communities. This study provides the first systematic experimental investigation of the SDCI under coupled thermo-mechanical forcings, addressing critical gaps in understanding shear behavior at ice contents exceeding 40%. Through cryogenic direct shear tests, we quantify the roles of temperature (-9 °C to -1 °C), ice content (40–90%), and normal stress (150–550 kPa) in governing failure modes, stiffness degradation, and strength thresholds. Key findings reveal that SDCI shear behavior is more sensitive to temperature variations than to ice content or normal stress. As the temperature increased from − 9 ℃ to -1 ℃, peak shear stress and shear stiffness decreased by approximately 80%. Shear performance degradation is more pronounced at lower ice contents. Critical thresholds for temperature and ice content were identified, marking transitions from strain-hardening to softening and further to elastic-brittle failure. A disturbed state concept (DSC) model, integrating linear and hyperbolic characteristics, was developed to simulate the shear stress-displacement relationship, supported by parameter sensitivity analysis. Additionally, an improved Mohr-Coulomb strength criterion was proposed to account for the effects of ice content and temperature on cohesion and friction angle. These advances provide a framework for predicting SDCI behavior under climate-driven thermal fluctuations.