Creep Experiment and Constitutive Model Study of the Frozen Qinghai-Tibet Silt-Concrete Interface

Description

In order to ensure the long-term safety and stability of bridge pile foundations in permafrost regions, it is essential to investigate the rheological effects on both the pile tip and pile side bearing capacities. Among these, the consideration of the creep characteristics of the pile-frozen soil interface is a key factor in determining the long-term stability of permafrost pile foundations. This study utilized a self-developed large stress-controlled shear apparatus to investigate the shear creep characteristics of the frozen Qinghai-Tibet silt and concrete interface. The study examined the influence of freezing temperatures (-1°C, -2°C, -5°C), contact surface roughness (0mm, 0.60mm, 0.75mm, 1.15mm), normal stress (50kPa, 100kPa, 150kPa), and shear stress on the creep characteristics of the contact surface. Incorporating the creep behavior and development trends of the contact surface, a creep constitutive model for the frozen Qinghai-Tibet silt-concrete interface was established based on the Nishihara model, introducing nonlinear elements and a damage factor.The results revealed significant creep effects on the frozen Qinghai-Tibet silt-concrete interface under constant load, with creep displacement approximately 2-15 times the instantaneous displacement, and a failure creep displacement ranging from 6mm to 8mm. Under different experimental conditions, the creep characteristics of the frozen Qinghai-Tibet silt-concrete interface varied. Larger roughness, lower freezing temperatures, and higher normal stresses resulted in longer sample attenuation creep time, smaller steady-state creep rate, greater long-term creep strength, and stronger creep stability. Building upon the Nishihara model, considering the influence of shear stress and time on the viscoelastic viscosity coefficient, and introducing a damage factor in viscoplasticity, the improved model effectively described the entire creep process of the frozen Qinghai-Tibet silt-concrete interface. The research findings provide theoretical support for the interaction between piles and soil in permafrost regions.

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