Shear behavior of precast pile-soil interface in warm permafrost regions

Precast concrete piles are one of the most popular foundations in warm permafrost regions due to their low thermal disturbance of the frozen ground. The mechanical behavior of the precast pile-soil interface needs to be understood to characterize the load transfer mechanism of these precast piles. However, limited studies have focused on precast pile-soil interfacial shear characteristics, especially in warm permafrost regions. To define these interfacial shear characteristics, this study conducted a series of precast pile-soil interfacial shear tests with different soil densities, water contents, shearing rates, and temperatures using an improved high-precision temperature-controlled direct shear apparatus. The results showed that the mechanical properties of the interface varied significantly with temperature, especially in the temperature range of −1.5 °C to −0.5 °C. When the interface was in a frozen state, the shear stress-shear displacement curve first increased rapidly, followed by a softening and a brittle failure. When the interface temperature increased from −1.5 °C to −0.5 °C, the peak shear strength of the interface decreased significantly, accompanied by a reduction in cohesion. A binary medium model for the precast pile-soil interfacial shear behavior under warm permafrost temperatures was proposed and was able to provide a good fit for the test data.