Nonlinear shear characteristics of frozen loess-concrete interface.

Under the different temperature environment, the precast pile-soil interface characteristics has an important impact on the safety and long-term stability for pile foundation. A large precast pile-soil shear experimental device is used to carry out the direct shear test of concrete-loess interface with different moisture contents under different freezing temperatures. The variation laws of shear strength parameters are revealed with influencing factors, and the shear mechanism of interface is discussed. The stress-strain constitutive equation of interface is proposed, and the shear strength criterion is established with considering the effects of temperature and moisture content on cohesion and internal friction angle. The results show the curve of shear stress and shear displacement can be divided into three stages: elastic deformation stage, plastic deformation stage and sliding failure stage, which macroscopically reflects the shear failure mechanism of the frozen soil-concrete interface. The shear strength of the interface is affected by the test temperature, sample moisture content and normal stress. The lower the test temperature, the greater the shear strength of the interface; With the increase of normal stress, the shear strength of interface increases; With the increase of moisture content, the shear strength of the interface increases and then decreases. The relationship of shear stress and shear displacement of frozen soil-concrete interface can be well described by the piecewise combination of hyperbolic function and linear function.