Effect of Roughness on the Shear Strength of Frozen Soil–Concrete Contact Surfaces in an Open Environment

Abstract

The roughness of the contact surface is closely associated with the shear strength characteristics of the pile–soil interface, and as the roughness of the contact surface increases, so does the contact area, resulting in a greater formation of ice crystals on that surface during freezing, which enhances the ice cementation force. Currently, there is no universally recognized method for quantifying the roughness of the contact surface. This paper proposes modifying the sand-filling method roughness formula based on the introduced morphological coefficient. Additionally, the low-temperature direct shear test of the frozen soil–concrete interface was carried out under the conditions of different contact surface roughness, normal pressure, soil moisture content, and other test factors. The results reveal the following findings: (1) The freezing shear strength at the contact surface is mainly determined by the ice cementation force and friction force, and the roughness corrected by using the morphology coefficient can characterize the contribution of biting friction to the freezing shear strength; (2) The effect of normal pressure on the biting friction of frozen soil–concrete contact surfaces shows a gradually increasing trend; (3) The influence of the test controlling factors on the freezing shear strength of the contact surface in the order of precedence is normal pressure > moisture content > test temperature > roughness > dry density. Normal pressure and moisture content have a strong and significant effect on the test results, the test temperature and roughness have a significant effect, and the effect of dry density is not significant; (4) The contact surface freezing shear strength is continuously improved with the increase of roughness, but the increase of normal pressure is able to weaken the degree of the effect of roughness on the enhancement of the antishear strength.