In-Situ Shear Test Study on the Contact Surface Between Gravity Anchor and Gravel Soil of a Suspension Bridge

The friction strength characteristics of gravity anchorages of suspension bridges at the contact surface between concrete and gravel soil have a decisive influence on the slip resistance stability of the anchorages. In order to study the friction strength characteristics of the contact surface between gravel soil and anchor concrete and to determine the friction coefficient of the contact surface, this paper carried out the shear fracture test, shear test, and reciprocating shear test of the contact surface between concrete and gravel soil, analyzed the change rule of the stress-displacement law of the three test phases, and utilized the least-squares method to fit the τ vs. σ relationship curve to obtain the friction coefficient of the contact surface. The result shows that in the shear resistance test, the contact surface showed strain softening phenomenon and pressure embedding effect in the shear damage process, and the depth of pressure embedding ranged from 2 mm to 5 mm; in the shear resistance test and reciprocating shear test, the contact surface did not show significant strain softening phenomenon, and the concrete was mainly sliding horizontally on the contact surface; in the shear section, the shear resistance, and the three phases of reciprocating shear test, the friction coefficient of the contact surface was calculated by the relationship curve between the concrete and the adhesion (c) of the contact surface decreased significantly, and the value of the friction coefficient f decreased at a rate of 1% to 2%, indicating that the occlusion and embedment of the contact surface was weakening; the value of the pure friction strength parameter f (0.48) in the reciprocating shear test was selected as the friction coefficient of the contact surface between concrete and gravel soil.