CHARACTERISTICS OF DIRECT SHEAR TEST FOR PLAIN CONCRETE JOINT WITH RUBBER AND ITS COHESIVE ZONE MODEL

The contact and friction characteristics of concrete specimens with rubber is studied by direct shear tests in conjunction with theoretical model, i.e., PPR's cohesive zone model, which was employed to describe the mechanical behaviors of the specimens under shear loading conditions. The experiment results show that the constitutive response of the shear stress-displacement in the interface can be approximately characterized by initial elasticity, elastoplastic hardening, and strain softening. When the normal pressures acted upon the concrete specimens are in the range of 1.5 MPa~13 MPa, the ratio of residual strength with respect to shear strength is about 55%~65%. When the normal pressures acted upon the concrete specimens are 17 MPa and 21 MPa, the ratio of residual strength with respect to shear strength are then about 70% and 80%, respectively. Furthermore, the rubber plays a good buffer role in the interfaces. Especially in the large normal pressure, the phenomena of significant softening and sliding are observed at the contact surface, in which the Archard nonlinear power law is used to describe the relation between peak shear stress and the normal stress in the friction contact, and the constants parameters k and m in the law are 0.97 and 0.33 respectively. Finally, the prediction by the PPR model employed in the numerical modelling is found in fair agreement with the experimental results, which is helpful to study the joint behavior of shield tunnel.