Experimental Study on Shear Behavior of Interface between Different Soil Materials and Concrete under Variable Normal Stress

At present, the interface shear test is mainly used to evaluate the anti-sliding performance of the new foundation base. However, the traditional interface shear test has certain limitations in simulating the load change during the construction process and cannot accurately simulate the interface shear characteristics between the structure and the soil under the continuous change of the normal stress. Based on the self-developed large-scale interface shear equipment, this paper carried out the interface shear test and mechanism research of cement soil concrete, sand concrete, clay concrete and other materials in different curing cycles under the loading and unloading modes of variable normal stress repeated steps and continuous loading modes of variable normal stress steps. In addition, this paper deduced the formula of the minimum interface friction coefficient based on Mohr–Coulomb criterion. The experimental results show that the curing effect of cement soil can significantly improve the shear mechanical properties of the interface, and the friction coefficient of the cement soil concrete interface will also increase step by step with the increase of the curing time of the cement soil. The sliding shear surface can be remolded under the preloading of normal pressure, so that the interface shear characteristics of each shear material under repeated loading and unloading can be approximately equal to the interface shear characteristics of multiple equivalent materials under separate loading. In the case of a continuous change of normal stress, the rapid increase of normal stress will lead to accelerated entry into the limit shear state, resulting in plastic failure of the shear plane as a whole. In the engineering with a continuous change of stress, the interface shear friction coefficient of the material with high cohesion fluctuates greatly. The minimum interface friction coefficient formula and test proposed in this paper can be used to evaluate the interface friction coefficient range, and the sand concrete interface shear performance under the continuous normal stress loading mode showed good consistency. The self-developed large-scale interface shearing equipment and its test data provide theoretical basis and solutions for the improvement of traditional interface shearing equipment.