Mechanical behaviors of interface between sand-gravel cushion material and concrete face slab by large-scale simple shear tests

A series of large-scale shear tests are performed to study the contact characteristics between sand-gravel cushion and concrete structure with two types of interfaces, coated with and without emulsified asphalt by a self-developed large-scale bidirectional low friction laminar-ring simple shear apparatus. The nonlinear elastic constitutive model parameters based on Clough and Duncan of the interfaces are determined, and the effects of emulsified asphalt on shear deformation mechanism of the interface are discussed. The results show that: (1) With the increasing shear displacement, the shear stress of interface coated without emulsified asphalt increases and the curves of shear stress and shear displacement exhibit a good hyperbolic relationship. The curves of shear stress and shear displacement of interface coated with emulsified asphalt exhibit a good hyperbolic relationship before the peak strength. Certain strain softening properties are shown after the peak strength, which is different from that coated without emulsified asphalt. The lower the normal stress, the more obvious it is. (2) For the both cases, with the increasing shear displacement, the deformation of soils in the upper box develops, and gradually increases from top to bottom and the largest relative movement displacement occurs in the contact surface between concrete slabs and cushion layer, which show that the shear strength of the interface is less than that of the sand-gravel cushion. (3)