Experimental study on deformation and strength characteristics of granular soil-structure interface under coupled monotonic shear and vibration using a modified direct shear apparatus

Soil-structure interaction under vibration becomes an important concern for the underground structure below or adjacent to a railway line as train speed is continuously raised. Although more and more related works have been conducted in recent years, the vibro-induced soil-structure interaction is not fully understood, especially for high-frequency vibration. By using a modified direct shear apparatus with a high-frequency vibration module, this work investigates the deformation and strength characteristics of granular soil-structure interfaces under vibration. The interface is prepared by dry sand specimens and a textured steel plate. Initially, monotonic shear tests of the interface are carried out as the control groups. Then a series of coupled vibration and monotonic shear tests, with a constant vibration frequency of 45 Hz, are performed to investigate the deformation and strength characteristics of the interface under vibration. The variation of major influence factors, including the vibration intensity, normal stress, pre-vibration specimen state (i.e., mobilized friction angle and density), initial relative density and vibration duration, are considered. By introducing shaking pressure, the strength criterion of the granular soil-structure interface under vibration is preliminary proposed.