Study on Sand-Steel Interface Shear Test Method and Mechanism

Soil-structure interface properties play an essential role in geotechnical engineering. The interface shear test is widely used to measure the interface properties. However, in the traditional interface shear test (TIST), distribution of shear stresses along contact surface is not uniform due to boundary effects. Thus, average mechanical response of the whole interface measured by TIST cannot be used to evaluate interface friction properties. In this paper, a novel interface shear apparatus (MIDST) is presented to investigate the shear behaviours of the soil-structure interface. A series of shear tests were conducted on Fujian standard sand-steel interface. Two shear force sensors simultaneously monitor the shear force along the interface: a pre-embedded sensor inside the interface/steel plate (responding to MIDST), while the other outside the interface (responding to TIST). Laboratory test results show that the pre-embedded internal sensor successfully detects the weakening characteristics of the interface, while the external sensor monitors the hardening law. The interface shear strength measured by internal sensor is significantly higher than that monitored by external sensor. A commercial DEM software Version 5.0, Particle Flow Code in Two Dimensions (PFC2D), is employed to study the soil-structure interaction mechanism, and numerical test results show that the main reasons for the internal and external differences are the uneven shear stress distribution at the soil-structure interface and the boundary effect. In addition, numerical test results agree with the laboratory test results, indicating that the shear behaviours monitored by MIDST are relatively accurate and can provide a reference for engineering design.