Image analysis measurement of soil particle movement during a soil–structure interface test

In this study, we describe a new microscopic measuring method, including equipment and analyzing software, for observing and measuring the movement of soil particles during a soil–structure interface test. The movement of soil particles can be recorded onto high-resolution digital image series. A correlation-based image analyzing algorithm is presented that measures the displacements of tracing points at sub-pixel accuracy from the image series. Based on the algorithm, two types of soil movement analysis, namely SMA (soil mass movement analysis) and PTA (soil particle tracking analysis), are proposed to meet the different requirements of practical measurements during an interface test. The proposed microscopic measuring method is validated by preliminary applications. The measurement results show that tangential displacements of the soil near the structure are significantly different from those of the interface. The interface thickness is estimated to be approximately five-times the average soil grain size. Structure roughness and normal stress have a marked effect on the movements of the soil particles near the structure.