Quick identification of expansive soil in the field based on PIV technique

Abstract

On-site quick identification of the degree of expansion of expansive soil is of great significance to practical engineering. A set of expansive soil identification device was developed based on Particle Image Velocimetry (PIV) technique, which can provide a constant temperature environment and stable image acquisition conditions under outdoor environment. This device was used to carry out laboratory tests on remolded expansive soils, and to establish a method of quick identification of the degree of expansion of expansive soil based on PIV technique. The results show that the average displacement of all the pixels in the sample first increases and then decreases in a certain period of time, and thereafter tends to be stable in the later stage of the experiment. The mean value of displacement increment (MVDI) was used as the criterion to judge the stability of the sample displacement when it was less than 0.01 mm for two consecutive times. The mean value of the accumulated displacement increment (MVADI) before the displacement stabilization of samples with different degrees of expansion shows a positive correlation with the free swell index under the same initial state (i.e., density and moisture content) of the sample. Undisturbed expansive soils were taken for field tests, and the relation between the MVADI and the free swell index obtained from standard testing procedure was established, which is consistent with the results of laboratory tests.