Fractal analysis of cracking in a clayey soil under freeze–thaw cycles

Under extreme climate conditions, clayey soils experience not only seasonal drying and wetting but also frequent freezing and thawing. Cracking would also occur in clayey soils under freeze–thaw cycles, but now less academic attention has been paid on this issue. In this study, a series of laboratory tests were conducted on a clayey soil to investigate the cracking behaviors under freeze–thaw cycles. Water loss, surface crack initiation and propagation processes were monitored after each freeze–thaw cycle. By using the image processing technique, the crack patterns were described and then quantitatively analyzed on the basis of the fractal dimension concept. It was found that for the tested clayey soil subjected to freeze–thaw cycles, the surface crack pattern slowly evolves from an irregularly rectilinear pattern towards a polygonal or quasi-hexagonal one; and the water loss, closely related to the sample thickness, plays a significant role in the process of the clay cracking; Upon cyclic freezing–thawing, the fractal dimension is well correlated to the surface crack ratio in a logarithmic equation. Fractal dimension concept can offer a new perspective on the quantitative understanding of cracking initiation and propagation in clayey soils under freeze–thaw cycles.