Mechanical and micro-CT study of frost-heave in silty sands

Soil freezing occurs naturally in cold regions where it affects many aspects of geotechnical practice and infrastructure. Moreover, artificial ground freezing can be used to stabilize sandy and silty soils prior sampling, but also as stabilization measure in tunnelling and open excavations. This paper reports a laboratory-based study on the frost-heave response of four silty sand soils from the Øysand Norwegian geotechnical test site. The combined effects of fines content and vertical effective stresses were investigated in a one-dimensional cell with parallel micro-computed tomography to assess the impact of a freeze-thaw cycle. As expected, the higher the fines content the higher the expansion noted on freezing and increasing the vertical effective stress reduced or eliminated frost-heave, the stress levels required to supress heave increasing with fines content. Additionally, micro-CT image analysis added important further insights and shows that freezing may disturb the soil fabric, even when the resulting global strains are too small to measure by conventional means (using an LVDT). The experiments provided crucial evidence regarding the circumstances under which ground freezing could be an effective aid to low-disturbance sampling in silty sands and provides useful information for other geocryological engineering applications in such strata.