Pore structure analysis of glacial till under freeze-thaw cycles based on calibration CT data

Acquiring the interior pore characteristics is essential to the utilisation of glacial till which is the material of permeability barrier to many engineering projects in cold regions. In this work, the pore space of glacial till samples with different cementation degrees and freeze-thaw cycles was investigated by CT technique. Representative elementary volume method (REV) was utilised to ensure a suitable scale of CT volume data, and a novel calibration method was proposed to detect the accuracy of CT segmentation. Subsequently, the effect of cyclic freeze-thaw action on the pore structure of glacial till samples was investigated. Quantitative pore structure analysis shows that cyclic freeze-thaw action resulted in a decrease in porosity of both well cemented and poorly cemented glacial till. The accessible porosity, fractal dimension, and coordination number of glacial till pores also decrease with the increment of freeze-thaw cycles. It can be observed that blocking of the channels of macropores is the main morphological evolution characteristic of glacial till with cyclic freezing and thawing, which can provide reference in designing permeability barrier in glacial till layers.