Micropore variation and particle fractal representation of lime-stabilised subgrade soil under freeze–thaw cycles

Abstract

This paper employs digital image analysis techniques to examine the scanning electron microscope images of the microstructure of lime-stabilised subgrade soil with different lime contents and under different numbers of freeze–thaw cycles. The variation in pores of soil and its surface fractal dimension is studied based on the Sierpinski carpet model and micropore parameter data. It is observed that the occurrence of micro cracks and the number of large pores in the lime-stabilised subgrade soil increase with an increase in the number of freeze–thaw cycles. Among the soil samples with lime content up to 8% (by weight), the samples with 4–6% lime content show the largest surface fractal dimension, which is in the range of 1.89–1.93. The surface fractal dimension decreases gradually with an increase in the number of freeze–thaw cycles. The rate of decrement was the slowest for the samples with 4–6% lime content, which possessed (a) strong binding force between lime and soil, (b) less free lime, and (c) limited damage due to freeze–thaw cycling. The variation in amplitude of the soil fractal dimension is the highest during the first freeze–thaw cycle, indicating that the first cycle has the greatest impact on the soil microstructure.