An investigation into the relationship between saturated permeability and microstructure of remolded loess: A case study from Chinese Loess Plateau

Abstract

Understanding the permeability law of remolded loess is important for engineering construction in the loess area. To gain insights into the changes of saturated permeability and microstructural evolution of remolded loess for different dry densities, the loess from the Chinese Loess Plateau was used as a test material and was remolded as samples with different dry densities at the optimum water content state. The saturated seepage test and scanning electron microscopy (SEM) imaging were conducted on the remolded loess samples. The microscopic properties of the loess pores in the SEM images were identified using Image-Pro Plus software. The relationship between the micro-parameters of the pores and permeability were explored using multivariate statistical analysis. Results from this study highlight that the dry density of samples can be classified into three categories: Group I (1.30 and 1.35 g·cm−3) shows permeability decreasing with seepage time, Group II (1.40 g·cm−3) shows permeability initially increasing and then decreasing with seepage time, and Group III (1.45–1.65 g·cm−3) shows permeability increasing with seepage time. Correspondingly, the dry densities of these groups were found to be unsuitable, doubtful, and suitable, respectively, for laboratory study on the saturated permeability of remolded loess. In addition, the evolution mode of remolded loess structure is basically overhead-interlocking-matrix with increasing compactness. In this process, the macropores transform into mesopores and then to small pores, while the change in micropore content is weak. Also, the directional distribution of the pores weakens, while the pore morphology changes little. Furthermore, the contents of macropores and mesopores, as well as the pore diameters, play a positive role in permeability, while the contents of small pores and micropores, and directional probability entropy have a negative impact on permeability.