Microstructure Quantification, Characterization, and Regional Variation in the Ma Lan Loess on the Loess Plateau in China

Abstract

The Ma Lan loess is a typical structural soil due to its water sensitivity, collapsibility, and seismic vulnerability. In this study, Ma Lan loess samples were extracted from 17 sites distributed on the Loess Plateau, and field and laboratory tests were conducted to ascertain the physical and mechanical parameters of the loess. The optical microscopy-based serial sectioning method was adopted to systematically research the characteristics and regional variation in the microstructure of the Ma Lan loess. The results show that the relationships of the equivalent diameter of loess particles, pores, and throats versus the corresponding quantitative percentages satisfy the rational and Gaussian distributions, respectively, and that the channel length of the loess throat versus the quantitative probability can be accurately fitted by adopting the gamma distribution. The distributions of particle size and orientation, pore size, throat radius, and channel length of the Ma Lan loess show obvious regional zonation on the Loess Plateau, which are influenced by the factors of source properties, aeolian power, migration distance, erosional history, and so on. The microstructure of the Ma Lan loess can be classified into the following three categories: particle aerial structure (I), aggregation aerial structure (II), and flocculated structure (III); the loess in the northern Loess Plateau is primarily Category I, and the loesses from other locations are primarily Categories II and III.