Permeability and microstructure evolution of loess-paleosol sequence: analysis of prediction model based on deposition time

Abstract

Saturated hydraulic conductivity (K_s) is a critical parameter for assessing water-induced loess collapsibility, erosion, and landslides. However, accurately determining K_s has long been a challenge in geological and geotechnical engineering due to the complexity and inherent spatial variability of loess-paleosol sequences. To address this issue, this study conducted shaft sampling and laboratory experiments to measure the K_s of loess with a deposition time (T) of up to 880 ka. By leveraging the well-defined deposition time scale and global relevance of loess, a predictive model incorporating K_s variability was developed with T as a variable. This paper provides a detailed discussion of the physical significance of the model’s parameters, their determination methods, and verifies its applicability. Pore distribution and scanning electron microscope (SEM) images were used to reveal the three-stage evolution of K_s over time, as well as the underlying microstructural mechanisms. Additionally, this paper explores the impact of commonly used merging layer methods on K_s variability in engineering practice. The model effectively captures the long-term evolution of K_s in loess and can predict the K_s of loess-paleosol sequences, along with their expected variability, at a lower cost. This provides more reliable parameters for geological hazard assessments and hydrological engineering design.