Since large-scale agricultural irrigation began in the 1980s, 92 landslides have occurred around the South Jingyang Plateau during the past 40 years. The geological disaster and soil erosion have caused numerous casualties and substantial property loss. In this work, several field investigations are carried out to explore the soil erosion and mechanical mechanism of these irrigated shallow loess landslides on the South Jingyang Plateau. (1) We investigated the spatial distributions, types and developmental characteristics of loess landslides. (2) We surveyed and monitored seasonal agricultural irrigation features and groundwater changes in the area since the 1980s and found that irrigation is a significant factor influencing groundwater changes, soil erosion and even causing landslides to occur. (3) Based on the field investigation, the occurrence of these irrigated shallow loess landslides was generalized, and it was found that the core process was due to the liquefaction of softening zone. We carried out a static liquefaction test and verified that the natural loess was prone to liquefaction. (4) The three main reasons for shallow loess landslides in the South Jingyang Plateau were discussed. This study provides a valuable reference for achieving an understanding of the relationship between seasonal agricultural irrigation and the occurrence of loess landslides in the area as well as similar irrigated agricultural areas.

According to a previous geological investigation, high-speed and long-distance loess landslides in the South Jingyang platform in Shaanxi Province are closely related to the static liquefaction of loess. Considering the typical loess landslides in this area, isotropic consolidated undrained (ICU) triaxial tests and scanning electron microscopy analyses were conducted in this study. The main conclusions are as follows: (1) The stress-strain curves indicate strong strain softening under different confining pressures. The pore water pressure increases significantly and then remains at a high level; (2) The liquefaction potential index (LPI) shows an increasing trend followed by stabilization; the larger the LPI is, the smaller the state parameter (Ψ) is. The steady-state points of the loess are in the instability region; however, the steady-state strength is not zero; (3) Based on the ICU test results, the average pore diameter decreases; the shape ratio remains essentially unchanged; and the fractal dimension and roundness show different trends. The proportions of the macropore and mesopore decrease; that of the small pore increases slightly; and that of the micropore increases significantly; (4) The compression deformation of the highly spaced pores causes rapid strain hardening. A rapid strain softening results from the pore throat blockage at the beginning of particle rearrangement and reorganization. A stable strain softening is related to the agglomeration blocking of the reconstructed pore throat in the gradually stable stage of particle rearrangement and reorganization.

Loess landslides represent a severe geohazard in the Loess Plateau, posing significant challenges to sustainable development and regional safety. This study analyzed 111 landslides (1976–2018) and 529 marginal fissures in the South Jingyang Tableland (SJT) to reveal the distribution and failure modes of the landslide cluster. Preparation factors, including stratigraphic lithology, geomorphic features, and discontinuity systems (vertical/tectonic joints, unloading fissures, weak layers, and marginal fissures), were evaluated alongside triggering factors such as precipitation, irrigation, and river erosion. The main takeaways of this study are as follows. (1) A comprehensive database of 111 loess landslides (1976–2018) and 529 marginal fissures was constructed for the SJT, representing the longest and most complete chronological record available for this region. (2) Landslide activity within the Jiangliu landslide cluster (LC) exhibits an approximately decadal clustering pattern, with a temporal spacing of 9.6 ± 2.8 years between successive active periods, providing a basis for medium-term hazard forecasting in comparable settings. (3) The evolution of marginal fissures is controlled by the margin’s geometry and their interaction with slope failure processes, and the strong correlation between fissure development and landslide initiation enables the use of fissure monitoring as an early warning indicator. (4) The evolutionary mechanism follows a sequence of initial tectonic activity → rising groundwater → formation of the critical slide structure → water accumulation in fissures → single landslide → subsequent clustering. This process, termed a “water-induced loess catastrophe” (WILC), provides a conceptual framework for understanding landslide clustering on loess tablelands. (5) The database construction methodology, the decadal clustering analysis, and the WILC model collectively offer transferable tools for medium-term hazard forecasting, fissure-based early warning, and sustainable land-use planning on loess tablelands, not only in the SJT, but also in other loess regions with similar geological and hydrological settings.