In this paper, the Huangtupo Riverside Slump 1#, a reservoir landslide with double sliding zones in the Three Gorges Reservoir Area of China, is selected as the prototype for a scaled physical model test subjected to water level fluctuation and rainfall. The spatial-temporal characteristics of the multi-physical monitoring data are thus obtained, including the pore water pressure, earth pressure, surface deformation, and deep deformation. Subsequently, the failure mechanism and evolution process of the landslide model are discussed. The results indicate that the rise and fall of reservoir water correspondingly increase and decrease the pore water pressure and earth pressure at the front edge of the model, while having almost no effect on the trailing edge. The rainfall increases the pore water pressure and soil pressure of the entire model, and the increase is proportional to its duration and intensity but limited by the height of overlying soil. Both the surface deformation and deep deformation increase with the fall of reservoir water and rainfall. Except for the weakening effect of the soil caused by the first rise of reservoir water, which results in a certain surface deformation and deep deformation, the surface deformation has almost no response with the subsequent rises, while the deep deformation decreases with the rises. The Riverside Slump 1-1# exhibits the characteristics of retrogressive failure with whole evolution phases, while the Riverside Slump 1-2# exhibits a composite evolution, in which its middle front belongs to the retrogressive failure within the initial deformation, and the trailing edge belongs to the progressive failure within the accelerated deformation.

Understanding the reactivation causes of ancient landslides is imperative for the prevention of landslides. However, the reasons for the reactivation of thick loess-mudstone ancient landslides and evolutionary mechanisms are unclear. This paper investigates the Gaojiawan thick loess-mudstone ancient landslide as an example using field investigation, InSAR time series analysis, and laboratory testing methods to analyze the reactivation deformation characteristics and reactivation causes of the thick loess mudstone ancient landslides, which were and verified by numerical simulation. The results show that fault fracture zones and groundwater primarily control the reactivation of Gaojiawan's thick loess-mudstone ancient landslide. Due to the fragmentation of rock mass and the development of structural planes in the fault fracture zones, as well as the excavation and unloading zone formed by the surrounding rock of the tunnel, it is beneficial to the enrichment of groundwater. It intensifies the interaction of groundwater-rock-fault fracture zones, especially for the red mudstone with more clay mineral content. The strength degradation is significant after encountering water, resulting in an imbalance in the stress state in deep strata and the reactivation of the landslide.

Loess tunnels are very common in the Loess Plateau, and they pose unique geological threats. Loess tunnels are often difficult to detect and control due to their concealment and sudden appearance. Thus far, research on the genesis and evolution of loess tunnels remains scarce. In this paper, the genesis and evolution mechanism of the loess tunnels in the Loess Plateau is studied in depth, and the location, shape, and size information are obtained via field investigations. The potential correlations between the loess sediment, the basic physical properties (depth, water content, particle size composition, collapsibility coefficient, and self-weight collapsibility coefficient), and the tunnel density are inferred based on the Pearson's correlation coefficients and tests on the physical and mechanical properties of the loess sediments. In addition, spatial statistical modelling is employed to justify and predict the observed spatial distribution of the loess tunnels assuming Gaussian Markov random fields. The formation of loess tunnels is due to a combination of factors, including the formation thickness, soil properties, joints and fissures, topography, hydrogeology, and climatic conditions. The thickness of the loess, loess sediment properties, and their spatial relationship jointly determine the material basis of the formation of the loess tunnels. The loess tunnels at different depths have different main controlling factors that are hierarchical by depth. The evolution process of loess tunnels can be divided into five stages: the incubation stage, formation stage, development stage, failure stage, and withered stage. The characteristics of each stage are discussed in detail. Our work provides novel insights into subsurface erosion from the aspect of soil tunnels. It improves our understanding of hill slope geomorphological evolution and also provides effective techniques for tunnel erosion control.

Under the heavy rainfall risk due to global warming, a new trend has emerged in geological disasters of loess, which have often evolved into a chain form of disaster chain of loess (DCL) in recent years. The DCL is characterized by multiple, hidden, catastrophic, and complex characteristics that seriously affect the construction and operation of large-scale infrastructure on the Loess Plateau. To understand the formation mechanism of a disaster chain of loess, we took the Shiyangpo DCL, a typical disaster chain occurring recently on the Loess Plateau, as an example to investigate the geomorphic features and deformation characteristics of DCL using new technologies and methods such as Unmanned Aerial Vehicle (UAV) mapping and Geographic Information Systems (GIS) spatial analysis technology. A series of special laboratory tests considering the vibration of the loess subgrade was conducted to explore the changes in physical and mechanical properties of loess samples in the study area under natural, saturated, and vibration conditions. Additionally, the trigger factors and evolution process of this DCL were analyzed, and the formation mechanism of recently emerging typical DCL was revealed as well. The triggering factors of the disaster were summarized as follows: loess nature, heavy rainfall, irrigation, irrational excavation, incomplete drainage channels, and long-term vehicle vibration of roadbeds. Furthermore, extreme rainfall was identified as the primary inducing factor of Shiyangpo DCL. Finally, the development and evolution of Shiyangpo DCL were divided into five stages: the formation of the loess sinkhole stage, the occurrence of the loess subsidence stage, the occurrence of the loess collapse stage, the occurrence of the loess landslide stage, and the formation of river -blocking and dammed lake stage. This study reveals the cause and evolution process of the newly emerged DCL in the Loess Plateau, and the new techniques and methods involved can provide references for the theoretical research and prevention of loess geological disasters in other places.

The cutting slope soil is easily damaged by earthquakes and rainfall owing to excavation disturbance. Soil damage and strength degradation can significantly affect the slope stability. However, research on the evolution process of cutting landslide considering damage accumulation effect is insufficient. Taking the Dayangyun highway under construction affected by the Yangbi earthquake as the study area, field electrical measurements were conducted and slope damage was determined on the basis of evolution law of soil damage under rainfall, which was determined by laboratory test. A discrete element model of the damaged slope was developed, and evolution process of landslide was analyzed with different damage factors. The results indicate that trailing edge crack appears when the damage factor is 0.19. As the damage factor increases from 0.19 to 0.33, the slope body starts to slide along the fissured soil layer. The cutting slope is pushed by the upper slide body, and soil particle displacements increase from 3.5 to 39.0 m.