The aim of this study is to provide a landslide susceptibility map of the Xunyang District of a mountainous terrain, at the southern part of the Qin-Ba Mountain Region, which has been highly exposed to widely distributed shallow landslides over the past few decades. The Weight of Evidence (WoE) method was adopted in this research considering both the presence of a certain landslide causative factor class and the absence of remaining classes, which was used for determining a clearly spatial correlation between a landslide occurrence and the causative factors. Intrinsic factors, including geomorphological factors, geological factors, and river flow networks, and external factors of anthropogenic engineering activities in terms of density of road network were all considered and involved in the Geological Information System (GIS) environment for reconstructing the thematic layers of factor dataset. Significant assumptions prior to the analysis were emphasized to ensure conditional independence between each pair of factors for this bivariate statistical approach. In addition, a detailed landslide inventory map was constructed through field investigation and a remote sensing interpretation process at a scale of 1:50000. The thematic layers and landslide map were overlapped to obtain a spatial statistical relationship by using the frequency ratio method. At last, the validation process for the derived susceptibility map was conducted by applying the ROC curve, indicating that more than 90% of the landslides were in categories of high and moderate susceptibility zones. The causative factor classes, including the slope angles ranging from 20 to 40°, strong weathered and fractured strata, and road network density were identified to considerably influence the landslide distribution in the study area. The results have proven to be significantly meaningful for landslide hazard risk mitigation and land use management for the local authorities responsible for these fields.

Wide area landslide detection is a major international research hotspot in the field of geological hazards, and the integration of multi-temporal optical satellite images and spaceborne interferometric synthetic aperture radar (InSAR) appears to be an effective way to realize this. In this paper, a technical framework is presented for wide area landslide detection: (i) multi-temporal satellite optical images are used to detect landslides with distinguishable geomorphological features; (ii) Generic Atmospheric Correction Online Service (GACOS) assisted InSAR stacking is employed to generate annual surface displacement rate maps in radar line of sight using satellite SAR images from both ascending and descending tracks, which are in turn utilized to automatically detect active landslides from ground motion using hotspot analysis, and (iii) the distribution characteristics of the detected landslides are investigated by examining their relationships with topographic and hydrological factors. Three expressways in Sichuan Province, China—namely the Yakang (Ya’an-Kangding), Yaxi (Ya’an-Xichang), and Lushi (Luding-Shimian) expressways—and their surrounding regions (a total area of approximately 20,000 square kilometers) were chosen as the study area. A total of 413 landslides were detected, among which 320 were detected using multi-temporal satellite optical images, and 109 were detected using GACOS-assisted InSAR stacking. It should be noted that only 16 landslides were detected by both approaches; these landslides all exhibited not only obvious geomorphological features but also ground motion. A statistical analysis of the topographic and hydrological factors shows that of the detected landslides: 81% are distributed at elevations of 1000–2500 m, over 60% lie within the elevation range of 100~400 m, and 90% present with medium and steep slopes (20°~45°), and 80% are located within areas seeing an annual rainfall of 950~1050 mm. Nine landslides were found to pose potential safety hazards to the expressways. The research findings in this paper have directly benefitted the Sichuan expressways; equally important, it is believed that the technical framework presented in this paper will provide guidance for hazard mitigation and the prevention of transportation hazards in the future.

Faults play a crucial role in shaping the formation and damage patterns of landslides in the mountainous region, particularly in Qinling-Daba (Qinba) area in China. On 6 October 2022, following a 4-day rainfall event totaling 221.5 mm, a landslide occurred in Hanwang Town, Shaanxi Province. The left boundary of the landslide coincided with a fault, which influence the formation and movement development of the landslide. To further understand and quantified the formation process and damage mechanism of the landslide, a comprehensive study was conducted, incorporating field investigations, local rainfall data, and various methods including unmanned aerial vehicles (UAVs), numerical simulations, and laboratory test. The results indicate that fault dictate the formation of the Lijiaping landslide by influencing the mechanical strength of the rock mass and the catchment topography in the landslide area. Due to fault, the rock mass in the landslide area is high fragmentation, with a softening coefficient of about 0.52. Weathering resulted in numerous residual and slope sediments in the landslide area, providing ample material for the landslide. Meanwhile, the fault activity led to a wedge-shaped topography in the landslide area, with an average Terrain Wetness Index (TWI) of 3.43, significantly higher than the Hanwang Township average of 1.47. This creates a hydrogeological structure favorable for landslides. Numerical simulations revealed that the maximum velocity of the landslide reached 5.05 m/s and the maximum displacement was 53.18 m, both occurring in the central part of the landslide. These findings offer crucial scientific insights for understanding and preventing similar geological hazards.

Over exploitation of groundwater in Changping District of Beijing city has caused serious land subsidence in the past decades. In recent years, the operation of the South-to-North Water Transfer Project has reduced the land subsidence rate. In this paper, Experimental tests are performed using the GDS Consolidation Testing System to characterize the compression and rebound of soils at depths of less than 100 m caused by groundwater withdrawal and recharge in Changping District. The results indicate that the compressible layers are the main contributors to land subsidence. The first compressible layer experiences greater deformation and more considerable hysteresis than the other compressible layers with the same decrease in the pore water pressure. Therefore, the exploitation of the adjacent aquifer should be controlled in the future. The deformation in the second and third compressible layers is a gradual and long-term process with little rebound; therefore, the subsidence should be seriously addressed when the groundwater in the two compressible layers is exploited on a large scale. In the same compressible layer, silty clay is more compressible and hysteretic than silt. For the same soil sample, the deformation rate decreases gradually as the pore water pressure decreases, whereas the creep deformation shows an overall increasing trend. A parameter named the subsidence index C_w is proposed in this paper to describe the soil compressibility during groundwater withdrawal. All the soil samples are characterized by elastic-plastic deformation, and the shallow soil samples with less pore water pressure decrease are more likely to rebound.

The micro pores in loess show regional variation in structure on the Loess Plateau and greatly influence the physical properties and macro behaviors of loess. In this study, the 3D microstructures of Malan loess from Lanzhou (LZ), Qingyang (QY), Hengshan (HS) and Jingyang (JY) were established based on μ-CT scanning, and the corresponding microstructural parameters were compared and analyzed quantitatively. The results indicate that the LZ and HS loess both show overall homogeneous structures with dominant inter-particle pores, while the QY and JY loess have more intra-aggregate and constricted pores. Overall, the LZ loess has the largest pore size, followed by the JY loess, QY loess and HS loess, which is consistent with the throat sizes of the four loess samples. The average coordination numbers (CNs) of the LZ and HS loess are lower than those of the QY and JY loess, while the throat lengths of the former two loess are larger than those of the latter two loess. Analysis of the correlation between the micropore parameters and macro behaviors of the loess suggests that the void ratio is the precondition for loess collapse, but it shows weak relevance to collapsibility; meanwhile, the size of pores contributing to the major pore space presents a strong positive correlation. The throat length representing the pore structure is more closely related to loess permeability compared with the void ratio, average CN and throat size.