Analysis of the Geological Controls and Kinematics of the Chgega Landslide (Mateur, Tunisia) Exploiting Photogrammetry and InSAR Technologies

Exploration of territories not previously analyzed by landslide experts provides interesting findings. The Chgega landslide, in northern Tunisia, represents a paradigmatic mass movement. It can be classified as a complex landslide, or more specifically as vast rock spreading that evolved into a block slide. It involves a great block of limestone—about 900 m long and 400 m wide—sliding over ductile clays and marls. The viscoplastic creep of the clays drives the landslide and creates, in its crown, a graben ~800 m long and ~120 m wide that breaks the summit of Chgega Mountain. Using Interferometric Synthetic Aperture Radar (InSAR) technologies, we demonstrate that this complex landslide is currently active and moreover shows progressive movement without clear episodic accelerations. The velocity of the limestone block is just above 2 mm/yr. The occurrence of gravity-induced joints indicates that the movement has an orientation towards 333° of azimuth on average, conditioned by the landscape around Chgega. These results were obtained through the analysis of a 3D model and a high-resolution orthoimage created from photographs acquired by an Uncrewed Aerial Vehicle (UAV). We may conclude that the landslide movement is determined by normal faults with directions N060°E and N140–150°E. This characterization of the Chgega landslide can serve as the basis for future studies about the origin of this slope movement. Furthermore, the data provided here may support the recognition of Chgega as a singular geological point that deserves to be declared a geosite.

The Disaster Mitigation of Slow-Landslide Movement Induced By Rainfall Based on Ps-Insar Method

Disaster management is a big issue in the past few years. Talking about the disaster, an aspect that should be focussed on is mitigation. The development and the ability of Remote sensing technology have a significant impact on disaster management and significantly contribute to disaster mitigation, such as for the disaster monitoring system. The slow-landslide movement is rarely considered in disaster mitigation, even though the acceleration can increase time by time and will be more dangerous than usual. Therefore, the observation of the remote sensing technology is needed for disaster mitigation. PS-InSAR as a space-based observation method can observe the continuous movement on a site location. Thus, this study illustrates the slow-landslide movement mechanism based on remote sensing technology using the PS-InSAR method compared with rainfall data. In this study, the Sentinel-1 images and STAMPS/MTI by Hooper (2004) successfully detect the displacement rate of the Kalibawang Village, Special Region of Yogyakarta, Indonesia, with the maximum displacement rate -23 mm/year along the Line of Sight (LoS) of the satellite. The PS-InSAR result was also compared with the rainfall data, and shows a correlation of the movement during the rainfall season. Therefore, further mitigation is needed to reduce the risk of the disaster.

ACTIVE DYNAMICS OF TECHNOGENIC LANDSLIDE ON THE LEFT BOARD OF THE KHANIKOMDON RIVER (NORTH OSSETIA)

The article is devoted to the technogenic triggering of the hazardous dynamic development of the landslide massif, which poses a threat of blocking the Khanikomdon stream with partial restrictions in the movement of residents of the mountain village of Dzuarikau. One of the main reasons for the intensive development of landslides in the Northern and Southern Jurassic shale depressions is the technogenic undercutting of slopes, caused mainly by the need of development of the mining industry or transport communications, although scientifically grounded pre-design solutions for minimizing the development of landslide processes can significantly reduce negative geoecological loads on the territory, which is especially important for the sustainable development of the mountainous areas. The aim of the work was to study the state of the landslide with modern measuring systems. Geophysical surveys were carried out by methods of vertical electrical and location-based sounding; the measurements of landslide movement were also carried out in the monitoring mode using surveys with a total station and a global positioning system GPS/GLONASS. The obtained results characterize a three-layer section of the “K” type with the thickness of a landslide high-resistivity massif of 18-21 m of crushed-loamy and gravelly composition, which is overlaid and underlain by more conductive clay strata. Geodetic observations show that the landslide body has moved throughout the entire monitoring period, but the velocities varied depending on the season. It is assumed that the seasonal variability in velocities is caused by the groundwater levels and associated pore pressures, which decrease when surface water is absent or cannot penetrate frozen landslide material, and increase when surface water from melting snow or rain penetrates the unfrozen landslide material.

Dynamic Analysis of the High-Speed and Long-Runout Landslide Movement Process Based on the Discrete Element Method: A Case Study of the Shuicheng Landslide in Guizhou, China

On July 23, 2019, a high-speed and long-runout landslide occurred in Jichang Town, Shuicheng County, Guizhou Province, China, causing 42 deaths and 9 missing. This paper used the discrete element software MatDEM to construct a three-dimensional discrete element model based on digital elevation data and then simulated and analyzed the movement and accumulation process of the landslide. The maximum average velocity of the source area elements reached 14 m/s when passed through the scraping area; meanwhile, the velocity of the scraping area elements increased rapidly. At 90 s, the maximum displacement of the source area elements reached 1358.5 m. The heat generated during the movement of the landslide was mainly the frictional heat, and the frictional heat increased sharply when the source area elements passed through the scraping area. The change of frictional heat has a certain positive correlation with the velocity of the scraping area elements. Finally, the volume of the scraping area elements was 2.4 times greater than the source area elements in the deposits. The scraping effect increases the volume of the sliding body and expands the impact area of the landslide disaster. Additionally, by setting different compressive and tensile strengths as well as internal friction coefficients to analyze the influences of their value changes on the landslide movement process, the results show that the smaller the strengths and internal friction coefficient of the model, the greater the depth and area of the scraping area, which will result in a thicker accumulation; meanwhile, the average displacement, average velocity, and heat will also increase.