Loess Landslides–Peculiarities of Deformation Mechanism

Loess on the Earth occupies an area of more than 13 million km2. The greatest spread of loess is in Europe and Asia (mainly south of 62°N), where vast areas are composed of loess from the surface, the thickness of which varies in Europe from a few meters to 20–30 m, and in the Caucasus, in intermountain hollows of Central Asia, China-from 50–60 m to 100 m and more. The peculiarity of loess is its predisposition to the development of subsidence-compaction during moistening under the action of both their own weight and external loads. As a result, in the areas of loess distribution, in addition to classical landslide forms, a special type of landslides is often observed, in the formation of which subsidence plays a significant role. The main factors in the formation of “subsidence landslides” are a decrease in the strength of loess as a result of increasing water cut. Underground water moistens the loess thickness from below to the state when its structure breaks under its own weight and subsidence begins with the formation of cracks on the day surface. Further moistening and destruction of the loess structure continues at the expense of both groundwater and atmospheric water absorbed through cracks. Such combination of conditions determines further development of subsidence phenomena and subsequent landslide deformations. The rate of displacement of such landslides depends on the extent and rate of subsidence development at the base of the slope. “Subsidence landslides” can be defined as a type of complex landslides.