Loess landslides have complicated deformation mechanisms. Accurately describing the internal failure deformation of loess landslides and establishing a theoretical method of landslide instability evaluation for the prevention of subsequent landslides have become important topics in western development project construction in China. This paper presents a case study of the Zhonglou Mountain landslide in Shaanxi Province, China. Based on field investigation results, a two-dimensional stability analysis model was constructed using the finite element method. Taking the deformation characteristics of the landslide as the research basis, the distribution laws of the displacement, stress, and shear strain of this landslide were identified with the strength reduction finite element numerical simulation method. Additionally, the safety factor was evaluated under normal and storm conditions. The numerical simulation results show that the horizontal tensile stress of the landslide was mainly distributed in the middle and upper parts of the landslide under normal conditions, while the vertical tensile stress was distributed near the sliding surface. Under heavy rainfall, the sliding force increased, and the anti-sliding force and anti-sliding section decreased; the location of the maximum shear strain shifted down from the middle and upper parts of the landslide body to the area with a shear crack, and the plastic shear strain area expanded along nearly the entire the sliding surface, leading to the occurrence of a landslide. Thus, the use of anti-slide piles to stabilize the landslide was proposed and tested. Monitoring points were arranged along the sliding surface to evaluate the displacement, stress, and strain responses. The on-site observation results agreed with the modeling results. The use of anti-slide piles was demonstrated to be an effective stabilization method for the Zhonglou Mountain landslide.

Since the 1970s, a large number of loess collapses and landslides have occurred in the Loess Plateau of China due to water diversion and irrigation projects. A large amount of ancient landslide deposits are accumulated at the foot of the tableland, which is likely to slide again in the case of a rapid increase in short-term rainfall or long-term irrigation. The weak characteristics of the sliding zone soil often become the key factor affecting the revival of old landslides. To explore the effects of water content and shear rate on shear behavior of the sliding zone soil, a series of ring shear tests were conducted on reconstituted loess in the South Jingyang Plateau. Experimental results suggest that under the condition of normal consolidation, the soil sample with the optimum moisture content has the highest shear strength. The increase in the shear rate effectively reduces the strength of the soil. Because of the high shear rate, the pore water that cannot be dissipated and fine particles accumulated at the shear plane form a weak base (slurry making theory), which cannot be easily stopped once the landslides start, leading to high-speed and long-distance landslides. In addition, the changes in the soil particles and pores were observed using a scanning electron microscope (SEM), and the observations were consistent with macroscopic results. From these studies, we come to the conclusion that the motion mechanism of reactivated landslide was associated with the interaction of water content and shear rate, which reduces the shear strength of the displaced materials to a great extent.

Wetting-induced soil deformation significantly impacts land stability and management on the Chinese Loess Plateau. This study analyzed silt soils from the Late Pleistocene (1 m depth) and Middle Pleistocene (25 m depth) to investigate compression and collapsible deformation during wetting. The compression in both soils progressed through three stages: slow deformation under low pressure, accelerated deformation under moderate pressure, and decelerated deformation under high pressure. Wetting intensified the compression in the 1 m sample but reduced it in the 25 m sample, with the deformation becoming more sensitive to the initial water content under higher pressures. Collapse tests showed contrasting behaviors: the 1 m sample exhibited collapsibility, while the 25 m sample displayed expansiveness (a negative collapsibility coefficient). Microstructural analysis revealed that the 1 m sample with abundant macropores and overhead structures had a lower structural stability than the 25 sample with more stable, rounded micropores. The wetting-induced deformation was governed by the balance between clay mineral expansion and structural collapse, with collapsibility prevailing when collapse dominated and expansiveness prevailing when expansion was predominant. These findings provide valuable insights into soil–water interactions and support improved land use and management strategies in the loess region.