Stability and deformation of Xiaozhuang landslide: A large-scale creeping landslide in Gansu, China

Information about the long-term spatiotemporal evolution of landslides can improve our understanding of the landslide development process and can help prevent landslide disasters. This paper describes the Xiaozhuang landslide triggered by a historical earthquake and rainfall in Tianshui, Northwest China. The landslide is dominated by rotational-sliding movement. Several new failures and many fissures formed in the landslide area as a result of the 2013 Ms 6.6 Minxian earthquake and rainfall. Accordingly, field investigations, borehole drilling, geotechnical laboratory tests, and numerical calculations were conducted to study the mechanism of the landslide and to forecast its stability. A triaxial creep test of the slip soil indicates that the axial deformation of the mudstone increases with increasing water content. Numerical simulations suggest that failure is prone to occur within the deep part of the landslide under earthquake conditions. If the input seismic acceleration exceeds 0.2 g, the landslide will become unstable. Furthermore, the horizontal peak ground acceleration near the surface of the landslide is greater than that at depth. During a strong earthquake, the unstable regions are primarily located in the middle of the landslide and at its crest. When the rainfall intensity rate is 200 mm/d, the factor of safety is 1.319 and a dangerous zone appears in the lower and middle parts of the landslide.