Evolution mode of retrogressive landslide

For the region of Heifangtai Plateau, in Gansu Province of China, centrifugal model tests and two sets of stress-path tests are conducted to investigate the evolution mode and the mechanism of retrogressive landslides. In the centrifugal model tests, the rising of groundwater level is controlled by a designed facility. Digital cameras, pore-water pressure transducers, laser sensors and tracking points are adopted to record the variations in the pore-water pressure, deformation, slipping surfaces and cracks during the rising of groundwater level. In the stress-path tests, the dead-load tests with increasing pore-water pressure are performed to simulate the initiation of a landslide during the rising of groundwater level. Anisotropically consolidated and undrained tests are conducted to simulate the transferring process from local failure to global one in a landslide. Based on the above results, the findings are summarized as follows: the saturated loess fails under overburden pressure due to the rising of pore-water pressure. Under unloading conditions, the re-distribution of stresses leads to the development of local shearing band into the connected global failure surface gradually, while the slope appears in a retrogressive mode. The results are helpful in understanding the evolution mode and clarifying the mechanism of retrogressive landslides, and they may provide scientific support to the landslide treatment.