Multi-period formation and possible high-position hazards of Chada gully deposits on the eastern margin of Tibetan Plateau

High-position rockslides on Tibetan Plateau are usually characterized by multiple in-situ events and multi-period movement. Better understanding on the evolution process of high-position rockslide deposits can help to predict its development trend in the future. In this paper, taking the Chada high-position rockslide-debris avalanche as an example, a series of technical methods, including field investigation, drilling, remote sensing, isotopic dating and engineering geological analogy, are adopted to study the formation and evolution of the Chada gully de-posits, and analyze the potential instability range of the jointed rock mass on the slope top. In view of the possible secondary hazards that may be induced by further movement of the top rock masses, the DAN3D software is adopted to simulate the dynamic processes and study the effects on the planning and construction of a railway station near the slope toe. The results show that the formation and evolution of the gully deposits can be divided into 4 periods as follows: 1) At around 43.5 ka BP ago, it was in a period of glacial deposition char-acterized by moraine deposits. 2) At around 17.5 ka BP, an earthquake induced a rockslide-debris avalanche in the gully. 3) At about 1.0 ka BP, an ice-rock avalanche occurred and formed a layer of purple-reddish boulders with a small thickness. 4) In modern times, during which some small-scale rock collapses were triggered by far -field earthquakes. The results also show that, no matter whether the entrainment effect is considered, the pre-dicted rockslide-debris avalanche deposits cannot fully reach the gully outlet. When the entrainment effect is considered, only a small amount of debris or boulders will roll down and reach the proposed railway station site. Based on the simulation results, some monitoring and protective measures are proposed accordingly.