The Dingqing landslide occurred on June 1, 2025, in Dingqing County, Changdu City, Tibet Autonomous Region, China at an elevation exceeding 5,000 m above sea level (Figure 1a). This catastrophic event involved the rapid failure of approximately 4.27×10⁶ m³ of rock and soil, which traveled 1011 m horizontally and formed a landslide dam. This disastrous landslide incident resulted in the death of 3 people and the disappearance of 7 others.
The landslide initiated as a bedding-parallel rockslide in a steeply dipping sedimentary sequence. Field observations showed that pronounced bedding planes acted as key failure surfaces, weakened over time by freeze–thaw cycles amid regional warming and wetting. In the weeks before failure, sustained rainfall infiltrated these planes, raising pore pressure and reducing shear strength, which triggered sudden detachment. The mass accelerated down a narrow gully and, upon impact, transferred high kinetic energy to the saturated, weathered sand below. This caused instantaneous strength loss, creating a liquefied basal layer that greatly enhanced mobility–carrying even large boulders far downstream. The flow entrained colluvium mid-gully, increasing volume and momentum, before rapidly decelerating and depositing as a coarse, matrix-supported dam at the outlet (Figure 1b, c).
To investigate subsurface water distribution at the Dingqing landslide, electrical resistivity tomography revealed a continuous low-resistivity zone along the gully, indicating a pre-existing saturated weathered sand layer. Undrained ring shear tests showed that saturation and impact loading cause significant strength loss and particle crushing, enhancing long-runout mobility and forming a low-permeability sliding zone. These results highlight the dual role of crushable, saturated sand in enabling both extensive transport and hazardous landslide-dam formation.

landslide,ring shear test