Progressive deformation and post-failure residual displacement of the 16 October 2025 Tongren loess landslide, Qinghai, China: insights for long-term extra-high voltage transmission line monitoring
摘要
The transition zone between the Qinghai-Tibet Plateau and the Loess Plateau is characterized by intense terrain incision. In recent years, climate change has led to concentrated seasonal rainfall, causing slopes to exhibit deformation characteristics where slow creep coexists with episodic acceleration. Once such deformation affects critical infrastructure like transmission lines, it can easily trigger cascading risks, including tower collapse, trip-outs, and power outages. However, there is still a lack of systematic analysis using multi-scale joint monitoring regarding the long-term progressive evolution process and post-disaster residual displacement of these landslides. On October 16, 2025, a large-scale loess landslide occurred in Nianduhu Township, Tongren City, Qinghai Province, with a volume of approximately 1.2 × 107m3. This event caused varying degrees of damage to four extra-high voltage (EHV) transmission towers and triggered local power supply interruptions. This study reconstructed the full-process deformation evolution trajectory of the landslide before and after failure through field geological surveys, post-disaster Ground-Based Synthetic Aperture Radar (GB-SAR) emergency monitoring (Oct. 21, 2025–Oct. 29, 2025), and SBAS-InSAR long-time series inversion (2019–2025). InSAR results indicate that the landslide underwent a progressive deformation accumulation process lasting several years before failure, with a maximum cumulative displacement of − 192.9 mm and a maximum annual average displacement rate of − 28.6 mm/year. The landslide exhibited long-term creep behavior prior to failure. Post-disaster GB-SAR emergency monitoring further confirmed that the landslide remained in a state of continuous slow displacement after overall failure. The maximum cumulative displacement within 8 days was − 13.58 mm. The main deformation zone was concentrated in the middle of the landslide body, spatially coinciding highly with the landslide cracks and terrace steps on the landslide surface identified in the field. Notably, the landslide was macroscopically still in a steady creeping stage during the operation of the transmission lines, highlighting the critical necessity for long-term dynamic monitoring of linear infrastructure during the operation period. This study provides a case reference and practical basis for the early identification of landslide hazards and post-disaster emergency response for transmission corridors in alpine complex mountainous areas.