Abstract
On February 8, 2025, an extra-large high-position landslide-debris flow disaster occurred at Jinping Village, Mu'ai Town, Junlian County, Yibin City, Sichuan Province, resulting in significant casualties and property losses. This study systematically investigates the chain-forming mechanism and emergency response effectiveness of this disaster based on field investigation, remote sensing monitoring, engineering geological data, and emergency monitoring data. The research indicates that the landslide occurred in a tectonic erosion middle mountain landform area at the transition zone from the Sichuan Basin to the Yunnan-Guizhou Plateau, featuring typical "L-shaped" high-steep terrain characteristics, with a vertical height difference of 283 m from the source area rear wall to the shear outlet and an average slope gradient of 42.7°. The regional geological structure is complex, situated at the eastern margin of the Sichuan-Yunnan rhombic block and adjacent to the Huayingshan fault zone, where fractured rock mass and soft-hard interbedded structures provided potential sliding surfaces. Winter freeze-thaw cycles under the influence of the "Kunming quasi-stationary front" caused progressive deterioration of the rock mass, while anomalous heavy rainfall exceeding 300 mm since January 2025 served as the direct triggering factor, leading to saturation of the rock-soil mass, a sharp increase in pore water pressure, and a sudden 40–50% reduction in shear strength. The landslide evolution followed a chain process of "fracture development–freeze-thaw deterioration–rainfall infiltration–through-going failure–high-speed movement–debris flow transformation," achieving a peak velocity of 56.29 m/s. The emergency monitoring system, which employed synergistic application of slope radar and rockfall radar, successfully issued early warnings for the secondary collapse on February 12, ensuring the safe evacuation of rescue personnel. This study reveals a compound disaster-causing pattern of "freeze-thaw deterioration + anomalous rainfall" in the Wumeng Mountain area, providing a scientific basis for geological disaster prevention and control in similar regions.
Full Text
Preamble
Title: A Study on the Cascading Formation Mechanism of the High-Position Landslide-Debris Flow Disaster and Its Emergency Monitoring and Early Warning in Junlian, Sichuan
Authors: ZHANG Shishu, ZHAO Xiaoping
Affiliation: PowerChina Chengdu Engineering Corporation Limited, Chengdu 610031, China
Abstract
On February 8, 2025, a catastrophic high-position landslide-debris flow disaster occurred at Jingping Village, Mu'ai Town, Junlian County, Yibin City, Sichuan Province, causing significant casualties and property losses. Based on field investigations, remote sensing monitoring, engineering geological data, and emergency monitoring records, this study systematically investigated the cascading formation mechanism of the disaster and the effectiveness of emergency response measures.
The study reveals that the landslide occurred in a tectonically eroded mid-mountain geomorphic region at the transition zone between the Sichuan Basin and the Yunnan-Guizhou Plateau, characterized by a typical "L-shaped" high-steep terrain. The vertical height difference from the source area's rear wall to the shear outlet measured 283 m, with an average slope gradient of 42.7°. The regional geological structure is complex, located on the eastern margin of the Sichuan-Yunnan rhombic block and adjacent to the Huayingshan fault zone. The fractured rock mass and interbedded soft-hard layer structure provided potential sliding surfaces for the landslide.
Winter freeze-thaw cycles influenced by the "Kunming quasi-stationary front" caused progressive deterioration of the rock mass, while abnormal heavy rainfall exceeding 300 mm since January 2025 served as the direct triggering factor. This rainfall led to saturation of the rock-soil mass, a sharp increase in pore water pressure, and a sudden drop in shear strength by 40–50%. The landslide evolution followed a cascading process of "fissure development–freeze-thaw deterioration–rainfall infiltration–through failure–high-speed movement–debris flow transformation," reaching a peak velocity of 56.29 m/s.
The emergency monitoring system, which employed collaborative application of slope radar and rockfall radar, successfully provided early warning for the secondary collapse on February 12, ensuring the safe evacuation of rescue personnel.
This study reveals a compound disaster pattern of "freeze-thaw deterioration + abnormal rainfall" in the Wumeng Mountain area, providing a scientific basis for geological disaster prevention and control in similar regions.
Keywords: high-position landslide; debris flow; freeze-thaw action; extreme rainfall; monitoring and early warning