Abstract
The "9.5" Luding earthquake induced extensive coseismic geological hazards in the Hailuogou Scenic Area at the epicenter, with 50% of the scenic area roads located within the seismic intensity IX (9-degree) impact zone, resulting in severe road damage and complete loss of traffic capacity. To investigate the development patterns of geological hazards along the Hailuogou Scenic Area roads and post-disaster reconstruction strategies, this study comprehensively employed multi-dimensional and three-dimensional approaches including remote sensing, LiDAR, UAV oblique photography, ground surveys, geological investigations, and automatic structural plane identification to conduct systematic research on geological hazards in the study area from regional to site-specific scales. The results indicate that: (1) A total of 503 coseismic geological hazards developed in the study area, covering a total area of 3.75×106 m2, primarily distributed on the right side of the road section K10~K15, within the elevation range of 1900 m~2900 m, and on slopes of 30°~60°. (2) The distribution patterns of geological hazard development are mainly controlled by geomorphology, lithology, epicentral distance, and river factors, with weak spatial coupling to the main fault. (3) The instability modes of geological hazards can be classified into three types: high-elevation collapse, accumulation landslide, and shallow slope surface collapse, characterized by large quantities, linear distribution, and varying scales. Among these, high-elevation collapses mainly occur in hard rock areas such as granite and dolomite, while landslides and shallow collapses primarily occur in soft rock regions like schist and slate, as well as on the banks of glaciofluvial deposits of the Moxi Terrace. (4) The deeply incised canyon terrain and high peak ground acceleration (PGA) generate seismic amplification effects in hard rock slope break zones, resulting in massive high-elevation collapses; under strong seismic action, the overall instability of thick accumulation landslides exhibits time-lag phenomena. (5) Based on the development and evolution patterns of geological hazards, the post-disaster reconstruction project for the Hailuogou Scenic Area roads adopted the concept of "hazard mitigation route selection," adhering to the principle of "avoiding major hazards while treating minor ones," utilizing 4 tunnels to bypass high-elevation collapses and 13 bridges to cross potential debris flow gullies, combined with in-situ treatment measures for earthquake-damaged slopes such as grouted steel pipes and anchor bolt frame beams, to enhance the disaster prevention and resistance capacity of the scenic area roads. The research findings systematically reveal the development patterns of geological hazards in the Luding earthquake epicentral region, and the proposed post-disaster reconstruction strategies have been comprehensively applied in engineering practice, providing important support for hazard identification, assessment, and road post-disaster reconstruction work in strong earthquake zones.
Full Text
Preamble
Development Patterns of Geological Hazards and Post-Disaster Reconstruction Strategies for Roads in the Hailuogou Scenic Area at the Epicenter of the Luding Earthquake
Wu Kai¹, Yi Xuebin¹, Fu Xiaodong²,³*, Zhang Lei¹, Kang Jingyu²,³, Yuan Quan¹, Shao Jiang¹
(1. Sichuan Highway Planning, Survey, Design and Research Institute Ltd., Chengdu 610041, China)
Abstract
The "9.5" Luding earthquake triggered extensive coseismic geological hazards throughout the Hailuogou scenic area. Approximately 50% of the scenic area roads were located within the intensity IX (9-degree) seismic influence zone, suffering severe damage that completely eliminated traffic capacity. To investigate the development patterns of these geological hazards and formulate effective post-disaster reconstruction strategies, we conducted a systematic, multi-scale study employing a comprehensive suite of techniques including remote sensing, LiDAR, UAV oblique photogrammetry, ground surveys, geological exploration, and automatic structural plane recognition.
Our findings reveal five key characteristics: (1) The study area developed 503 coseismic geological hazards covering a total area of 3.75×10^6 m², predominantly distributed on the right side of road sections K10–K15, within the elevation range of 1900–2900 m and on slopes between 30°–60°. (2) Hazard distribution patterns were primarily controlled by topographic, lithological, epicentral distance, and riverine factors, exhibiting weak spatial coupling with the main fault. (3) Three distinct failure modes were identified: high-position collapse, deposit landslide, and shallow slope surface collapse. These hazards are characterized by numerous occurrences, linear distribution patterns, and variable scales. High-position collapses predominantly occurred in hard rock formations such as granite and dolomite, whereas landslides and shallow collapses were mainly confined to soft rock zones comprising schist and slate, as well as the banks of Moxi terrace glacial deposits. (4) The combination of deep-cut valley topography and high peak ground acceleration generated significant seismic amplification effects at hard rock slope breaks, resulting in massive high-position collapses. Additionally, thick deposit landslides exhibited delayed failure phenomena under strong seismic shaking. (5) Guided by the principle of "hazard-reduction route selection," the post-disaster reconstruction strategy adopted the approach of "avoiding major hazards while treating minor ones." This involved constructing four tunnels to bypass high-position collapse zones, building thirteen bridges to span potential debris flow channels, and implementing in-situ reinforcement measures such as grouted steel pipe umbrellas and anchor frame beams for seismically damaged slopes, thereby enhancing the overall disaster resistance of the scenic area road network.
These research findings systematically elucidate the development patterns of geological hazards in the Luding earthquake epicentral region. The proposed reconstruction strategies have been comprehensively implemented in engineering practice, providing crucial support for hazard identification, assessment, and road reconstruction in seismically active areas.
Keywords: Luding earthquake; Hailuogou scenic area road; high-position collapse; seismic damage characteristics; development pattern; reconstruction strategy