Risk regulation of debris-flow damming and back-silting amidst bridge clearance limits and retention-drainage coordination
LIANG Binqi1, YANG Dongxu1, 2*, ZONG Xin1, WAN Fangkai1, ZHANG Wenwen1, LU Shuai3, LIU Yulin4, WANG Dongpo2
(1. College of Environment and Civil Engineering, Chengdu University of Technology, Chengdu, Sichuan 610059, China; 2. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu, Sichuan 610059, China; 3. Sichuan Geological Environment Survey and Research Center, Chengdu, Sichuan 610081, China; 4. State Key Laboratory of Intelligent Geotechnics and Tunnelling, Southwest Jiaotong University, Chengdu, Sichuan 610031, China)
Abstract：When mountain railway bridges traverse debris-flow gullies characterized by “tributary stronger than main river” dynamics, they face not only direct impact risks during normal flow but also the potential for burial due to backwater sedimentation caused by main river blockage. Existing design standards for bridge heights rarely account for this latter factor. To quantitatively assess the real-time sediment depth at the bridge girder and its implications under blockage-induced backwater conditions, this study employs a case study of a railway bridge crossing debris-flow gully Z on a major trunk line in western China. Given certain height restrictions, a depth-integrated continuum mechanics model was utilized. Using Massflow, the entire dynamic process—including debris-flow outflow, river blockage, and backwater sedimentation—was simulated both before and after the construction of a check dam within the gully. From this, the critical storage capacity and optimal dam height were determined. The results indicate that: (1) Prior to dam construction, backwater sedimentation following blockage reached 10.93 m, exceeding the bridge clearance limit of 6.65 m. (2) Using the clearance limit as the post-regulation control target for sediment depth, the critical storage capacity of the check dam was calculated to be 6.08×104 m³ based on the necessary reduction in total outflow. The optimal dam height was subsequently established at 6 m according to the capacity-height relationship. (3) After regulation by the check dam, the maximum backwater sediment depth at the bridge site was reduced to 6.16 m, satisfying the clearance requirement. (4) To address the dual objectives of peak flow reduction and outflow volume regulation, a configuration of two beam-type slit dams was identified as the optimal spatial arrangement. Numerical simulations confirmed that their regulatory effectiveness corresponded with the design objectives. This research offers theoretical methods and design references for enhancing the disaster resilience of linear transportation infrastructure traversing debris-flow hazards in high-mountain gorge regions.
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2026, Vol. 45 
