Impact Force of Boulders Conveyed in Debris Flows on Bridge Piers and Collision Protection Measures

Authors

  • Quancai Wang Key laboratory of Mountain Hazards and Earth Surface Process, Chinese Academy of Sciences, Chengdu
  • Jian Chen Key laboratory of Mountain Hazards and Earth Surface Process, Chinese Academy of Sciences, Chengdu
  • Hao Wang School of Civil Engineering and Architecture, Henan University, Kaifeng
  • Qunli Zhang School of Water Resources and Environmental Engineering, East China University of Technology, Nanchang

DOI:

https://doi.org/10.15273/ijge.2016.02.008

Keywords:

debris flow, impact force, boulders transport, bridge pier, energy dissipation

Abstract

It is quite common in highway engineering that building a bridge across a debris flow gully to prevent roadbed from damage by strike of debris flows. As bridges are designed with the purpose to protect their piers against debris flows, it is crucially important for engineers to determine the magnitude of the Impact Force Exerted by Boulders Transported (IFEBT) in rush torrents. In view of the theory of energy conservation, a formula is introduced in this paper to calculate the IFEBT with appreciable improvement compared to the commonly used equations, in which only the two types of structures (cantilever and simply supported) are taken into account in modelling. The Thornton elastoplastic contact criterion is included in the formula in consideration of buffer effect of two-phase debris flow on bridge piers and dynamic responses of bridge upper-structure. Comparisons on calculation accuracy are elaborately made between our improved formula and previous methods in a case study of Den Jigou Bridge. It is found that according to our proposed method the values of IFEBT obtained in circumstances of varied velocity and boulders sizes are lower than the ones calculated by previous methods. Providing the depth of debris flow body in the two-phase condition is up to 2.4 cm, there is a considerable decrease of 21% in the value of IFEBT. In the meantime, a decrease of 1.4% in the IFEBT value is attained in consideration of the inertia force of the bridge‘s upper-structure. In addition, it is feasible to dissipate impact energy of IFEBT when low elasticity modulus and high decrement material are used in practical engineering.

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Issue

Vol. 2 No. 2 (2016)

Section

Technical Notes

License

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