ISSN 1003-8035 CN 11-2852/P

    DEM-FDM耦合方法的碎屑流冲击双柱式桥墩损伤机理研究

    Damage Mechanism of Double-Column Bridge Piers under Debris-Flow Impact Based on DEM-FDM Coupling

      摘要
    • 摘要:
      目的 为揭示碎屑流冲击作用下双柱式桥墩的柱间荷载差异与损伤演化规律，给山区桥梁抗冲击设计提供量化依据。
      方法 本研究采用离散元法(Discrete Element Method, DEM)与有限差分法(Finite Difference Method, FDM)耦合数值模拟方法，通过构建碎屑流-双柱式桥墩耦合冲击试验模型，结合滑槽堆积试验及混凝土单轴压缩试验验证，系统探究了碎屑体粒径和碎屑流体积对桥墩冲击力、损伤及应力演化和分布的影响规律。
      结果 结果表明：碎屑体粒径与体积对双柱式桥墩的冲击作用均具有显著调控作用。随粒径增大，近柱墩峰值冲击力由174 N增至747 N（增幅329%），损伤主要集中于墩柱中下部，而远柱墩因近柱拦挡遮蔽效应响应微弱；随体积增大，近柱峰值冲击力从747 N增至1034 N（增幅38.4%），桥墩损伤由分散分布发展为连片破坏，近柱遮蔽效应逐步弱化。应力场演化呈现从均匀受力到局部应力集中、再到大范围连片破坏的时序特征。
      结论 经验证的DEM-FDM耦合模型可有效模拟碎屑流-双柱式桥墩的动力相互作用过程。碎屑流通过改变粒径调控近远墩柱的冲击动力响应，碎屑流体积主导桥墩的累积损伤规模与分布范围。双柱式桥墩近柱为抗冲击防护的重点构件，远柱响应取决于碎屑流绕流能量的大小，防护设计需重视绕流能量耗散效应。

       

      Abstract:
      Objective This study aims to reveal inter-column load differences and damage-evolution patterns of double-column piers under debris-flow impact and to provide a quantitative basis for impact-resistant design of mountain bridges.
      Methods A coupled numerical simulation method combining the Discrete Element Method (DEM) and Finite Difference Method (FDM) was adopted. A coupled debris-flow-double-column-pier impact model was established and validated using chute deposition tests and concrete uniaxial compression tests. The effects of debris particle size and debris-flow volume on impact force, damage, and stress evolution and distribution in bridge piers were systematically investigated.
      Results The results show that debris particle size and volume both significantly control the impact response of double-column piers. As particle size increases, the peak impact force on the near pier increases from 174 N to 747 N, an increase of 329%. Damage is mainly concentrated in the middle and lower parts of the pier, whereas the far pier responds weakly because of the shielding effect of the near pier. As debris-flow volume increases, the peak impact force on the near pier rises from 747 N to 1034 N, an increase of 38.4%; pier damage evolves from scattered damage to connected failure, and the shielding effect of the near pier gradually weakens. The stress field evolves temporally from uniform loading to local stress concentration and then to large-area connected failure.
      Conclusions The validated coupled DEM-FDM model can effectively simulate the dynamic interaction between debris flow and double-column piers. Debris-flow particle size regulates the impact dynamic response of near and far piers, whereas debris-flow volume controls the scale and distribution of cumulative pier damage. The near pier of a double-column bridge pier is the key component for impact protection, and the far-pier response depends on the magnitude of debris-flow bypass energy. Protective design should therefore emphasize dissipation of bypass-flow energy.

       

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