碎屑流冲击下桩梁组合结构拦挡效果及受力特征研究

以高位泥石流、碎屑流区桩梁组合新型拦挡结构为研究对象, 在总结已有桩梁组合结构的基础上, 运用颗粒流分析仿真程序、通用显示动力分析程序分别对碎屑流冲击下单排、多排桩林及桩梁组合结构拦挡效果、不同位置桩梁组合结构拦挡效果对比模拟以及桩梁组合结构受力特征模拟研究, 探讨了拦挡结构阻挡后碎屑流堆积特征和结构应力传递特征。计算结果表明: 碎屑流中较大粒径颗粒与拦挡结构、两侧沟道边界接触形成的桩-巨石力链拦挡效应可有效阻挡、迟滞后续碎屑流运动, 桩梁组合结构桩-巨石力链拦挡效应最佳; 第一排桩和第二排桩之间改流区进一步抑制了碎屑流速度; 桩梁组合结构在设计布置位置时, 一方面要考虑在碎屑流启动、势动转换过程中尽早抑制碎屑流速度, 另一方面仍需重视库容的设计, 谨防跃顶造成部分碎屑流逃逸, 在上述二者之间选择最优解进行位置布置; 碎屑流巨石冲击桩梁组合结构时, 冲击应力将通过连梁分散传递到后排桩, 连系梁两端连接部分的应力几乎达到屈服强度, 需加强配筋。 

Effectiveness and mechanical characteristics of a pile-beam composite structure in blocking debris flows

The pile-beam composite structure in high-elevation debris flow areas is selected as the research object. Based on characterizing the pile-beam composite structure, the particle-flow simulation analysis program and the explicit dynamic analysis program were used to study comparatively the blocking effects of single-row piles and two-row piles, as well as that of a pile-beam composite structure at different positions. Besides, We simulated the mechanical characteristics of the pile-beam composite structure and discussed debris flow accumulation and structural stress transfer after the blocking. The calculation results show that the blocking effect of the pile-boulder force chain formed by the contact between large-size particles in the debris flow with the blocking structure and side boundaries on both sides of the gully could effectively block and delay the subsequent debris flow movement. The blocking effect of the pile-beam composite structure is the best. Meanwhile, the transition zone between the two-row piles further suppressed the flow velocity. When choosing the position for a pile-beam composite structure, we should consider suppressing the debris flow velocity as early as possible at the beginning and the potential energy-kinetic energy conversion process. Meanwhile, we also need to emphasize the design of the reservoir capacity, beware of the escape of debris flow due to a low-head barrier, and choose the optimal solution for the layout. The impact stress by debris flow boulders will be transmitted to the rear pile through the connecting beams, and the connecting parts at both ends of the beam almost reach the yield strength, which needs reinforcement to strengthen.