山区公路高陡边坡引导式柔性缓冲系统的设计方法

为了进一步推广引导式柔性缓冲系统的工程应用，验证其防护性能和可靠性，依托渝黔线高速公路区间内某山区桥梁的高陡边坡落石防护工程，开展了工程设计计算，并对引导式柔性缓冲系统的防护性能进行分析。首先利用无人机航测建立防护区域的三维模型，明确了桥梁结构与边坡的空间位置关系和防护需求；基于危岩体实际特征对5个边坡纵断面开展了落石运动轨迹分析，根据弹跳高度和冲击动能包络值确定防护高度和防护能级指标；初步设计了引导式柔性缓冲系统的部件规格参数，建立了系统的有限元模型，并通过与关键部件试验数据对比验证了数值模型的有效性；基于离散元-有限元耦合算法，分别验算了相同初始动能的单体落石和多体落石2种工况下引导式柔性缓冲系统的内力，对比分析了有无防护时落石灾害对桥梁结构的侵害情况，从而验证了防护效果。计算结果表明：满足设计要求的引导式柔性缓冲系统能够有效抑制落石弹跳高度，从而避免落石侵限和撞击桥梁结构；引导式柔性缓冲系统关键部件内力响应均未超过设计限值，但不同工况下相同部件的内力峰值差异较大，因此，应采用各工况内力包络值进行设计，且关键构件的承载力安全储备系数不应小于1.2；防护全过程的耗能机制主要由系统塑性变形、系统阻尼以及落石与边坡和系统的摩擦碰撞3部分构成，其中塑性变形和摩擦碰撞耗能占主导地位，可分别按40%和60%的比例进行设计；拦截区段和引导区段的设计耗能比例系数可分别按0.7和0.3考虑，各区段中的主要耗能部件均为耗能器和环形网片。在此基础上，提出了基于能量匹配原理的引导式柔性缓冲系统的工程设计方法及流程，并建议了针对不同性能目标的多水准设计策略，以期发挥系统更大的防护潜能。

Design Approach of Guided Flexible Protection System for High and Steep Slope of Mountain Highways

To further promote the engineering application of a guided flexible protection system, as well as validate its effectiveness and reliability, engineering design calculations and performance analyses of the system were conducted based on a high and steep slope rockfall protection project for a mountainous bridge on the Qianyu highway. First, a three-dimensional model of the protection area was established via drone aerial survey, and the spatial position relationship between the bridge structure and the slope, and protection requirements were also clarified. Based on the actual characteristics of the dangerous rock mass, the movement trajectory analysis of the falling rock was carried out on five slope longitudinal sections, and the bounce height and impact kinetic energy envelope values determined the protection height and protection energy level index. A preliminary design was conducted by specifying the configuration of the components. Then, the finite element model of the system was established and its validity was verified by comparison with the test data of the key component. By using the discrete element-finite element coupling algorithm, the internal forces of the system in two cases, involving a single rockfall and multi-body rockfalls with the same initial kinetic energy, were checked. The impact of the rockfall disaster on the bridge structure with and without protection was compared and analyzed to verify the protective effect. The calculation results show that the guided flexible protection system that meets the design requirements can effectively restrain the bounce height of falling rocks, thereby avoiding falling rock intrusion and impact on bridge structures. The internal force response of the key components of the guided flexible protection system does not exceed the design limit, but the peak value of the internal force of the same component under different working conditions varies significantly. Therefore, the internal force envelope value of each case should be used for the design, whereas the reserve coefficient should not be less than 1.2. The energy dissipation mechanism of the entire protection process is mainly composed of the internal energy, damping energy of the system, and the friction between the rockfall and the slope and the system, in which the internal energy as well as the friction energy dissipation are the most dominant approaches so that proportions of 40% and 60% can be accounted for design, respectively. The design energy-dissipating proportional factors for the intercepting stage and guiding stage can be considered as 0.7 and 0.3 respectively, while the essential energy-dissipating components are dissipators and wire-ring net. Furthermore, the design method and procedure of the guided flexible protection system based on the energy allocation principle were proposed, and a design strategy for multiple performance objectives was suggested to realize the potential of the system.