高植被覆盖下铁路隧道口危岩落石风险评估

Risk Assessment of Falling Rocks at Tunnel Entrance of High Plant-covered Railway Tunnels

山区铁路选线受地形条件制约,高陡边坡或陡崖地段的隧道洞口常面临危岩落石风险,传统人工调查方法困难,尤其是高植被覆盖地区,受现场条件限制不能完全查明危岩分布,同时常用的落石运动轨迹模拟缺少横向范围控制,存在一定的安全隐患。以某铁路隧道进口工程为研究对象,以机载LiDAR和三维倾斜摄影数据为基础,查明了危岩形成机制及分布特征,利用自主研发的Rockfall Hunter软件分析不同破坏形式的危岩三维运动特征,并给出防护措施建议。研究表明:(1)基于定性分析和定量计算,建立的“数据、方法、意义”三阶段高植被覆盖区危岩落石风险综合评估方案行之有效;(2)利用精细化三维实景模型可准确提取危岩体几何信息,危岩落石发育区数字地表灰度影像表面坎坷不平、具粗糙感,危岩体截面地面点棱角显著、地势陡峭,原生孤石或滚石截面呈凸起状、有明显界限;(3)研究发现可能对工程造成危害的危岩体120处,总体积约15541 m^(3),以倾倒、坠落式破坏为主,局部发生组合式破坏;(4)落石进入隧址区最大速度为17.3 m/s,最大弹跳高度为12.5 m,最大冲击能量超过8000 kJ,建议采用避让、清理、加固等措施。

Railway line selection in mountainous areas is restricted by terrain conditions.Tunnel portals of steep slopes or cliffs often face the risk of falling rocks.Traditional manual investigation methods are difficult,especially in high vegetation-covered areas.The field conditions cannot completely ascertain the distribution of dangerous rocks,and the commonly used simulation of falling rock trajectories lacks lateral range control,which poses certain safety risks.Taking a railway tunnel entrance project as the research object,this paper uses on-board LiDAR and three-dimensional oblique photography data as the basis to ascertain the formation mechanism and distribution characteristics of dangerous rocks,and uses the self-developed Rockfall Hunter software to analyze the three-dimensional motion characteristics of dangerous rocks with different destruction forms,and gives protection measures suggestions.The research shows that(1)the“data,method,and significance”three-stage comprehensive risk assessment scheme for dangerous rocks in high vegetation-covered areas established based on qualitative analysis and quantitative calculation is effective;(2)using a fine-grained three-dimensional real-scene model can accurately extract the geometric information of dangerous rocks;the digital surface gray-scale image of the dangerous rock development area is uneven and rough;the cross-section of the dangerous rock body is sharp and the terrain is steep,the cross-section of the original solitary rock or rolling stone is convex and has obvious boundaries;(3)120 dangerous rocks that may cause harm to the project are found,with a total volume of about 15541 m^(3),mainly destroyed by tipping and falling,and partial combined destruction;(4)The maximum speed of falling rocks entering the tunnel area is 17.3 m/s,the maximum bounce height is 12.5 m,and the maximum impact energy is more than 8000 kJ,and it is recommended to adopt avoidance,cleaning,reinforcement and other measures.