北太行山泥石流沟铁路工程地质选线研究

Study on Engineering Geological Route Selection for Railway Across Debris Flow Gully of North Taihang Mountain

某高速铁路穿越北太行山脉艰险复杂山区,沿线环境敏感区众多,不良地质极发育,为研究铁路穿越麻黄沟泥石流沟选线问题,本文采用遥感、地质调绘、勘探、试验和Flo-2D数值模拟等综合勘察方法查明该沟工程地质条件,评价该沟泥石流易发性及工程适宜特性,评价认为麻黄沟小流域处于地形下切时期且近百年未存在明显泥石流堆积事件,但物源及地形条件具备,在极端降雨条件下具备发生泥石流的条件,该沟属于轻度易发、发展阶段为衰退-停歇期、坡面侵蚀型、水石型、稀性、暴雨型激发的低频沟谷泥石流;采用对比分析的方法研究了隧道和桥梁通过方案的工程风险和工程处理难度,结果表明泥石流发生后,对于隧道方案,可能会对右侧岸坡产生冲击和冲刷,对下穿沟谷段产生揭底作用,风险较高,工程处理难度较大,而对于桥梁上跨方案,位于沟内的桥墩将遭受主沟泥石流的淤埋、冲击和揭底,可通过排导、加强桥墩防护等措施处理,风险可控。结论表明桥梁上跨方案穿过该泥石流沟是比较合理的。

A high-speed railway is proposed to cross the difficult and complex North Taihang Mountains,and there are many sensitive areas along the route and bad geological pole is developed.In order to study the route selection across the Mahuang debris flow gully,the engineering geological conditions of the gully are ascertained by using in-tegrated exploration methods such as remote sensing,geological mapping,exploration,experiment and Flo-2D nu-merical simulation in this paper,and the occurrence probability of debris flow and engineering suitability of the gully are evaluated.The evaluation shows that the Mahuang watershed is in the period of topographic cutting and there is no obvious debris flow accumulation event in the last hundred years,but the source and terrain conditions avail the gully of debris flow under extreme rainfall conditions,it is a low-frequency gully debris flow gully of light proneness and its development stage is recession-resting period,slope erosion type,water-stone type,dilute type and rainstorm type.The engineering risk and difficulty of tunnel and bridge passing schemes are studied by means of comparative analysis,the results show that after the occurrence of debris flow,as for the tunnel scheme,it may have impact and scouring on the right bank slope,and have bottoming effect on the lower penetration gully seg-ment,which is of high risk and difficult to deal with;for the bridge span scheme,the pier located in the gully will suffer from the siltation,impact and the bottom of the main gully debris flow,which can be treated by drainage,strengthening the pier protection measures,and the risk is controllable.The conclusion shows that it is reasonable to cross the debris flow trench with bridge span scheme.