襄渝铁路新建二线马鞍山隧道进口滑坡分析

研究目的:提出软质岩、极软岩地段勘察、选线时应注意的工程地质问题,指出隧道洞口选线时应避免的位置。研究方法:通过分析滑坡形成的原因及滑坡性质,提出治理措施。研究结果:提出软质岩、极软岩地段铁路选线应注意的工程地质问题。研究结论:存在顺层或不利结构面时,工程施工应自上而下分段进行,严禁对坡体下部进行大面积坡脚开挖,必要时应进行稳定性检算和分析论证,并尽量避开雨季施工;对于路堑两侧基岩性质相差较大或路堑、隧道段存在极软岩的情况,开挖时应进行必要支挡工程并进行边坡监测;路堑两侧土层较厚时,应先进行支挡工程,并加强对两侧边坡的监测;铁路选线时应避开两侧边坡有较厚土层或两侧岩性相差较大的沟槽;隧道洞口尽量远离沟槽,并选择基岩出露良好、无不良地质处;对于路堑边坡,在勘察阶段应调查至两侧的坡顶及坡底,必要时应翻过山顶。对于路堑边坡应布置足够钻孔,必要时可离线路较远。对于两侧岩性差别较大,存在顺层地段、尤其是沟槽的情况,在设计时应引起注意。

Analyses of Landslide at Ma′anshan Tunnel Entrance on the Second Line of Xiangfan-Chongqing Railway

Research purposes: The issues on engineering geology that should be pay attention to in the course of survey and alignment of the track in soft and softer rock foundation section are presented and the places in which the tunnel entrance should not be located when doing alignment are pointed out.Research methods:Through making analyses of the causes and features of landslide,the treatment measures are proposed.Research results:The issues on engineering geology that should be pay attention to in the course of survey and alignment of the track in soft and softer rock foundation section are presented.Research conclusions:At the bedding area or unfavourable structural surface,the construction should be done by section from up to down and the excavation at the base of slope by large scale is not allowed.If necessary,the calculation,analysis and verification of the stability should done and the construction should be done except in rainy season.When the excavation is done at the embankment and tunnel with large different lithology on the both side foundation or softer rock,the support and shelter facilities and monitoring for slope are needed.When the soil on both sides of embankment is thick,the support and shelter facilities should be prepared first and the monitoring should be done for the slopes on both sides.The railway line should avoid the side slopes with thick soil and ditches with large different lithology.The tunnel portal should be far away from ditches and located at the place with good foundation rock and without unfavourable geological condition.The surveys should be made for the slope top and bottom of side slope during period of survey.The enough holes should be drilled for the side slope of embankment and the side slope should be far away from the track if necessary.In the course of design,the attention should be paid to bedding area with large different lithology on both sides,especially to ditches.