西宁至成都铁路弱胶结地层结构特征及水稳性评价研究

西宁至成都铁路拉脊山越岭段南、北麓广泛分布第三系、白垩系含水弱胶结地层,研究地层结构、评价其水稳性成为勘察阶段需要解决的难点。通过系列地表调查、钻探、颗粒分析、黏土矿物含量测定、现场浸水试验等,在考虑地层赋水特性下,对各套地层岩性进行工程水稳性综合评价研究。研究表明:第三系贵德组、白垩系民和组砂、砾岩属弱胶结,黏粒含量以伊/蒙混层为主,水稳性极差,建议线路尽量绕避;西宁盆地、化隆盆地中心均具备形成承压水的条件,建议线路选择尽量走行于盆地边缘,降低承压水头高度或绕避承压水对隧道工程的影响。

Study on the Structural Characteristics and Water Stability of the Weakly Cemented Strata in Xi'ning-Chengdu Railway

Wide distribution of weakly cemented stratigraphies of Tertiary and Cretaceous has been discovered in the southern and northern slopes of La Ridge Mountain where the Xining-Chengdu Railway is located.Through a series of surface investigation,drilling,granulometric analysis,clay mineral testing and field submerging test,detailed study and comprehensive evaluation on the water stability of the Tertiary and Cretaceous strata are conducted with the consideration of the strata water-bearing capability.The study reveals that the cementations of the sandstone and conglomerate strata of the Guide formation of Tertiary and the Minhe formation of Cretaceous are weak,and the clay minerals in these layers are mainly interlayed illite/smectite with extremely poor water stability.Thus,passing round these areas as much as possible are recommended in the route design.As confined water is well developed in the centers of the Xining and Hualong Basins,it is suggested that the line should be possibly passing along the edge of the basin so as to reduce the height of the confined water head or avoid its influence on the tunnel project.