宝兰高铁天水北山滑坡群地质选线研究与工程实例

甘肃省天水市地处西秦岭北麓向陇西黄土梁峁过渡的低山丘陵区,区内黄土滑坡分布广、发育密集、危害程度高,尤其是耤河北岸的天水北山滑坡群,严重制约宝兰高速铁路线路方案的选择。平面外绕天水市区及北山滑坡群会使得线路加长和投资增大,而采用隧道内设Ⅴ形纵坡下穿耤河宽谷区及北山黄土滑坡群,既绕避了滑坡群又解决了外绕方案投资大的问题,一举两得。勘察设计中通过分层抽水试验确定了隧道埋深,优化隧道凹坡段最低点的位置及高程;通过滑坡推力检算确定隧道拱顶基岩安全厚度,确保隧道施工及运营安全;同时设计中还采用双层全包防水措施,避免了水土流失造成的地面沉陷。

Study and Engineering Example of Geological Route Selection of Tianshui Beishan Landslide Group in Baoji-Lanzhou High-speed Railway

Tianshui City of Gansu Province is located in the low hilly area of the transition from the northern foot of the Western Qinling Mountains to the loess ridge region in Long-xi.The loess landslides in the area are widely distributed,developed intensively and harmful.Especially,the Tianshui Beishan landslides on the Northern bank of Xi-he river seriously restrict the selection of Baolan high-speed railway route scheme.The scheme of out-of-plane bypassing Tianshui urban area and Beishan landslide group will lengthen the line and increase the investment.The tunnel passes through the Xihe River wide valley area and the Beishan landslide group in the form of a V-shaped longitudinal slope can not only avoid the landslide group but also solve the problem of large investment in the scheme of out-of-plane bypassing.In the investigation and design,the depth of tunnel is determined by stratified pumping test,and the lowest position and elevation of concave slope section are optimized;the safety thickness of tunnel vault bedrock is determined by landslide thrust calculation to ensure the safety of tunnel construction and operation.Meanwhile,the double-layer full-enclosure waterproofing measures are adopted in the design to avoid ground subsidence caused by soil erosion.