关键词: 川藏铁路隧道, 高海拔斜井, 高悬洞口, 零刷坡, 安全进洞, 综合施工

Abstract:  The construction of Longbagou inclined shaft in SichuanTibet railway faces the problems of highhanging portal, narrow site, broken surrounding rock, fragile ecology, alpine cold and hypoxia. In order to solve the above problems and ensure green, safe, and efficient construction of the project, some measures have been adopted during construction. Firstly, reasonable planning of the cave site, construction with slurry stone and gravity retaining wall, backfilling wall back and other measures are used, which not only protect the ecological water source but also overcome the problem of narrow construction work site. Then, the active and passive protection network is applied on the roof of the cave, pipe roof and the guide wall to move the cave entrance ahead, and the elevated concrete retaining wall is constructed at the foot of the cave entrance slope. The above measures are adopted to ensure the stability of the elevation slope of the cave entrance, forming the technology of "zero brush slope (without slope cutting) into the cave, support first and then open the cave." Finally, the microbench excavation method in the cave achieves rapid closure of the primary support structure into a ring, and effectively controls the deformation of the surrounding rock. At the same time, the warming and antifreezing measures such as the warming shed are adopted to, guarantee the construction quality of the concrete of support structure. The above tunnel construction system solves the problem of highhanging tunnel entry construction in plateau area and provides reference for the subsequent construction of similar projects.