工程简介拉脊山隧道平行导洞扩建主洞属于青海省西久公路改造工程,穿越拉脊山地段,海拔3250m,隧道长5580m,净宽10.25m,净高5m。设计地质以微弱风化石英闪长岩为主,围岩破碎,地质变化快,经常穿越小型断裂带,设计围岩以III级为主,局部为IV级、V级围岩,V级围岩为较大断层和强风化石英闪长岩区。地下水以基岩裂隙水为主, Brief introduction of the project The main tunnel of Lajishan tunnel parallel guide expansion belongs to the reconstruction project of Xijiu Highway in Qinghai Province. It passes through Lajishan section at an altitude of 3250m. The tunnel is 5580m long with a net width of 10.25m and a net height of 5m. The design geology is mainly faintly weathered quartz diorite, the surrounding rock is fragmented and the geological change is rapid, and often crosses the small fault zone. The design grade of the surrounding rock is dominated by Class III, with the local grade IV and V grade of surrounding rock, and the grade V surrounding rock is Larger faults and strongly weathered quartz diorite zones. Groundwater to bedrock fissure water-based,