There are multiple hazard inducers brought about by geological conditions and man-made conditions during the construction of soft rock tunnels in difficult and dangerous mountainous areas, all of which have result in various challenges for the builders. Based on the Jiuzhaigou-Mianyang Expressway (JME), located on the eastern edge of the Qinghai-Tibet Plateau and the northwestern edge of the Sichuan Basin, many on-site investigations and monitorings of surrounding rock pressure and structural mechanical behavior have been conducted on the soft rock tunnels with different hazard inducers, including layered rock tunnels, tunnels strongly affected by underground water and rainwater, tunnels that cross fault fracture zones, and twin tunnels with small clear distance. The results show that the failure characteristics and mechanical behavior of structures are different for different disaster inducers. Layered rock mass leads to asymmetry of structural failure and mechanical behavior; abundant groundwater and a complete rainfall runoff system reduce the self-bearing capacity of surrounding rock; tunnel failure and structural stress through fault zones are generally concentrated at the vault and spandrels with poor stability; the approaching excavation with small clear distance will cause secondary disturbance to the middle rock column, resulting in a prominent decrease in the structural stability of the middle rock column, which may seriously lead to collapse. In addition, the secondary lining of these tunnels gradually becomes the main load-bearing structure during the pressure release of the surrounding rock.

在困难险险山区软岩隧道施工过程中，地质条件和人为条件带来的致灾因素有很多，给施工人员带来了各种挑战。以位于青藏高原东缘、四川盆地西北缘的九绵高速公路（JME）为依托，开展了多项围岩压力和结构力学行为现场调查监测。不同致险因素的软岩隧道，包括层状岩石隧道、受地下水和雨水影响较大的隧道、穿越断层断裂带的隧道、净距较小的双隧道等。结果表明，不同的灾害诱发因素，结构的破坏特征和力学行为是不同的。层状岩体导致结构破坏和力学行为的不对称；丰富的地下水和完整的降雨径流系统降低了围岩的自承能力；隧道破坏和穿越断裂带的结构应力一般集中在拱顶和拱肩处，稳定性较差；近距离开挖对中部岩柱造成二次扰动，导致中部岩柱结构稳定性显着下降，严重可能导致塌方。此外，这些隧道的二次衬砌在围岩卸压过程中逐渐成为主要的承重结构。