The construction of tunnels through mountainous regions is fraught with risks, particularly the reactivation of old landslide bodies, which poses significant threats to transportation safety. A recent study conducted on the Walibie Tunnel (WLBT) along the Shangri-La to Lijiang expressway has unveiled the complex interaction between tunnels and landslides, highlighting key deformation characteristics and mechanisms of failure.
Utilizing methods such as engineering geological investigation, slope deformation monitoring, and numerical simulations, the researchers found two unstable slopes above the tunnel, including new active landslides. Analysis confirmed the presence of shallow and deep creeping deformation zones within the landslide area. Notably, they determined the failure mode of the tunnel was primarily due to longitudinal tensile fractures, which arose from significant tensile forces exerted as the unstable slope underwent continuous opening and expansion.
The need for detailed investigations stems from the alarming trend of landslide-related incidents during tunnel construction. Historical records reveal catastrophic events, including the collapse of the Yezhuping Tunnel after rockfalls and water seepage, as well as severe structural failures on the Yibin-Zhaotong expressway tunnel due to rainfall. Such incidents underline the necessity of establishing preventative measures and comprehensive evaluations of slope stability during tunnel projects.
According to the study, the unstable slopes corresponding to the Walibie Tunnel were characterized by steep gradients and varied geological formations indicative of complex structural movements associated with the Tibetan Plateau. The tunnel’s construction path traversed older landslide deposits, indicating the necessity for constant monitoring and analysis, particularly as geological conditions contribute to increased stability risks.
Field investigations identified distinct features of both old and new landslide deposits at the WLBT, with past events indicating prolonged stability followed by sudden reactivations under certain conditions, such as heavy rainfall and seismic activity. Deformation characteristics of the sloping terrain suggest stable states can unexpectedly shift, demanding vigilance and adaptive engineering strategies to mitigate risks.
Through numerical simulations, researchers were able to model the anticipated stresses and deformation arising from tunnel construction. The results decisively indicated areas where tensile fractures occurred, often coinciding with transitions between stable and unstable geological zones. Such simulations complement field observations, providing substantial data for future projects and governing safety regulations.
The study not only identifies damaging mechanisms associated with the interaction between tunnels and landslides, but also provides engineering insights relevant for future infrastructure projects. Proper monitoring and management strategies are required to avoid the pitfalls of prior tunnel constructions affected by landslides.
Overall, this comprehensive inquiry offers valuable references for tunneling operations intersecting with landslide terrains, enhancing knowledge for engineering professionals engaged with tunnel safety assessments. Continuous research and development are necessary to establish effective interventions for managing the challenges posed by dynamic geological features, thereby advancing safer construction practices across vulnerable terrains.