Abstract:

The aeolian sand tunnels in plateau and alpine region are always characterized by fast instability, easy collapse, high deformation rate of primary support, and influenced by regional climate, slow construction progress and short effective construction time are common phenomena. In order to solve the problems of sand leakage, collapse of tunnel roof and deformation control after support completion in aeolian sand tunnel excavation and ensure safe and rapid construction, three advance reinforcement schemes, i.e. horizontal jet grouting pile in tunnel, vertical jet grouting pile on surface and surface grouting, are selected according to hydrology, geology and surrounding environment for aeolian sand section of Eton Brack No. 1 Tunnel on Geku Railway. The economy, construction period and technical difficulty are compared and demonstrated, and the vertical rotary jet grouting pile on the surface is determined and implemented effectively. The results of field implementation and monitoring show that the advance reinforcement of vertical jet grouting pile on the ground surface can effectively prevent sand leakage and cave top collapse, ensure the stability of tunnel working face, realize parallel operation of advance reinforcement and excavation, and achieve the goal of safety, economy and rapid construction.

Key words: plateau alpine region, railway tunnel, aeolian sand, advance reinforcement, scheme comparison and selection