Abstract:

Analysis is made on the causes for the ground surface collapse, large deformation of primary reinforcement structure, excessive crown settlement and horizontal convergence of tunnel in poor geological sections in loess, with a large crosssection tunnel in loess on LanzhouChongqing railway as an example. Countermeasures, including ground consolidation by installing jet grouting piles from the ground surface, advance grouting executed in tunnel and improving the strength of the primary reinforcement structure, are recommended on basis of the geological conditions in the ground surface collapse section and numerical simulation results. The paper can be served as reference for similar projects in the future.

Key words: loess tunnel, ground surface collapse, numerical simulation, monitoring