Stability analysis of surrounding rock of unlined highway tunnel in Chongqing

Taking the Daxihe unlined tunnel located at Fuling-to-Pengshui section of 319 federal highway partly in Three Gorges Reservoir Region as project background and choosing its typical sections, numerical analysis for the stability of surrounding rock, based on coupled fluid-solid theorem, was done with Fast Lagrangian Analysis of Continua in three-dimension(FLAC3D). Meanwhile, effects of multiple factors such as unsymmetrical pressure, rock mass weathering degree, change of groundwater tables etc on the stability of surrounding rock were studied when considering fluid-solid coupled effect, resulting in obtainment of principal stresses, placements, plastic zones and pore water pressure distribution of the unlined tunnel under a variety of conditions during its open for trial service. The achieved results are expected to be applied successfully to guidance of the unlined tunnel disease treatment. Furthermore, the study results can also provide a theoretical basis for the disease management of similar tunnels containing water-rich strata.