Countermeasures to treat collapse during the construction of road tunnel in fault zone: a case study from the Yezhuping Tunnel in south Qinling, China

To ensure the safety of the tunnel construction, it is very important to take the appropriate treatment measures after the collapse happened. Especially the tunnel goes through the fault fracture zone. This paper sets forth the process of the collapse that occurred in the Yezhuping Tunnel affected by the fault fracture zone and introduces the treatment for the collapse. The deformation characteristics of the surrounding rock are analyzed according to the monitoring results. Based on the research regarding the effect of the fault on the tunnel by using the general Hoek–Brown failure criterion and the field monitoring results, it is shown that the fault is the main reason for the collapse; it induces the attenuation of the Young modulus and the compressive strength and the enlargement of the plastic zone. The research results have some reference significance for similar projects.