Concrete lining work analysis of mountain railway tunnels in geodynamical active regions

Abstract

Concrete lining work analysis of mountain railway tunnels in geodynamical active regions. Railway tunnel concrete lining stress-strain state located in a geodynamical active mountainous region were discussed in this article. The study aims to assess the external factors influence, such as gravitational and seismic effects, on concrete lining deformation and cracking. The concrete lining work analysis was performed on the Severomuisk railway tunnel section example. The tunnel is located in different soil conditions and has a variety of supporting structures; the work analysis was performed for a site located in weakly fractured granite rocks. To assign the seismic impact level, the adjacent to the tunnel area seismic setting was calculated based on historical data and the area seismic monitoring. It has been established that the occurrence of earthquakes with a magnitude of 7–8 on the MSK-64 scale is expected every 10 years on average, the obe level with a recurrence period of 1 time in 50 years corresponds to an 8.7 points intensity. The tunnel structures’ stress-strain state calculation was performed by the finite element method in the GTS NX program. The analysis takes into account the main tunnel design features, drainage and transport adits, and cross slit. The calculations were performed in a linear-elastic formulation for the main tunnel concrete structures, the cross slit, and the adit’s cast-iron structures. The soil mass is modeled by materials according to the Hawke-Brown strength criterion (Hoek E.; Brown E.T.). It has been established that with an isotropic structure of the enclosing rock mass, tunnel structures resist well the destructive strong earthquakes impact. Crack formation in concrete lining only occurs in the event of a strong design-basis earthquake. At the same time, the various niches presence, cross slit, and other load-carrying structure complex geometry leads to the stress concentrations appearance and, as a consequence, cracks in concrete at lower seismic effects. Crack distribution patterns are consistent with field survey data.