Abstract: Squeezing deformation of soft rock tunnels in layered biased strata is typically large and uneven. Therefore, a novel yielding element based on a reserved deformable angle is proposed. A three-dimensional detailed numerical model is built to analyze the bearing characteristics and the support effect of the yielding element under bias loading. To validate the feasibility of the model, it is applied in the formation of the Ganzhuang tunnel of the China-Laos railway. The research results show the following: (1) The deformation in the tunnel support under bias loading is dominated by bending deformation. The traditional yielding element is prone to tensile damage under the action of the bending moment. The yielding element with the reserved deformable angle can effectively release the bending moment of the steel arch and adapt to larger bending deformation. (2) Under bias loading, the overall stress level of the steel arch with the yielding element is significantly reduced, and the bearing capacity of the arch meets the strength requirements. (3) The field application shows that after installation of the novel yield element, tunnel deformation is controlled within the permissible range after 18 days of excavation; the stress concentration of the primary support is less pronounced, and the steel arch is no longer damaged by bending.

Key words:  , squeezing soft rock tunnels, bedding biased strata, yielding support, reserved deformable angle