Shear Slip Deformation Mechanism and Model Construction of Gently Inclined Rock Layer

ABSTRACT

Tunnel construction in gently inclined layered soft rock strata often encounters challenging asymmetric shear slip deformation. However, the quantitative influence of rock layer dip angle on this asymmetry, especially under high in situ stress, is not fully understood. This study integrates theoretical analysis and three‐dimensional numerical simulation to investigate the shear slip mechanism. A mechanical model considering dip angle variation was developed to derive critical slip conditions based on the Mohr‐Coulomb criterion. Using finite element software Midas GTS NX, a series of models with dip angles ranging from 0° to 40° were simulated under a high lateral stress coefficient ( λ  = 1.2). Key findings reveal that: as the dip angle increases from 0° to 40°, vault settlement decreases by 27.0% while invert uplift increases by 23.1%, and the plastic zone area expands by 43.6%. The in situ stress ratio significantly affects stability; increasing it from 1.0 to 2.2 reduces the critical slip angle from 20.8° to 11.2°. The deformation exhibits pronounced asymmetry, for example, the displacement of the right sidewall can be 35.4% greater than the left. This study quantitatively elucidates the coupled control effect of the dip angle and the ground stress ratio on deformation asymmetry and proposes an engineering risk criterion based on the critical slip angle. The study provides a theoretical basis for asymmetric support design in such tunnels, highlighting the need for dip angle and stress‐dependent risk control measures to enhance construction safety.