Deformation Characteristics and Stability Analysis of Soft-Hard Interbedded Tunnels

The deformation characteristics and patterns of interbedded tunnels with soft and hard strata significantly differ from those of tunnels in homogeneous surrounding rock, posing substantial challenges to tunnel construction. To address this issue, discrete element numerical software was employed for a systematic analysis of the deformation characteristics and patterns of soft-hard interbedded tunnels. The results indicate that the extent of significant deformation in soft-hard interbedded tunnels depends on the positioning of the soft rock layer. When the thickness of the soft rock layer surpasses the hard rock layer, the displacement and deformation area are large. Except for horizontal interbedded tunnels, all show asymmetric deformation characteristics. At the same layer-thickness ratios, there is no obvious linear relationship between the deformation of the arch crown and sidewall and the variation of the rock dip angle. The plastic damage area in the hard rock layer is smaller than that in the soft rock layer, and the main damage form is tensile fracture. However, the damage form in the soft rock layer is relatively complex, with more shear damage mixed with tensile damage. The results can provide valuable references for the design and construction of soft-hard interbedded tunnels.