Shallow tunneling in Bimrocks

Shallow tunneling within block-in-matrix rocks (Bimrocks) poses considerable geotechnical challenges due to their varied composition and unpredictable mechanical properties. This thesis explores the behavior of shallow tunnels situated in bimrocks, with a particular emphasis on how the Volumetric Block Proportion (VBP) influences tunnel stability and surface displacement. A detailed numerical analysis was performed utilizing RS2 modeling, which examined different VBP scenarios (25%, 40%, 55%) to evaluate deformation characteristics. The research incorporates stochastic modeling techniques to replicate the random distribution of rock blocks, thereby providing an accurate depiction of bimrock formations. The findings demonstrate that an increase in VBP contributes to enhanced tunnel stability by mitigating surface settlement and deformation, with a notable 62.16% reduction in vertical displacement as VBP escalates from 0% to 55%. Conversely, the Von Mises stress exhibits an upward trend with higher VBP levels, attributed to the redistribution of stress around rigid blocks. The research identifies 40% VBP as the optimal point for achieving maximum shear strain, where stress concentration and deformation are most significant. These results underscore the necessity of accounting for bimrock heterogeneity in geotechnical design, especially in the context of urban tunneling initiatives. Future investigations should focus on aspects such as block size distribution, anisotropy, and the effects of dynamic loading to further refine predictive models and advance tunneling practices in intricate geological environments.