156 4. MINING-SPECIFIC TBM ENGINEERING AND ADAPTATION While the structural advantages of continuous excavation are conceptually evident, their applicability in underground mining depends on the ability to address mining-specific boundary conditions. These include steep gradients, variable geology with fault zones and water-bearing formations, restricted underground logistics, and interface requirements with conventional mining fleets. Engineering adaptations for mechanized tunnelling in rock are documented in international guidelines (ITA Working Group 3, 2019). Successful TBM implementation in mining therefore requires targeted engineering adaptation rather than direct transfer from civil infrastructure tunnelling. Previous studies have highlighted both the challenges and opportunities of TBM deployment in mining environments (Zheng et al., 2016). 4.1 Alignment, Gradient Capability, and Transferable Experience Underground mining access and infrastructure drives frequently involve inclined alignments, restricted logistics, and variable geological conditions. The technical feasibility of mechanized excavation under steep gradients has been demonstrated in recently completed hydropower projects executed with Herrenknecht TBMs. The Ritom inclined tunnel in Switzerland was successfully excavated at an inclination of approximately 42° (approximately 90% gradient) with a tunnel diameter of 3.2 m under complex geological conditions. Similarly, the Limburg hydropower project in Austria and the Limmern hydropower project in Switzerland involved TBM excavation at comparable gradients with diameters of approximately 5.8 m and 5.2 m, respectively. These projects were completed under challenging boundary conditions, including faulted zones, water-bearing formations, and constrained underground logistics.
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