Full-lifecycle TBM construction in deep steeply inclined water-conveyance shafts: A case study of the Luoning pumped-storage hydropower project

Large-diameter, long-distance, steeply inclined water-conveyance shafts impose coupled challenges in continuous layout, confined-space launching, anti-backsliding control, gravity-based mucking, and terminal recovery. This paper presents a full-lifecycle TBM construction case from the Luoning pumped-storage hydropower project, where a 7.23 m diameter TBM excavated two upward-driven shafts with inclinations of 36.24° and 38.74°. To maintain construction continuity, the conventional two-stage layout was replaced by a single-stage continuous scheme. A curved foundation and stepping launch system with four synchronous hydraulic cylinders enabled staged assembly and controlled alignment adjustment in limited underground space. During excavation and stepping, two X-shaped gripper assemblies and two independent anti-backsliding systems (ABSs) formed a redundant restraint system with sequential load transfer. Gravity-driven muck transport was coupled with six-state image recognition, probability-level multi-model fusion, and 2 s closed-loop water regulation. Terminal recovery adopted staged dismantling, with independent restraint established before ABS were released, followed by TBM transfer and reuse. Based on project-specific reference quantities, eliminating two intermediate caverns was estimated to avoid approximately 24,000 m 3 of additional cavern excavation and approximately 12 months of associated cavern construction. No overall backward sliding was observed during recorded operation. The fusion model achieved a weighted F1 score of 0.92, while cumulative flushing-water consumption decreased from 6.25 to 5.37 m 3 during a 700 s field comparison. After transfer and reconditioning, the same TBM excavated 859.68 m of the No. 2 shaft over 132 calendar days, corresponding to 6.51 m/d. The case provides project-specific field evidence for coordinating the principal stages of steep upward TBM shaft construction.