On October 3, the cutterhead of the "Dayu · Xuedun" TBM for the Lesotho Polihali Water Transfer Tunnel Construction Project was successfully lifted into place and precisely docked with the front shield, marking that the assembly of the project's second TBM has officially entered a new stage and laying a solid foundation for the successful completion of equipment assembly and the subsequent start of tunnel excavation.

As one of the project's core tunneling machines, this TBM has a total length of 325 meters, a total weight of approximately 1,200 tons, and an excavation diameter of 5.38 meters. It is responsible for tunneling from Polihali toward Katse. Its core component, the cutterhead, weighs 65 tons and is the single heaviest component of the TBM. To meet the project's requirement for ultra-long-distance tunneling on the order of 20 kilometers, the cutterhead adopts a heavy-duty hard-rock integral forging process, with high-strength chromium carbide alloy material applied to its surface. At the same time, structural optimization and thickening reinforcement were carried out on key parts such as the face plate, rib plates, and flange connection plates, greatly improving structural strength and toughness.

Since the start of main unit assembly for this TBM, the project team has directly confronted multiple challenges, including heavy rain, strong winds, and cross-operation at the working face. By refining the assembly plan and clarifying daily task milestones, the team achieved dynamic allocation of personnel, materials, and machinery resources and optimized construction organization. The team strictly complied with safety regulations and conducted comprehensive inspections of lifting operations, work at height, hot work, and other processes. It established and improved a quality control mechanism and implemented the "three-inspection system" of self-inspection, mutual inspection, and specialized inspection. Specialized work instructions and dedicated briefing documents were prepared for major processes, ensuring the cutterhead installation task was completed on schedule through refined management. This cutterhead assembly took 18 days in total, 7 days less than the first TBM cutterhead assembly, representing a substantial improvement in efficiency.

At present, main unit assembly of the "Dayu · Xuedun" TBM has exceeded 80%. Next, the project department will begin assembly of the upper segments of the inner and outer telescopic shields, the upper segment of the shield tail, and the connecting bridge, making every effort to ensure the smooth realization of the milestone target for launching excavation of the inlet TBM.

Installation of the "Dayu · Xuedun" TBM cutterhead completed