On November 14, the "Pioneer No. 1" composite TBM broke through the rock in the receiving shaft at the large-mileage end of Waziba Station on Chongqing Rail Transit Line 24, marking the successful completion of the left line of the first long-distance, steep-gradient shield tunnel (Waziba Station–Chafu Road Station section) in the first phase of the Line 24 project.

Guo Junyong, commander of the Chongqing Rail Transit Line 24 general contracting department of China Railway Construction, introduced that the Waziba–Chafu section is a single-tube, double-track tunnel, with the left line about 1.7 kilometers long. The longitudinal profile of the section is a "V"-shaped slope with a maximum gradient of 36‰, and the maximum buried depth at the tunnel crown is about 32 meters. The tunneling route mainly passes through backfill areas, where the complex geological conditions tend to cause problems during excavation such as segment uplift, misalignment, water leakage, and low tunneling efficiency.

During construction, the project's shield tunneling team analyzed the trial excavation parameters of the first 100 rings, summarized the excavation performance and tunnel formation effect, and adjusted and optimized personnel and machinery allocation, work efficiency, and materials. At the same time, with the help of advanced electronic monitoring equipment and an intelligent construction site management system, monitoring during construction was strengthened, enabling informatized monitoring throughout the entire construction process and effectively ensuring construction safety.

After the breakthrough of the left line of the Waziba–Chafu section, the "Pioneer No. 1" composite TBM will be disassembled for a comprehensive "health check," with worn cutters and tail brushes replaced, in preparation for shield launching on the Chafu Road Station–Shangmaocheng Station section.