The world's largest-diameter underwater shield tunnel boring project — located in Jinan, capital of East China's Shandong province — successfully completed excavation of the Yellow River section on June 22, in a milestone of the project's construction.

The Jinan Huanggang Road Yellow River Crossing Tunnel spans about 5,755 meters, with a shield tunneling section of about 3,290 m. It's designed as a single-tunnel, double-deck structure with a design speed limit of 60 kilometers per hour.

The tunnel passes beneath sensitive areas such as the embankments on both sides of the Yellow River, with the deepest earth cover reaching 49.2 m and maximum water and soil pressure at 6.3 bars, making it a challenging construction endeavor.

The tunneling breakthrough was achieved using the Shanhe tunnel boring machine or TBM, which measures 163 m in length, weighs 5,200 metric tons and boasts a maximum excavation diameter of 17.5 m.

The Shanhe TBM has safely traversed the primary water source protection area, sedimentation ponds and embankments on both sides of the Yellow River, completing 83.6 percent of the total shield-driven section.

The entire tunnel on completion aims to boost connectivity between Jinan's main urban area and the city's New and Old Growth Driver Conversion Pilot Zone — accelerating regional development and bolstering ecological conservation and high-quality growth in the Yellow River Basin.

The workers let out a cheer after completing the tunneling beneath the Yellow River. [Photo/Xinhuanghe app]