The 1st section of the Shenzhen Mawan Cross-Sea Passage, constructed by Shanghai Tunnel Engineering Co., Ltd. (STEC) under Tunnel Engineering Co., Ltd., has a total length of 2,060 meters (1,030 rings). The full-face hard rock stratum accounts for 37.5%, and the rock strength distribution in the hard rock section is uneven, with an average uniaxial compressive strength of 65 MPa and a maximum value of 169.8 MPa.

Shield tunneling underground is like shuttling between "underground walls" cast from high-strength concrete, making the project highly difficult. "Hard rock, slow excavation, and frequent cutter changes" pose "hardcore" challenges to the project's shield tunneling and ring segment quality control.

With hard rock strata, a large proportion of hard rock, slow shield tunneling, and severe cutter wear, what should be done in the face of such "hardcore" objective construction conditions?

Technical measures tougher than the "hardcore" difficulties

● Adopt cutter rings with round edges and gradient hardness to alleviate cutter wear and breakage;

● Innovatively adopt measures such as a "seven-shaped plate" for cutter barrel fixation to improve cutter barrel sealing;

● Replace with front-mounted cutter barrels to prevent cutter retraction and improve efficiency;

● Organize a construction technology research team to monitor cutter wear 24 hours a day and ensure efficient and safe tunneling.

With the full cooperation of all parties, the cutter change efficiency and cutter wear of the "Pengcheng" super-large-diameter shield have been significantly improved. The average number of cutters removed per ring decreased by 65.7%, the proportion of abnormal cutter wear decreased by 34.4%, and the tunneling efficiency in hard rock strata has been significantly improved.

At present, the shield has completed the advancement and assembly of the 740th ring, successfully passed through the full-face hard rock stratum section, driven out of the "hardest" section, and overcome the "most difficult" challenge. Next, the shield will accelerate the completion of the remaining 300 rings.