Abstract:

To address the complex challenges of constructing a superlargediameter shield tunnel in stronglydeveloped karst areas, highviscosity soil, and hard rock strata, a case study is conducted on the Nanhu section of the Lianghu tunnel in Wuhan, China. Through analysis of field exploration data, literature research, and expert consultation and demonstration, several major difficulties of the project are identified: (1)  high construction risks when tunneling through stronglydeveloped karst areas, which can result in disasters such as nose down, collapse, and water gushing; (2) formation of mud cakes on the cutterhead in viscous strata, leading to increased thrust and decreased tunneling rates; (3) wear and damage of the shield cutterhead and cutters in hard rock strata, resulting in low tunneling efficiency; (4) difficulty in controlling the attitude of the shield in small curve radii, leading to the tunnel deviating from the designed axis; (5) floating of largediameter segments, resulting in segment misalignment, damage, and leakage. Based on the above difficulties, the selection technology of superlargediameter shield under complex geological conditions is analyzed, and countermeasures are proposed for superlargediameter shield tunneling in stronglydeveloped karst areas, highviscosity soil, and hard rock strata.

Key words: superlargediameter shield tunnel, karst stratum, mud cake, hard rock stratum, small curvature radius construction, segment floating