Research on Construction Technology for Shield Tunnelling with Small Curve Radius under Shallow Cover Conditions

This article takes the shield tunnelling project of the southern entrance of Line 7 of Changsha Metro as a practical background, focusing on extremely complex working conditions including shallow cover (with a minimum thickness of only 3.8m, equivalent to 0.62 times the shield diameter D), small curve radius (R only 250m), low strength rock strata (unconfined compressive strength ranging from 2.25 to 5.96MPa), and the cutting line reception process.The conventional shield tunneling method typically faces challenges in controlling surface settlement and increased risks of segment misalignment and deviational errors under extreme conditions such as shallow overburden and tight curvature radii. In this context, a systematic and in-depth study of the key technologies during the shield reception phase was conducted. Through optimized earth pressure balance control, synchronous grouting process, dynamic regulation of the articulated system, and the application of precise guidance technology, combined with numerical simulation and real-time monitoring methods. Ultimately, the surface settlement was controlled within 12.5mm, segment misalignment to ≤10.0mm, shield posture deviation within ±25mm, and reception portal seal leakage to ≤0.05L/min. These results provide valuable technical references for shield reception construction in shallow cover with small radii, and have significant guiding implications for similar projects.