3D numerical analysis of ground settlement considering nonuniform tail-grouting pressure in large diameter slurry shield tunnelling

Ground settlement induced by large diameter slurry shield tunnelling is strongly affected by tail grouting, yet tail-grouting pressure is commonly simplified as a uniform or vertically distributed load in numerical analysis. Such simplifications may be insufficient to represent the circumferential pressure nonuniformity generated by multiple field injection ports. This study presents a three-dimensional numerical framework for analyzing ground settlement considering field-informed nonuniform tail-grouting pressure and grout hardening evolution. Field pressures recorded from six grouting ports are reconstructed into equivalent active grouting pressures by considering the mean pressure level, gravity-induced vertical gradient, circumferential pressure difference and active pressure attenuation. The grout behind the shield tail is divided into fresh, semi-hardened and hardened zones, with the active grout-pressure influence length linked to grout curing time and shield advance rate. The framework is applied to a large diameter slurry shield tunnelling project and validated against field settlement measurements. Compared with the conventional circumferentially uniform model, the proposed model better reproduces both settlement development and the outward offset of the settlement trough. Sensitivity analyses indicate that circumferential pressure nonuniformity mainly governs trough asymmetry, while semi-hardened pressure retention and grout hardening properties mainly influence later-stage settlement magnitude. Under the adopted grout-hardening assumptions, a shorter construction time per ring extends the active-pressure range, reducing settlement magnitude while increasing the calculated trough offset. The proposed framework provides a practical approach for incorporating field grouting records and grout hardening evolution into three-dimensional settlement analysis of large diameter slurry shield tunnelling.