Statistical analysis of key parameters for shield tunneling in water-rich soft soil areas

This study statistically analyzes on-site measurements of key tunneling parameters (including thrust, soil chamber pressure, and advance speed) and surface settlement in a shield tunneling project on a Tianjin Metro line, aiming to investigate the variation patterns of shield tunneling parameters and their influence on surface settlement. Through statistical analysis and correlation studies of the parameters, the following findings are obtained: soil chamber pressure exhibits a positive correlation with overburden thickness; during shield advancement, it stabilizes at 0.9~1.1 times the lateral static earth pressure at the tunnel burial depth. Thrust fluctuates within the range of 1.8~2.4 times the force exerted by soil chamber pressure on the excavation face. Surface settlement monitoring indicates that both the arrival settlement and post-construction consolidation settlement of the leading tunnel are greater than those of the trailing tunnel. Cross-sectional settlement is sensitive to the tunnel net distance: when the net distance is less than 2.5 times the tunnel diameter (15 m), the settlement trough morphology transitions from a "W-shape" to a "V-shape". This study further identifies key shield parameters affecting surface settlement using Spearman correlation heatmaps and random forest-based feature importance analysis. Results show that soil chamber pressure, synchronous grouting volume, and muck discharge volume have a significant impact on settlement and thus require strict control during construction. The findings provide a scientific basis for optimizing shield tunneling parameters and controlling surface settlement, offering valuable references for similar projects and contributing to enhanced safety and efficiency in metro construction.