Theoretical analysis of stratum horizontal displacements caused by small radius curve shield tunneling

Abstract

For small radius curve shield tunneling, over excavation is required on the inner side of the curve to corner the shield machine. Currently, there is no corresponding analytical solution for horizontal displacements. In this paper, using the image method and Mindlin solution and considering four factors: additional thrust on the excavation surface, frictional resistance of the shield shell, ground loss, and grouting pressure at the shield tail, a formula for calculating stratum horizontal displacements caused by small radius curve shield tunneling is derived. Based on the 220 kV Rhinoceros Station cable shield tunnel project in Guangzhou, the stratum horizontal displacement law and influencing factors are analyzed. Through comparison and verification with on-site measured data, the results indicate that the theoretical formula derived is reasonable and reliable, providing a new approach for predicting the stratum horizontal displacements induced by curve shield tunneling. The law of stratum horizontal deformation exhibits that the horizontal displacement caused by the over excavation side of the curve moves toward the tunnel side. The outer side of the curve shifts away from the tunnel. The peak appears near the axis of the shield tunnel. The ground loss has the most significant influence on stratum horizontal displacements. Furthermore, on the same tunnel cross-section, the closer the soil is to the tunnel, the greater the horizontal displacement of the soil, and vice versa. The change in shield shell length profoundly affects horizontal displacements. The friction difference coefficient has a significant impact on the stratum horizontal displacement outside the curve.