Deformation and reinforcement effects of soft soil deep foundation pits for shield tunnel launching.

Soft soil layers are characterized by high sensitivity, high compressibility, and low bearing capacity, making them prone to deformation and uneven settlement under external loads and vibrations. Based on the foundation pit project of the Mangzhou Tunnel in Zhuhai City, this study combines field monitoring and numerical simulation to analyze the horizontal displacement of diaphragm walls, surface settlement, and axial forces of lateral supports. The study aims to investigate the deformation development pattern of deep excavations in soft soil and the impact of passive zone reinforcement. The results show that the curve of the wall horizontal displacement exhibits a "spoon-shaped" pattern, with the maximum value occurring at around 1. 4 times the excavation depth of the pit; passive zone reinforcement reduces the maximum value of wall horizontal displacement by 33%. The surface settlement follows a "settlement trough" curve, with the maximum value occurring at a distance of 0. 3 times the excavation depth from the edge of the pit, and passive zone reinforcement limits the maximum surface settlement to less than 0. 1% of the excavation depth. Excavation of the soil rapidly increases the axial force of current support, but the installation of next layer support effectively reduces the growth rate of axial force of the previous support, and passive zone reinforcement reduces the maximum support axial force by 25%. It is proved that passive zone reinforcement is an effective measure for controlling deformation of deep excavations in soft soil. The findings of this study can provide valuable references for the construction and monitoring of deep excavations in soft soil. [ABSTRACT FROM AUTHOR]