Settlement Control Techniques for Urban Rail Transit Station Entry/Exit Large Profile Pipe Jacking Engineering through Urban Roads

Objective To ensure the smooth implementation of urban rail transit station entry/exit pipe jacking construction project, it is essential to study the impact of ground settlement and explore settlement control measures for its engineering through urban roads. Method With reference to the long-distance bus station entry/exit pipe jacking engineering on Jinan Rail Transit R2 Line , and based on the description of project geological conditions and key difficulties, a 3D numerical calculation model for large profile pipe jacking engineering through urban roads with dense underground pipelines is established. Land subsidence curves at different distances from the excavation face and settlement curves at different depths of the soil layer are obtained. A comparison is made between the simulated vertical displacement values of land monitoring points above the pipe central axis and the field-measured values changing with excavation distances. Corresponding construction optimization measures are proposed, and the optimization effects are analyzed and verified based on field-measured data. Result & Conclusion During the jacking process, as the distance from pipe central axis increases, the land subsidence gradually decreases. With increasing depth, the deep layer displacement of the soil layer gradually increases, and the settlement curve gradually transitions from ′stout and short′ to ′slender and tall′. Factors such as significant fluctuations in soil chamber pressure and frictional disturbance between the pipe and the stratum on-site lead to an outcome of the maximum simulated settlement, which is slightly less than the maximum field-measured settlement, posing certain discrepancy. By adopting measures such as controlling excavation speed and rational grouting for reducing friction, the subsequent construction settlement control effect is evident, with a maximum land subsidence of 18.18 mm, and the deformation is within construction allowable range.