Abstract：
Based on the new three pipe jacking utility tunnel crossing over existing metro tunnel in Nanchang City, a three-dimensional numerical model was established to study the deformation of the existing tunnel and ground surface under four construction sequences: first the middle, then both sides; first both sides, then the middle; right to left; and simultaneous construction of the three pipe jacking. The optimal construction sequence was selected by comparing the impact of these construction sequences on the deformation of the existing tunnel and the ground surface. The study further investigates the effect of different grouting pressures, face pressures, and anti-floating counterweights on the deformation of the existing tunnel and the ground surface. Finally, field monitoring was conducted to verify the accuracy of the simulation results and reveal the displacement and deformation patterns of the existing tunnel and the ground surface. The results show that: (1) The two-sides-first construction sequence is the optimal one, resulting in the least surface settlement, vertical tunnel displacement, and horizontal tunnel displacement, reducing them by 18.2%, 30.7%, and 23.8%, respectively, compared to the maximum values; (2) Increasing grouting pressure can suppress the development of surface settlement and tunnel displacement. Increasing face pressure can re? duce surface settlement but will increase tunnel displacement. The ratio of grouting pressure to vertical soil pressure should be controlled between 2.5 and 3.8, and the ratio of working face pressure to lateral soil pressure should be controlled between 1.88 and 2.5; (3) Applying anti-floating counterweights can suppress tunnel displacement, causing the floating of the tunnel vault to rise to a maximum value before decreasing. The reduction in displacement for counter weight ratios of 0.5 and 1 is 17% and 30%, respectively; (4) During the successive pipe jacking process, the surface settlement, settlement trough width, and tunnel displacement increase with each construction step. Due to the isolation effect, the displacement of the metro's downward line is smaller than that of the upward line; (5) Field monitoring showed a maximum surface settlement of 13.5 mm, with the maximum vertical displacement at the tunnel vault, the maximum vertical displacement at the track bed, and the maximum horizontal displacement at the tunnel waist being 1.5 mm, 1.1 mm, and 0.8 mm, respectively, all within safe limits.
CHEN Wang1 PENG Yanfeng1 LIU Weizheng2 ZHANG Siyu2 CHEN Changhui1
.Analysis of the Impact of the Three Pipe Jacking Over-crossing Construction on Existing Tunnel and Surface Deformation[J] MODERN TUNNELLING TECHNOLOGY, 2025,V62(1): 170-182
2025, Vol. 62 