Abstract
The main challenge for metro station construction is to ensure the construction schedule while minimizing the impact on the surrounding environment. Based on the characteristics of the upper-soft and lower-hard stratum in the Dalian city of China, a special structure with six pilot tunnels and three spans of the pile-beam-arch (PBA) method is proposed and applied to the construction of the Labor Park metro station. In this study, laboratory experiments, numerical simulation analysis, and field monitoring data are used to investigate the applicability of six pilot tunnels and three spans of the PBA method in the process of construction. In the process of numerical simulation, the ground surface settlement, arch vertical displacement, the horizontal displacement of rock mass on both sides of the station, and vertical stress of support structure are analyzed. The numerical simulation results are found to be in good agreement with field measurement. Furthermore, the results indicate that, in the construction of six pilot tunnels and three spans of the PBA method, pilot tunnel construction and arch construction have a great influence on the surface settlement. The part of the initial vertical support of the pilot tunnels is removed, which caused the change of the position of maximum vertical stress and the redistribution of vertical stress. Because of reinforcement by side piles on both sides of the station, the horizontal displacement of the rock mass was reduced by 44.76% compared with that without reinforcement. The six pilot tunnels and three spans of the PBA method can effectively control the surface settlement, arch vertical displacement, and horizontal displacement of the rock mass.
Highlights
Academic Editor: Yilin Gui e main challenge for metro station construction is to ensure the construction schedule while minimizing the impact on the surrounding environment
The results indicate that, in the construction of six pilot tunnels and three spans of the PBA method, pilot tunnel construction and arch construction have a great influence on the surface settlement. e part of the initial vertical support of the pilot tunnels is removed, which caused the change of the position of maximum vertical stress and the redistribution of vertical stress
E ground settlement and horizontal displacement of rock mass on both sides of the station are compared and analyzed in the two cases of construction with side piles and without side piles, under the use of side piles, the ground surface settlement decreased by 20.62%, and the horizontal displacement of the rock mass on both sides of the station decreased by 44.76%. e use of side piles effectively limited the surface settlement and the horizontal displacement of the rock mass on both sides of the station
Summary
To effectively monitor the impact of the station construction process on the surrounding environment, a surface settlement monitoring section is arranged every 10 m along the excavation direction of pilot tunnels. E earliest ground settlement is located directly above the excavation pilot tunnels in the early stage of the construction of pilot tunnels. After the construction of the pilot tunnels, the maximum settlement value on the surface is −7.54 mm. Is shows that when several adjacent pilot tunnels are excavated at the same time, each pilot tunnel would affect each other, and the construction disturbance will be amplified, showing the “effect of group cavities.” [19] After the construction of the pilot tunnels, the maximum settlement value on the surface is −7.54 mm. is shows that when several adjacent pilot tunnels are excavated at the same time, each pilot tunnel would affect each other, and the construction disturbance will be amplified, showing the “effect of group cavities.” [19]
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