Abstract
Due to a lack of engineering experience, research on ground deformation during shield machine tunneling in sludge layers is limited, especially in areas with plastic drainage plates installed for ground stabilization. When the shield passes through this area, the shield cutterhead may be jammed by the drainage plates, resulting in excavation surface instability, excess ground deformation, and schedule delay. In this work, a Mindlin solution for ground deformation in such a layer is obtained, considering four factors: the frontal additional pressure generated by the shield cutterhead due to the soil squeezing effect, the uneven lateral friction between the shield shell and the soil, the frontal friction generated by the shield cutterhead when cutting through the drainage plate, and the shield machine restart after shutdown. The results show that the theoretical curve is in good agreement with the measured values. The maximum settlement was approximately 10 m behind the excavation surface, and the maximum uplift was approximately 5 m in front of the excavation surface. The most influential factor among all the studied factors was the additional pressure on the shield cutter, which accounted for approximately 56% of the maximum settlement and 60% of the maximum uplift. The soil settlement mainly occurred within 12 m on both sides of the tunnel axis. The maximum settlements at the different soil depths tested were all directly below the tunnel axis.
Highlights
With the development of urban construction in China, various types of municipal projects, such as subways, crossriver tunnels, sewage pipes, and utility tunnels, have been carried out
Some scholars [28,29,30,31,32,33,34,35] have considered the impact of multiple factors, such as additional thrust Q, frontal friction force fd on the cutter plate, lateral friction fs on the shield shell, and grouting pressure P, on surface settlement based on the Mindlin solution. e existing research results show that these three factors, the frontal additional pressure generated by the shield cutterhead, the uneven lateral friction between the shield shell and the soil, and the frontal friction, are the main causes of formation deformation during tunneling. erefore, the above three factors are essential for the theoretical analysis method proposed in this paper
Based on the Mindlin solution, four factors that affected formation deformation during shield tunneling were considered in this paper: the frontal additional pressure generated by the shield cutterhead due to the soil squeezing effect, the uneven lateral friction between the shield shell and the soil, the frontal friction generated by the shield cutterhead when cutting through the drainage plate, and the shield machine restart after shutdown. en, the formula for calculating the vertical displacement of a stratum during construction was obtained
Summary
With the development of urban construction in China, various types of municipal projects, such as subways, crossriver tunnels, sewage pipes, and utility tunnels, have been carried out. Erefore, the above three factors are essential for the theoretical analysis method proposed in this paper These studies did not take into account the impact of machine restart on the soil layer displacement after machine shutdown or the impact when the shield passes through special layers, such as sludge layers installed with plastic drainage plates. Based on the Mindlin solution, four factors that affected formation deformation during shield tunneling were considered in this paper: the frontal additional pressure generated by the shield cutterhead due to the soil squeezing effect, the uneven lateral friction between the shield shell and the soil, the frontal friction generated by the shield cutterhead when cutting through the drainage plate, and the shield machine restart after shutdown. Based on a project case, the calculated value and the measured result were compared and analyzed to verify the rationality of the calculation method proposed above
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