Mechanical Behavior of Single and Group Piles with a Low Cap Adjacent to Shield Tunneling in Composite Ground: Insights from Centrifugal Model Testing

• Published in: Geotechnical and geological engineering Vol. 42; no. 8; pp. 7451 - 7480
• Main Authors: Wu, Tianhua, Gao, Yongtao, Huang, Changfu, Zhou, Yu, Li, Jianwang
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.11.2024; Springer Nature B.V
• Subjects: Axial forces; Bending moments; Centrifugation; Centrifuging; Civil Engineering; Deformation; Digital imaging; Earth and Environmental Science; Earth pressure; Earth Sciences; Engineering; Flight; Flight conditions; Geotechnical Engineering & Applied Earth Sciences; Grouting; Hydrogeology; Hydrostatic pressure; Load; Load transfer; Mechanical properties; Model testing; Original Paper; Pile groups; Piles; Pore pressure; Pore water; Pore water pressure; Scale models; Sensitivity analysis; Soil analysis; Soil-pile interaction; Subway construction; Subway tunnels; Terrestrial Pollution; Three dimensional composites; Tunnel construction; Tunneling; Tunneling shields; Tunnels; Waste Management/Waste Technology; Water pressure; Tunneling; Single pile; Centrifugal experiment; Pile group; Soil-pile interaction; DIC technology
• ISSN: 0960-3182; 1573-1529
• DOI: 10.1007/s10706-024-02935-w

Shield tunneling adjacent to existing piles is common occurrence in subway construction. This study proposes a novel tunnel model capable of simultaneously simulating ground loss, unloading effects, and void grouting under in-flight conditions. Several three-dimensional (3D) centrifugal scale model tests are implemented in a silty-silty clay composite to investigate the response of a single pile (Test SP) and pile group (Test GP) with a sinking low cap subject to adjacent tunneling. The results indicate a critical influence area, i.e., 0.75D in front and 0.25D behind the centerline of the existing piles, is observed for the pile head settlement, in each test, and the induced bending moment in the piles above the tunnel spring line is more sensitive to tunneling than that below it. A decreasing trend in axial force along the pile shaft is observed in Test SP, whereas Test GP shows the opposite behavior. The maximum variations in axial force and bending moment occur near the tunnel invert and crown in Test SP, respectively, however, they all appear near the tunnel spring line in Test GP. There is a law of load transfer for downward migration in Test SP. In Test GP, however, the load on the upper part of pile P1 decreases and shifts to the lower section of pile P1 and the whole pile P2. Subsequently, the load on the upper part of pile P2 reduces and transfers to the lower part of pile P2 and the whole pile P1. A significant increment in the earth pressure near the pile toe is observed. The pore water pressure increases slightly at first and then dissipates. Digital image correlation (DIC) has been preliminarily demonstrated as a valuable tool for visually capturing the progressive behavior of pile-soil interactions during in-flight tunneling, proving advantageous for analyzing tunnel-soil-pile interaction issues under centrifugation conditions.