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Ground Deformation During the Construction of a Shield Tunnel in Sand and Gravel Layers
Sand and gravel layers are a special geological environment which is prone to ground instability and consequently ground settlement when the shield is tunnelled through the sand and gravel layers. In order to study the ground settlement pattern during shield construction in sand-cobble strata, the discrete element software was used to simulate the disturbance pattern of sand-cobble strata during shield tunnelling and the distribution pattern of ground settlement when the shield crosses the sand-cobble strata. The simulation results show that: When the shield machine excavates, a wedge-shaped moving surface appears in front of the palm face, and the sand and cobbles in the loosened area are all shifted to this area; the pressure at the palm face of the shield excavation is relatively small, and the disturbance of the sand and cobble soil in front of the palm face becomes more and more significant with time, which is the direct cause of the soil deformation above the palm face. The settlement of the ground above the left and right tunnels was distributed in a roughly symmetrical manner and became progressively more concentrated during the shield driving, while becoming progressively smaller towards the two flanks. The results indicate that soil loss created two zones of heterogeneity at approximately 45°above the tunnel on either side, forming a triangular area of relief and significant changes in soil stresses around the hole after shield construction. The depth of tunnel burial has a direct influence on the occurrence of hysteresis settlement. The orientation of the stratigraphic voids has a significant influence on the area where hysteresis settlement occurs.
Ground Deformation During the Construction of a Shield Tunnel in Sand and Gravel Layers
Sand and gravel layers are a special geological environment which is prone to ground instability and consequently ground settlement when the shield is tunnelled through the sand and gravel layers. In order to study the ground settlement pattern during shield construction in sand-cobble strata, the discrete element software was used to simulate the disturbance pattern of sand-cobble strata during shield tunnelling and the distribution pattern of ground settlement when the shield crosses the sand-cobble strata. The simulation results show that: When the shield machine excavates, a wedge-shaped moving surface appears in front of the palm face, and the sand and cobbles in the loosened area are all shifted to this area; the pressure at the palm face of the shield excavation is relatively small, and the disturbance of the sand and cobble soil in front of the palm face becomes more and more significant with time, which is the direct cause of the soil deformation above the palm face. The settlement of the ground above the left and right tunnels was distributed in a roughly symmetrical manner and became progressively more concentrated during the shield driving, while becoming progressively smaller towards the two flanks. The results indicate that soil loss created two zones of heterogeneity at approximately 45°above the tunnel on either side, forming a triangular area of relief and significant changes in soil stresses around the hole after shield construction. The depth of tunnel burial has a direct influence on the occurrence of hysteresis settlement. The orientation of the stratigraphic voids has a significant influence on the area where hysteresis settlement occurs.
Ground Deformation During the Construction of a Shield Tunnel in Sand and Gravel Layers
Lecture Notes in Civil Engineering
Duc Long, Phung (editor) / Dung, Nguyen Tien (editor) / Ding, Chuanjin (author) / Kuang, Jun (author) / Li, Xuedong (author) / Tang, Qiang (author)
International Conference on Geotechnics for Sustainable Infrastructure Development ; 2023 ; Hanoi, Vietnam
2024-07-11
15 pages
Article/Chapter (Book)
Electronic Resource
English
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