Abstract: Based on the crossing of the water-rich fault zone at the bottom of the Yangtze River for the Wuhu Chengnan River Crossing Tunnel, the three-dimensional seepage method was adopted to numerically simulate the shield tunnel seepage. The influences of the relative position of the excavation face to the fault zone, river water level, fault zone permeability and anisotropy, and mud-water pressure on tunnel seepage were systematically analyzed. The research results showed that tunnel seepage was affected by crossing the fault zone, and when the excavation face advanced into the fault zone, the leakage amount and the water pressure decrement obviously increased. The influence range of the fault zone on water pressure distribution was greater than its width. The larger the river water level, the higher the risk of tunnel leakage, and a rise in the water level from 5.64 m to 12.21 m would cause a 13% increase in tunnel leakage. The permeability and anisotropy of the fault zone both affected the tunnel seepage. The greater the permeability and anisotropy ratio of the fault zone, the greater the decrease in water pressure at the front of the excavation face and the greater the tunnel leakage amount. The mud-water pressure could reduce the disturbance of water pressure in the fault zone and the risk of tunnel leakage. However, a sudden increase in mud-water pressure would cause a rapid water pressure increase near the excavation face, which may be detrimental to fault zone stability. The research results can provide support for the safe construction of this project and reference for similar engineering studies.
Keywords: three-dimensional seepage; underwater tunnel; numerical simulation; water pressure; leakage