| dc.description.abstract | The permanent surface displacement caused by active fault movement is a critical issue for nearby underground structures. The rapid development of underground mass transit networks in Taiwan′s metropolitan areas has led to an increase in tunnel density year by year. Taiwan is located in the seismically active Pacific Ring of Fire, with numerous active faults and frequent earthquakes. When a strong earthquake occurs, tunnels can deform or even displace. If a tunnel is near an active fault, the near-fault effects and the development of shear zone in the ground can also affect the tunnel. Additionally, when urban renewal projects involve terminology for new structures, the relationship between existing tunnels and shear zones needs to be considered during an earthquake.
This study employs centrifuge model simulations to investigate the interaction behavior between a rectangular tunnel and a shear zone under a reverse fault movement with a dip angle of 60 degrees. The focus is on the tunnel′s response when subjected to fault movements at different horizontal and vertical positions. The prototype dimensions are discussed in the experimental content, with the soil layer composed of silica sand having a thickness of 16 m. Rectangular tunnels are placed at depths of 3.7 m and 7.5 m (defined by the tunnel center point). The tunnel centroid height is 1.86 m, and the contact stress is 56.8 kPa. During the experiments, fault movement, tunnel inclination, tunnel displacement, shear zone development, and ground surface elevation changes were recorded.The study found that when the tunnel burial depth is twice the tunnel height and located above the fault extension line or in the downward direction at 0.5 times the tunnel width, the tunnel′s inclination, horizontal and vertical displacements, and ground surface impact range are larger. Conversely, when located in the upward direction at 0.5 times the tunnel width or in the downward direction at 1 time the tunnel width from the fault extension line, these impacts are smaller. Thus, the danger zone can be defined as within 0.5 times the tunnel width in the upward direction to 1 time the tunnel width in the downward direction from the fault extension line. At the same burial depth, the closer the tunnel is to the fault extension line, the greater the inclination, horizontal and vertical displacement, increasing by up to 17.6 degrees, 30.5%, and 36.3% of the tunnel width, respectively. At the same horizontal position, the shallower the burial depth, the greater the tunnel′s inclination, horizontal and vertical displacement, increasing by up to 8.9 degrees, 5%, and 6.4% of the tunnel width, respectively.When the tunnel is located within the shear zone, the shear zone bypasses the tunnel, and the angle between the envelope line and the extension line increases by up to 37 degrees (at the same burial depth with different horizontal positions) and 10 degrees (at the same horizontal position with different burial depths). The larger the angle between the shear zone and the fault extension line, the greater the ground surface impact range, increasing by up to 90% of the soil layer thickness at the same burial depth and up to 40% when the burial depth becomes shallower.In conclusion, tunnel design needs to consider the impacts of burial depth and horizontal position on its stability and ground surface impact range to ensure tunnel safety. | en_US |