Abstract: This paper presents a case history of the shielded tunnel excavation in the saturated weak soils in Suzhou Metro #4 Line. The twin tunnel tubes were underneath a masonry building structure. During the tunnel excavation, the deflections at the ground surface and the building structure were monitored. The results indicate that, when the blade was in the range of 18 m to 5 m to the monitored point, a vertical settlement of 2 millimeters was observed. A ground heave of 0.5 ot 1.0 millimeter could be monitored when the shielded blade is zero to 5 meters to the survey point. A fast deformation rate was observed when the blade is reached the monitored point and the deformation became stable one or two days after the excavation. The settlement control would be different if the saturated weak soil were disturbed. An increase in settlement at the ground surface and the building if the shielded excavation was stopped. Due to its poor stiffness, large differential settlement was observed in the masonry building. If the tunnel was under one side of the masonry building, tilting in the building could be observed.

Key words: Saturated Weak Soils, Shielded Tunnel Excavation, Masonry Building, Settlement