Abstract: This paper presents a case history of construction monitoring and analysis of foundation excavation of Metro No. 6 Line at Youth Road Station in Hangzhou. The ground subsidence, deflection at the slurry wall and in various soils and the axial force in the supporting system are monitored and analyzed. The results indicated: the deep excavation resulted in the ground subsidence to a wide zone around the excavation and more importantly, the acuminated settlement at the majority of the monitored points exceeded the threshold value. Construction methods that could better control the adjacent ground subsidence are therefore needed in the similar subsurface conditions. The lateral deflection data measured from the ground inclinometer can reflect the local soil conditions; the deflection in various soil depths are closely related to the slurry deflections. The results also recommended that the frequency of axial force monitoring is necessary so that the first layer of internal support system separate with the slurry wall due to the excessive axial force. In addition, the internal support system could be further optimized.

Key words: metro foundation excavation, construction monitoring, spatial and time effect, ground subsidence