Abstract: The spatial and temporal distribution of the horizontal displacement and settlement of a metro tunnel adjacent to the foundation pit is analyzed. Due to the creep effect of the soft soil, the space-time effect caused by the excavation of the foundation pit should be considered, in addition to the limit of the horizontal support structure of the foundation pit supporting system. The influencing scope of excavation on adjacent metro tunnel is 2.5 times the depth of excavation, and for the right line far away from the foundation pit, the influence scope is smaller, even lower to 1.5 times the depth of excavation. Based on the monitoring data of foundation pit and adjacent tunnels, the ratio-horizontal distance relation curve is obtained. Then the horizontal and vertical displacements of tunnel are estimated based on the monitoring data of foundation pit and fitting formula. The ratio between horizontal displacement of tunnel and that of the adjacent soil at the same depth, which corresponds to the maximum accumulative displacement, generally ranges from 0.60 to 0.65, and becomes stabilized at 0.60 after the foundation slab casting is finished. The ratio between settlement of tunnel and that value of the adjacent earth’s surface, which corresponds to the maximum cumulative settlement, is largely located within the range from 0.50 to 0.60, and becomes stable at the level of 0.52±0.05.

Key words: metro tunnel, excavation of foundation pit, time-space effect, time-history analysis, conjoint analysis