Sometimes

at the condition that a confined aquifer is not completely cut off

its pressure-relief can occur when dewatering via pumping is conducted to prevent the heave failure of pit formation above. Such pressure-relief can have negative effect on ground settlement considerable larger than that due to pit excavation. Therefore

such effect on the existing shield tunnel adjacent to the pit has to be considered. The effect is simulated with finite element method in this paper. The stress field of surrounding soil

the deformation and internal forces of the cross-sections of tunnel at different locations relative to the confined aquifer are analyzed. The results show that

when either most part of tunnel or the whole tunnel is located in the confined aquifer

its pressure-relief can cause not only overall upheaval or settlement

but also vertical convergence deformation of the tunnel. When the tunnel is located in the aquiclude above or under the confined aquifer

the pressure-relief only produces little influence on the tunnel deformation. However

when it is located in the upper aquiclude

the tunnel would exhibit obvious settlement due to the pressure-relief in the confined aquifer.