Characterization of Underlying Twin Shield Tunnels Due to Foundation-Excavation Unloading in Soft Soils: An Experimental and Numerical Study

Excavation near or above existing shield tunnels often results in adverse impacts on tunnel stability. To ensure the serviceability of tunnels, this paper presents experimental and numerical studies with reference to a foundation pit case history excavated twin-tube soft soils. The tests were firstly applied study deformation characteristics structural response tunnels. Thereafter, an extensive investigation was performed determine influence some factors such as cover-to-excavation depth ratio, length-to-depth unloading ratio displacement behaviors. It demonstrated that heaves excavation proceeds, horizontal displacements reach their maximum values when is finished. earth pressure around symmetrically distributed gourd shape, larger reduction at crown invert smaller side walls. Additionally, changes more significantly than other parts. moment increment affected by depth. axial force walls most sensitive effect induced activity.