2021 Volume 16 Issue 4 Pages 343-354
It has recently been urgent to deal with various deterioration of support structures on tunnels particularly in urban areas. Serious cracks on support segments of shield tunnels in soft clay deposits as well as deterioration phenomena such as free lime and rebar corrosion that is illustrated in the literature1) are observed. It is true they have many previous studies of consolidation induced problems due to change load condition but there are some cases where problems occur in the absence of remarkable external factors. As one of these problems, the influence of shield tunnel excavation on the long-term deformation of the soft alluvial clay deposits is discussed based on triaxial compression and extension tests and numerical analyses in the present paper. Both experimental and calculated results show that long-term compressive deformation possibly occurs induced by compression and extension shear forces in the stress state lower than pc due to tunneling excavation. The reason why this phenomenon occurs is found to be that the extension shear stress causes great damage to the structure of the quasi-overconsolidated clay.
