Analysis of heaving phenomenon in mountain tunnel and consideration to shallow shaped invert as countermeasures

Heaving in some mountain tunnels after completion occurs in roadbeds that were built without an inverted arch structure because the ground was relatively stable during construction. The stress-release by excavation, along with subsequent swelling by groundwater, cause the roadbed to lose strength, allowing upheaval of the road surface. In this study, we analysed geological degradation characteristics and the state of past tunnels in cases where inverts were installed. We also analysed measurement data for axial forces of inverts. The necessary performance was discussed through the result obtained by numerical analysis to compare support effectiveness of the invert shape and consider a shallow structure.