China Rock 2022 Keynote-Dr. Vojkan Jovičić, Temporary and Final Portal Structures for Tunnels in Soft Rock

Lecturer: Dr. Vojkan Jovičić
Dr. Vojkan Jovičić finished Faculty of Civil Engineering at University of Belgrade, Serbia in 1989. He specialized in Geotechnics and took the Master Science degree at the same University in 1993. He obtained his PhD in Geotechnical Engineering at City University in London, UK at 1997. Dr. Vojkan Jovičić is Assistant Professor at Faculty of Civil Engineering at University of Ljubljana and Director of Institute for Mining, Geotechnology and Environment in Ljubljana, Slovenia. He published more than 70 scientific papers on wide area of topics including small strain stiffness of soils and rocks, soil anisotropy, soil structure, mechanical behavior of sands, constitutive modelling of hard soils and soft rocks and others. Dr. Vojkan Jovičić designed more than 70 km of road and railway tunnels, which were built in Slovenia, Bosnia and Hercegovina, Montenegro and Italy. Dr. Vojkan Jovičić is Vice President of International Society for Rock Mechanics and Rock Engineering, ISRM.

Report Summary
The prevalence of existing transport routes and further urbanization of green field sites dictate conditions in which becomes extremely difficult to position the routes for major traffic infrastructure （i.e., motorways and railways） in a geologically convenient manner. The infrastructure routes are mainly determined considering socio-economic factors resulting in the fact that the routes could not be alternated to avoid difficult ground conditions which are characteristic for tunnel portals in soft rock. Tunnel construction in soft rock is usually initiated with excavations of pre-cut within quaternary deposits or weathered rock, which are typically subjected to surface erosion associated with sliding and creeping. These processes occasionally form landslide bodies of different size, which cannot be avoided by tunnel layout. Typically, temporary cuts are formed to start underground excavation while the final structures of tunnel portals are constructed later. In the case, in which the tunnel construction must start within the active landslide body or can cause the landsliding, this concept must be reconsidered so that final portal structures are constructed first to prevent excessive ground movement and enable remediation of landslide. The lecture summarizes the main design principles for the construction of temporary and permanent portal structures in soft rock. The balance between the inevitable impact of tunnel construction on initiation of new or reactivation of old landslides and the safe passage of tunnel construction to underground excavation is highlighted and several case example solutions to this design challenge are presented in the lecture.