Three-dimensional critical slip surface locating and slope stability assessment for lava lobe of Unzen volcano

Even Unzen volcano has been declared to be in a state of relative dormancy, the latest formed lava lobe No.11 now represents a potential slope failure mass based on the latest research. This paper concentrates on the stability of the lava lobe No.11 and its possible critical sliding mass. It proposes geographic information systems (GIS) based three-dimensional (3D) slope stability analysis models. It uses a 3D locating approach to identify the 3D critical slip surface and to analyze the 3D stability of the lava lobe No.11. At the same time, the new 3D approach shows the effectiveness in selecting the range of the Monte Carlo random variables and locating the critical slip surface in different parts of the lava lobe No.11. The results are very valuable for judging the stability of the lava lobe and assigning the monitoring equipments.