ABSTRACT
An alternative to field studies is to model the natural hazard either analytically (including numerical studies) or physically, or in a combination of both. Both approaches have their limitations and strengths and a detailed comparison is outside the scope of this paper. In the case of analytical/numerical modelling, it is necessary to define the constitutive behaviour of the geomaterials and the boundary conditions of the physical process (e.g. such as the volume of a slope and the run out area for a flow slide) together with modelling accurately the trigger for the process. In physical models, it is necessary to use appropriate materials and to be aware of scaling conflicts. It is necessary also to ensure that, with due regard to the appropriate scaling laws (and the potential conflicts within these), the scale of the model and its boundary conditions are appropriate to replicate accurately the physical phenomena being studied. The combination of physical and analytical modelling to investigate a potential natural geohazard is a particularly powerful technique because-as real events in their own right-physical models may be used to validate numerical or other analytical techniques that may then be used to model a field
1 INTRODUCTION
The term “natural hazards” may be applied to a wide range of natural phenomena. It has been defined more specifically by Burton et al. (1978) as “those elements of the physical environment, harmful to man and caused by forces extraneous to him”. It has now become accepted generally that there are seven major classes of natural hazard, i.e. earthquakes, floods, hurricanes, landslides, tsunamis, volcanoes, and wildfires. Whilst all could, to a greater or lesser extent, result in a potential geotechnical hazard, this paper will concentrate on natural hazards that have direct geotechnical implications. It is important that fundamental mechanisms associated with such natural hazards are well understood because this knowledge forms a vital component of geotechnical risk assessment. These mechanisms can be studied in a number of ways. The most direct is through field observation. However, since generally this can be done only after a catastrophic event, it is not always possible to establish reliably trigger mechanisms that initiated the phenomenon or how subsequent mechanisms developed in the immediate aftermath of the trigger. Long term field monitoring provides a possible solution to this, but it is not generally possible to determine when and where a physical event
(i.e. full scale or “prototype”) situation where the scale is too large or the boundary conditions too complex to model satisfactorily in a physical model, (e.g. Anastasopoulos et al. 2007).
