Andrea Wolter

Rock slope failure in a recently deglaciated permafrost rock wall at Piz Kesch (Eastern Swiss Alps), February 2014

In February 2014, a rock pillar with a volume of around 150 000 m collapsed at Piz Kesch in the Eastern Swiss Alps. A reconstruction of the conditions prior to the event and of the event itself is presented on the basis of different sources of data. The methods applied include photogrammetry, terrestrial laser scanning, structural geological analysis, examination of meteorological data, carbon-14 (C) dating of organic material in permafrost ice from a tension crack and numerical modelling of likely modes of failure. Despite a complete lack of in situ measurements in the rock wall prior to the event and of direct observations during the event, the available data allow the determination of the approximate timing of the event as well as the structural predisposition, the probable mode of failure and the timescale of several millennia involved in the triggering of the failure of the rock pillar. The interdisciplinary analysis of this event contributes towards understanding the complex interaction of processes involved in large rock slope failures currently occurring in warming mountain permafrost regions. Copyright

Assessment of rock slope stability using remote sensing technique in the Gold Coast area, Australia

Rock falls and landslides along major roads cause significant damage to infrastructure in the Gold Coast area, Australia. Current methods of hazard assessment, which mostly include field mapping and data collection for site characterization, are inherently labor intensive and subject to bias due to safety issues and time constrains. However, many of these problems have recently been addressed through the development and deployment of digital imaging technology based on photogrammetry. This method involves the use of high-resolution digital stereo-photographs, from which a three-dimensional image of the slope can be constructed. Such images can highlight the surface texture of slopes and identify potentially unstable zones, thus providing engineers with valuable information regarding the slope design. Photogrammetry is still a relatively new remote sensing technique in Australia and has mostly been used in the mining industry. Little has been done to study the feasibility of its application in civil engineering to solve geotechnical problems related to the stability of natural slopes and road cuts. This paper presents the results of a pilot study aimed at assessing the stability of rock slopes in the Gold Coast area. Field surveys including photogrammetry were performed to study the geological settings of the sites, and characterize the slopes topography and type of discontinuities. Based on the 3-D models, the potentially unstable zones were identified, and slope stability analysis of those areas was performed. The obtained results indicated that photogrammetry can be a helpful tool in assessing geohazard related to slope stability problems.