Terrain Instabilities
| Teaching team |
|
| About the Terrain Instabilities module |
|
| Objectives |
|
| Associated field trips |
|
| Related links |
|
Teaching Team |
|
- Christophe Bonnard (Landslide monitoring and modelling) - MODULE RESPONSIBLE
- Olivier Lateltin (Landslides mapping and management) - MODULE RESPONSIBLE
- Nico Goldscheider (Karst)
- Michel Jaboyedoff (Rock Instabilities)
 |  |
| |
| Randa Rockfall (Valais, Switzerland) that occurred in April and May, 1991, representing a total volume of 33 million cubic meter. | La Clapière Landslide (Alpes de Haute Provence, France) which has been moving for more than 20 years without blocking the valley of La Tinée, but represents a risk of acceleration. |
| |
About the Terrain Instabilities module |
|
General Introduction and Typology of Landslide Phenomena, Case Studies
Landslide processes are reviewed, with a description of their main features. Their classification is presented, according to the classification by Varnes, as well as their possible activity and rate of movement. Their significance on buildings, human life and environment is discussed.
The interpretation of morphological landforms and slope stability indicators is explained, allowing the student to describe the various landslide phenomena.
Instability of Rock Masses
The detection of potential rock instabilities is explained with respect to the presence of various systems of discontinuities that can be monitored and mapped, allowing a kinematic analysis. Limit equilibrium analyses are then performed on rock masses.
Mapping Methodology and Interpretation of Air Photos
The identification of landslides based on the interpretation of air photos is explained, as well as the determination of some features according to the scale of the photographs.The legend to produce landslide phenomena maps is detailed, as well as the standard Swiss representation of landslide hazards.
Landslide Planning and Management of Landslide Hazards
In order to determine landslide hazards, it is necessary to assess the intensity and the probability of a phenomenon. The system of hazard levels in use in Switzerland will be detailed and its application in land planning policy will be presented, as well as other systems in use in neighbour countries. The aspects of landslide risk management (prevention, mitigation) will also be discussed.
Geotechnical Bases and Characteristics
After a brief presentation of the main characteristics allowing the definition of a soil, the parameters related to shear strength, as well as how they can be measured, will be discussed. The basic approaches to assess slope stability conditions will be presented, including the effect of groundwater.
Slope Stability Analysis
The various methods of slope stability analysis will be discussed, with a definition of the factor of safety and of its meaning. Some simple examples will be analyzed.
Monitoring of Landslides
After a presentation of the conditions required to obtain significant monitoring data, the various techniques available to determine surface and underground slope movements, groundwater conditions as well as other parameters will be detailed. The concepts allowing the preparation of a monitoring campaign will be discussed.
Stabilization Measures
After commenting on the classification of stabilization measures, the principles and techniques used in drainage schemes, anchoring programs and mass movements projects will be explained. The stabilizing and protective effects of vegetation will also be discussed, as well as their sustainability and maintenance.
Introduction to karst geomorphology and hydrology
The general geological, geomorphological and hydrogeological characteristics of karst landscapes and aquifers will be presented. Collapse features, terrain instabilities and other geotechnical problems in karst areas are related to groundwater. At the same time, groundwater in karst aquifers is an important drinking water resource and requires specific protection measures. The course intends to provide a holistic view of karst terrains, their value for humanity, their vulnerability to human impacts, and the associated geotechnical hazards.
 |  |
| |
| Sechilienne Rockfall (Isère, France) shows a progressively disaggregating front causing some occasional falls of limited volume. The expected volume liable to fall at a short notice is 3 million cubic meter. | General view of La Frasse Landslide (Vaud, Switzerland) that is presented to the CERG students. |
| |
Objectives |
|
- To provide an understanding of the various landslide phenomena, of their causes and of their mechanisms
- To comment the tools and techniques available for their identification and assessment of their characteristics
- To present how they can be monitored and modelled
- To explain the various prevention and protection mitigation actions
- To develop the hazards and risk they imply
- To present how they can be taken into account in land planning policy
- To make students aware of the specific nature of karst terrains, the importance and vulnerability of their water resources and associated geotechnical problems
Associated Field Trips |
|
Visit of a Large Slide and Field Work
A field trip is organized to the La Frasse Landslide in the Prealps of the Canton of Vaud, near Aigle, where a large permanently active slide experiences occasional crises. This landslide has been extensively investigated and a new hazard mitigation drainage system is about to be built to replace boreholes equipped with pumps.
Landslide mapping at Peney landslide
The students will discover and map a small slide along the River Rhone downstream of Geneva.
Field work in the region of Schwarzsee (Canton of Freiburg)
The students will be introduced to a large landslide phenomenon that destroyed a village some 13 years ago. Then in the same region they will proceed to the mapping of a landslide and assessment of landslide hazard and risks.
Field trip to the Swiss Jura Mountains
On this field trip, the students will visit some karst systems in the Swiss Jura Mountains. We will see some typical geomorphological and hydrological karst phenomena, like closed depressions, dolines, karren, swallow holes and big karst springs. The focus will be on groundwater contamination, protection and exploitation, but we will also see and discuss some karst related hazards, like flooding.
 |  |
| |
| La Chenaula Landslide, near Lausanne (Vaud, Switzerland) experienced a sudden acceleration in April, 1983, with a total horizontal movement of 8 to 13 m in 3 days. | In October, 2000, a major debris flow reached the town of Fully (Valais, Switzerland). |
| |
Related Links |
|
- USGS Landslide Hazards Program
- Gruppo Nazionale per la Difesa dalle Catastrofi Idrogeologiche (GNDCI)
- Geoscience Australia: Where do landslides occur?
- Landslides in Japan
- What causes landslides?
- Karst Waters Institute
- Speleogenesis
- Centre d'Hydrogéologie, Université de Neuchâtel