This presentation demonstrated the role and use of numerical analysis by discontinuum and continuum modelling for the understanding of rock slope behavior. The objective was to find well-proven engineering solutions to slope stability problems. Following a short overview of the numerical methods available, FEM, DEM and FEDEM, the presentation considered two case studies.

The First Case Study described the rock mechanics and rock engineering activities carried out in order to assess the stability of a 120m high rock slope in a limestone quarry. The rock slope is characterized by the presence of a large size rock volume, in limit equilibrium conditions, which impairs quarrying activities. In situ investigations including detailed geological mapping and 3D imaging with a laser scanning equipment are described. The results of real-time monitoring by ground based interferometric synthetic aperture radar (GBInSAR) images were also presented. Three-dimensional discontinuum modeling involving a back analysis of a plane sliding instability at the toe of the slope and detailed slope stability studies of the rock volume, aimed at the definition of the likely instability scenarios, were described. 

The Second Case Study considered the interaction between twin tunnels and a deep-seated landslide. The geological, hydrogeological, and geotechnical conditions, the available monitoring data on the landslide movements, based on interferometric synthetic aperture radar (InSAR) images, real-time monitoring through multi-purpose electronic surveying instruments and inclinometers were described. Three-dimensional continuum modelling is discussed with the purpose to back-analyze the monitored surface and subsurface deformations, in order to gain insights into the interaction, during excavation, between the twin tunnels and a deep- seated landslide. The modelling results obtained in terms of induced displacements on the ground surface and below, the induced plastic zones, and the shearing strains along the shear surface, were compared with the performance monitoring data.

In conclusion, an attempt was made to assess the potentials and limitations of computer modelling of complex conditions as a means for forecasting the slope behaviour, based on the real-time monitoring data obtained at a given site.

Agenda

• Welcome
  David Quinn, NAFEMS
  
• An Introduction to COGAN
  Dr Andrew Lees, Geofem
  
• The Importance of Numerical Analysis for Understanding Rock Slope Behaviour
  Giovanni Barla, Former Professor of Rock Mechanics at Politecnico di Torino, Honorary Professor of Chongqing University
  
  

Q & A Session

Closing

This webinar was the second of two sponsored by the COGAN project (link to first webinar), which is funded by the EU under the Leonardo initiative.  For some years there has been a need in the geotechnical industry to address the inconsistent implementation of increasingly powerful numerical analysis software (e.g. finite element analysis).

Previous benchmark studies have suggested that the inconsistency is primarily a result of users of analysis software lacking the necessary competency.

Therefore, the primary goal of COGAN is to improve competency in geotechnical numerical analysis.

Further information is available on the project website at COGAN.