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.
Q & A Session
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.
Giovanni Barla graduated in mining engineering from Politecnico di Torino in 1965. He moved to Columbia University, New York, where he obtained the MScEng degree in 1967 and the PhD degree in 1970, defending a thesis on the analytical and numerical (finite element method) analysis of stress distribution around underground excavations. He came back to Italy and joined the Politecnico di Torino as assistant professor and was in charge of the first course on rock mechanics taught in the Italian universities.
Subsequently, Giovanni Barla became associate professor and the t the Politecnico di Torino Giovanni Barla has been vice-president of the n full professor of rock mechanics at the Politecnico di Torino in 1980. There he developed and taught courses on rock mechanics principles, advanced topics in rock mechanics and rock engineering, and numerical methods in geotechnical engineering. His lectures are published in Italian and are available in ppt format and note-books. Also available is a 25 hour lecture series on rock mechanics fundamentals prepared in 2005, currently broadcasted by the Nettuno TV Open Sky University Network.
School of Engineering and head of the Department of Structural and Geotechnical Engineering from 2003 to 2011. In the mid-seventies he was appointed as associate professor of rock mechanics at Columbia University,
New York, where he taught post graduate courses on rock mechanics and rock engineering, and numerical methods. He carried out research in the framework of contracts financed by the US Department of Energy and by the US Bureau of Mines.
Andrew Lees is Director of the geotechnical analysis consultancy Geofem and coordinator of the COGAN project.