SYNOPSIS

Even with excellent site characterization, assumptions are needed to enable reliable analysis of slope stability.  Commonly, in what are known as General Limit Equilibrium (GLE) methods, the slide mass,  with circular or non-circular slip surface, is divided into slices.   Assumptions then have to be made about inter-slice forces and the safety factor is assumed to be the same in all slices.  Recent analyses replace the assumption of inter-slice forces with finite element analysis of stress distributions and permit evaluation of variable safety factors along slide surfaces.  
Analyses that rely on total stress strengths are known to be unreliable.  Effective stress strengths provide more reliable answers but require a sound understanding of pore water pressures when failure did occur, or will occur.  This means that consideration must be given to transient hydraulic potentials at the toe, in the slope itself, at the ground surface in the form of rainfall or evapotranspiration, and in underlying aquifer(s).  
The lecture will provide an overview of this background material and present short case studies of riverbank instabilities, a highway cut that failed after rainfall destroyed suction forces, and a water-retention dike that failed when seepage dissolved gypsum cementation.  


PROFILE OF SPEAKER

Jim Graham holds PhD and DSc degrees from Queen’s University, Belfast, N.Ireland. He is a Fellow of the Engineering Institute of Canada, and a Professional Engineer in the Province of Manitoba. He has been Scientific Editor of the Canadian Geotechnical Journal; and President and Secretary General of the Canadian Geotechnical Society.  He is currently Professor Emeritus, in the Civil Engineering Department, University of Manitoba, where he spent many years developing innovative courses for teaching geotechnical engineering at undergraduate and postgraduate levels.  He has published widely on this topic and received the Saunderson Award for Excellence in Teaching.  
Dr. Graham has received awards from the Engineering Institute of Canada, the Canadian Council of Professional Engineers, and the R.F. Legget Medal from the Canadian Geotechnical Society.  
He has published over 200 articles on a wide range of topics in geotechnical engineering and has been a consultant for local engineering consulting companies.