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11/17/08
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Shawn Kenny, Ph.D., P.Eng.
Assistant Professor
Faculty of Engineering and Applied Science
Memorial University of Newfoundland
Lecture 15 – Slope Stability
ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Lecture Goals
!!Students will be able to:
!! identify slope failure modes,
!!characterize methods used to improve slope
stability,
!!characterize the primary methods used to
analyse slope stability, and
!!select appropriate techniques based on the
engineering problem to be examined.
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Reading List
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Das (2006). Principles of Geotechnical Engineering. 6th Edition
Section Title
14.1 Factor of Safety
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Factors Influencing Slope Stability
!!Slope Gradient, Orientation and Landform
!!Geological and Geotechnical Conditions
!!Terrain Characteristics
!!Precipitation and Water Table Levels
!!Natural Process or Human Modification
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Changed Conditions for Existing Slopes
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McCarthy (2007)
ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
New Slopes from Construction
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McCarthy (2007)
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Failure Mechanisms
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McCarthy (2007)
ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Failure Mechanisms
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McCarthy (2007)
ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Rotational Slide Characteristics
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McCarthy (2007)
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Slope Failures
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Slope Stability Analysis Techniques
!! 2-D Limit Equilibrium !! Analytical
!! Wedge method
!! Mass procedure
!! Method of slices
!! Graphical !! Force polygon
!! Design charts
!! More Complex Procedures !! Numerical analysis
!! FLAC
!! SLOPE/W
!! UTEXAS
!! STABL
!! General finite element packages
!! 3-D limit equilibrium
!! Probabilistic techniques
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
General Procedure – Slope Stability
!! Define Soil Characteristics !! Boreholes, cross-section and layering
!! Soil type, strength properties !! Groundwater and seepage conditions
!! Analysis Framework !! Select slope stability technique
!! Define design conditions !! End of construction
!! Steady state seepage
!! Rapid or sudden drawdown
!! Earthquake
!! Assume slip surface
!! Determine critical slip surface !! Estimate factor of safety
!! Compare with recommended practice
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USACE (2003)
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ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Methods to Improve Slope Stability
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McCarthy (2007)
ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
Methods to Improve Slope Stability
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McCarthy (2007)
ENGI 6723 Geotechnical Engineering II – Lecture 15 © 2008 S. Kenny, Ph.D., P.Eng.
References
!!Das, B.M. (2006). Principles of
Geotechnical Engineering, 6th Edition.
ISBN 0534551440
!!McCarthy, D.F. (2007). Essentials of Soil
Mechanics and Foundations, 7th Edition.
ISBN 0131145606
!!USACE (2003). Slope Stability.
EM-1110-2-1902, 205p.
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