Volume 6 – Geotechnical Manual, Site Investigation and Engineering ...

Chapter 6 SLOPE STABILITY
Table of Contents
Table of Contents .................................................................................................................... 6-I
List of Tables ....................................................................................................................... 6-III
List of Figures ...................................................................................................................... 6-III
6.1 INTRODUCTION ..................................................................................................... 6-1
6.2 TYPE OF SLOPE INSTABILITIES ............................................................................... 6-1
6.2.1 Infinite Slope Failure .............................................................................. 6-1
6.2.2 Sliding Block Failure ............................................................................... 6-1
6.2.3 Circular Arc Failure ................................................................................. 6-2
6.3 GENERAL PROCEDURE FOR ANALYSIS ..................................................................... 6-3
6.3.1 Obtaining Subsurface Information ........................................................... 6-3
6.3.2 Determining of Soil Shear Strengths ........................................................ 6-3
6.3.3 Determining a Potential Slide Failure Surface ............................................ 6-3
6.4 PRINCIPLES OF ANALYSIS ...................................................................................... 6-4
6.4.1 Method of Analysis ................................................................................. 6-4
6.4.2 Stages of Stress Analysis ........................................................................ 6-4
6.4.2.1 Short-Term (or At-the-end-of-construction) .............................. 6-4
6.4.2.2 Long-term ............................................................................. 6-5
6.5 CIRCULAR ARC ANALYSIS ....................................................................................... 6-5
6.5.1 General Principles................................................................................... 6-5
6.5.2 Location of the Critical Slip Surface .......................................................... 6-6
6.5.4 Required Safety Factors .......................................................................... 6-7
6.5.5 Cut Slope in Clay .................................................................................... 6-7
6.5.6 Filled Slope/Embankment on Clay ............................................................ 6-8
6.5.7 Effects of Water ..................................................................................... 6-8
6.5.7.1 Effects on Cohesionless Soils ................................................... 6-9
6.5.7.2 Effects on Cohesive Soils ........................................................ 6-9
6.5.8 Method of Slides for Circular Failure ......................................................... 6-9
6.5.9 Finite Element Methods ........................................................................ 6-11
6.6 SLIDING BLOCK FAILURE ...................................................................................... 6-12
6.7 SLOPE STABILIZATION METHODS ......................................................................... 6-13
6.7.1 Slope Flattening ................................................................................... 6-13
6.7.2 Drainage ............................................................................................. 6-13
6.7.3 Buttressing or Counter Berm ................................................................. 6-14
6.7.4 Soil Nailing .......................................................................................... 6-14
March 2009 6-i