Table of Contents SLOPE/W
Page ii
3.10
Sarma method ................................................................................................................... 48
3.11 Janbu’s Generalized method ............................................................................................ 49
3.12 Finite element stress-based method ................................................................................. 51
3.13 Commentary on finite element stress-based method ....................................................... 56
3.14 Selecting an appropriate method ...................................................................................... 57
3.15 Rapid Drawdown Analysis Methods ................................................................................. 58
The Simple Effective Strength Method ....................................................................... 59
The Rigorous Effective Strength Method ................................................................... 59
The Staged Undrained Strength Method .................................................................... 60
4 Slip Surface Shapes ......................................................................... 63
4.1 Introduction and background ............................................................................................ 63
4.2 Grid and radius for circular slips ....................................................................................... 63
Single radius point ...................................................................................................... 65
Multiple radius points .................................................................................................. 66
Lateral extent of radius lines....................................................................................... 66
Factor of Safety contours ........................................................................................... 67
4.3 Composite slip surfaces .................................................................................................... 68
4.4 Fully specified slip surfaces .............................................................................................. 71
4.5 Block specified slip surface ............................................................................................... 73
General cross-over form ............................................................................................. 73
Specific parallel form .................................................................................................. 75
4.6 Entry and exit specification ............................................................................................... 77
4.7 Optimization ...................................................................................................................... 79
4.8 Effect of soil strength......................................................................................................... 82
Purely frictional case .................................................................................................. 82
Undrained strength case ............................................................................................ 84
Cause of unrealistic response .................................................................................... 84
Minimum depth ........................................................................................................... 86
Most realistic slip surface position .............................................................................. 86
4.9 Tension cracks and exit projections .................................................................................. 86
Tension crack angle ................................................................................................... 86
Constant tension crack depth ..................................................................................... 87
Tension crack fluid pressures ..................................................................................... 87
Toe projection ............................................................................................................. 87
4.10 Physical admissibility ........................................................................................................ 88
4.11 Invalid slip surfaces and factors of safety ......................................................................... 89
