ABSTRACT
CONTENTS 11.1 Introduction ................................................................................................................... 486
11.1.1 Required Minimum Factors of Safety ......................................................... 487 11.2 Analysis of Finite Slopes with Plane Failures.......................................................... 487 11.3 Method of Slices............................................................................................................ 489
11.3.1 Ordinary Method of Slices ............................................................................ 492 11.3.2 Bishop’s Simplified Method.......................................................................... 492
11.4 Slope-Stability Analysis Using the Stability Number Method.............................. 496 11.4.1 Stability Analysis of a Homogeneous Slope Based
on an Assumed Failure Surface.................................................................... 496 11.4.1.1 Plane Failure Surface...................................................................... 497 11.4.1.2 Circular Failure Surface................................................................. 497
11.4.2 Stability Analysis of a Homogeneous Slope Based on the Critical Failure Surface ...................................................................... 498 11.4.2.1 Closed-Form Solution.................................................................... 498 11.4.2.2 Use of Taylor’s Stability Charts ................................................... 498
11.5 Stabilization of Slopes with Piles ............................................................................... 503 11.5.1 Lateral Earth Pressure on Piles..................................................................... 503 11.5.2 Analysis Using the Friction-Circle Method................................................ 504 11.5.3 Design Methodology ...................................................................................... 505
11.6 Reinforcement of Slopes with Geotextiles and Geogrids....................................... 506 11.6.1 Reinforcement with Geotextiles ................................................................... 506 11.6.2 Geogrid Reinforced Slope.............................................................................. 507
11.7 Reliability-Based Slope Design................................................................................... 507 11.7.1 Reliability Estimates with Random Loads ................................................. 509
11.7.1.1 Use of the Lognormal Distribution.............................................. 510 11.8 Slope Instability and Landslides ................................................................................ 512
11.8.1 Factors Causing Landslides .......................................................................... 512 11.8.1.1 Bedrock Geology............................................................................. 512 11.8.1.2 Hydrology........................................................................................ 513 11.8.1.3 Surface Overburden ....................................................................... 513 11.8.1.4 Slope Range ..................................................................................... 513 11.8.1.5 Land Use .......................................................................................... 513 11.8.1.6 Landform ......................................................................................... 513
11.8.2 Impact of Rainfall on Slope Instability........................................................ 513 11.9 Investigation of Slope Failures ................................................................................... 514 11.10 Approximate Three-Dimensional Slope-Stability Analysis ................................... 514 11.11 Additional Examples.................................................................................................... 515
Construction of building foundations and highways on sloping ground or embankments can present instability problems due to potential shear failure. Therefore, geotechnical designers are often required to design stable embankments that would allow additional construction such as highways and buildings on top of them. On the other hand, instability could also result due to partial excavation of slopes during foundation construction. Furthermore, when one designs a structure in the vicinity of a slope, then safety considerations would naturally warrant a stability analysis of that slope. Hence, designers are often required to perform a ground stability analysis in addition to the foundation design. Stability analysis can be performed more effectively and accurately if the analyst comprehends the specific causes of potential slope failure under the given geological conditions.
