1.
Slope Stability Analysis
Under Seismic Loading
SVNIT, SURAT

2.
Slope stability is the process of calculating and assessing how
much stress a particular slope can manage before failing.
Examples of common slopes include roads for commercial use,
dams, excavated slopes, and soft rock trails in reservoirs, forests,
and parks.
What is slope stability ?

3.
SLOPE:
An exposed ground surface that stands at angle with the horizontal is called an
unrestrained slope
Two types of slopes
I. Natural slopes
II. Man made slopes
INTRODUCTION

4.
INTRODUCTION
Natural slope Man made slope

5.
Landslide occurs in both natural and man made slopes
Earthquake –induces landslides have caused great amounts of damage and loss
of life throughout history
Earthquake induced ground shaking is one of the most frequent causes of
landslides
Thus, evaluation of seismic slope stability is one of the most important activities
of earthquake
INTRODUCTION

6.
Types of slope failures
There are a main four types of
failures.
I. Plain failure
II. Rotational failure
III. Wedge failure
IV. Circular failure

7.
Evaluation of slope stability
The collection of information on
geological, hydrological,
topographical, geometrical and
material characteristic.
Field reconnaissance
Monitoring of slope movement.
Subsurface investigation.
Laboratory test.

8.
• The explicit finite element method is used to analyze the seismic slope stability.
• Engineers analyze slope to calculate quantitative indicators of performance
such as factor of safety, lateral deformation, probability of failure and reliability
index. Slope stability analysis includes static and dynamic stability of earth
slopes, natural slopes, cut slopes, embankments, landslides, etc.
• Limit equilibrium method and slices-based method, which are more traditional
methods, are used in the analysis in the stability of soil slopes under seismic
loading.
Slope stability analysis under seismic load

9.
Software used
FLAC3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) is numerical
modeling software for geotechnical analyses of soil, rock, groundwater,
constructs, and ground support.

10.
• Different from the LEM and the FE-SRM.
• The factor of safety therein is defined as the ratio of projection of vector sum of
ultimate resistance forces to that of current driving forces in the potential
sliding direction.
The VSAM under seismic load

11.
The factor of safety can be obtained with the VSAM:
𝑘 =
𝑅
𝑇
𝑅 = 𝑠
(𝜎′𝑠 𝑑)𝑑𝑠
𝑇 = 𝑠
𝜎′
𝑠
−𝑑 𝑑𝑠
where R and T are the total anti-sliding force and the total sliding force in the potential sliding direction,
respectively; and d is the global potential sliding direction.
The maximum shear stress can be expressed as
𝜎′𝑇 = −(𝑐 − 𝜎𝑛𝑡𝑎𝑛∅)𝑑𝑡
where c is the cohesion of the soil, φ is the friction angle, and dr is the direction of unit shear stress at any
point on the sliding face.
The VSAM under seismic load

12.
Procedure of seismic stability with VSAM

13.
The Effect of Earthquake to Stability and Run Out Distance of Landslide
During Rainfall :
• a case study of landslide prone area in West Java, Indonesia
• Indonesia lies within a convergent zone between three plates, the Pacific plate, the Eurasian plate, and
the Australian Indian plate.
Case study

14.
• Earthquakes are natural disasters characterized by vibrating earth's surface.
• Occurrence of landslide.
• the movement of a mass of rock, debris, or earth down a slope is called landslide.
• The possibility of earthquake induced landslides must also be linked to several factors
including topography, geological structure, other landslide causing factors and land use.
Case study (introduction)

15.
The information is used as the material properties of the avalanche material and the slip fields of the slope model.
To determine the prediction of run-out and landslide speed, use numerical simulation of rainfall intensity using Geo-
Seep/W, Earthquake Acceleration using Quake/W, and slope stability can be analyzed using Geo-Slope/W
Materials and methods

16.
Result and discussion

17.
The safety factor will decrease with the increasing slope angle as shown in
Figure, It shows that under the same soil parameters conditions, the larger the
slope angle, the slope conditions will be more unstable.
Result and discussion

18.
• The intensity of rainfall and earthquake can decrease the value of safety factor.
• Factor will decrease along with the enlargement of the slope angle. The larger the angle of the slope, the
slope will be more unstable.
• As the soil friction angle increases, so does the horizontal displacement of the soil particles applied to
seismic loading, but the velocity amplification of the soil particles also decreases as the soil friction angle
rises.
Conclusion

19.
The larger the angle of the slope the greater the thrust caused by the increase in the shear strength of the
soil. This is the effect on the run-out, the greater the angle of the slope the lower run-out landslides.
The difference of landslide run-out value is caused by the difference in slope, positive water-pore pressure
zone and slope shear angle.
Case study