The document discusses slope stability analysis. It defines slopes and describes types of natural and man-made slopes. Slope stability is important for earth dams and natural slopes to prevent catastrophic failures. Factors that cause slope instability include gravitational forces, seepage water, surface erosion, lowering of adjacent water levels, and earthquakes. Common types of slope failures are rotational, translational, compound, and wedge failures. Rotational failures occur along a circular or non-circular slip surface. Translational failures occur along failure surfaces parallel to infinite slopes. Compound failures combine rotational and translational slips. Wedge failures involve separation of soil blocks along inclined planes of weakness.

1. STABILITY ANALYSIS OF SLOPES
DEPT. OF CIVIL ENGINEERING
SIR C R REDDY COLLEGE OF ENGG.
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2. Contents
• Slope-Definition
• Types of Slopes
• Slope Stability
• Causes of Slope failure
• Factor of Safety
• Stability Analysis of
infinite slopes
▫ Slopes in Sand
▫ Slopes in Clay
• Stability Analysis of finite
slopes
▫ Swedish Slip Circle Method
• Taylor’s Stability Number
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3. Slope
• Slope is an unsupported and inclined soil mass
used to maintain level in Engineering works.
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4. Slopes are
Natural Slopes Man made Slopes
Natural Slopes are those that
exist in nature and are formed
by Natural Causes. Such
Slopes exist in Hilly areas.
Man made Slopes are
constructed by cutting or
filling for various purposes.
▫ Drains
▫ Irrigation canals
▫ Railway Embankments
▫ Highway Embankments
 Hills
 Mountains
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5. Slopes are
Infinite Slopes Finite Slopes
The term infinite slope is used to
designate a constant slope of
infinite extent.
Ex: The long slope of the face of
a mountain.
The term infinite slope is used to
designate a slope of limited
extent.
Ex: Embankments
Cuttings
Earthen Dams
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6. Slope Stability
Slope Stability is an extremely important
consideration in the design and construction of
earth dams. The stability of a natural slope is
also important. The results of a slope failure can
often be catastrophic, involving the loss of
considerable property and many lives.
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7. Failure of Slopes: Causes
The important factors that cause instability in a
slope and lead to failure are
1. Gravitational force
2. Force due to seepage water
3. Erosion of the surface of slopes due to flowing
water
4. The sudden lowering of water adjacent to a
slope
5. Forces due to earthquakes
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10. Failure of Slopes: Types
A slope may have any one of the following types of
failures.
• Rotational failure
▫ Toe failure
▫ Slope failure
▫ Base failure
• Translational failure
• Compound failure
• Wedge failure
• Miscellaneous failure
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11. Rotational failure
This type of failure occurs by rotation along a slip surface
by downward and outward movement of the soil mass.
The slip surface is generally circular for homogeneous
soil conditions and non-circular in case of non-
homogeneous conditions. Rotational slips are further
divided into 3 types.
a. Toe failure, in which the failure occurs along the surface
that passes through the toe (Fig.a).
b. Slope failure, in which the failure occurs along a surface
that intersects the slope above the toe (Fig.b).
c. Base failure, in which the failure surface passes below
the toe (Fig.c).
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12. Rotational failure: Types
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The slope failure occurs when a weak plane exists above the toe. The base
failure occurs when a weak stratum lies beneath the toe. If a strong
stratum exists below the toe, the slip surface of the base failure is
tangential to that stratum. In all other cases, the failures are generally toe
failures. Toe failures are most common.

13. Translational failure:
A constant slope of unlimited extent and having
uniform soil properties at the same depth below
the free surface is known as an infinite slope. In
practice, the slopes which are of considerable
extent and in which the condition on all verticals
are adequately represented by average
conditions are designated as infinite slopes.
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14. Translational failure occurs in an infinite slope
along failure surface parallel to the slope. The
shape of the failure surface is influenced by the
presence of any hard stratum at a shallow depth
below the slope surface. Translational failures
may also occur along slopes of layered materials.
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15. Compound failure:
A compound failure is a
combination of the
rotational slip and the
translational slip.
A compound failure
surface is curved at the
two ends and plane in
the middle portion.
A compound failure
generally occurs when a
hard stratum exists at
considerable depth
below the toe.
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16. Wedge failure:
A failure along an inclined plain
is known as plane failure or
wedge failure or block failure.
It occurs when distinct blocks
and wedges of the soil mass
become separated.
A plane failure is similar to
translational failure in many
aspects. However unlike
translational failure which
occurs in an infinite slope, a
plane failure may occur even
in a finite slope consisting of
two different materials or in a
homogeneous slope having
cracks, fissures, joints or any
other specific plane of
weakness.
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18. Thank You
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