landslides.pptx

Landslides
GROUP MEMBERS SAP ID
 SIBGHAT ULLAH ( 70100133)
 ZUBAIR ASIF ALI (70102578)
 M. SUDAIS (70101135)
 NOUMAN KHAN (70102169)
 HARIS HAMEED (70102707)
 TAIMOOR BABAR (70099919)
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• Most humans consider Earth to be
“terra firma.”
• Earth’s surface, however, is mostly
unstable ground.
• This is a consequence of
weathering and erosion.
• We may be reminded of this
instability without warning.
Landslides

• Landslide (also called mass movement) is defined as the
downslope movement of material under the direct influence
of gravity .
• Most types of mass movement are aided by weathering
and usually involve surficial material.
• Landslides are an important geologic process that can
occur at any time and almost any place.
• While they are mostly associated with steep and unstable
slopes, they can also occur on near-level and given the
right geological conditions.
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Landslides

• The landslide starts with slow movements
along a slip surface, followed by a more rapid,
movement of the separated portion of earth
mass.
• The slip surface is usually bounded by a crack
• The chief types of landslides are :
(i) Slump,
(ii) Rock slides and
(iii)Rock falls
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Landslides

• When the gravitational force acting on a slope exceeds its
resisting force, slope failure (landslide) occurs.
• The resisting force helping to maintain slope stability
include the slope material’s strength; cohesion and the
amount of internal friction between grains and any
external support of the slope.
• These factors collectively define a slope’s shear strength.
• Opposing slope’s shear strength is the force of gravity.
Gravity operates vertically but has a component acting
parallel to the slope, thereby causing instability.
• The greater a slope’s angle, the greater the component
of force acting parallel to the slope and the greater the
chance for mass movement.
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Landslides

The. factors which promote landslides are :
i. Water
ii. Slopes
iii.nature of rocks
iv.structure of rocks, and
v. disturbance of equilibrium.
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Causes of Landslides

• The essential conditions which cause landslides are lack
of support in front and lubrication behind.
• Thus water is an important factor in causing landslides.
• It acts in following ways
 Water diminishes the strength of rocks and thus help
in their movement.
 Water seeps into the rock or soil produces lubrication
and also exerts additional force on the grains tending
to displace them along the direction of water
movement.
• It adds weight to the material. Hence
many landslides occur after rains.
• On freezing it exerts an expansive force.
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i. Water

• It has been observed that majority of the earth or rock
failures are confined to slopes.
• This indicates that slopes are directly responsible for
landslides. As a rule, steeper the slope, greater is the
instability of such a mass.
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ii. Slope

SLOPE CAN CAUSES
LANDSLIDES
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• Unconsolidated sediments, such as clay, sand, gravel,
etc. can not stand permanently along slopes greater
than their angle of repose (about 35°) and are likely
to be affected by landslides.
• Where weak and slippery rocks like shale, volcanic
tuff are present, they are not likely to remain stable
on steep slopes for a considerable period of time.
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iii.Nature of Rocks.

• Joints, fractures, shear zones and bedding planes
usually become the slip surface in case of rock slides.
12 iv.Structure of Rocks

1. Rotational slide:
This is a slide in which the
surface of rupture is curved
concavely upward and the
slide movement is roughly
rotational.
Types of Landslides
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Rotational
Slide
14 Types of Landslides

2. Translational slide:
In this type of slide, the
landslide mass moves along a
roughly planar surface with
little rotation or backward
tilting.
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Types of Landslides

3. Block slide:
It is a translational slide
in which the moving
mass consists of a
single unit or a few
closely related units
that move downslope
as a relatively coherent
mass.
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Types of Landslides

Falls are abrupt movements of masses of
geologic materials, such as rocks and
boulders, that become detached from
steep slopes or cliffs.
Separation occurs along discontinuities
such as fractures, joints, and bedding
planes, and movement occurs by free-fall,
bouncing, and rolling.
Falls are strongly influenced by gravity,
mechanical weathering, and the presence
of interstitial water.
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4. Fall:
Types of Landslides

5. Earthflow:
This is a variety of
very rapid to
extremely rapid
earth material flow.
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Types of Landslides

6. MUDSLIDES/Debris flow:
A debris flow is a form of rapid mass movement in which a combination
of loose soil, rock, organic matter, air, and water mobilize as a slurry
that flows down slope. Debris flows include less than 50% fines.
Debris flows are commonly caused by intense surface-water flow, due
to heavy precipitation or rapid snowmelt, that erodes and mobilizes
loose soil or rock on steep slopes.
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Types of Landslides

7. MUDSLIDES/Mudflow:
A mudflow is an earthflow consisting of material that is wet
enough to flow rapidly and that contains at least 50 percent
sand – silt - and clay - sized particles. Sometimes, mudflows
and debris flows are commonly referred to as "mudslides”
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Types of Landslides

8. Lateral Spreads:
Lateral spreads are distinctive because they usually occur on very gentle
slopes or flat terrain. The dominant mode of movement is lateral
extension accompanied by shear or tensile fractures. The failure is
caused by liquefaction, the process whereby saturated, loose, cohesion
less sediments (usually sands and silts) are transformed from a solid
into a liquefied state. Failure is usually triggered by rapid ground
motion, such as that experienced during an earthquake, but can also be
artificially induced.
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Types of Landslides

9. Creep:
Creep is the imperceptibly slow, steady, downward movement of
slope-forming soil or rock. Movement is caused by shear stress
sufficient to produce permanent deformation, but too small to
produce shear failure. Creep is indicated by curved tree trunks,
bent fences or retaining walls, tilted poles or fences, and small
soil ripples or ridges
Types of Landslides
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Effects of Landslides
Landslides can disturb the social and economic environment with the number of other damages
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Short Term Impacts
 The natural beauty of the area is damaged.
 Loss of life and property
 Roadblocks
 Destruction of railway lines
 Channel blocking because of the falling of rocks.
 It leads to the diversion of river water, which can cause floods as
well.
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Long Term Impacts
 Landscape changes can be permanent.
 The loss of fertile land or cultivation land.
 Erosion and soil loss can lead to environmental problems.
 Population shifting and migration.
 Effects on the sources of water.
 Some roads can be damaged or closed permanently.
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The methods which are commonly used for prevention of
landslides are follows
1. Slides in the impervious material are prevented by
reducing slopes.
2. Efforts should also be made not to allow the
additional water to enter into the material.
3. To check/limit the surface water to enter into the
unstable ground, it is diverted and made to run off as
rapidly as possible away from that area.
4. In pervious materials, landslides may be prevented
by increasing the internal friction of the mass by
lowering the water content.
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Prevention of Landslides.

5. Their water may be removed by drain pipes, by
drainage through tunnels or by pumping from wells.
6. In situations where slides may cause loss of life and
property, the loose rock material is prevented from
sliding by constructing retaining walls, concrete piers
or by use of piling.
7. At some places the unstable unconsolidated material
may be consolidated by cement grouting, chemical
means, and artificial freezing.
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Prevention of Landslides.

How to Prevent a Landslide
Landslides can range from minor inconveniences that leave debris on
your property to major accidents that can cause severe damage.
Naturally, if you live in a landslide-prone area, you’d want to do all
you can to protect your property. While you can’t always prevent
them, there are a number of precautions you can take to lower the
risk of a landslide occurring on your property and decrease the
damage you’ll experience if one happens
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Keeping Material and
Structures Away from Slopes
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Remove loose or heavy material
from the top of the slope
Rocks, fallen trees, and other debris at the top of a hill can put your
property at risk for a landslide. Clean off all the slopes on your
property to remove material that might come loose. Move this debris
away from the slope, on the base, or off your property altogether.
• You might need a professional with heavy equipment to remove
heavy rocks and soil. Consult a contractor on hauling away heavy
material like this.
• Be courteous to your neighbors when you relocate this material.
Don't put them in a place where they could slide onto your
neighbors' property.
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Controlling the Water on
Your Property
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Fix any leaks in your pipes or
drainage system.
Leaks in your water system can gradually erode the soil under your
property. Have a professional go through your pipes and make sure
there are no leaks. If they do locate leaks, fix them right away.
• There are a few signs that you might have a water leak. These
include an unusually high water bill, a musty smell in some areas of
your home, or puddles on your property when it hasn’t rained
recently.
• Remember to check your outdoor water lines as well, like your
hose, pool, and sprinkler system if you have one. Leaky pools are a
particular cause of gradual soil erosion.
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Remove loose soil and replace
it with more dense material
Over time, soil can erode and grow more prone to landslides. Speak
with a contractor about replacing your topsoil with denser, sandy soil
that’s more tightly-packed. This can help make the land on your
property more stable.
• This is a professional job that requires machinery and equipment.
Don’t try to do it on your own.
• Do not push any old material back up the slope or towards the
edge. This increases the landslide risk.
• Take other measures to protect the soil besides replacement. Over
time, the new soil will erode as well and become landslide-prone
without other steps.
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Build retaining wall at the base
of a slope to protect your home
If you live in a landslide-prone area or at the base of a hill, then this
is your best chance for protection. Extend the wall for the entire
length of your property for the best protection. A reinforced retaining
wall with metal spikes drilled into the ground rock is the best method
to guard against landslides. The footing should be behind the wall and
as wide as the height of the wall. This can prevent landslides or divert
the flow away from your home.
• If you build a wall, putting drainage behind the wall is extremely
important. This will prevent the wall from tipping over and sliding
down the hill if any pressure buildup or water accumulates in front
of it.
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Dig a ditch to divert landslides
away from your home.
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Even with other preventative measures, landslides can still happen. In
this case, you can still protect your home with a ditch surrounding
your property. This can capture or divert the debris to another
location, protecting your home
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LANDSLIDES
Landslide Remediation
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LANDSLIDES
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LANDSLIDES
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LANDSLIDES
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