Land slide

By- Akhtar KamalBy- Akhtar Kamal

LandslideLandslide It is refers to the downward sliding of huge quantities of

land mass Downward movement of slope forming material

composed of rocks and soil or combination of all these material along surfaces of separation by FALLING, SLIDING AND FLOWING either sudden or slow from one place to another place.

05/03/23Prepared by AKHTAR KAMAL

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Classification of Earth MovementsClassification of Earth Movements All movement of land masses are referred as landslides, but differ in

many respects, therefore all types of landslides are categorized as Earth Movements.


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SolifuctionSolifuction Solifuction is a downward movement of wet soil along the

slopes under the influence of gravity.


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Soil CreepSoil Creep Creep is extremely slow

downward movement of dry surfacial matter.

Movement of the soil occurs in regions which are subjected to freeze-thaw conditions. The freeze lifts the particles of soil and rocks and when there is a thaw, the particles are set back down, but not in the same place as before.

It is very important for CEs to know the rate of movement


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Rapid FlowsRapid Flows Rapid flow is similar to the creep, but differ in terms of

speed and depth. It is faster.

Creep is involved up to shallow depth (app. 1-2 m), whereas the rapid flow is involved to greater depth (app. up to 5 m or more)


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LandslidesLandslides If a mass of earth moves along a

surface the failure is termed as Landslide

Large block known as a slump block moves during the landslide.

The scar above a landslide is easily visible.

They can occur along a slope where the internal resistance of the rocks are reduced or they loose their holding capacity.

Common after earthquakes or after removal of part of the slope due to construction, particularly for construction of roads. 05/03/23Prepared by AKHTAR KAMAL

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During the movement landslide can result into the Debris slides - are failure of unconsolidated material on a surface; Rock slide or Rock Fall – where movement of large rock block rolls

They are also common along the steep banks of rivers, lakes etc.

Pore Water Pressure is the key to monitoring landslides. Shear strength (a resisting force) decreases and the weight (a driving force increases).


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Talus – accumulation formed Talus – accumulation formed by the coarser rock fragments by the coarser rock fragments resulted from the mechanical resulted from the mechanical weathering along a slope weathering along a slope under influence of gravityunder influence of gravity

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SubsidenceSubsidence It represents the downward movement of the surface It may occur due to plastic outflow of the underlying

strata or due to the compaction of the underlying material1) Subsidence due to Plastic outflow:

It may occur when a plastic layer like clay bed is squeezed outward due to overlying heavy load

2) Subsidence due to collapse It occur due to extensive pull out of large volume of underground

water or due to subsurface solution activity in limestone terrain.05/03/23Prepared by AKHTAR KAMAL

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SubsidenceSubsidence The Leaning Tower of Pisa, Italy, the tilting of which

accelerated as groundwater was withdrawn from aquifers to supply the growing city.


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Causes of LandslidesCauses of Landslides LANDSLIDES OCCUR DUE OF VARIOUS REASONSLANDSLIDES OCCUR DUE OF VARIOUS REASONS Internal Causes:Internal Causes: Geological Weak Material

Weakness in the composition and structure of rock or soil may also cause landslide.

Erosion Erosion of slope due to cutting down of vegetation, construction of road might

increase the vulnerability of terrain to slide down. Intense rainfall

Storm that produce intense rainfall periods as short as several hour also result in land slide. heavy melting of snow in the hilly terrains also result in landslide.

Influence of slope Provides favourable condition for landslides; steeper slope are prone to slippage

of land. It is known that most of the materials are stable up to certain angle- “Critical angle” or “angle of repose” – it varies from 300 for unconsolidated sediments to 900 for massive rocks and 600-900 for partially jointed rocks.05/03/23Prepared by AKHTAR KAMAL

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Geological structures Occurrence of inclined bedding planes, joints, fault or shear zone are the planes of

weakness, which create conditions of instability. Human Influence

Undercutting along the hill slopes for laying roads or rail tracks can result into instability.

Deforestation in the uplands, result into more erosion during the rainy season. Ground water or associated water

Main factor responsible for slippage. Suppose the hard or massive rocks are underlined by softer rocks (shale or clay bed)

When rain water percolates through some fractures or joints the clayey beds becomes very plastic and acts as slippery base, which enhance the chances of loose overburden to slip downward.

Water is the most powerful solvent, which not only causes decomposition of minerals but also leaches out the soluble matter of the rock and reduces the strength.05/03/23Prepared by AKHTAR KAMAL

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External factorsExternal factors Most common is the vibration resulted due to earthquakes;

blasting to explosives; volcanic eruption etc.

Earthquakes often initiate mass failures on large scale eg. 1897 Assam quake produced gigantic landslide ever recorded in the region.


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Effects of LandslidesEffects of Landslides Landslides are a major catastrophe the world as it is widespread and

significant impact. The effects of landslides is dangerous to humans and to other living things

For example, the slope of the saturated with water to form debris flows or mudflows. Concentrated mixture of rock and mud may destroy the trees, houses, and cars and blocking the bridge. Mud mixed with river flow can cause devastating flooding along the route.

Similarly, the ice floes formed in the river caused by ice clogging the rivers and flows more slowly. However, it can produce enough energy to destroy the bridge. Ice may accumulate on the edge or on top of weak layers of snow or unstable causes crash occurred.

Pyroclastic flows (pyroclastic) arising from dust debris of ash, poisonous gas and hot rock from volcanic eruptions that spread quickly to eat anything that travelled to the effects of destruction and death. Among the social effects that can be described as…


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1. Economic Decline 1. Economic Decline Landslides are certainly cause damage to property. This brings losses to the economy of a country. Economic

rehabilitation is also needed in the area that has experienced a landslide.

This would cost a lot and some of the offending country economy.

Example: A average, these landslides caused loss of $ 1-2 billion U.S.

dollars and 25disaster in the United States each year. At Utah, U.S., in 1983, the total cost to repair the landslide

area of 500 million dollars and it is financing the cost of the most expensive landslide in U.S. history

Loss due to landslides in the United States is estimated at 1.5 billion dollars annually.

Earthquake the earth Loma Prieto in October 1989 caused thousands of landslides covering an area of 5400 square feet. Causing losses of at least $10 million dollars 05/03/23Prepared by AKHTAR KAMAL

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2. Damage To Infrastructure.2. Damage To Infrastructure. Landslides can lead to damage to property resulting

from the force flow or mud. Infrastructure land such as buildings, roads, places of

leisure and so on can be destroyed by the landslide occurred.

Example:A. Destruction a building and placement.B. Land massive collapse can cause the destruction of a city.C. Damage to roadsD. Affect

communication system of roads and communication systems.

E. Earthquake the earth in October 1989 resulted in tens of thousands of experienced landslides with an area up to 5400 square feet. Cause affected road communication system, property damage and destruction of homes. 05/03/23Prepared by AKHTAR KAMAL

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3. Loss Of Life.3. Loss Of Life. Loss of life is a dangerous

effect upon the occurrence of a landslide and it is difficult to avoid.

Many lives will be lost upon the occurrence of landslides.

Example: Landslide Estate Park Hill

View occur on 20 November 2002 destroyed a house killing eight bungalows and family life.

Landslide in Highland Tower, Ulu Kelang cause of 48 people were killed and many injured.


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4. Changes In The Surface 4. Changes In The Surface Landscape.Landscape.

Landslide causes significant changes in the landscape of the earth's surface.

Pile of soil and mud from the landslide activity caused the high ground may be flat and settling sediment can become thick very quickly.

Consequently, dam rivers or lakes become more shallow to hold a lot of water. Water level becomes higher and the ground becomes waterlogged areas.

Landslides can also cause soil or rock slope becomes increasingly steep and unstable. 05/03/23Prepared by AKHTAR KAMAL

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Preventive MeasuresPreventive Measures The main factors which contribute to landslides are Slope,

water content, geological structure, unconsolidated or loose sediments, lithology and human interference.

Slope Retaining wall may be constructed against the slopes, which

can prevents rolling down of material. Terracing of the slope is an effective measure.

Effect of water Make proper drainage network for quick removal of

percolating moisture or rain water by constructing ditches and water ways along the slope

Geological structures Weak planes or zones may covered or grouted to prevent

percolation of water, this increases the compaction of loose material.


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Landslides And MudflowsLandslides And Mudflows Plant ground cover on slopes and build retaining walls. In mudflow areas, build channels or deflection walls to

direct the flow around buildings. Install flexible pipe fittings to avoid gas or water leaks.


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Major Landslide HazardMajor Landslide Hazard ALASKA:ALASKA: The 1964 prince William

sound earthquake triggered a large volume landslide at turn again heights.

Millions of cubic meters of soil and rock moved down slope.


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ALASKAALASKA Slope failure was

induced by ground shaking of “Quick Clay.”


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JAPANJAPAN


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A view of the landslide site in Aizawl, Mizoram on A view of the landslide site in Aizawl, Mizoram on May 12, 2013.May 12, 2013.


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Thank Thank youyou


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Land slide

Engineering

Transcript of Land slide