landslide

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Introduction A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments.

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Definition“A landslide is an catastrophic event where a block of earthen mass slides downhill”.

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The causes of landslides are usually related to instabilities in slopes. It is usually possible to identify one or more landslide causes and one landslide trigger. The difference between these two concepts is subtle but important. The landslide causes are the reasons that a landslide occurred in that location and at that time.

Geological causes

Weathered materialsJointed or fissured materialsAdversely orientated discontinuitiesMaterial contrastsRainfall and snow fallEarthquakesWorking of machinery

Morphological causes

Slope angleUpliftReboundWave erosionGlacial erosionErosion of lateral marginsSlope loading

Physical causesIntense rainfallRapid snow meltRapid drawdownFreeze-thawGround water changesSoil pore water pressureSurface runoff

Human causes

• Loading• Drawdown• Land use change• Water management• Mining• Vibration• Water leakage• Deforestation

Types of landslides Debris flow:- Slope material that becomes saturated with

water may develop into a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses and cars, thus blocking bridges and tributaries causing flooding along its path.

Debris flow is often mistaken for flash flood, but they are entirely different processes.

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Amboori debris flow, occurred on 9 November 2001 in Kerala, India. The event killed 39 people.

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Earth flow

Earthflows are downslope, viscous flows of saturated, fine-grained materials, which move at any speed from slow to fast. Typically, they can move at speeds from 0.17 to 20 km/h. Though these are a lot like mudflows, overall they are slower moving and are covered with solid material carried along by flow from within. The velocity of the earthflow is all dependent on how much water content is in the flow itself: if there is more water content in the flow, the higher the velocity will be.

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A earth flow in Guerrero, Mexico

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Debris avalanche

A debris avalanche is a type of slide characterized by the chaotic movement of rocks soil and debris mixed with water or ice (or both). They are usually triggered by the saturation of thickly vegetated slopes which results in an incoherent mixture of broken timber, smaller vegetation and other debris. Debris avalanches differ from debris slides because their movement is much more rapid. This is usually a result of lower cohesion or higher water content and commonly steeper slopes.

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Goodell Creek Debris Avalanche, Washington.

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Shallow landslide

Landslide in which the sliding surface is located within the soil mantle or weathered bedrock (typically to a depth from few decimetres to some metres). They usually include debris slides, debris flow, and failures of road cut-slopes. Landslides occurring as single large blocks of rock moving slowly down slope are sometimes called block glides.

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Shallow landslide in Hotel Limone at the Garda Lake. Part of a hill of Devonian shale was removed to make the road, forming a dip-slope. The upper block detached along a bedding plane and is sliding down the hill, forming a jumbled pile of rock at the toe of the slide.

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Deep-seated landslide

Landslides in which the sliding surface is mostly deeply located below the maximum rooting depth of trees (typically to depths greater than ten meters). These typically move slowly, only several meters per year, but occasionally move faster.

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Deep-seated Landslide in Pakistan

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Examples “Landslides in India”mumbai landslide 2000

2010 Leh floods

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Karanjadi train crash

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Konkan railway landslides 2011Maharashtra

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Malpa landslide

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Examples given is clearly an artificial situation of landslide

Landslides Prediction

Although a basic understanding of the landslides is available, system that predict the occurrence of a landslide do NOT exist.

Why?The lack of field measurements over large

temporal and spatial scales.

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Continue….The development of a landslide is a

temporal processtakes as long as a year to developMovement speed, several cm per month

Landslides are spatial in nature.Position Movement direction

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System ArchitectureSensor Column

GeophoneStrain GaugePore Pressure Transducer

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System Architecture

DeploymentA network of sensor columns Placed in vertical holes drilled over

the hill surfaceUsing sensor columns to detect

movements28

Solution OutlineGeophones estimate displacement dij(t)

Based on distance matrix D=[dij(t)]Detection

Determine whether slip surface has formedClassification

Estimate subset of sensors that movedLocalization

Compute location of slip surface

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ExampleDetection & Classification & Localization

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DetectionUse strain gauges on each sensor columCan measure changes in their length due to

deformation

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LocalizationLocalize moved nodes using trilaterationSlip surface estimation

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EvaluationEvaluation metrics

Average and std. dev of localization errorMax. distance between actual and

estimated slip planeAbstract network model

Communications are error-freeNodes do not fail

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ConclusionPropose a WSN for the

prediction of landslidesDesign a system to

detect the early signals preceding a landslides.

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Prediction

Finite Element Analysis

Simple Measurement

Temporal & Spatial Measurement

Civil Engineering

WSN

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Thanks!