Land Slide Mitigation by Sahibzada Uzair Ullah

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Sahibzada Uzair Ullah

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y Landslide mitigation refers to lessen the effect of landslides by constructing various man made projectsat the slopes which are vulnerable to landslidesplanning for landslides hazard mitigation as itsphenomenon is instant.

Now different techniques are in use to sort out landsliding which are:

1. Geometric methods: in which the geometry of thehillside is changed

2. Hydro geological methods: in which an attemptis made to lower the groundwater level or to reduce

the water content of the material; 3. C hemical and mechanical methods: in whichattempts are made to increase the shear strength of the unstable mass or to introduce active externalforces or passive to contrast the destabilizing forces.

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Based on the mineral composition of

land masses of earth there aredifferent methods which areapplied on different parts of land

masses.In this regard the methods of

treatment of rocky strata & soil forland sliding are different from eachother.

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Treating Rock Slopesy R ocks are treated for land sliding by:

1. R einforcement Measures

2. Meshing3. Geometry Modification

4. Surface & sub surface drainage

5. Other Protection measures

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Rock Bolting/Reinforcement

Measuresy One of the most prevalent method used for stability in

rocky strata.

y

The rock to be bolted should not be weathered.Comparatively hard strata.

y Contain plain steel rods with chemical or mechanicalanchors , face plate and a nut.

y R ocks are bored before installation.

y Plates are installed & tensioned.

y Grouted or un-grouted on the basis of short or longterm usage.

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Geometry Modificationy Usually the slope is of the rock is changed and adapted

to a reasonable magnitude for the project.

y Excavation is done with help of excavators or by controlled blasting of rocks.

y R etaining walls and rigid covers are constructedagainst the slopes which control and minimize the

effect of sliding

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Rock Meshingy R ock meshing is done on rocks where there comparatively

less chance of sliding.y Also used in hilly areas where there are greater chances of

ice avalanche.y Large rolls of mesh of high tension wires.y Nailing is done on rock where meshing is to be done.y One end of the mesh is fixed in nails at the upper end & the

mesh is rolled down.

y Nailing is done at the lower end and in the mid . Fixed atthe lower the lower end.

y Sometimes the meshes are shortcreted to have betterstability.

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y Meshes prevent rock avalanche and ice avalanche by entrapping the rock mass or the ice mass in them.

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Surface and Sub-Surface Drainagey R ain water & air moisture percolates through the

surface of slope and can cause the retaining walls and

slopes to slide due to stress on them.y Surface drains are made to collect water and avoid it

from percolating through the rocks.

y Subsurface drains are installed within the slopes.

Percolating water reaches the drains expelled out side.

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Soil Slopesy Soils are mainly treated for land sliding by:

1. Geometric Modification

2. Lowering of ground water table. (care should betaken because to much lowering of water table cancause strata to settle down which can also causehazards )

3. R einforcements4. Vegetation

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Geometric Modificationy Same phenomena as for rocks.

y Slope is reduced to a reasonable magnitude.

y Slope reduction minimizes the danger of land sliding.y Mass of land is cut by excavator s.

y Vegetation are grown on the land masses.

y R etaining structures are built.

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Reinforcementsy Anchors are applied to the surface that is vulnerable to

land sliding.

yBeing horizontal they increase the normal stress &hence the friction against sliding.

y Geo grids are synthetic materials used to reinforce theground

y R einforcements usually inserted in the direction of deformation.

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Vegetationy Usually applied with another treatment.

y R oots anchor the soils and reduce erosion of land.

y

Act as reinforcements. Increases resistance dueincrease in friction .

y Care should be taken while choosing plants for vegetation.

y Plants should have soft roots. Large roots cause cracksin rocks.

y Water consumption of the vegetation should be less.More water can increase the chances of land sliding.

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y Apart from these meshes are also applied along theabutments to prevent the sliding of pieces of land in

the rivers or streams.y Slopes can also be covered by tarpaulin sheets which

minimizes the effect of land sliding.

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y People can also take some precautionary measures toprotect themselves form land sliding.

1. Homes shouldnt be built on steep slopes.2. The slopes should be kept safe from too mush

watering.

3. The rock mass or land mass above should be cut if

there some probability of its falling.4. Growing vegetation with soft roots can also

minimize the threatening hazards of land sliding.

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THANK YOU 6/2/2011 8:10 AM 33

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Land Slide Mitigation by Sahibzada Uzair Ullah