Environment Management

Environment Management

Adhish LuitelPrasil KoiralaPranav BhandariZubin Raj BhandaryBegin Presentation >>>Copyright

Mass WastingDefinition: Geomorphicprocess by whichsoil,regolith, androckmove down slope under the force ofgravity.Mass wasting occurs on both terrestrial and submarine slopes, and has been observed onEarth,Mars,Venus, and Jupiter's moon.

When the gravitational force acting on a slope exceeds its resisting force, slope failure (mass wasting) occurs. The slope material's strength and cohesionand the amount ofinternal frictionbetween material help maintain the slope's stability and are known collectively as the slope'sshear strength. The steepest angle that a cohesionless slope can maintain without losing its stability is known as itsangle of repose. When a slope possesses this angle, its shear strength perfectly counterbalances the force of gravity acting upon it.

Mass Wasting

Types of Mass MovementTypes of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types:CreepsLandslidesFlowsTopplesSlump

Home > Types of Mass Movement

Types of Mass MovementTypes of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types:CreepsLandslidesFlowsTopplesSlump

Home > Types of Mass Movement >Creeps+ It is the combination of small movements of soil or rock in different directions over time are directed by gravity gradually downslope.

+ The steeper the slope, the faster the creep. The creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing.

+ The surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope formingterracettes. This happens at a rate that is not noticeable to the naked eye.

Types of Mass MovementTypes of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types:CreepsLandslidesFlowsTopplesSlump

Home > Types of Mass Movement > Landslides+ Where the mass movement has a well-defined zone or plane of sliding, it is called alandslide. This includesrock slides,slumpsandsturzstroms.

+ It is also one of the common classification of mass wasting

Types of Mass MovementTypes of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types:CreepsLandslidesFlowsTopplesSlump

Home > Types of Mass Movement > Flows

+ Movement of soil and regolith that more resembles fluid behavior is called a flow.

+ These includeavalanches,mudflows,debris flows,earth flow,laharsandsturzstroms.

+ Water, air and ice are often involved in enabling fluidlike motion of the material.

Types of Mass MovementTypes of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types:CreepsLandslidesFlowsTopplesSlump

Home > Types of Mass Movement > Topples

Topples are instances when blocks of rock pivot and fall away from a slope.

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Types of Mass MovementTypes of mass movement are distinguished based on how the soil, regolith or rock moves down slope as a whole. It is basically categorized into 5 basic types:CreepsLandslidesFlowsTopplesSlump

Home > Types of Mass Movement > Slump

A slipping of coherent rock material along the curved surface of a decline. Slumps involve a mass of soil or other material sliding along a curved surface (shaped like a spoon). It forms a small, crescent-shaped cliff, or abrupt scarp at the top end of the slope. There can be more than one scarp down the slope.

Factors triggering mass wastingGravitational pull of the earthseismic shakingincreased overburden from structuresincreased soil moisturereduction of roots holding the soil to bedrockundercutting of the slope byexcavationor erosionweathering byfrost heaveBioturbationEarthquake- Violent shaking due to an earthquake can cause unstable slopes to collapseQuick Clay- Soil liquefaction causes land to collapse

> Factors triggering mass wasting

EffectsMass movements affects the following elements:The topography of the earth's surface, particularly themorphologies of mountain and valley systems

The quality of riversand streams and groundwater flow

The forests that covermuch of the earth's sub aerial surface

> Effects of mass wasting

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Social & Economical ImpactsCause floods by damming up bodies of water and result to huge loss of lives and property.

Affect the agricultural lands

Loss of industrial productivity because of interruption of transportation system by landslides.

Increase the number of environmental refugees.

Mass wasting causing road damageAvalanche as an example of mass wasting

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Flows and AvalanchesIn a flow the material moved is not coherent but moves in a more chaotic, disorganized fashion.

It flows with mixing with particles within the flowing mass as a fluid flows. Snow avalanches are one kind of flows.

Where soil Is the flowing material these flos are described as mudflows. When a flow involves a wide variety of material is known as a debris avalanche.

Avalanche

SCALES AND RATES OF MOVEMENT

+ Mass movement can occur on a variety of scales and at a variety of rates. They may involve a few cubic meters of material or more than a million cubic material.

+ In the most rapid mass movements which include most rock falls and avalanches and mudflow s, materials can travel at speeds of hundreds of kilometers per hour.

+ There is little time for people to react once these events start and such events are the cause of the greatest proportion of mass movement casualties. They also cause extensive damage to buildings.

Landslides : can also be the cause of floods. A stream in the process of cutting a valley may cause unstable slopes. Landslides into the valley can dam up the stream flowing through it, creating a natural reservoir. The filling of the reservoir makes the are behind the dam uninhabitableConsequences of mass movement

Impacts of human activitiesMany types of construction lead to over steeping of slopes. Removal of material at the bottom of a hill may leave large rock masses unsupported.Building of houses on an unstable slope can lead to excess pressure being put on the slope.Planting of vegetation like trees can reduce the risk of unstable slopes and slides.Irrigation and use of septic tanks increase the flushing of water through soils and sediments. Artificial reservoirs can cause earthquakes as well as landslides.As the volume of the reservoir increases in volume, pressure exerted on the rocks along the reservoirs increases and the strength of the rocks also decreases.This may cause the dam to collapse.

Preventive MeasuresSlope reductionRetention StructuresFluid removalOther slope stabilizing methodRecognizing the hazardLandslide Warnings

Slope reductionReducing the steepness of the slopeStrengthening the slope by providing supporting materials at the base of the slopeReducing the load on the slope by removing all the large rocks or soil at the higher parts of the slope

The measures that should be taken depend upon the stability of the slope. A highly unstable slope might require all these preventive measures to be taken at once. These steps should be carried out cautiously. For example, if earthmoving equipment is used the load of the equipment or the vibration caused by it might trigger the landslide

Retention structuresThe groundcover should be increased by the means of plantation. A plant that grows quick and that has a strong root system is preferred.Strong walls can be constructed on the basis of the magnitude of force that could act on the wall.

The success rate of these kinds of structures has generally been low. Generally, high and thin walls have not been successful.

Fluid removalWater is the most significant cause of mass movement.

One of the basic ways of preventing landslide is to reduce the water pressure in the slope. Subsurface drainage can also be a method.

Any kind of moisture removal system is highly encouraged due to which it become difficult for the rocks and soil to slide off as the frictional resistance to sliding increases.

Other slope stabilizing methodVertical piles are placed on the base of the slope where the particles in the slope are solid.

This is not to be used anywhere. If the soil contains more fluid, the soil will just come out or flow within the vertical piles. It is also not applicable in highly steep slope. Generally, this technique is not very successful.The use of rock bolts to stabilize rocky slopes and rock slides has had a greater success. Rock bolts have been used in tunneling and mining. Sometimes the process of driving giant steel bolts in to the stable rocks below the slip planes is also used. This works best in low angle slopes.

Recognizing the hazardBasic climatic feature, topography and geology cause mass movement in a place; they are independent of any human activities.

Mass movements tend to recur in the same place where they commonly occur.

It is very easy to recognize past rock falls in a vegetated area. Large rocks are not suitable in a vegetated area and remain barren. Lack of vegetation might also lead to past debris avalanche and slides. These kinds of factors lead the landscape to slope instability. .

When there are small slips in the soil. The trunk of the tress grows a bit slanted but later vertical growth continues. If the gradual movement of soil is prolonged then the tree trunks maybe curved.

Slanted utility poles and fences, tilting over of object can also act as an indicator of soil movement

Landslide warningLandslide warning system was developed by U.S. geological survey after the rain triggered landslide in San Francisco Bay in 1982. The basis of the warning system was to establish a quantitative relationship among rainfall intensity, storm duration, and a variety of slope and soil characteristics relating to slope instability like slope angle, fluid pressure and so on.

These relationships are established using factual data of past landslides. It became possible to estimate the limits of storm intensity and duration which when crossed might result in landslide, given it was known how saturated the ground was due to the recent precipitation.The system though incomplete was tested in February 1986. Of the ten landslides predicted, eight took place when forecasted.

Landslide warning

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