We would like to express our special thanks of gratitude to our teacher ,MRS. Rajashri Behera, who gave us the golden opportunity to do this wonderful project on the topic –LANDSLIDE. It also helped in doing a lot of research and we came to know about various types of new things. We would also like to thank our parents who helped us a lot in this project. There should also be a special thanks to our group members who cooperated in all the activities and group discussions and worked with harmony.
DEFINATION OF LANDSLIDES
THE CAUSES OF LANDSLIDES. TYPES OF LANDSLIDES. EFFECTS OF LANDSLIDES
PREDICTION OF LANDSLIDES.
Landslides occur when the stability of slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include: •Groundwater (porewater) pressure acting to destabilize the slope •Loss or absence of vertical vegetative structure, soil nutrients, and soil structure(e.g. after a wildfire) •Erosion of the toe of a slope by rivers or ocean waves •Weakening of a slope through saturation by snowmelt, glaciers melting, or heavy rains •Earthquakes adding loads to barely stable slope .Earthquake -caused liquefaction destroying slopes. •Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes and landslides around the world. Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water.
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 and various types of landslides. MUDDY DEBERIS FLOW in alpine areas cause severe damage to structures, infrastructures and often claim human lives. The solid -liquid mixture can reach up to 2 tones/ms and velocities of up to 14m/s.
Landslides that occur undersea have an impact into the water. They can generate tsunamis .Landslides can also generate mega tsunamis .These mega tsunamis are very dangerous and cause a lot of harm
An avalanche, similar in mechanism to a landslide, involves a large amount of ice, snow and rock falling quickly down the side of a mountain.This causes flood in many areas. A pyroclastic flow is caused by a collapsing cloud of hot ash, gas and rocks from a volcanic explosion that moves rapidly down an erupting volcanoes. This increases the temperature of earth.
LANDSLIDE HAZARDS ANALYSIS
Landslide hazard analysis and mapping can provide useful information for catastrophic loss reduction, and assist in the development of guidelines for sustainable land use planning. The analysis is used to identify the factors that are related to landslides, estimate the relative contribution of factors causing slope failures, establish a relation between the factors and landslides, and to predict the landslide hazard in the future based on such a relationship. The factors that have been used for landslide hazards analysis can usually be grouped into GEOMORPHOLOGY, GEOLOGY, LAND USE, and HYDROGEOLOGY. Thus the future conditions can be predicted before time.
Earth flows are down slope, 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. They are different from fluid flows because they are more rapid. Earth flows occur much more during periods of high precipitation, which saturates the ground and adds water to the slope content.
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. Steep coastal cliffs can be caused by catastrophic debris avalanches. These have been common on the submerged flanks of ocean island volcanoes such as the Hawaiian Islands and the Cape Verde Islands.
A sturzstom is a rare, poorly understood type of landslide, typically with a long run-out. Often very large, these slides are unusually mobile, flowing very far over a low angle, flat, or even slightly uphill terrain.
Landslide in which the sliding surface is located within the soil mantle or weathered bedrock(typically to a depth from few decimeters to some meters)is called a shallow landslide. They usually include debris slides, debris flow, and failures of road cut-slopes. Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low permeable bottom soils.