Landslides Causes and Prevention ppt

The Causes of Landslide along with Techniques to overcome Landslide

1. LANDSLIDES Umair Azam MS Earth Sciences Karakoram International University

2. CONTENTS INTRODUCTION CAUSES OF LANDSLIDE PREVENTION TECHNIQUES ENVIRONMENTAL IMPACTS METHOD OF MITIGATION  

3. CAUSES OF LANDSLIDE There are multiple type of events that causes of landslides, three that cause most destruction around the world are these :   Landslides and Water Landslides and Seismic Activity Landslides and Volcanic Activity

4. CAUSES OF LANDSLIDE Landslides and Water When it comes to water rain is the primary source for Landslides especially along the slop. Landslide depends intensity and time period of rain. Land sliding and flooding are closely allied because both are related to precipitation, runoff, and the saturation of ground by water. Landslides can cause flooding by forming landslide dams that block valleys and stream channels, allowing large amounts of water to back up . Water saturation of ground weakens the sediment and allows eroded material to move down the slope

5. CAUSES OF LANDSLIDE Landslides and Seismic Activity Many mountainous areas that are vulnerable to landslides have also experienced at least moderate rates of earthquake occurrence in recorded times. The occurrence of earthquakes in steep landslide-prone areas greatly increases the likelihood that landslides will occur, due to ground shaking alone or shaking- caused dilation of soil materials, which allows rapid infiltration of water. The 1964 Great Alaska Earthquake caused widespread land sliding and other ground failure, which caused most of the monetary loss due to the earthquake .

6. CAUSES OF LANDSLIDE Landslides and Seismic Activity 1964 Great Alaska Earthquake

7. CAUSES OF LANDSLIDE Landslides and Volcanic Activity Landslides due to volcanic activity are some of the most devastating types. Volcanic lava may melt snow at a rapid rate, causing a deluge of rock, soil, ash, and water that accelerates rapidly on the steep slopes of volcanoes, devastating anything in its path. These volcanic debris flows (lahars “Indonesian word”) reach gr eat distances, once they leave the flanks of the volcano, and can damage structures in flat areas surrounding the volcanoes. The 1980 eruption of Mount St. Helens, in Washington triggered a massive landslide on the north flank of the volcano, the largest landslide in recorded times. 

8. CAUSES OF LANDSLIDE Landslides and Volcanic Activity

9. CAUSES OF LANDSLIDE   Groundwater (pore water) pressure acting to destabilize the slope. Loss or absence of vertical vegetative structure, soil nutrients, and soil structure   (e.g. after a wildfire, fire in forests lasting for 3–4 days) Erosion of the toe of a slope by rivers or ocean waves weakening of a slope through saturation by snow melt , glaciers   melting , or heavy rains Earthquakes adding loads to barely stable slope Volcanic eruption Natural C auses

10. CAUSES OF LANDSLIDE Deforestation, cultivation and construction, which destabilize the already fragile slopes. Vibrations from machinery   or traffic Blasting   Earthwork which alters the shape of a slope, or which imposes new loads on an existing slope In shallow soils, the removal of deep-rooted vegetation that binds colluvium to bedrock   Construction, agricultural or forestry activities which change the amount of water which infiltrates the soil. Anthropogenic Causes

11. ENVIRONMENTAL IMPACTS Landslides cause property damage, injury, and death and adversely affect a variety of resources. For example, water supplies, fisheries, sewage disposal systems, forests, dams , and roadways can be affected for years after a slide event. The economic effects of landslides include the cost to repair structures, loss of property value, disruption of transportation routes, medical costs in the event of injury, and indirect costs, such as lost timber and fish stocks.

12. Landslides that occur undersea, or have impact into water, can generate tsunamis. Massive landslides can also generate megatsunamis , which are usually hundreds of metres high . Water availability, quantity, and quality can be affected by landslides. Geotechnical studies and engineering projects to assess and stabilize potentially dangerous sites can be costly.

13. METHODS OF MITIGATION Vulnerability to landslide hazards is a function of location, type of human activity, use, and frequency of landslide events. The effects of landslides on people and structures can be lessened by total avoidance of landslide hazard areas or by restricting, prohibiting, or imposing conditions on hazard-zone activity. . Local governments can reduce landslide effects through land-use policies and regulations. Government can help in its reduction by educating local communities through the past hazard history of a site and restriction on construction without authorized survey of the area by competent authority.

14. WARNING SIGNS Small slips, rock falls and subsidence at the bottom of slopes. Sticking doors and window frames. Gaps where frames are not fitting properly. Outside fixtures such as steps, decks, and verandas moving or tilting away from the rest of the house. New cracks or bulges on the ground, road, footpath, retaining walls and other hard surfaces. Tilting trees, retaining walls or fences.

15. Landslide Prevention Techniques Different techniques could help in preventing Landslide and decreases the chances of human and property loss. Some of them are: Retaining Walls Geogrid Expansive anchor bolt  Hydrological approach   Keeping Material and Structures Away from Slopes Controlling the Water Drainage on Property

16. Retaining Walls A retaining wall needs to be built on level ground. To avoid back-filing excavate deep enough for the base material which is crushed stone base. Installation of drainage p ipes in the wall reduces the saturated soil pressure.

17. Geogrid Geogrids are materials for erosion control that ensure the soil capacity to grow plants, reducing the damage caused by heavy rains and wind in slopes and embankments. They are two-dimensional structures made by polymers to supplement soil stress. The best application is in soft soils such as sand or clay.

18. Expansive Anchor Bolt They are made from tubular steel and through a high-pressure water injection pump (pneumatic, hydraulic or electric) expand and generate additional contact stress between the bolt and soil. Tow main forces take action: a perpendicular axil pressure through the whole length and a static friction, also in the whole length. The bolt tensile strength ranges between 120 and 240 KN/linear length and depends on the kind of rock. 

19. Hydrological   Approach S lope stability model SSHV-2D , is developed that considers various aspects of hydrological effects and vegetation impacts on the stability of slopes.  The rainfall infiltration and water uptake of roots change the water content of the unsaturated zone.  Vegetation impacts through roots on hydraulic conductivity and the influence of vegetation weight on slope stability. It is also observed that the existence of trees with high density on a slope can increase the factor of safety about 50% and prevent shallow landslides . https://www.mdpi.com/2073-4441/11/10/2146/htm

20. LANDSLIDE PREVENTION TECHNIQUES

21. UMAIR AZAM