2. Main Menu
1. Definition
2. Causes
3. Types of landslides
4. Effects and Losses
5. Solutions https://www.thethirdpole.net/en/climate/bhutan-landslides-climate-change/
3. 1. Definition
A landslide, also known as a landslip, is defined as the downward and
outward movement of slope forming materials composed of rocks, soils, artificial
fills or combination of all these materials along surfaces of seperation by falling,
sliding and flowing, either slowly or quickly from one place to another
Landslides can occur in offshore, coastal and onshore environment.
Althought the action of gravity is the primary driving force for a landslide to
occur, there are other contributing factors affecting the original slobe stability
https://www.somersetlive.co.uk/news/somerset-news/huge-landslide-causes-biggest-rockfall-
5302453
https://blogs.agu.org/landslideblog/2020/10/26/landslides-and-roads-recent-examples/
4. 1. Definition
Classification with respect to depth of slide
Types
Surface slide
Shallow slide
Deep slide
Very deep slide
Maximum depth (m)
< 1.5
1.5 - 5
5 - 20
> 20
5. 2. Causes of landslides
Natural factors
Gravity
Geological factors
Heavy rainfall
Earthquakes
Waves, tides
Volcanoes
Human factors
Water management
Pollution
Excavation
Mining, quarrying
Vibration
Deforestation
Land use pattern
6. 3. Types of landslides
https://www.coroflot.com/jeremygleason/UGS-Landslide-Illustrations
Rotational slides move along a surface
of rupture that is curved and concave
Translational slides occurs when the
failure surface is approximately flat or
slightly undulated
https://www.wsgs.wyo.gov/hazards/landslides.aspx
7. 3. Types of landslides
https://www.coroflot.com/jeremygleason/UGS-Landslide-Illustrations
Rock fall: free falling of detached bodies of
bedrock from a cliff or steep slope
Rock toppling occurs when one or more rock
units rotate about their base and collapse
https://www.wsgs.wyo.gov/hazards/landslides.aspx
8. 3. Types of landslides
https://www.coroflot.com/jeremygleason/UGS-Landslide-Illustrations
https://www.coroflot.com/jeremygleason/UGS-Landslide-Illustrations
Lateral spreading occurs when the soil mass
spreads laterally and this spreading comes
with tensional cracks in the soil mass
Earthflow: downslope, viscous flows of
saturated, fine-grained materials, which move
at any speed from slow to fast
9. 4. Effects and Losses
Positive
Negative
Effects
• Create new habitats
• Increase biodiversity
• Provide raw materials
• Tool for studying the environment
• Impact on water quality
• Wipe out forest land
• Dam up or flood streams
• Harm agriculture
• Damage built infrastructure
Losses
Economy
Productivity of agriculture
Reduced property values
Lives and social disruption
https://www.wsj.com/articles/hiroshima-landslides-claim-lives-of-seven-1408508525
https://www.nst.com.my/opinion/letters/2017/10/294801/hillslope-development-explain-penang-landslide
12. Group members
Nguyễn Đỗ Gia Huy Nguyễn Quốc Hưng
Đoàn Thanh Nam Phạm Đình Nguyên Phương
Nguyễn Lê Hòa Lê Đàm Khánh
Phan Hữu
Editor's Notes
Good morning teacher and everyone, our group has decided to talk about landslide
Specifically, we are going to find out what is a landslide, why does it occur, types, how it effects on human, material wealth and ways to stop the landslides
First of all, let’s start with the definition
A landslide, also known as a landslip, is defined as the downward and outward movement of slope forming materials composed of rocks, soils, artificial fills or combination of all these materials along surfaces of seperation by falling, sliding and flowing, either slowly or quickly from one place to another
Most types of mass movement are aided by weathering and usually involve surficial material. The material moves at rates ranging from almost imperceptible to extremely fast
Landslides are an important geologic process that can occur at any time and almost any place. While they are mostly associated with steep and unstable slopes, they can also occur on near-level and given the right geological conditions
Classification with respect to depth of slide
Next up, we have a classification with respect to depth of landslide. As you can see, there are basically 4 levels of depth, you can read the table carefully
In the next section
The causes of landslides are usually related to instabilities in slopes. When the gravitational force acting on a slope exceeds its resisting force, slope failure will occur. 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. Landslide causes include geological factors, morphological factors, physical factors and factors associated with human activity
So in a more understandable way, we will divide these into 2 main causes
Natural factors
Including geological, morphological and physical factors
Gravity: gravity works more effectively on steeper slopes, but more gradual slopes may also be vulnerable
Geological factors: many slides occur in a geology setting that places permeable sands and gravels above impermeable layers of silt and clay or bedrock
Heavy rainfall: slides occur often with intense rain by creating zone of weakness, also water tables rise with heavy rain makes some slopes unstable. More clearly, storm water runoff saturates soils on steep slopes or infiltration causes a rapid rise in groundwater levels. As water tables rise, some slopes become unstable that cause landslide
Earthquakes: When plate tectonics move, the soil that covers moves with it. When earthquakes occur on areas with steep slopes, many times the soil slips causing landslides. These are relatively rare events, but a few have occurred in historical time
Waves: wave action can erode the beach or the toe of a cliff, cutting into the slope and setting the stage for future slides. Tides are also important in washing away eroded bluff sediment which helps wave action move inland. Storms that create wind, waves, and flooding can cause more extreme erosion at the base of a bluff, increase the bluff slope, and make a landslide more likely
Volcanoes: strato volcanoes are prone to sudden collapse, especially during wet conditions. The conditions commonly prevail after volcanic eruptions that kill vegetation over extensive areas and spread loose volcanic rocks over the landscape
Human factors
Inappropriate drainage system: surface runofff of irrgated water on slopes exposes soil under cultivation to erosion. Part of this water is absorbed by soil increasing its weight, which can put an additional load on the slope
Cutting and deep excavations on slopes for buildings, roads, canals and mining: developmental activities like construction of buildings, road cutting, embankments, cut and fill structures causes modification of natural slopes, blocking of surface drainage, loading of critical slopes and withdrawal to toe support promoting vulnerability of critical slopes
It has been observed that if a deep excavation is made, it takes away the lateral support of the adjoining area which facilitates the landslides
Finally is
Change in land use pattern, deforestation, agriculture practices on steep slopes: deforestation and cultivation of seasonal crops and increase in settlements. Improper land use practices such as heavy tilling, agriculture practices and settlement patterns have contributed to creep and withdrawal of toe support in many cases
In general, human activities that increase the amount or rate of natural processes may contribute in various ways to landslide risk
Now, we would like to move on to the third part
These are common types of landslides, we have:
Rotational slide: This is a slide in which the surface of rupture is curved concavely upward and the slide movement is roughly rotational about an axis that is parallel to the ground surface and transverse across the slide
Translational slide: A translational slide often has a solid block or rock sliding down a surface, which has been translated to a new, lower position on the hillside. In this type of slide, the landslide mass moves along a roughly planar surface with little rotation or backward tilting
Rock Fall: a rock fall is a sudden movement of rock, separated along fractures of bedding planes. There is no fluidity in the motion, only bouncing, rolling and free fall
Rock toppling: occurs when one or more rock units rotate about their base and collapse
Lateral Spreads: are distinctive because they usually occur on very gentle slopes or flat terrain. The dominant mode of movement is lateral extension accompanied by shear or tensile fractures. Failure is usually triggered by rapid ground motion, such as that experienced during an earthquake, but can also be artificially induced. When coherent material, either bedrock or soil, rests on materials that liquefy, the upper units may undergo fracturing and extension and may then subside, translate, rotate, disintegrate, or liquefy and flow
Earthflow: are downslope, viscous flows of saturated, fine-grained materials, which move at any speed from slow to fast. These flows usually begin when the pore pressures in a fine-grained mass increase until enough of the weight of the material is supported by pore water to significantly decrease the internal shearing strength of the material. Earthflows occur much more during periods of high precipitation, which saturates the ground and adds water to the slope content
In addition to the above types, there are also block slide, debris flow, creep and slump, et cetera…
According to the features and classification of landslide above, we can see they are unforeseeable hazards, threatening to both inhabitant and material wealth. However, they somehow still have a variety of advantages:
Effects
As with all natural hazards, landslides offer some important service functions
Positive
Create new habitats: One of the most important beneficial effects of landslides is that they create new habitats. When landslides occur, they obviously change landscapes. In this way, many micro-environments like ridges form. These features can be warmer, drier, wetter, more exposed, less exposed than the surrounding regions. Very often, repeated debris flows and slides can deepen gullies resulting in expanded water flows. Then, new habitats form
Increase biodiversity: As these new habitats result, biodiversity in that particular region can also increase. It provides opportunities for organisms to colonize the slide sites and grow or survive
Provide raw materials: like firewood, medicinal plants and mineral. Similarly, landslides can expose mineral deposits. Over time, mineral grains like gold and diamonds detach due to weathering. They can concentrate at the base of slides or in nearby streams.
Tool for studying the environment: As it is common with disasters, humans can learn from them. Thus, in many instances, landslide sites are good tools for studying the environment
(HỮU)
Negative
In contrast, obviously landslide also have negative impacts, such as:
Impact on water quality: When landslides occur, they can seriously damage or destroy ecosystems. Sometimes the effects can last for thousands of years. They can pollute streams and water bodies with sediment and debris. This invariably has severe repercussions on water quality and marine life
Wipe out forest land: What’s more, these hazards can wipe out large tracts of forests, wildlife habitats and remove productive soils from slopes
Dam up or flood streams: Also, they can dam up rivers and streams. In so doing, water flow is restricted. Marine and terrestrial organisms that depend on the water flow may eventually die
Harm agriculture: One of the most damaging effects of landslides is the destruction of agricultural land. Debris spread over farms, cultivation and pastures, covering important agricultural land. They destroy seeds, plants, food stocks and grazing land. These lands can remain inaccessible for years ultimately impacting on farmers’ livelihoods
Damage built infrastructure: Landslides can cause serious damage to the built infrastructure, destroy or damage houses, buildings and infrastructure close to hills and mountains
(HÒA)
About the losses of landslide
Losses
As it currently stands, economic losses due to these hazards have been increasing during the past decades. This is mostly linked to increasing development and investment in landslide-prone regions
They are very dangerous, responsible for a number of deaths, injury to people, damage to housing, infrastructure and agricultural lands. Sometimes, such events can impact on the mental health of people also; children and youngsters especially at more at risk. Moreover, victims of landslides can develop crush injuries or crush syndrome after they have been rescued from the debris
(Đợi chiếu hình lên xong mới nói đoạn này) You can see on the pictures, as we mentioned in the causes part. The left one, flood and heavy rainfall has softened the soil, melting and draging it down to residential area, neighborhood. On the right one, activities like excavation and vibration on construction site have caused modification of natural slopes
We would like to finish the topic by provide you with several latest mitigation strategies that we have found out:
Draining water: draining water is a common mitigation technique to help stabilize slides, a horizontal drain can be used to drain water to reduce pressure on the soil Drainage is needed in civil work
Retaining wall: gabions, blocks or rocks wrapped in steel mesh, are commonly used to fortify vulnerable slopes. Unlike concrete wall, gabions allow free drainage through themselves, benefitting the slope from both sides
Soil nailing: is a cost-effective way to create a reinforced ground zone. You can use a work platform suspended from a crane to install them on steep slopes like a bluff. For temporary or permanent excavation support, a gravity retaining wall is created using grouted, tension-resisting steel to reinforce soil
Vegetating slops: Landslides can quickly and easily happen in sloped areas on your property due to the influence of gravity as well as the environmental pressures alluded to above. One of the quickest and easiest ways to prevent this is by planting vegetation. The presence of plants on your slopes will lead to excess water being absorbed, lessening the chance of rain infiltrating any cracks in the soil and causing a landslide
So that is the end of our presentation, we hope these information and knowledge of landslide would contribute to your work beneficially afterwards. Thank you for your all listening
