Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

EOSC 114 > Landslides > Flashcards

Landslides Flashcards

1
Q

What are the main similiaries and differences between earthquakes and landslides?

A 
Earthquakes:
Shear failure
Deep/shallow
Slip on planar fault
Shear stress driven
Technoic process/builds topography
Landslides:
Shear failure
Surface phenomenon
Slip on planar or curved surface followed by flow
Gravity Driven
Erosional process, Destroys topography
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What happens when soil is saturated with water?

A

It resembles liquefaction, it becomes much more sucseptible to failure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the most deadly slide in canada?

A

Frank Slide, Alberta killing 70, “the mountain that walks”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the impacts of landslides? What are they govered by?

A

Human and economic

1) population density (lives and injuries)
2) cost of infrastrucutre ($$$)
3) population preparedness (both)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How many geohazards account for death by landslide?

A

24% in canada

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are most common human inpacts? Why are they underestimated?

A

Low deaths

Underestimated (usually landslides are triggered by volcanos/earthquakes and are attributed to those

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some estimates of economic impacts?

A

1.4 Billion in canada
3.35 billion in USA
Venesuala 62 million

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is BC susceptible to landslides?

A

Mountainous
Rain- saturated ground
Complex geology (glacial sediment with elevation gain)
Triggers that cause landslides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the return period of a landslide that has 20 mil m3 of material?

A

25-70 years..

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how do you classify landslides?

A

type of material
type of movement
rate of movement
name is the 1st 2 combo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are types of materials?

A

rock
soil/earth
mud
debris (mixture)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what are types of motion?

A

falls (rock breaks lose under gravity)
slides (block moves on a surface)
- curved shape failure (rotational)
- flat failure surface (translational slide)
flows (fluid motion)
-complex movements (combo: slide that becomes a flow)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

where do falls occur?

A

steep rock slopes, detaches because of weakness/fractures etc and gravity. very fast

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are characteristics of slides?

rotational vs translational

A

slow or fast, soil/rock/debris
moves as ONE MASS along a surface

Rotational: slump, intermediate speed, weak material (sediment) curved failure plane
curved ‘scarp’ above the slide

Translational: slow-fast, strong material on planes of weakness, cohesive motion along flat surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are flows?

A

slow-fast
kind of like lahars
water very important
fluid or plastic flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is gravity counteracted by on a slope?

How does water effect this?

A

1) internal strength of material
2) friction of that material on a slope

Water increases weight and reduces friction. It decreases NORMAL FORCE.
Decrease strength, promote landslides

always a fight between friction>< downhill

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is slow moving stuff called?

A

x creep

18
Q

What is the angle of repose?

A

GOOD: the angle of repose shear stress is exactly balanced by shear strength. Factor of safety is equal to or just above 1.

OR BAD: steepest angle a slope can contain without collapsing.
Depends on material

19
Q

What are the forces involved in the stability of slopes?

A

Driving force:

  • Gravity
  • manifests as “shear stress” (T), parallel to the slope. Force of gravity parallel to the slope

Resisting force:
Friction - resistance to sliding (proportional to formal force/stress)
Cohesion - how material holds together
Together they make “shear strength” (Tf)
- which is the ability to resist shearing motion

20
Q

When (mathematically) is a slope stable/unstable?

translational slides

A

When Driving forces are greater than resisting force, motion/failure occurs. When shear stress is greater than shear strength
Fs = Tf/T (shear strength over shear stress)
When Fs > 1 stable!

21
Q

What happens when you add water into the equation?

A

normally: Tf=u*normal force (which is frictional resistance)
with water
Tf= u(normal force - pressure of water)

water pressure lowers Tf!!
*** look at equations one more time unless u can write them out no problem

22
Q

how do you calculate stability of slopes in rotational slides?

A

material itself fails, the strength depends entirely on the material, becuase of the ability to ‘interlock’
- internal frictional strength, cohesive strenght (rotational slides dont happen in solid rock)

23
Q

What is the average material strength of certain materials discussed in class?

A

Ignoues/metamorhpic: high shear strength
Sedimentary rock: moderate shear strength
Sediments: LOW

24
Q

Whats a cause vs a trigger?

A

causes (long term) factors that lead to instability of a slope
causes reduce shear strength OR increase shear stress
do not initiate movement

triggers translate instability into motion (can be many causes, but only one trigger)

25
Q

What are external causes of mass movement?

A

factors that affect stability

1) slope angle
2) undercutting: lower part of slope removed, which could be supporting slope, (rivers/roads/buildings etc)
3) overloading: adding weight to top of unstable slope
4) vegetation: roots bind loose material, removing roots can make unstable, but heavy trees can decrease stability which is overloading
5) climate: high rainfall, increased weathering of rocks, temp (internal causes)

26
Q

what are internal causes of mass movement?

A

factors inside slope that affect its stability
1) water:
in all slopes
-adds weight (overloading)
-decreases normal stress, decreasing friction and shear strength
-increases weathering
-acts as medium for flows
in sediments
-depends on how much water is present
in solid rock
-water reduces shear strength along planes of weakness, acts as lubricant and reduces effective normal stress
-frost wedging/freezing thaw (water gets into cracks, as it freezes it expands, forcing fractures apart)
landslideshappen more often in colder temperatrures

2) inherently weak material
-fail at low angles
-volcanic rock (??), quick clay
CLAY: so small (0.002mm) that vanderwalls forces apply (electrostatically) - when in salt water clay is attracted to other clay particles

3) Bad geological structures
- bad bedding/fracture orientation
- structures angled in an instable direction, layered precariously

27
Q

how does water content in sand effect its angle of repose?

A

in sand sediment
-water helps/hinders cohesion depending on HOW MUCH
a) unsaturated: surface tension is an important force with films of water and sand grains
b) saturated: grains are forced apart and material flows
no water: low/medium angle of repose
some water: very high angle (almost verticle)
too much water: very LOW ANGLE

28
Q

what are quick clays?

A

a “house of cards” structure, that when is shaken, becomes compact
Salt content is lowered by percolating groundwater
***
not very common to cause slides

29
Q

What are some triggers?

A

Force/event that disrupts equilibrium of a slope and initiates mass movement
- earthquakes, snow melt, heavy rainfall, rain on snow, loud noises, vehicles, volcanic eruptions, excavation, skiing, jumping

30
Q

Describe the Oso Landslide

A 
Causes? 45 days of heavy rain
Trigger: collapse of layers of glacial sediment 
Name?
Protect ppl?
***
31
Q

What is the landslide disaster scale?

A 
A velocity class based on its speed. 7 classes with ranges  from slow to very fast!! 
16 mm/year to 5m /second (1-7)
32
Q

What are telltale signs that a slope is unstable

A

Steep loose sediments and rock
PISTOL BUTT tress: shows slope is slowly going down (makes trees tilt and they try to right themselves)
Tilted things
Erosion

  1. cracking tilted house elements
  2. cracks on slope
  3. cracks in retaining walls
  4. water pooling at base of slope
  5. bulges on slope
  6. leaning trees and utility posts
  7. sunken road beds
33
Q

What are landslide cause and effects?

A

Cause: reduce shear strength
Trigger: initate motion
Effect: fall/slide/flow/complex

34
Q

What is migitation?

A

Solving the problem, investigating/monitering.

sometimes cheaper to repair than remove cause alltogether :)

35
Q

What are some forms of investigation?

A
  1. looking for previous failures
  2. Geostatics: frequency and magnitude diagrams, look at historical record and develop stats for a region (logarithmic plot)
  3. Hazard mapping (plan best route for a highway/pipeline etc.)
  4. Modeling: see slopes and valleys, see where dangerous areas are
36
Q

what are the 3 paths to mitigate landslides?

A
  1. Avoidance (move away)
  2. Prevention: make sure they don’t occur when ppl or there or at all
  3. Protection: strengthen/armour area that might be affected by landslide if it happens
37
Q

What are avoidance strategies?

A

Often too expensive

  • buying property in a town
  • moving a highway
  • convincing ppl to leave a home
38
Q

What are prevention strategies?

A

Removal of material
Stabilizing slopes with
-resisting forces, retaining walls, gabions
-stabilizing by cables anchored in rock that pull layers together
Remove water with drainage
Rock scaling: removing pieces that will fall

39
Q

What are protection strategies?

A

Minimize hazard
Let them occur but control what happens
1. Rock barrier (i.e. on a highway)
2. Rock net (to keep rocks close to wall and not fly out)
3. ROckfall shed, go ontop of road
4. Rock fences: catch falling rocks and dissipate kinetic energy
5. Debris flow retention structures
(water and debris, remove debris from water = no more flow!!)

40
Q

what does frost wedging cause?

A

rock falls!

EOSC 114 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions